351C H code 2V to 4V Carb and Manifold Swap

[griffbl]

I am trying to do a few little mods on my very original 1971 Mach 1 351C H Code 2V.  Car is stock, save for a nice dual exhaust setup and a Petronix ignition module inside the distributor. I do not want to really do anything that cannot go back to bone stock, as I am not really trying to hot rod it hard, and again, I don't want to do anything so major to alter its' originality very much.  Has FMX and 3.00 Open Rear End. Car has Factory A/c, but will be receiving a Sanden Type Compressor to save weight, and most importantly, to reduce engine drag.  The only other modification I was considering is to go to an Edelbrock Air Gap type intake, in the interest of weight savings and an appropriate 4V carb. It seems to have bosses for my factory accelerator cable assembly.  My inclinations are to use a Holley 600, in aluminum, (again because it is lighter) with electric choke and provision for the kick down rod for the FMX A/T.  I may need to bump up the axle to a 3.25, but I was going to try it with the factory ratio first. I am running the stock Air cleaner, but I did install a lid which only covers the air filter itself so as to leave an open area around the filter.  I always thought the stock covered unit breathed poorly from just the snorkel alone, but that is just me. Since I am nor running any kind of ram air set-up, I don't think I will have any hood clearance problems.  My hunch is this will knock 30 pounds +/- off the front end.  In theory, the car should run a little better. I thought about a set of shorty headers, for weight and slightly better exhaust flow, but it would disrupt heat shields, and other factory stuff I thought better left alone vs. the minimal gains.  I think the 1971 H code runs about 9.0 to 1 in compression, and my engine is stock with very good compression. Let me know if you guys think this is a good plan or not, and as to my choice of carburetor and manifold.  Many thanks in advance!

 

[rvrtrash]

You should think of engine mods as a complete system and not just individual parts. If you aren't going to be hot rodding it and want to do minimal changes, I would probably just look at a new Holley 2 barrel. Your limiting factor in total air flow will be the factory exhaust manifolds. 30 lbs of weight savings isn't much in a 3200 lb car. If you did decide to go with a 4 bbl, I'd consider the Holley 570 Street Avenger.

Steve

 

[griffbl]

You should think of engine mods as a complete system and not just individual parts. If you aren't going to be hot rodding it and want to do minimal changes, I would probably just look at a new Holley 2 barrel. Your limiting factor in total air flow will be the factory exhaust manifolds. 30 lbs of weight savings isn't much in a 3200 lb car. If you did decide to go with a 4 bbl, I'd consider the Holley 570 Street Avenger.

Steve

Steve-

I agree I am not rational when it comes to weight.  But these cars are front end heavy, so it is an added bonus to do those mods.  Maybe I should consider shorty headers also.  I also might go with some aluminum wheels as that represents 40 pounds total or so savings of unsprung weight.  Back to the carb.... your suggestion at 570 cfm with the holley street avenger is even better than my 600 cfm example, especially if i can get an example with  electric choke and Ford Kick down for the A/T.  I could use the Holley 2v on the existing manifold, and that is plenty of CFM, just no weight savings....but a LOT less hassle also! Do you know the CFM rating of the stock 2150 Carburetor?  Maybe I should consider the shorty headers, as after all, those mods are reversible also, and it probably cuts another 10 pounds? It will require modifying the exhaust down pipes again if it is changed back to stock, but that is no big deal.

Many Thanks!

Brad

 

[Mister 4x4]

I have (had) almost the same car as you ('71 H-Code Mach 1, FMX & 3.00 rear gears).  I stuck with the 2V heads, but went with an Edelbrock 1406 on a Performer 351C-2V intake with Hooker ceramic-coated Competition headers (along with some other go-fast goodies - the laundry list is in my Garage thread).  I went that route because being an H-Code, means being some of the least-rare (read... valuable) Mach 1s produced in '71, as well as my engine was seized and I decided to hot rod it since it needed a complete rebuild anyway.  

Going from a 2bbl to 4bbl means an intake manifold swap, but there's nothing saying you can't hang on to the stock 2V manifold/2150 combo and reinstall if you need to at some point down the road.  You won't likely notice a huge increase in power... based on how much you'd spend, anyway.  Things will run better [once adjusted] and you'll notice some 'seat of pants dyno' gains... but a tune-up and rebuild of the carb would probably get you pretty close to that feeling as well.

