Cyl head sizing discussion, anyone?

[Herr_Poopschitz]

I’d been out of the Mopar circle since the late 90’s, when I got into late model Mustangs, Camaros, and Vettes. In putting together a combo for my own car, I’m trying to apply much of what I learned to my 440, and glad the aftermarket has stepped up over the last 15 years. I’m presenting this solely as a topic for discussion…no attacks on any one person’s combo. I’m hoping we’ll have an educated conversation of the way an engine works and how certain cylinder heads can help or hinder in achieving certain owner’s goals, and possibly addressing different, and potentially cheaper, paths of getting there.

First, for comparison, I'm helping a friend put together a combo for his 71 Chevelle...I convinced him to go w/ a naturally aspirated LS3 based combination, specifically.

During my research, I’d found the LS3 heads use an intake port that measures 2.55 x 1.25 (3.19 sq in), w/ a 2.165 valve...also w/ an offset rocker, so ‘no’ pushrod pinch reducing the port cross section. This is on 376 ci.

That seemed like quite the intake port, so I looked up a BBM for comparison’s sake. A Fel-Pro 1218 Max Wedge gasket measures 2.622 x 1.3265, and because of the valvetrain geometry the port will have a slightly smaller cross section due to the pinch. Using the industry standard BBM Al head, the RPM has a 2.14 intake valve.

Let's say it's a wash as far as port size goes, to keep things easy. So…the newest tech engines using pushrods are using heads similarly sized to that which most Mopar guys are afraid to use on an engine that's 65 ci larger. This begs the question of why we’re seeing so many put a head smaller (std BBM) than this on 500+ ci engines (more than 125 ci larger).

Why can they get away w/ such a big head and we can’t, even though we are using much larger, and in many cases ‘warmed over’ or ‘performance’, engines?

Please educate me.

 

[IQ52]

We can use the bigger heads Mein Herr, we can. For so long we have heard, "Oh, don't use the bigger valve, you'll lose veelawsotee!" Everyone is scared spitless.

We will soon begin tests on a .030" over 440 with different variations of well ported iron heads and top it off with some tests of our Indy EZ Max Wedge heads flowing 370 cfm. We are just beginning to scrounge together the short block.

 

[Cranky]

I have no problem using large valve/port heads. My first 'drag' car had max ported 906's with 2.14/1.88's on it....back in 84

 

[Redhorse719]

We can use the bigger heads Mein Herr, we can. For so long we have heard, "Oh, don't use the bigger valve, you'll lose veelawsotee!" Everyone is scared spitless.

We will soon begin tests on a .030" over 440 with different variations of well ported iron heads and top it off with some tests of our Indy EZ Max Wedge heads flowing 370 cfm. We are just beginning to scrounge together the short block.

Will you post some results here? What do you need to complete the short block? I have a few stock parts stashed.

 

[Herr_Poopschitz]

We can use the bigger heads Mein Herr, we can. For so long we have heard, "Oh, don't use the bigger valve, you'll lose veelawsotee!" Everyone is scared spitless.

We will soon begin tests on a .030" over 440 with different variations of well ported iron heads and top it off with some tests of our Indy EZ Max Wedge heads flowing 370 cfm. We are just beginning to scrounge together the short block.

Dangit, you weren't supposed to reply so early to this thread! Now no one will try to convince me that a Stealth belongs on a mountain motor! X2 on 'velocity'.

I've shared this before, but I'm going to be using home ported Vic's on my 440 w/ a very mild cam. Everyone is telling me the head is 'too large' and I'm wasting my time. Even Hughes says on their website that Vic's are a 'RACE' head. Phooey.

I keep referring people to this article...Note the cam duration on each....

http://www.hotrod.com/techarticles/...gine_shootout/ford_boss_302_chevy_dz_302.html

 

[67 B-body]

Use the Vics, and don't look back!!!!!!!
I LOVE how mine are working out!!!!! I did a home porting too, and if you haven't got them yet,,,, wait till you see how the port doesn't get pinched down by the valve guide!!! You can see the valve through the port from across the room!!! It's a straight shot with the raised port windows!!!!!
I use an old MP 590 solid cam with 1.6:1 ratio rockers in my standard stroke 440 .030" oversized bores, and .140" domed forged pistons attached to Scat H-Beam rods.

 

[IQ52]

Will you post some results here? What do you need to complete the short block? I have a few stock parts stashed.

