73 351 Cleveland

[da55]

Good Morning Yall,

I want to do some moderate upgrades to my engine. I have been researching but wanted yalls take on this topic:

What moderate upgrades could give my stock 351 Cleveland a major increase in power/speed. I dont want anything major, no major changes, no big modifications. Everything is stock on this car as far as motor. Any clues?

Thanks.

 

[brushwolf]

If it is all stock, it probably has a 2 barrel carb and points ignition. 4 barrel carb and aftermarket aluminum intake for 2v heads, plus switch ignition to electronic using one of the conversion kits. 400M exhaust manifolds are also better than the 2v exhaust manifolds. Get a 1970 timing chain and gears, the later ones are retarded timing from the factory. While you are in there, might as well do a better cam too, though..

 

[da55]

It is 2bbl. Holley carb. I wanna keep the carb, not a fan of EFI. In a sense im a purist. It is 2V. I have seen into the 2v vs 4v debate. Of course more flow would be better but ive read the 4v does sacrifice some power when compared to the 2v. Any idea on this? Would it affect the RAM Air intake i plan to install?

400M exhaust manifolds? Ill look into it...

1970 timing chain/gears? Would this be an easy swap?

The cam, what can i get for this? An easy install? 

What about boring the engine out?

 

[brushwolf]

Some 2v will pull better at low rpm on takeoff. No contest overall though, generally the 4v is going to add probably 15 hp by itself. If that were not the case why would hi-po cars not all be using 2v carbs?  The 2v can't process enough fuel and air at higher rpm. Not much point in switching the intake, if retaining a 2v carb.

The engine is an air pump. More gas and fuel going in and out creates more power.

Boring the engine by itself adds a few CI, that's it.  That is major, major engine work and part of a complete rebuild. And you said nothing radical, which a total rebuild would be imo, if engine is mechanically sound now.

Cam selection depends on compression ratio, intended rpm use, transmission and rear gears, tire sizes etc.  Many cams available, but just the non-retarded version of timing sets will be noticeable. Any cam company like Crane or Crower, Edelbrock can advise what will work best with your other components.

Changing timing set requires pulling water pump and front cover off engine, belts, pulleys, etc. But, if you are also switching intake then you are most of the way to changing out the cam anyway.

 

[c9zx]

"What moderate upgrades could give my stock 351 Cleveland a major increase in power/speed. "  Moderate begets moderate, not major. If you are just looking for better acceleration, consider a rear gear change. Chuck

 

[c9zx]

"but ive read the 4v does sacrifice some power when compared to the 2v" My experience does not support that claim. If a person tries to mate a 4v Cleveland to a car with 2.75:1 gears and a 1400 stall speed convertor, it will be sluggish from a dead stop. Once you hit 3000 RPM the 4V will rapidly out pace the 2V. Most of this "legend" was propagated by people installing cams that are not suited the the 4V head. The Chevy guys also wanted to tell the story so they could race  2V Clevelands instead of 4V Clevelands. Chuck

 

[da55]

Thanks guys, it makes sense. I still have a lot to learn and i know so little about this. I think the CAM and 4V would be a good start?

Thanks again.

 

[jakosaur]

I'll go ahead and put in my $0.02. I have an Edelbrock Performer 600 CFM carburetor, Edelbrock Performer intake, Comp Cams 260H camshaft, and headers. It runs like a beast even with a lousy rear gear ratio and stupid transmission, and I love it. I am planning to upgrade the ignition, transmission, and rear end. If anything, I'd say the cam is a little weak for the rest of the setup, and if I ever get rich & bored I'll put in the next-level cam. Like others mentioned though, you can't look at single pieces and expect a major change. The whole picture is required, from the air cleaner to the exhaust tip & everything in between. Just a carb on with no other change will be an expensive few HP. Camshaft only would run like garbage, since it can't breathe enough (ask me how I know). You need to decide what you want, how much you're willing to spend to get there, and make a few changes at once. I'll just say that the stock setup is made for emissions, so very mild replacements to carb, intake/exhaust manifolds, and camshaft will make a big difference.