Your best bet for maintaining originality would be to just rebuild the 2150 and throw in a set of 3.25s or 3.50s in the rear end.  Nobody will ever 'see' that the gears aren't original, and you'll have a LOT better 'off the line' performance.  The 2150's a solid carb (when treated right... i.e. fresh rebuild and periodic cleaning with some in-tank carb cleaner) - I have one on my Jeep.

 

[griffbl]

I have (had) almost the same car as you ('71 H-Code Mach 1, FMX & 3.00 rear gears).  I stuck with the 2V heads, but went with an Edelbrock 1406 on a Performer 351C-2V intake with Hooker ceramic-coated Competition headers (along with some other go-fast goodies - the laundry list is in my Garage thread).  I went that route because being an H-Code, means being some of the least-rare (read... valuable) Mach 1s produced in '71, as well as my engine was seized and I decided to hot rod it since it needed a complete rebuild anyway.  

Going from a 2bbl to 4bbl means an intake manifold swap, but there's nothing saying you can't hang on to the stock 2V manifold/2150 combo and reinstall if you need to at some point down the road.  You won't likely notice a huge increase in power... based on how much you'd spend, anyway.  Things will run better [once adjusted] and you'll notice some 'seat of pants dyno' gains... but a tune-up and rebuild of the carb would probably get you pretty close to that feeling as well.

Your best bet for maintaining originality would be to just rebuild the 2150 and throw in a set of 3.25s or 3.50s in the rear end.  Nobody will ever 'see' that the gears aren't original, and you'll have a LOT better 'off the line' performance.  The 2150's a solid carb (when treated right... i.e. fresh rebuild and periodic cleaning with some in-tank carb cleaner) - I have one on my Jeep.

Eric-

You are right it is not a super valuable car, but it is a beautiful, super clean, example in a great color combination.  I might add the shorty headers if it would all add up to a noticeable difference when combined with the intake and carb.  The 2150 has had a fresh re-build.  Car feels good as is after I advanced the ignition timing to 14 degrees.  I had a bone stock 72' H code back in 1975.  It had 2.75's! Uggh.......sort of fast, but not quick.  At 60MPH, when it shifted into 3rd, it just died in terms of acceleration as a result of the tall gearing.  I can say that this 71 H code is a stronger car, as the compression ratios were higher in 71'.  The HP rating is higher for 71'  vs. 72' as a result, and I can feel the difference.  3.25's may be the way to go as you point out. My mechanic says you can feel every ratio change.  I have seen the difference in other cars, but they were bigger jumps in ratio. Come to think of it, I can certainly feel this car is better balanced with 3.00's than my old 2.75 car, so maybe you really can feel every ratio change.  I built a 400 HP M code 71' with 3.50's, and I think 3.25's might be perfect for a cruiser.  This car will leave a long scratch with the open 3.00 as it sits today.  Just a question now as to whether the shorty headers, manifold and carb would improve upon the car's performance materially or not? 

Thanks!

Brad

 

[griffbl]

One other thought? Are there some aluminum roller rockers available that I can bolt on are replacements? Without having to go to studs on my stock heads? My experience is that these are nice additions on any engine. I do NOT want to pull the heads at this time, simply to bolt on better, lighter rockers for a small incremental gain. Thanks so much

 

[Hemikiller]

You would do well with a 4V swap. I've done the old school boneyard swap of a stock 4V iron intake & Holley 3310 750 VS on a 2V engine and it really woke it up. The port mismatch is no big deal and it keeps the carb low for clearance. Keep in mind that a 351C can handle much more carburetor than an SBC or a 302/351W, so the metrics for those engines do not apply evenly. The Holley 750VS will work just fine and leaves you room to grow. I run 800 double pumpers on my 351C4V cars and one that had 3.00 rear gears would pull down 20mpg.

That said, a Performer would be a better match and the Air Gap really won't gain you much of anything on an otherwise stock engine except a lighter wallet.

If you want to go the header route, the Hooker Comp made specifically for the 71-73 cars with 351C engines fit great and don't hang low enough to cause problems.

