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Big red mach 1,

Hemikiller mentioned 2 very important things that should not be overlooked, fuel pressure and lifter preload.

Very unusual to have both a mechanical and electric fuel pumps.

Do you know what your actual fuel pressure is ?

You might want to consider disabling one of your 2 pumps , most holleys with standard needle seats don't like to see over 6 psi of fuel pressure or they tend to run rich.

lifter preload should be from 1/2 to 3/4 of a turn from zero (being able to spin the pushrod with fingers with the valve closed)

You should at least try slipping a feeler gauge under the secondary throttle blades, then when rpm comes up , lower the primary idle speed screw and try re-adjusting the idle mixture screws.

You may not be getting enough air but that would be not enough air for the excessive amount of fuel that you are trying to burn at idle. (eyes burning)

Boilermaster

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General consensus is go with DuraSpark, Performance Distributors made to order by the looks of it. Cheaper too! https://performancedistributors.com/product-category/distributors/ford-distributors

I've run MSD 6AL boxes for many years with good success. Be aware that any of the CD boxes that power the coil directly (MSD, Taylor etc) will require the use of an MSD 8920 Tach Adapter to maintain f

I just finished a Duraspark 1 conversion on my 429, used a box and coil from Rockauto and a new custom-curved distributor from Scotty J http://reincarnation-automotive.com/services Seems to run g

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Big red mach 1,

Hemikiller mentioned 2 very important things that should not be overlooked, fuel pressure and lifter preload.

Very unusual to have both a mechanical and electric fuel pumps.

Do you know what your actual fuel pressure is ?

You might want to consider disabling one of your 2 pumps , most holleys with standard needle seats don't like to see over 6 psi of fuel pressure or they tend to run rich.

lifter preload should be from 1/2 to 3/4 of a turn from zero (being able to spin the pushrod with fingers with the valve closed)

You should at least try slipping a feeler gauge under the secondary throttle blades, then when rpm comes up , lower the primary idle speed screw and try re-adjusting the idle mixture screws.

You may not be getting enough air but that would be not enough air for the excessive amount of fuel that you are trying to burn at idle. (eyes burning)

Boilermaster

 

Agree completely, and by no means overlooked. Just wanted to search for obvious vacuum leaks first. 

Left to do on the vacuum side is check the intake manifold at engine and at base of carb for leaks with unlit propane torch.

Then lifter preload. Didn't want to run right to that one without checking out the simple stuff first.

It still seems odd to me that vacuum increases with rpm up to 15hg. Typically it drops under load in my experience. No matter where it is, it's steady it does not bounce. I would have thought valve adjustment would cause a bouncing reading. Maybe I'm not correct there.

 

On the fuel side, I will definitely get a gauge on it this weekend and check fuel pressure heading into the carb.

I'll look at that before making any further adjustments in the carb. Once we like the fuel pressure, and maybe have solved the vacuum issue, I feel like that's the better time to start making deeper carb adjustments.

Chris - Born in '73 - Drive a '73

Former Mechanic U.S. Army

1st Infantry Division - The Big Red One

BIG RED MACH 1

Learning a lesson (or three) on the Cleveland every day.

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big red mach 1,

your vacuum is GOING to increase as rpm increases in park because you are increasing spark timing.

in park, there is no load to bring the vacuum down.

Here would be my plan for finding highest manifold vacuum.

1 find out how much mechanical advance you have in your distributor 

A limit that to 10 degrees distributor (20 balancer)

2 adjust timing to highest reading before spark knock with the gasoline you will be using. (warm engine)

3 make certain valve lash is correct and you have no vacuum leaks. (1/2 to 3/4 from zero lash)

4 adjust idle mixture (with correct pcv valve) using both primary and secondary throttle blades

5 when highest reading is achieved, lean the idle mixture screws to just when the vacuum needle starts to drop

as to not be over rich at idle.

Boilermaster

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These are just my thoughts that may or may not be the case or relevant. 

