OK here are some Pics of the ProComp 190 cc / 64 cc Heads. Look good to me and have to flow better than 34 yr old GM smog heads!!

 

To me that don't look to good...

 

Take a high resolution clos uppix of a recent GM iron head and post side by side and then comment???

 

big_G: What would you have to do to get them cleaned up...have a shop CNC port them?

 

CNC porting would cost a lot. Maybe just good street bowl and port job. Look at the core shift around the exhaust valve guide. I'm not saying G.M. did much better, but comparing a head cast yesterday against one cast 30 years ago is wrong...lol. The intake ports look good, though. P.S....My Vic. Jr heads looked much better, but they are on the 'Vette..

 

Now if you want CNC type heads you are in the $1300 to $1500 price range. I will have less than $700 when I am done. It would have cost me that much to rebuild my old iron heads. With 190 cc runners and 202 valves they will out flow and out perform the original smog heads. I am not looking for a racing head just a decent replacement head. I believe I will have a decent performing head. Down the road if I have to rebuild the bottom end I will go to a 383 setup. These heads will support a 383.
I think they are decent heads. Escpecially for the money. My first choice would be the AFR's...but they are over $1300, second choice would be the Vic Jr's but the 215-220 intake runners are too big for my set up...Intake runners look good, exhaust could be cleaned up a little. I may do a gasket match on the intake side also.
I considered the Edelbrock RPM heads. But from I have read here on the forum there are some issues with these heads too.....

 

I'm not going to debate the D.C. issue again, but it is without a doubt a "variable". Maybe someone else will explain about timing chain stretch, pushrod "flex", valve lash changes, etc. It's a variable. I don't care about valve closing event, this is directly related to the previously mentioned issues. I posted in another location here that when we build a unit using a "nylon" timing set, we actually see 10/20 HP higher numbers upstairs than a conventional true-roller setup!

I came back with respect to the heads, I'm not sure where you guy's are purchasing those Pro-Comp's in the above photo's, but they look nothing like any of the ones I have in inventory. The photo's below are not "close-ups", but the MAJOR differences are apparent. Thanks, Gary in N.Y.



P.S. The heads pictured flow, from the boxes, no porting whatsoever, 260 CFM @ .600" intake and 170 CFM @ .600" exhaust. With some 3-4 hours of work these numbers can be brought up substantially.

 

This might clear up the DCR vs cylinder pressure issue

http://www.empirenet.com/pkelley2/DynamicCR.html

 

Below is a copy of one of a thousand posts up here the web. What happens to your dynamic numbers when the timing chain stretches? when the pushrods flex? when you use "Rhoads" lifters? "Variable cam timing" alone comes in many forms! Read the article down below.

The next time you check P/D (piston to deck) clearances turn the entire unit over (check it upside down, let the piston hang down) and remeasure it. Even the bearing clearances you have will change the number upside down! Probably by a good portion of the overall clearances. Maybe a .005" difference.
Thanks, Gary in N.Y.

P.S. Many of those calculators up on these sites are in "left-field". For instance where they want a gasket bore, what would you enter for non-round bore? I don't know if you're familiar with a Flathead gasket, but it's about as far from round as it gets. I do understand alternative measurements, gasket cc's, which is much more accurate, but the way they are entered in the ones I've seen, is not the best. The D.C.R. is VARIABLE, period. I'm glad I didn't have to type all the following!