 

[griffbl]

You would do well with a 4V swap. I've done the old school boneyard swap of a stock 4V iron intake & Holley 3310 750 VS on a 2V engine and it really woke it up. The port mismatch is no big deal and it keeps the carb low for clearance. Keep in mind that a 351C can handle much more carburetor than an SBC or a 302/351W, so the metrics for those engines do not apply evenly. The Holley 750VS will work just fine and leaves you room to grow. I run 800 double pumpers on my 351C4V cars and one that had 3.00 rear gears would pull down 20mpg.

That said, a Performer would be a better match and the Air Gap really won't gain you much of anything on an otherwise stock engine except a lighter wallet.

If you want to go the header route, the Hooker Comp made specifically for the 71-73 351C engines fit great and don't hang low enough to cause problems.

Thanks so much Hemikiller! The Edelbrock Performer is a time proven option.  In the past, most after market manifolds were specifically made for 2v heads or 4v heads, but not both.  NOW I see Edelbrock makes heads that fit either!  I think I will use either an Edelbrock Performer or Airgap, or possibly the Weiand 2v manifolds.  If I painted any of them the correct blue except the airgap, they would even look close to stock.

I had looked at the Doug's Shorty Headers #D6512, but they are pricey.  I will look at the Hooker Comps also.  Thanks again for the tips!

Many Thanks!

Brad

 

[Canted 393]

One other thought? Are there some aluminum roller rockers available that  I can bolt on are replacements? Without having to go to studs on my stock heads? My experience is that these are nice additions on any engine.  I do NOT want to pull the heads at this time, simply to bolt on better, lighter rockers for a small incremental gain. Thanks so much

scorpion makes pedestal mount rocker arm kits, and here is what I like to do is use crane cams conversion kit

 

[griffbl]

One other thought? Are there some aluminum roller rockers available that  I can bolt on are replacements? Without having to go to studs on my stock heads? My experience is that these are nice additions on any engine.  I do NOT want to pull the heads at this time, simply to bolt on better, lighter rockers for a small incremental gain. Thanks so much

scorpion makes pedestal mount rocker arm kits, and here is what I like to do is use crane cams conversion kit

Thanks so much. Another good option!  I do prefer, I think, Crane or Comp cams rockers to Scorpion's, and either Crane or Comp's rockers do necessitate the Crane conversion kit.  Either will require changing pushrods also, of course.  I think your Crane kit is a higher quality option, than using scorpion rockers and makes it possible to use shims should I need them.  I think it will require my monkeying with the baffles a bit on the valve covers for clearance, and maybe doubling up a valve cover gasket for a bit more room. I think Comp or Crane aluminum rockers will come closer to clearing my stock valve covers than would the Scorpion bolt ons.

Many thanks!

Brad

 

[kcmash]

When I bought mine it wan an unmolested H-code with the exact power train you mention and single exhaust,  If you want a nice car to drive with little effort, tuning, or adjustment, keep it stock.

If you opt to spice it up it looks like others have provided some good input.   I decided to load quench 4-v heads and a factory 4 bbl intake on mine in highschool to be cool like the other kids, and it never was the highly reliable driver again.  Of course I should have made some camshaft upgrades instead of just leaving the 2-v cam in there.

Just my 2 cents.

kcmash

 

[griffbl]

When I bought mine it wan an unmolested H-code with the exact power train you mention and single exhaust,  If you want a nice car to drive with little effort, tuning, or adjustment, keep it stock.

If you opt to spice it up it looks like others have provided some good input.   I decided to load quench 4-v heads and a factory 4 bbl intake on mine in highschool to be cool like the other kids, and it never was the highly reliable driver again.  Of course I should have made some camshaft upgrades instead of just leaving the 2-v cam in there.