I have no real knowledge on cams. I did try to find the specs for the comp cams 270 with 519 lift, but could not find that info. Summit Racing do not list that spec for a 351C, but I think there was a 550 lift. From what was described, the PO was a drag racer (or thought he was) so who knows what he thought was going to get him down the strip quicker. I would think that cam is quite aggressive and that alone would cause lower vacuum, but I would think it should still be around 15"Hg. at a guess.

So, if it were me, I think I'd start at the beginning as it's a 'new to me' engine. 

1) pull the spark plugs and do a static compression test and see if all 8 are within 10% of each other. 

2) check the plugs for color, are they all the same light to mid brown color? If one or more are black, note the cylinder(s).

3)If all is good there, check all the vacuum connections and hoses and intake manifold for a massive leak. Pull the carb and reinstall it with new base gaskets or at least spray some starter fluid around the base when it's running. No increase in rpm, no leak.

4)next go to the distributor. I don't think it was mentioned if it is a factory Mastercraft/Autolite. Does it have points or electronic module? If electronic, what brand and type. If it is anything else other than a factory type or DuraSpark, I'd be ditching it especially if it's an HEI type Chevy thing.

5) The Carb. So it's a Holley Street Avenger 770. I have a 670 on mine which is probably enough carb for my stockish engine. IF I were to replace my carb, my choice would be the Quick Fuel HR 735 VS and that's more than big enough for a 351C. I'll go into your question that jpazz reffered to later.

6)Timing light. A light with adjustable digital read-out would be best choice. That way, you can see exactly what degrees of advance there are. 

I know you're a mechanic, so you know that basic stuff, not trying to belittle you in any way.

 

This is what I did with my engine when I was having similar issues. To recap, it's a 71 351C M code 4V with a new Holley 670 S/A electronic choke, vacuum secondaries.

The vacuum reading was around 18 "Hg with the stock 6.5 power valve and stock jets, 65 & 67 if I remember.

When the engine was first rebuilt, it had Kieth Black flat top pistons at zero deck. Heads are 63cc CC with stock rockers. Melling MTF 2 cam (Hydraulic flat tappet) Int 204 exh 214 duration with gross lift of 510 exh. Long story, but the motor had to be re-rebuilt under warranty so I dropped the compression ratio from  11:1 to 10:1 by using KB 13cc dished pistons, still zero deck. 

I was having two main issues, one was timing and the other too much fuel at idle. 

The fuel issue was soon solved by a local specialist. He drilled a 3/32" hole in each primary throttle plate and set the primary and secondary's correctly. He told me this is done to many of the stock car race engine he does. I did have the ability to use a fuel/air ratio meter as there was oxygen sensor plugs already installed in the exhaust pipes.

The timing proved to be quite the challenge along with a steep learning curve. Fortunately, I had the ability to to rework and re-curve the factory Autolite dist.

As you know, these engines seem to like about 14-16 degrees of initial advance with a max all in of 34 -36 deg., vac lines plugged.  Mine seems to like 14 and 34 best at 3000 rpm.

The factory setting for the 71 distributor has an initial of 6 deg., but with 30 degs. on the crank shaft = 36 total. To get the higher initial, the crank shaft degrees must be dropped to no more than 20. This is done by either welding up the slot and re-cutting to .410" or what is known as a 10L slot. Typically, the factory slot plates I have seen are all 15L = 30 deg. or 13L  =26 deg. If you have a slot plate with a 13L, you can cut this down by using a piece of 3/16"nylon tube over the post. Then it's picking the appropriate springs. My choice was to use the factory heavy spring and a Mr.Gasket 925 D light spring. The heavy one is set with just slight free-play.

The trouble I was having was too much spark rattle on heavy acceleration with 14 -16 initial and the 11:1 compression ratio. Dropping to 10:1 and reworking the slot plate cured the issues. Oh, I forgot to mention I installed a Pertronix Ignitor II electronic module and matching Flamethrower coil. Do NOT use the Pertronix Ignitor III, it's a piece of crap imo.