(Quote)
The dynamic compression as you mentioned increases with RPM and follows the VE/Torque curve. The reason for this as you might already know is that due to cam timing, intake runner length/dia, header length/dia, and all the other factors that affect cylinder filling, there is an increase of air and fuel being shoved into the cylinder. This is greatest at the point where torque is at its peak. Torque output peaks here cause the ramming affect of the inlet charge is, in essence, super charging itself. In some race engines like Nascar they achieve greater than 100% VE, with out turbos or blowers. This is due to intake and exhaust tracts tuned exactly and specifically to the cam, etc.
The air is drawn through the intake runners in chunks. The intake valve opens, the piston draws the air into the cylinder, air flow is speeding up, the intake valve closes, the air still has momentum and we all know air has weight/density, the air charge compresses behind the intake vale and surges back, much like a wave hitting a wall and coming back. Then it comes back again with almost the same force so as the intake valve opens the air is already moving toward the vale so the piston doesn't have to draw it in, it is quite literally shoving itself in the cylinder. The greater this ramming effect, the greater the VE.
OEM street engines usually don't exceed 85% VE. Hot street engines rarely don't exceed 90%-95% VE, full race engines are around 100%-110% VE.
In short, VE varies with RPM and is greatest at torque peak. Thus more air is being shoved into the cylinder so cylinder pressure is greater, therefore MORE TORQUE.
Now don't be confused, the compression "ratio" never changes, just cylinder pressure.
VE= the amount of air actually being drawn into the cylinder versus the actual volume of the cylinder.
Technical Dept Home (End quote)

 

So, the $64,000 question is this....If you have 10.2 SCR, but a 9.75 DCR, are you OK to run pump gas with iron heads or do you have to go aluminum?

 

THat just tells me that someone else is getting mixed up between the terms dynamic compression and cylinder pressure.

Here's a definition, I can't imagine a definition is wrong :

"Definition: The Compression Ratio (CR) of an engine is the ratio of the cylinder volume compared to the combustion chamber volume. A cylinder with 10 units of volume (called the sweep volume) and a chamber with a volume of 1 has a 10:1 compression ratio. Static Compression Ratio (SCR) is the ratio most commonly referred to. It is derived from the sweep volume of the cylinder using the full crank stroke (BDC to TDC). Dynamic Compression Ratio, on the other hand, uses the position of the piston at intake valve closing rather than BDC of the crank stroke to determine the sweep volume of the cylinder."

To answer dgruenke's question 9.75 DCR is way too high for pump gas. You want to shoot for ( if I remeber correctly ) 8.5 :1 DCR. There are dynamic compression calculators on the net, do a search.

 

That's what I was afraid of. I am trying to find a head and rotating assembly combination that will give me some power. In determining the static compression ratio, you have to use the piston to deck clearance. It is fair to assume that a standard 350 with stock cast pistons have about a 0.025 piston to deck clearance? If this is true and you use a 383 setup, won't the piston to deck clearance be less because you have a greater stroke (pushing the piston closer to the deck)?

Sorry for all of the questions. I just want to get this thing right if I am going to spend a good deal of money on it.

 

The piston pin location will be different on 383 pistons this will compensate for different rod lengths. Piston manufacturers will give you CR based on that particular piston and the cc of the heads you have or are going to buy and the stock deck height.. For a mild buildup this is generally all you need. For iron 10:1 and aluminum 11:1 and run a cam that is compatible with the CR and you will be OK as far as pump gas is concerned

 

Hi Mark See you bought the Procomp's. Why didn't you get them assembled ready to go? Going to use better components and do it yourself??
P.S. 190's are much better for that 383 than my 180's would have been.
Good Luck
Eddie

 

Thanks Eddie, these popped up on Ebay and I got them for $404. The assembled heads are about $750-800. I wanted to use springs and other parts that are matched to the cam. Not any real savings just a more custom set up. I am leaning towards the Comp Cams XE 268 or XE 270 4x4...."K" kit (Cam, springs, retainers. keepers, gears and chain etc..)
Mark

 

My 2cents even though nobody will follow it. These heads were made in China from some Pro-Action samples (now owned by Comp Cams but, made in New Zealand.) The fit of the the vale seats is SUSPECT and we have seen some CATASTROPHIC failures, the fit of the valve guides is SUSPECT and we have seen one CATASTROPHIC failure. Go ahead and save some money today while spending a lot later when the parts fail or buy American made Canfield/Brodix heads for around $650/pr, use some quality parts in them, sleep soudly at night knowing your motor is "bullet-proof". Both Brodix and Canfield (try Jegs or Competition Products for Canfield heads) make quality products in the USA take your pick, both are good quality products. One last thing, have any of you found an intake manifold to match these heads? We haven't been able to find anything close to these ports, the heads may flow but, nothing matches these ports that we can find. To all those "happy savers" I wish you luck, I'll stick with USA products for my Chevy.