Just my 2 cents.

kcmash

Thanks KC! Sometimes, if it aint broke, don't fix it!  This car runs good, for what it is, as is! I do not want to pull the heads, etc. So anything must be bolt on.  When I was in High School, in 1975, I had a 12k mile 1972  H code Mach 1.  It had no a/c, and a 2.75 or a 2.79 rear end I cannot remember which one...both bad answers).  I just KNEW I needed a 4BBL and headers to make it go fast. Actually, it was kind of fast....but NOT quick. First gear in the FMX was good. But when it shifted into 2nd, it fell down. I lost a race to a Buick Skylark with a 350 2BBL Buick engine. I held my own against a 400 4BBL Firebird....until shortly after my FMX shifted into 2nd, then I was blown away. Depressing! (expected with the Firebird, not with the Buick!)  I remember the local speed shop owner asked me if it had 2 bbl or 4 bbl. heads as to which intake was required...that is when I learned Clevelands were not like Chevys! Then he asked me what gears I had in back.  I kind of gave him a puzzled look. He pointed out, after I determined I had 2.79's, he pointed out, in a way I could understand, that "it was as if my ten speed bike only had gear 10".  That made sense to me! My car would have run worse, not better, with a 4 BBL without a gear change....so I ended up doing nothing.  My 1971 today runs better than did my 1972.  More compression and therefore HP in 1971 vs 1972, and a 3.00 is better than a 2.75 in the 9" Diff.  I do think a modest 4bbl like a 570 Holley, and or headers, and maybe one notch up to a 3.25 in gears will help, not hurt.  I do already have dual exhaust, and maybe the smart move is to go to a 3.25 to one rear end, and then see if I need anything else.  I have other go fast cars.  This one is not going to be a hot rodded example....I am just considering bolt ons to warm it up a bit, if possible!

Many Thanks,

Brad

 

[kcmash]

When I bought mine it wan an unmolested H-code with the exact power train you mention and single exhaust,  If you want a nice car to drive with little effort, tuning, or adjustment, keep it stock.

If you opt to spice it up it looks like others have provided some good input.   I decided to load quench 4-v heads and a factory 4 bbl intake on mine in highschool to be cool like the other kids, and it never was the highly reliable driver again.  Of course I should have made some camshaft upgrades instead of just leaving the 2-v cam in there.

Just my 2 cents.

kcmash

Thanks KC! Sometimes, if it aint broke, don't fix it!  This car runs good, for what it is, as is! I do not want to pull the heads, etc. So anything must be bolt on.  When I was in High School, in 1975, I had a 12k mile 1972  H code Mach 1.  It had no a/c, and a 2.75 or a 2.79 rear end I cannot remember which one...both bad answers).  I just KNEW I needed a 4BBL and headers to make it go fast.  Actually, it was kind of fast....but NOT quick.  First gear in the FMX was good.  But when it shifted into 2nd, it fell down.  I lost a race to a Buick Skylark with a 350 2BBL Buick engine. I held my own against a 400 4BBL Firebird....until shortly after my FMX shifted into 2nd, then I was blown away.  Depressing! (expected with the Firebird, not with the Buick!)  I remember the local speed shop owner asked me if it had 2 bbl or 4 bbl. heads as to which intake was required...that is when I learned Clevelands were not like Chevys! Then he asked me what gears I had in back.  I kind of gave him a puzzled look. He pointed out, after I determined I had 2.79's, he pointed out, in a way I could understand, that "it was as if my ten speed bike only had gear 10".  That made sense to me! My car would have run worse, not better, with a 4 BBL without a gear change....so I ended up doing nothing.  My 1971 today runs better than did my 1972.  More compression and therefore HP in 1971 vs 1972, and a 3.00 is better than a 2.75 in the 9" Diff.  I do think a modest 4bbl like a 570 Holley, and or headers, and maybe one notch up to a 3.25 in gears will help, not hurt.  I do already have dual exhaust, and maybe the smart move is to go to a 3.25 to one rear end, and then see if I need anything else.  I have other go fast cars.  This one is not going to be a hot rodded example....I am just considering bolt ons to warm it up a bit, if possible!

Many Thanks,

Brad

Yep,  I am with you.  

My original FMX and block are sitting under the workbench with Some quench chamber 4v heads and a 4v Ford intake.  The original heads and intake are still there too.

I am restoring mine to be close to the Boss 351 I always wanted but never found.  351C, balanced with Boss 351 Heads and a Ford Motorsport cam backed by a 4-speed and a 3:25 posi.  The only original stuff I sold were the front drum brake setup.

We gotta make them fun!

kcmash

 

[griffbl]

When I bought mine it wan an unmolested H-code with the exact power train you mention and single exhaust,  If you want a nice car to drive with little effort, tuning, or adjustment, keep it stock.