Here's a couple of pics that may explain the distributor rework.

IMG-0432-2020-02-13-19-50-52-UTC.jpg

 

IMG-0435-2020-02-13-19-50-52-UTC.jpg

A piece of 3/16" Nylon tube over post to limit advance.

 

DSC00253-LI-3-2020-02-13-19-50-52-UTC.jpg

 

Hope this helps,

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Geoff.

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One more item that is often overlooked, or done incorrectly, is setting the idle opening for the secondary throttle. This can really mess up the primary idle speed and mixture.

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Stanglover,

Good stuff there.

Camshaft could be comp 32-224-4

Did not know or catch that PO was a drag racer, perhaps the camshaft was set up 4 degrees retarded.

The 32-224-4 should have 4 degrees advance built into it, but pretty easy to retard that by 4 degrees.

lobe lift @ TDC comes to mind here to check valve timing without having to remove front cover.

better leave that alone till big red mach 1 gets the rest sorted.

Boilermaster

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Stanglover,

Good stuff there.

Camshaft could be comp 32-224-4

Did not know or catch that PO was a drag racer, perhaps the camshaft was set up 4 degrees retarded.

The 32-224-4 should have 4 degrees advance built into it, but pretty easy to retard that by 4 degrees.

lobe lift @ TDC comes to mind here to check valve timing without having to remove front cover.

better leave that alone till big red mach 1 gets the rest sorted.

Boilermaster

 Boilermaster, thanks. I know squat about cams other than they make the valves go up and down!!

 We need Big Red Mach 1 to describe in detail what exactly he knows about the engine, i.e. Distributor type, coil, plugs plug wires etc. etc. The carb is already over sized imo, and S/A are really not the best offering from Holley in the first place. Pictures would help also.

Geoff.

 I learn something new every day!

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Okay. So that's clearly wrong on mine. Thanks, Chuck. I think I've got stuff wrong all over the place. I also have one of the two vac lines under the main 4 on the firewall (the two coming from the dash area going to the carb). That doesn't seem right either.

 

 

20200315-113428.jpg

Thank you for your service. I was also born in 73 but drive a 72. Carbs are not that hard you will become a master at them after this. Ron

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Mallory Unilite Distributor Part number 4756701H (Rebuilt and Recurved) https://www.summitracing.com/parts/maa-4756701

 

Procomp module inside. https://speedmaster79.com/Unilite-And-E-Spark-37-38-45-46-47-83-86-91-93-Style-Mallory-Replacement-Module?page=1

 

Mallory Pro Sidewinder 8mm wires. https://www.summitracing.com/search/part-type/spark-plug-wire-sets?fr=part-type&SortBy=BestKeywordMatch&SortOrder=Ascending&keyword=mallory%208mm%20sidewinder

 

Mallory Coil Part. No. 29216 https://www.summitracing.com/parts/maa-29216

 

Written on a note that had the UPS tracking number that said distributor rebuilt and recurved by Mallory, he has the note that says "16-18 initial. 18-20 mechanical".

 

I'm glad to take photos of anything else you would like. Just let me know. Thanks!!

Chris - Born in '73 - Drive a '73

Former Mechanic U.S. Army

1st Infantry Division - The Big Red One

BIG RED MACH 1

Learning a lesson (or three) on the Cleveland every day.

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Over the years it seems a fair number of theses mystery low vacuum issues turn out to be from an internal vacuum leak caused by a failure of the bottom of the intake gasket either from incorrect angles between the head and intake, oil contamination or loose bolts..

 

Once you have completely wrung out the vacuum and ignition systems and you are sure they aren't the issue the intake gasket is the next place I would look.

 

Just my 2 cents.

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73 conv. 460, D0VE large valve heads, Performer RPM manifold, Voodoo 227/233 cam, Holley 950 HP carb, C6 trans, 3.25 trak-loc.