Post results? You Bet! Thank you for the offer. If we're missing something, I'll check with you.

Dangit, you weren't supposed to reply so early to this thread! Now no one will try to convince me that a Stealth belongs on a mountain motor! X2 on 'velocity'.

I've shared this before, but I'm going to be using home ported Vic's on my 440 w/ a very mild cam. Everyone is telling me the head is 'too large' and I'm wasting my time. Even Hughes says on their website that Vic's are a 'RACE' head. Phooey.

I keep referring people to this article...Note the cam duration on each....

http://www.hotrod.com/techarticles/...gine_shootout/ford_boss_302_chevy_dz_302.html

You forgot to PM me the rules!!!!!!

So the Stealth belongs on a mountain motor. Okay?

But the port might go supersonic at 2400 rpm.

 

[67 B-body]

BTW.. You'll need custom length pushrods too... I don't remember the length I came up with off the top my head, but I think I still have the package with the length out in the garage... Mine were a bit different than others using solid cams, because I used Hughes cool face lifters and they are taller than stock.

 

[Herr_Poopschitz]

But the port might go supersonic at 2400 rpm.

Hahaha

Use the Vics, and don't look back!!!!!!!
I LOVE how mine are working out!!!!! I did a home porting too, and if you haven't got them yet,,,, wait till you see how the port doesn't get pinched down by the valve guide!!! You can see the valve through the port from across the room!!! It's a straight shot with the raised port windows!!!!!

Yep, got em a while ago but haven't started work on them yet...minitub, footwell replacement, trans tunnel work, fuel cell mnt, engine compart, etc have all come first. My car is actually going to look almost identical to yours on the outside but a sedan and I'm planning diff wheels. And yeah, they make the 906s look tiny. Ever since doing my first set of Trick Flows for SBF and the results I got out of them I've been on the 'no pinch' kick...this was years ago. Glad to see more and more of it.... I am excited about running a raised port too...not common in the BBM world.

BTW.. You'll need custom length pushrods too... I don't remember the length I came up with off the top my head, but I think I still have the package with the length out in the garage... Mine were a bit different than others using solid cams, because I used Hughes cool face lifters and they are taller than stock.

I was originally planning on a solid roller, but thinking twice about it. I was really thinking about throwing a bunch of $ at this motor, but jeez roller stuff is stupid money for these engines...too much time in the roller 5.0 world spoiled me, I guess. Might have Bullet do a custom solid flat tappet...kinda up in the air at this point...couple things might affect this decision. I did make an adjustable pushrod out of one that came out of the engine I have on the stand. Cutting wasn't bad, but tapping it sure wasn't a lot of fun...who woulda thunk hardened steel was hard?

 

[Cranky]

I compared a one of the RPM's to my old 906's before selling them and they flowed pretty much the same but of course, the RPM's would most likely do better since they are a better head. Anyways, the car ran a best of 10.50 but wasn't consistent so I tuned it down to where it was consistent. Leaving on the converter it ran 10.68 and leaving at an idle it ran a 10.69 and the thing ran a Weiand TR with two 750 DPs (TR carbs of course) on top...4500 comverter, 4.88's.

 

[Herr_Poopschitz]

I compared a one of the RPM's to my old 906's before selling them and they flowed pretty much the same but of course, the RPM's would most likely do better since they are a better head. Anyways, the car ran a best of 10.50 but wasn't consistent so I tuned it down to where it was consistent. Leaving on the converter it ran 10.68 and leaving at an idle it ran a 10.69 and the thing ran a Weiand TR with two 750 DPs (TR carbs of course) on top...4500 comverter, 4.88's.

Cam?

 

[Meep-Meep]

I'll point out that people have run 351 Clevelands on the street. Heck, even the factory put one in my buddies 70 Cougar convertible and that car was originally bought by a lady.

My 72 Porsche 911 T with a 2.4 liter 6 cyl had 1.88" x 1.60" valves, 7.5:1 compression (I bumped it to 8.0:1) and it still blew 150 PSI of cranking pressure. All this produced one HP per CI and ran so smooth you could sleep on it.

How many rectangle port BBC came out in production cars and were driven daily?

The secret I believe is matching the compression to the cam profile to the port, all in an effort to keep things moving properly. I think the more efficient the port the less cam you need to get the job done and the better all around performance.

