Back Pressure

[goodnigh]

I read many articals on the 351 cleveland...And over and over i read where the stock cast irons are super restrictive on the 351 cleveland's......big gains with headers on them....get that motor breathing...And remmeber...even with headers and a slightly bigger carb...." Counts on your cam lift and duration "....But should still be a bit less horse power than a 351 boss with less compression....So should last quite a long long time with the right treatment

And with all the info i see now days...And headers just in the last 10 years have really stepped up...Better copper gaskets so they dont leak...they fit better and tighter...I use to hate them...Cause i had them on my old chev truck and they leaked..But they was old school..lol...New ones now are better and well worth it too me..But not too everyone..I still got my stock originals in a box...But i can see at one time some one fixed them too...Got a weld on one..lol...but must of been a good fix..i was driving on them for 15 years....All of them are doomed too fail...So if you got matching cast iron originals..Mite be good idea too stick them in a box too..lol

But originals are just fine if you wanna use them..I got my motor torn down right now....Im going 5.25 lift...holley 750...hooker headers...and rest pretty much stock...Should be pushing 425hp..And im still way under what the motor was intended too run...Beauty of the cleveland...Monster gains with little effort..No need for big heads..You got them already...Thats where most people have to spend money on their motor...lol...Not with 4v cleveland guys...But its all up too you...I think your motor built proper will last just as long with headers and the right matching carb...As a pretty much stock 351c.

That is what I love about this forum. After reading all the info in this

thread I have come to the conclusion it is perfectly safe to put

headers on the Cleveland as long as I make adjustments to the

carburetion. My original concern was just mounting headers without taking into consideration what effect that may have on the rest of the engine. My current carb is a Holley 670, dual feed, single pump with

vacuum secondaries which works pretty well with the stock

intake/exhaust manifolds. The engine is pure stock except for the

mild cam and Pertronix ignition. Whoever did the rebuild job installed a cam we measured at 0.58 lift. The pistons have standard Cleveland

markings with '030' stamped at the end. Other than that I don't know

what else they did to the engine.

mike

 

[droptop73]

Hey Mike, replacing the carb when you switch to headers is probably not necessary. Stepping up the jet size is going to be necessary when you make the switch.

.580 is not what I'd call a "mild" cam the .030 marking on the piston tells you the cylinders have been bored oversized by .030".

 

[Tnfastbk]

Congrats Mike on the change of heart.

.580 is not what I'd call a "mild" cam Big Grin

Really:huh:

 

[goodnigh]

Congrats Mike on the change of heart.

I was never against headers just needed to clear up my mind about

what that means to the engine. I was pretty sure you could not just

slap headers on a car and drive away without making some other

changes that were unknown to me at the time. I appreciate your

patience but I stood my ground until I found what I was looking for.

That is what I love about this forum. Yeh, a nice fat double pumper

with mechanical secondaries and headers would give it some zip.

Start using the 100 octane stuff, I can see that.

mike

 

[Tnfastbk]

Congrats Mike on the change of heart.

I was never against headers just needed to clear up my mind about

what that means to the engine. I was pretty sure you could not just

slap headers on a car and drive away without making some other

changes that were unknown to me at the time. I appreciate your

patience but I stood my ground until I found what I was looking for.

That is what I love about this forum. Yeh, a nice fat double pumper

with mechanical secondaries and headers would give it some zip.

Start using the 100 octane stuff, I can see that.

mike

::welcome:: to the dark side

 

[hyena429]

Congrats Mike on the change of heart.

I was never against headers just needed to clear up my mind about

what that means to the engine. I was pretty sure you could not just

slap headers on a car and drive away without making some other

changes that were unknown to me at the time. I appreciate your

patience but I stood my ground until I found what I was looking for.

That is what I love about this forum. Yeh, a nice fat double pumper

with mechanical secondaries and headers would give it some zip.

Start using the 100 octane stuff, I can see that.

mike

::welcome:: to the dark side

Lmao! Ditto!! Its is good you stood your ground and wanted real proof...And sorry if we gave you too much hell over it

 

[goodnigh]

::welcome:: to the dark side

Lmao! Ditto!! Its is good you stood your ground and wanted real proof...And sorry if we gave you too much hell over it

I kind of like the Dark side. It was that new engine from Don

that started all this. Currently running a Holley 670 and thinking

about getting a 770 to start things off. No Hell, just Great answers.

mike

 

[1971mach1]

I kind of like the Dark side. It was that new engine from Don

that started all this. Currently running a Holley 670 and thinking

about getting a 770 to start things off. No Hell, just Great answers.

mike

The 670 should be plenty for a 351.

Let us know how much better it runs with headers.

Are you going longtube, or shortys? Don't get the cheep ones, they leak.

And ceramic coating is supposed to keep your engine compartment cooler (heat is a problem with headers).

I was thinking about them too but they only seem to make (hi-quality)longtubes for 351c-4v w/automatic. I got a cable clutch and power steering too plus driveway clearance issues. I hear shortys are not much better than the stock 4v manifolds.

 

[goodnigh]

The 670 should be plenty for a 351.

Let us know how much better it runs with headers.

Are you going longtube, or shortys? Don't get the cheep ones, they leak.

And ceramic coating is supposed to keep your engine compartment cooler (heat is a problem with headers).

I was thinking about them too but they only seem to make (hi-quality)longtubes for 351c-4v w/automatic. I got a cable clutch and power steering too plus driveway clearance issues. I hear shortys are not much better than the stock 4v manifolds.

The problem with a 670 carb is the cam. 670 is more than enough

for a stock Cleveland, but the stock cam measures around 0.44 lift.

Whoever rebuilt this engine put in a cam we measured at 0.58 lift.

That has to complicate the formula. When I start the engine, before

I get ignition, you can hear the carb sucking air which lasts about one

second before it fires. When we do go with headers they will probably

be these http://www.summitracing.com/parts/HOK-6915-3HKR/

mike