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Isn't this Eddie's (FastE) old Mach? I can tell you from personal experience when he had it... it RAN! I believe there was another owner in the mean time.

 

Eddie may be a good resource for specifics on the combination.

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[align=left]Jeff T.

 

When I die I want to die like grandpa, peacefully in my sleep... not screaming, like his passengers. [/align]

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Mallory Unilite Distributor Part number 4756701H (Rebuilt and Recurved) https://www.summitracing.com/parts/maa-4756701

 

Procomp module inside. https://speedmaster79.com/Unilite-And-E-Spark-37-38-45-46-47-83-86-91-93-Style-Mallory-Replacement-Module?page=1

 

Mallory Pro Sidewinder 8mm wires. https://www.summitracing.com/search/part-type/spark-plug-wire-sets?fr=part-type&SortBy=BestKeywordMatch&SortOrder=Ascending&keyword=mallory%208mm%20sidewinder

 

Mallory Coil Part. No. 29216 https://www.summitracing.com/parts/maa-29216

 

Written on a note that had the UPS tracking number that said distributor rebuilt and recurved by Mallory, he has the note that says "16-18 initial. 18-20 mechanical".

 

I'm glad to take photos of anything else you would like. Just let me know. Thanks!!

Thanks for posting this info up for all to see. From our PM conversation, I don't think timing is the issue now, but as Tommy K suggested, perhaps time to pull the intake. I would do that if it were me with a low vacuum problem, knowing everything else seems good. "Frustrating" is the word for it!

Something else that others have suggested in the past with other members, is pull the valve covers and check that all the rockers are all working the same. That would rule out the cam would it not?

Geoff.

 I learn something new every day!

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Isn't this Eddie's (FastE) old Mach? I can tell you from personal experience when he had it... it RAN! I believe there was another owner in the mean time.

 

Eddie may be a good resource for specifics on the combination.

 

Yes sir, this is Eddie's old car. I have been chatting with him outside of this site. This is where I've gotten the list of specs that I do have from. He sold the car in 2016 to a "collector" who for the most part just let the thing sit. That's how the story goes, but I dunno. 

 

What I do know from Eddie is that this car under his care for 42 years, was always in top shape and ran like a scalded dog. So he's been a bit surprised to hear of the issues I've been having. He's a good guy, and a great person to talk to about what the car has in it, but without him here looking at it, he's just guessing like the rest of us. again, he's surprised that it's running poorly at all.

Chris - Born in '73 - Drive a '73

Former Mechanic U.S. Army

1st Infantry Division - The Big Red One

BIG RED MACH 1

Learning a lesson (or three) on the Cleveland every day.

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Isn't this Eddie's (FastE) old Mach? I can tell you from personal experience when he had it... it RAN! I believe there was another owner in the mean time.

 

Eddie may be a good resource for specifics on the combination.

 

Yes sir, this is Eddie's old car. I have been chatting with him outside of this site. This is where I've gotten the list of specs that I do have from. He sold the car in 2016 to a "collector" who for the most part just let the thing sit. That's how the story goes, but I dunno. 

 

What I do know from Eddie is that this car under his care for 42 years, was always in top shape and ran like a scalded dog. So he's been a bit surprised to hear of the issues I've been having. He's a good guy, and a great person to talk to about what the car has in it, but without him here looking at it, he's just guessing like the rest of us. again, he's surprised that it's running poorly at all.

Big red mach 1,

 At this point you will probably get more from FastE than you will get from the rest of us.

Would ask, was cam installed 4 degrees retarded and how much vacuum was he seeing at hot idle.

Intake manifold leak would make sense, as it could have started to leak over time, could just check and see if any of the bolts have worked loose, carb spray (or propane) will only tell you if it is sucking air from external, not internal.

Would not rule out faulty carb work either.

Boilermaster

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Isn't this Eddie's (FastE) old Mach? I can tell you from personal experience when he had it... it RAN! I believe there was another owner in the mean time.