$0.02, you probably overpaid.

Jake

 

[detritusmaximus]

It is 2bbl. Holley carb. I wanna keep the carb, not a fan of EFI. In a sense im a purist. It is 2V. I have seen into the 2v vs 4v debate. Of course more flow would be better but ive read the 4v does sacrifice some power when compared to the 2v. Any idea on this? Would it affect the RAM Air intake i plan to install?

400M exhaust manifolds? Ill look into it...

1970 timing chain/gears? Would this be an easy swap?

The cam, what can i get for this? An easy install? 

What about boring the engine out?

I don't have any great advice on this as I haven't reached the point of actually doing anything myself, but I thought I might clarify something here....

The 2v versus 4v debate is pretty much about the difference in 2v and 4v cylinder heads. That is a different thing entirely from putting an aftermarket 4v manifold designed to fit with 2v heads on your car.  The Ram Air could be affected by the specific choice of manifold and carb. Ask anyone that has swapped a four barrel intake and carb onto their 2v heads to see what they say about the power difference and the Ram Air.

In 72 the cam timing was retarded. I don't recall if this was solely in the grind of the cam or if the cam drive gear also was retarded. The idea is to get the cam timing back to what it was in 70.

Before boring the motor out, a swap to flat top pistons would be good to get back some compression lost to the dished pistons.

Better exhaust manifolds or headers could help, but that is a better question for those that have actual experience.

 

[Carolina_Mountain_Mustangs]

I do know here at the 1/8 mile you never see 4-V heads on 351C. I know there will be those that say they put the wrong cam or intake for a fair comparison but here is a link to dyno test rand with 2-V and then pulled the heads and put on 4-V leaving everything the same. The 2-V does better on the lower end and the 4-V has to be way wound up to have a benefit.



I have both 2-V heads with 4-V performer intake and holley 4-V. Also have 351 4-V. I am not a believer in winding and engine way up. I feel you should always build for torque. You are not going to be trying to gain a tenth or two just want good results.
My 351 - C is bored .050" over flat top pistons, cam that I have no idea of specs I did not build. Has long tube headers and dual exhaust. Eldebrock Performer 2-V to 4-V intake and the holley. C-4 auto with shift kit and MSD ignition. Has AC, PS and stock Ford radiator. Can drive anywhere and runs decent never taken to strip. Ran a few on the street and beat a Corvette one day and gave him the hit. I would use the 2-V unless you are going to race 100% then use 4-V. Here is couple pics of the intake. There are two versions one has the place for heat riser to carb but can have a cover on it to block the other does not have the heat riser. I picked this one up used for $35.00 was a real deal. He had just put on engine and crashed the car.

 

[c9zx]

The video: Lets start with a cam selected for 2V heads that peaks at 5500 RPM, then add 4V heads, and a single plane intake. Wow nice selection of parts, NOT. The characteristics of 2V heads and 4V heads are significantly different and require significantly different cam profiles. Limiting RPM to 6000 is silly with a stock stroke 351C and a single plane intake. The Clevor build is nothing more than a paid advertisement for Edelbrock.  The Clevor with aftermarket heads, roller cam, and stroked to 408 CID made 468 HP @5400 rpm and 502 TQ @3900 RPM. That is 1.15 HP/CI. Mediocre at best. But it is on a "professional" You Tube channel so it must be true.

 

[Carolina_Mountain_Mustangs]

I am sure we would al love to see some dyno results using proper parts but nobody will do them costs too much. RPM hardly ever wins a race except on drag strip Torque at low RPM is how we always built track cars that had to run 2,000 mile back in the 60's. They did not have the money for a new engine ever race. RPM means little without torque to go with it. Talking with Holman Moody they said same thing. Torque is king.