If you opt to spice it up it looks like others have provided some good input.   I decided to load quench 4-v heads and a factory 4 bbl intake on mine in highschool to be cool like the other kids, and it never was the highly reliable driver again.  Of course I should have made some camshaft upgrades instead of just leaving the 2-v cam in there.

Just my 2 cents.

kcmash

Thanks KC! Sometimes, if it aint broke, don't fix it!  This car runs good, for what it is, as is! I do not want to pull the heads, etc. So anything must be bolt on.  When I was in High School, in 1975, I had a 12k mile 1972  H code Mach 1.  It had no a/c, and a 2.75 or a 2.79 rear end I cannot remember which one...both bad answers).  I just KNEW I needed a 4BBL and headers to make it go fast.  Actually, it was kind of fast....but NOT quick.  First gear in the FMX was good.  But when it shifted into 2nd, it fell down.  I lost a race to a Buick Skylark with a 350 2BBL Buick engine. I held my own against a 400 4BBL Firebird....until shortly after my FMX shifted into 2nd, then I was blown away.  Depressing! (expected with the Firebird, not with the Buick!)  I remember the local speed shop owner asked me if it had 2 bbl or 4 bbl. heads as to which intake was required...that is when I learned Clevelands were not like Chevys! Then he asked me what gears I had in back.  I kind of gave him a puzzled look. He pointed out, after I determined I had 2.79's, he pointed out, in a way I could understand, that "it was as if my ten speed bike only had gear 10".  That made sense to me! My car would have run worse, not better, with a 4 BBL without a gear change....so I ended up doing nothing.  My 1971 today runs better than did my 1972.  More compression and therefore HP in 1971 vs 1972, and a 3.00 is better than a 2.75 in the 9" Diff.  I do think a modest 4bbl like a 570 Holley, and or headers, and maybe one notch up to a 3.25 in gears will help, not hurt.  I do already have dual exhaust, and maybe the smart move is to go to a 3.25 to one rear end, and then see if I need anything else.  I have other go fast cars.  This one is not going to be a hot rodded example....I am just considering bolt ons to warm it up a bit, if possible!

Many Thanks,

Brad

Yep,  I am with you.  

My original FMX and block are sitting under the workbench with Some quench chamber 4v heads and a 4v Ford intake.  The original heads and intake are still there too.

I am restoring mine to be close to the Boss 351 I always wanted but never found.  351C, balanced with Boss 351 Heads and a Ford Motorsport cam backed by a 4-speed and a 3:25 posi.  The only original stuff I sold were the front drum brake setup.

We gotta make them fun!

kcmash

KCMash-

My Mach 1 in high school had drums....thankfully, my current example has the power assist front discs.  I am going to upgrade to higher quaility pads and shoes WHEN they need them, but otherwise they work very well.  I did build a 400 HP 400 lbs TQ M code that I sold at Barrett Jackson https://www.barrett-jackson.com/Events/Event/Details/1971-FORD-MUSTANG-MACH-1-FASTBACK-161938 back in 2014.  I think those close chambered heads are the way to go on a serious build-up.  This car I sold was very strong.  I used a Blue Thunder intake, as it was aluminum, had it benched to flow equally, mated the ports, did a good three angle valve job, used about 10 to 1 pistons, stock .030 over bore (i.e. not stroked), a pretty strong hydraulic comp cam, and stuck with the cast iron exhaust manifolds running through good dual exhaust system.  Converter had about 2500 RPM worth of stall. 3.50 gears in back.  Ran good, but I had that common CLeveland starting issue, as a shop dialed up the timing so much it was hard to crank. (but it didn't ping!)  I never really loved that car, and I did everything I thought I ever wanted to it! It did not have a tach, and I am doing one of Rocketman's in mine which converts the clock.  I like my current car better as it is a bit prettier, and, well, seems so dead solid reliable.  I will remember that as I limit my mods to things that will not affect the many things I really love about it!

Thanks Again,

Brad

 

[Mister 4x4]

If you check out my engine specs in my Garage thread, you'll see the CompCams Hi-Energy roller rockers and Crane Cams 7/16" screw-in studs I went with, in addition to the cam kit and other goodies I loaded up along with the original 2V heads.