 

Eddie may be a good resource for specifics on the combination.

 

Yes sir, this is Eddie's old car. I have been chatting with him outside of this site. This is where I've gotten the list of specs that I do have from. He sold the car in 2016 to a "collector" who for the most part just let the thing sit. That's how the story goes, but I dunno. 

 

What I do know from Eddie is that this car under his care for 42 years, was always in top shape and ran like a scalded dog. So he's been a bit surprised to hear of the issues I've been having. He's a good guy, and a great person to talk to about what the car has in it, but without him here looking at it, he's just guessing like the rest of us. again, he's surprised that it's running poorly at all.

Big red mach 1,

 At this point you will probably get more from FastE than you will get from the rest of us.

Would ask, was cam installed 4 degrees retarded and how much vacuum was he seeing at hot idle.

Intake manifold leak would make sense, as it could have started to leak over time, could just check and see if any of the bolts have worked loose, carb spray (or propane) will only tell you if it is sucking air from external, not internal.

Would not rule out faulty carb work either.

Boilermaster

Yeah, I never thought to ask him that about the cam and whether he installed it that way. I want to say he didn't. He wanted this motor to be very similar to a 71 Boss 351. 

 

I personally believe that the bulk of my issue is in fact the low vacuum issue. I also believe that the lifter prelaod is probably not correct. Symptoms of improper adjustment are hard starting, very rough abnormal idle, low vacuum. I have all 3. Also, when I brought the car home, everything on this motor was loose. Valve covers loose, intake manifold loose, tree on back of manifold loose. I'm talking all finger tight. All have since been tightened back up and in the case of the intake properly re torqued. I have to believe those nuts on the rockers aren't right also. I think the mission this weekend is to do 3 things. 1. Check for a leak at the intake as you have suggested. 2. Re-adjust the lifter preload, hope for better idle and more vacuum. 3. Compression test as Stanglover suggested. I'll do this after the preload adjustment. 4. I will check fuel pressure into the carb as another member mentioned that I am running dual fuel pumps and could be ending more fuel to the carb than the Holley wants.

I'll post my findings. 

Chris - Born in '73 - Drive a '73

Former Mechanic U.S. Army

1st Infantry Division - The Big Red One

BIG RED MACH 1

Learning a lesson (or three) on the Cleveland every day.

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And, that brings up another potential issue. The 351C intakes are very sensitive to proper alignment, and if not sitting square and straight will create vacuum leaks and suck oil from the valley. Installing studs in the four center bolt holes, and using them for aligning the intake during installation really helps. And then torque in three steps, the first one being just above finger tight.

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And, that brings up another potential issue. The 351C intakes are very sensitive to proper alignment, and if not sitting square and straight will create vacuum leaks and suck oil from the valley. Installing studs in the four center bolt holes, and using them for aligning the intake during installation really helps. And then torque in three steps, the first one being just above finger tight.

 

Outstanding information right there. I feel like I should just replace it. Will make the preload adjustment go easier with the intake off anyway. Is there a preferred type/style/brand everyone likes best? I have seen the gaskets sold with and without a pan.

Chris - Born in '73 - Drive a '73

Former Mechanic U.S. Army

1st Infantry Division - The Big Red One

BIG RED MACH 1

Learning a lesson (or three) on the Cleveland every day.

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I don't use the pan. Stay away from Fel-Pro "Print O seal" gaskets they delaminate causing vacuum leaks and oil being pulled into the heads. If you need a special thickness gasket contact SCE or Cometic. Chuck

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I've used Mr Gasket UltraSeal before with good results, but I also used to use Felpro, hopefully Mr Gasket hasn't fallen as far as Felpro.

 

Use Right Stuff gasket maker on the ends instead of the cork or rubber end gaskets that come in the set.

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Use Right Stuff gasket maker on the ends instead of the cork or rubber end gaskets that come in the set.

 +1 and more on using "The Right Stuff". Good point.

Geoff.

 I learn something new every day!

