Head Flow rates improved

[trainey]

Here are the flow rate improvements after having my 4V CC heads ported. These are going on my .040 over block.

Nice improvement on the exhaust side!

 

[BrandonDindorf]

Wasn't the problem with 4v head is the exhaust flowed too well? It didn't have enough back pressure to flow correctly. That's why people added restrictor plates to the exhaust and had major performance gains... I could see correcting flow restrictions or poor casting designs on the intake but not exhaust.

 

[caspianwendell]

Misleading titles...:dodgy:

 

[trainey]

Wasn't the problem with 4v head is the exhaust flowed too well? It didn't have enough back pressure to flow correctly. That's why people added restrictor plates to the exhaust and had major performance gains... I could see correcting flow restrictions or poor casting designs on the intake but not exhaust.

This is from my builder when he first flowed the heads for me, and we started talking about building the motor. Now I am no expert for sure, he has built race motors for a long time...

"As you can see the exhaust averages 68% of the intake. 65% is considered the minimum with 75% being really good on a naturally aspirated engine and 80 % for blowers or turbos.

If you just swap in the stainless valves from the other heads you will be super close to 70%."

I did go with the single piece stainless valves, then he cleaned up the obstructions in the ports, and the results are that average of 77% exhaust to intake. Thinking of the engine as an "air pump" it makes sense to me that you would want the exhaust to be closer the intake.

 

[droptop73]

Remember higher flow volumes do not necessarily translate into more power. Sometimes flow velocity is sacrificed at the expense of cylinder filling and volumetric efficiency.

 

[Paul of MO]

I will bet your builder is a big block Ford and Chevy expert.

You did not hurt your heads but you will not see any actual horse power gains from this unless you are planning to spin it to around 8 thousand RPM.

Your optimal RPM range on the street will be 500 or so higher depending on the cam you use but you can adjust for that with a deeper gear or a higher RPM stall convertor.

Like others have noted 4V heads are insanely great right out of the foundry. Even the odd little bumps have a purpose.

We used to do the hi port exhaust on all of our race engines but that was more to get rid of the sharp bends and to better position the headers in the chassis. The exhaust cross section did not change all that much but mearly moved up on the head.

I have welded up and or epoxyed 4V exhaust runners for street driven cars over the years. This lowers the power range to a more street friendly level.

Our last "invention" was a simple steel plate that bolts between the head and the header that reduced the overall exhaust opening and had a ramp that stuck back into the head. We created 4V clevelands that made great power from 1500 rpm to 4000 rpm instead of 4000 and up.

When Clevelands fell out of favor in prostock and we lost our contract we sold our remaining inventory to bracket racers and finally to street vehicle owners.

It looks to me like Clevelands are having somewhat of a revival. I have not built a Cleveland for a paying customer in years and now I have had 2 inqueries in the last month. FUN!

I have found a local engine builder who knows Clevelands that I have forwarded these people to - he is going to do the work and I am going to sit on a chair and tell old man stories for a small fee. I think think that is a good arrangment!

Paul

 

[Mesozoic]

Your Cleveland's post porting exhaust flow rate is pretty impressive! If I were still running a 351C I would definitely opt for more stroke and displacement to take advantage of those giant ports.

Your flow sheet was interesting to look at because I just had my RHS 215 heads ported and flowed as well. They outflow your Clevelands, but that's to be expected for an expensive set of ported aftermarket heads. Exhaust/intake percentage is in the 70s throughout. I didn't think that small block Ford Windsor heads could ever outflow Clevelands, but alas.