 

[Carolina_Mountain_Mustangs]

One other thought? Are there some aluminum roller rockers available that  I can bolt on are replacements? Without having to go to studs on my stock heads? My experience is that these are nice additions on any engine.  I do NOT want to pull the heads at this time, simply to bolt on better, lighter rockers for a small incremental gain. Thanks so much

scorpion makes pedestal mount rocker arm kits, and here is what I like to do is use crane cams conversion kit

Thanks so much. Another good option!  I do prefer, I think, Crane or Comp cams rockers to Scorpion's, and either Crane or Comp's rockers do necessitate the Crane conversion kit.  Either will require changing pushrods also, of course.  I think your Crane kit is a higher quality option, than using scorpion rockers and makes it possible to use shims should I need them.  I think it will require my monkeying with the baffles a bit on the valve covers for clearance, and maybe doubling up a valve cover gasket for a bit more room. I think Comp or Crane aluminum rockers will come closer to clearing my stock valve covers than would the Scorpion bolt ons.

Many thanks!

Brad

You mention the baffles in the valve covers. Only the early 351 C had the baffles they later put a small stamping on the rocker to control the oil coming out of the rocker from the push rod so a later set of valve covers will not have the baffle. Don't put two gaskets will leak for sure.

This pic shows what was added to the rocker to control the oil much better.

This 73 vert was 351 H code with FMX also. The PO changed to a C-4 with shift kit and higher stall converter. He also put the edelbrock performer 4 V intake and holley on with tube headers and cam that I have no idea what he used. He also put MSD ignition on. I never drove before the changes and only 20 miles since I got the car going.

Any changes that are bolt on or even cam changes can go back. Changing a color or putting a different suspension system on will be more difficult to reverse. If you can is not anything special build it how you want. I doubt the aluminum wheels will take any weight off. I might weigh one today and see difference in steel to alu.. Yes getting un sprung weight down will help handling and is always good.

 

[griffbl]

scorpion makes pedestal mount rocker arm kits, and here is what I like to do is use crane cams conversion kit

Thanks so much. Another good option!  I do prefer, I think, Crane or Comp cams rockers to Scorpion's, and either Crane or Comp's rockers do necessitate the Crane conversion kit.  Either will require changing pushrods also, of course.  I think your Crane kit is a higher quality option, than using scorpion rockers and makes it possible to use shims should I need them.  I think it will require my monkeying with the baffles a bit on the valve covers for clearance, and maybe doubling up a valve cover gasket for a bit more room. I think Comp or Crane aluminum rockers will come closer to clearing my stock valve covers than would the Scorpion bolt ons.

Many thanks!

Brad

You mention the baffles in the valve covers. Only the early 351 C had the baffles they later put a small stamping on the rocker to control the oil coming out of the rocker from the push rod so a later set of valve covers will not have the baffle. Don't put two gaskets will leak for sure.

This pic shows what was added to the rocker to control the oil much better.

This 73 vert was 351 H code with FMX also. The PO changed to a C-4 with shift kit and higher stall converter. He also put the edelbrock performer 4 V intake and holley on with tube headers and cam that I have no idea what he used. He also put MSD ignition on. I never drove before the changes and only 20 miles since I got the car going.

Any changes that are bolt on or even cam changes can go back. Changing a color or putting a different suspension system on will be more difficult to reverse. If you can is not anything special build it how you want. I doubt the aluminum wheels will take any weight off. I might weigh one today and see difference in steel to alu.. Yes getting un sprung weight down will help handling and is always good.



Thanks so much! I would never change the color, or really even mess with the suspension much, other than replacing springs and shocks, maybe beefing up a sway bar IF that could be done by utilizing existing holes, etc.  Car will simply not be driven that hard.  My experience, is that if you use a comparable sized tire, and rim, that I can knock about 10 pounds per tire & rim assembly by going to aluminum.  That plus an aluminum intake, carb, a modern a/c compressor, and or headers will knock off 100 pounds or more in total.  Will I feel that? Probably not, except in my own mind.  There is always weight variances from one rim style to another, but my experience is that is about what it is. Thanks for the info as to the baffles.  On my HIPO 289, I had to remove just a little bit of one baffle with a grinder to clear the poly locks.  I doubt I will have poly locks in this application. I do not know if my engine is an "early" or later 351C, but the car was built 12/70 and engine is original to the car.  I may leave the rockers alone if they look good. Lower friction rockers will necessitate changing pushrods in all likelihood, and that is probably better left alone for now the way I use the car. You know how it is, once you start on something, it gets hard to stop sometimes! 