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I just had to re-install my Blue Thunder aluminum intake and used the Mr Gasket #214 gaskets. They are just a plain gasket and I have never had a problem with them. Gaskacinch the head side and nothing on the intake side. I also use The Right Stuff on the valley ends instead of the cork gaskets. My intake is not stock of course, so not designed for use the turkey pan.

I had some lifter issues, so I had to change them. When I removed the intake I noticed that the shop that built my engine recently used those crappy printo seal gaskets. Looked like I had a couple of them failing. I’ve had problems with the seal blowing out like Chuck described.

John - 72 Q Code

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Printo seal translates to Printo leak. The other Fel-Pro gaskets seem to be OK. Chuck

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Hey all, how tight do you torque your carb down? Mine was torqued to 25ftlbs. which seems like way too tight. Gaskets were gas soaked. I've now read that 80 inch pounds or 6 foot pounds is more like it. What do you prefer?

 

Also - just FYI, this issue existed before the carb was more recently torqued down to that value. So this is not the source of my issue. But I do want to torque the carb down properly upon reassembly this weekend.

 

My intake I did 3 passes on. I did a pass at 10, 20 and 25 ft. LBS. I plan on doing that again when reassembling this time also unless anyone has a better suggestion.

 

I did buy "The Right Stuff" 90 minute variety. I think they had a 1 minute type, but I'm never a fan of things that cure that quickly. I've always been of the opinion that a slower cure time produces a better result.

 

What do you guys like as far as letting it set up for a few before placing the intake? Do you like to set it on right away, or let it set for 15 or so to where it just starts curing before setting the intake down? I'm sure everyone has their preferred method, and why they like it that way.

Chris - Born in '73 - Drive a '73

Former Mechanic U.S. Army

1st Infantry Division - The Big Red One

BIG RED MACH 1

Learning a lesson (or three) on the Cleveland every day.

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Big red mach 1,

25 lb.ft. is WAY too much 6 lb.ft. sounds much better.

If it were mine I would remove the carb and check the base for flatness and perhaps draw file it flat again.

also remove the carb studs and check the carb base of intake, (possibly find a raised area at the carb studs)

Please let us know what your valve lash (preload) was and what you re-adjusted it to.

I usually go about 20 minutes on the sealant (Permatex ultra gray) with good results.

then walk away till the next day before starting.

Boilermaster

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Hey all, how tight do you torque your carb down? Mine was torqued to 25ftlbs. which seems like way too tight. Gaskets were gas soaked. I've now read that 80 inch pounds or 6 foot pounds is more like it. What do you prefer?

 

Also - just FYI, this issue existed before the carb was more recently torqued down to that value. So this is not the source of my issue. But I do want to torque the carb down properly upon reassembly this weekend.

 

My intake I did 3 passes on. I did a pass at 10, 20 and 25 ft. LBS. I plan on doing that again when reassembling this time also unless anyone has a better suggestion.

 

I did buy "The Right Stuff" 90 minute variety. I think they had a 1 minute type, but I'm never a fan of things that cure that quickly. I've always been of the opinion that a slower cure time produces a better result.

 

What do you guys like as far as letting it set up for a few before placing the intake? Do you like to set it on right away, or let it set for 15 or so to where it just starts curing before setting the intake down? I'm sure everyone has their preferred method, and why they like it that way.

 Personally, I don't actually torque my carb down, I just go diagonally back and forth until 'tight' then go another 1/2 turn. Never had a leak that way. I only use a 1/4" drive socket, but I guess about 70 -80 inch pounds would be about right. Even tightness is important though.

As for using "The Right Stuff" follow the directions on the tube. Also on the ends, go up the heads as well for about 1/2" or so to make sure the corners seal. I clean the surfaces with alcohol first, but that's just me. Use a good 1/4" bead, don't skimp! It can be cleaned up after if needed.

Before long, that baby will be purring like a kitten and you'll be a happy camper.

Geoff.

 I learn something new every day!

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