 

[cwalker509]

Do you intend to pull heads or replace cam? Some folks are intimidated to go too far into an engine. If you do not want to break into the engine then headers and a dual exhaust with h pipe.  If you wanna get into engine just a little move to the ignition next. Pertronix preferred but dual points ok (depends on your budget and what you may be able to find used). Next replace with a dual plane 4v intake designed for the 2v heads. Vacuum secondary with electric choke around 600 cfm. Ford used these stock on many of their engines (Holley often). Some folks swear by Holley or Edelbrock or the Summit carbs. Can often find these parts used too. Next up is to remove any retard on the cam (pull timing chain cover and associated stuff). Could also replace with roller timing chain. Gear drives can be a bit noisy. Cam next but would need new lifters as well. If you go so far as to pull heads then roller rockers and decent valve job and porting of heads. Money of these could be done over time (not all at once). Just my .002 and how I would approach it.

 

[cwalker509]

I am sure we would al love to see some dyno results using proper parts but nobody will do them costs too much. RPM hardly ever wins a race except on drag strip Torque at low RPM is how we always built track cars that had to run 2,000 mile back in the 60's. They did not have the money for a new engine ever race. RPM means little without torque to go with it. Talking with Holman Moody they said same thing. Torque is king.

Agree that torque is probably more important than pure top end horsepower for a street car. If you had the money to dyno various configurations I would look for area under a torque vs rpm curve from around 1000 - 4500 RPM unless you plan to go to 6000 frequently. Depends on how YOU plan to drive it.

 

[Don C]

Any modifications to a car has to be well thought out and a plan formulated. Most of us don't have the money to buy a bunch of parts and start throwing them at the engine, transmission, and rear end, then have something not work as intended and have to start over.

The car weight and front to rear balance must be considered, to start with, and how you want it to handle. The engine choice needs to match desired handling. The engine build, cam selection, intake manifold, and heads need to be compatible. And then the transmission strength and gearing for manuals and automatics and torque converter for automatics need to match the engine performance curve. And then the differential gearing needs to match what is in front of it, and don't forget about traction and keeping the tires planted on the road when accelerating, stopping, and turning. Lack of low end torque can be somewhat compensated for by lower rear end gearing, at the expense of top speed and higher engine speed when cruising down the freeway, unless overdrive is added.

 

[cwalker509]

Any modifications to a car has to be well thought out and a plan formulated. Most of us don't have the money to buy a bunch of parts and start throwing them at the engine, transmission, and rear end, then have something not work as intended and have to start over.

The car weight and front to rear balance must be considered, to start with, and how you want it to handle. The engine choice needs to match desired handling. The engine build, cam selection, intake manifold, and heads need to be compatible. And then the transmission strength and gearing for manuals and automatics and torque converter for automatics need to match the engine performance curve. And then the differential gearing needs to match what is in front of it, and don't forget about traction and keeping the tires planted on the road when accelerating, stopping, and turning. Lack of low end torque can be somewhat compensated for by lower rear end gearing, at the expense of top speed and higher engine speed when cruising down the freeway, unless overdrive is added.

Good input. I tend to think performance as strictly how and torque but improving handling on these cars is something well worth considering.

 

[Robsweden]

Bore the motor 0.30 if needed.
Refurbish rods, polish crank.
Flat tappet cam will be fine, hydraulic lifters and  choose the cam after how you gonna use the car and transmission.
New timing chain and gears.
Electric ignition pertronix, new wires , coil
Use the 2v heads they will do fine, change the valve to one piece. Mill the heads for a compression around 9.5  thats about 67.68 cc chamber
Maybe a better intake RPM Airgap or similar.
New bolts ARP, in critical places.
Stock oil pump will be fine, arp driveshaft for oilpump,
Headers.
Lots of this stuff you wont even see, but feel   

Correctly done this will produce around 350-375 hp easily and good torque for street driving.

 

[c9zx]

"I am sure we would al love to see some dyno results using proper parts but nobody will do them costs too much. " This is not an optimal build but it did make 1.3 HP/CI. Another half point in compression and a roller cam instead of the flat tappet used would have gained another 15-20 in HP and TQ. ChuckView attachment 408C dyno sheet copy.pdf

 

[c9zx]

Here is one for a 347CID Boss 302, again with a flat tappet cam. Chuck

View attachment Boss 347 Dyno Sheet.pdf