Thanks Again!

Brad

 

[Spike Morelli]

Hello griffbl,

I own an identical vehicle to yours, a '71 Mach with H code ( 351c and 2v ), fmx, and 3.00:1 in rear. Years ago, when I first got it, the first thing I did was to go to dual exhausts, even added the dual exhaust rear valence with chrome tips as stock 4v's. The car sounded better, no proof of power increase but likely something was helped there. I drive the car every day, and tow with it, so I wanted more "oomph" to pull with so I changed out my open rear end with a Trac-Loc with 3.50:1 gearing, and had the fmx gone through with a Trans-Go shift kit installed/ stock stall converter. I believe the trans shift kitting was a major improvement. Eventually, the engine needed overhauling, and I did so, with the only changes being a high volume oil pump, hardened valve seats, and a new 4v cam instead of the 2v cam, for just slightly more breathing but within the envelope of "stock". Final addition was a Pertronix trigger and coil, and 86ed the points.

I have been driving it this way for 20 years now, everyday, NO problems.

Still, I have visions of putting an Edelbrock Performer 2v, 600 vacuum secondary carb, Hooker Comps with turbo mufflers on. I want to, and I don't want to. Maybe I'll wait until the day comes that this engine needs freshening up...by then I will have talked myself into a bit more camshaft.....and so it goes. We're all human that way.

For now though, I have no complaints about how it runs ( albeit relatively stock ), and I had the car re-painted ( original color again ), and new upholstery put in ( 3rd re-do ), so it's attractive and runs good to boot. Like you, I am trying to resist straying too far from original.

 

[griffbl]

Hello griffbl,

                     I own an identical vehicle to yours, a '71 Mach with H code ( 351c and 2v ), fmx, and 3.00:1 in rear. Years ago, when I first got it, the first thing I did was to go to dual exhausts, even added the dual exhaust rear valence with chrome tips as stock 4v's. The car sounded better, no proof of power increase but likely something was helped there. I drive the car every day, and tow with it, so I wanted more "oomph" to pull with so I changed out my open rear end with a Trac-Loc with 3.50:1 gearing, and had the fmx gone through with a Trans-Go shift kit installed/ stock stall converter. I believe the trans shift kitting was a major improvement. Eventually, the engine needed overhauling, and I did so, with the only changes being a high volume oil pump, hardened valve seats, and a new 4v cam instead of the 2v cam, for just slightly more breathing but within the envelope of "stock". Final addition was a Pertronix trigger and coil, and 86ed the points.

      I have been driving it this way for 20 years now, everyday, NO problems.

      Still, I have visions of putting an Edelbrock Performer 2v, 600 vacuum secondary carb, Hooker Comps with turbo mufflers on. I want to, and I don't want to. Maybe I'll wait until the day comes that this engine needs freshening up...by then I will have talked myself into a bit more camshaft.....and so it goes. We're all human that way.

      For now though, I have no complaints about how it runs ( albeit relatively stock ), and I had the car re-painted ( original color again ), and new upholstery put in ( 3rd re-do ), so it's attractive and runs good to boot. Like you, I am trying to resist straying too far from original.

Spike-

Thanks for your comments.  I have left the intake and carb alone for now.....I do have a good dual exhaust, that flows just fine and is not loud at all. Your suggestion (and that of some others) as to possibly going a little shorter on the gears would make more difference than almost anything.  It is for sure the most bang for the buck.  You can feel every incremental change.  Since I am 3.00 now, I might just go to 3.25.  I have ran 3.50's before also.  Not a bad choice for the way this car is used, which in reality, is not very much!!  In any event, to use more fuel, it needs to rev a bit more to be sure, and the gear change helps that a bunch.  It will be gears first, and if I want to do more, carb and intake.  PROBABLY best to leave well enough alone! My 2015 GT is fast enough, and this car will never run like the newer ones! Thanks again so much for your input!