 

[Cranky]

Cam?

Isky .660 lift roller 320 degrees advertised. I think I still have the spec sheet on it....man, ran that thing back in 84-85.

 

[Herr_Poopschitz]

The secret I believe is matching the compression to the cam profile to the port, all in an effort to keep things moving properly. I think the more efficient the port the less cam you need to get the job done and the better all around performance.

This is the trend that I've seen. Two engines, same hp...one w/ small heads and lumpy cam, one w/ big efficient heads and a small cam. Depending on what a person wants, a big head/small cam combo can provide drivability the other can't provide, as well. Also, w/ the big heads, all that's needed to make more power, if desired, is a cam/spring swap. If an individual has limited themselves to a small head, the only choice is to buy a diff set of heads, which costs a whole lot more.

Not sure who started the 'velocity' talk. I can understand in a racing-specific application where an engine has a narrow operating window, but don't understand the obsession w/ street cars. Also think that if the port is sized reasonably, the cam has quite an influence on 'v' that no one ever talks about.

Sometimes I think it was companies like AFR, which if you've seen their SBC lineup, have convinced everyone that they need 'x' head for this combo, and 'y' for a different one. They have so many freaking heads available it's crazy. A guy I know went through 3 different sets of AFR's in like 5 years for only a minimal difference in power...while using the same cam...all because of the promises made for the 'latest greatest'. More $ than brains. He's an engineer too...retard.

I do think that to maximize a big head combo, 'especially' for BBM, normal off the shelf cams probably aren't going to do them justice...

 

[67Satty]

Let's look at the from the opposite end too. I've always wondered why the big mopars do so well with their dinky ports and valves. I'm assuming when the engineers designed these things way back when and starting from a clean slate, there was a reason they decided on the valve and port sizes they did.

Also, from road tests and even stock eliminator results from back in the day during the musclecar era, you can see that the 440 six packs with their small valves and ports held their own against the big block Chevs and sometimes even the Hemis with their much larger valves and ports and I've always wondered how it's possible.

From what I've seen on the street and at the strip the big block Chevies don't dominate as much as you'd think there either even though they have the bigger valves and ports advantage.

Another weird Mopar thing that makes them so interesting...like why is it that the big block Mopars, even the mild ones, seem to respond so well to throwing a tunnel ram on them???

Another eye-opener is doing a search on the various Mopar boards for quickest ET with stock, unported heads. Some pretty crazy times for stock heads.

Not argueing that the bigger heads aren't better, because I'm sure they are, just wondering how the small heads are able to perform so well on a Mopar.

 

[Lazarus]

Does the wider lifters not allow us more open time for breathing with all things being equal? Doesn't that explain why we can get away with less aggressive stuff, since the valves open sooner and close later? Of course, more airflow is a good thing, to a point, just two different manufacturers and two ways to get there. Basically, the chebby and fjord guys require bigger heads to keep up because their valves are open less time. Is that right, or am I off in left field? That would explain why our small valves keep up with their big ones, to a point..

 

[Cranky]

Another weird Mopar thing that makes them so interesting...like why is it that the big block Mopars, even the mild ones, seem to respond so well to throwing a tunnel ram on them???

Mine (from the post above) even drove around at low rpm real well but it did have a loose converter but a buddy of mine borrowed my intake for a 68 440 Charger with 3.91's, 2800 converter. Even tho it had smaller carbs on it, it still ran pretty damn good and even had decent street manners.

 

[Herr_Poopschitz]

I'm assuming when the engineers designed these things way back when and starting from a clean slate, there was a reason they decided on the valve and port sizes they did.

Sure there was a reason...does this make it ideal? I think we all can agree that technology and our understanding of things has come a long way in the last 50 years, can't we?

Also, from road tests and even stock eliminator results from back in the day during the musclecar era, you can see that the 440 six packs with their small valves and ports held their own against the big block Chevs and sometimes even the Hemis with their much larger valves and ports and I've always wondered how it's possible.

From what I've seen on the street and at the strip the big block Chevies don't dominate as much as you'd think there either even though they have the bigger valves and ports advantage.

Too many variables. Tune? Camshaft? Are you talking hp or ET? If ET, that opens another can of worms w/ drivetrain and chassis tuning.... Also, daily drivers w/ few boltons and a tune these days are ET'ing like racecars did 'back in the day'.

Another weird Mopar thing that makes them so interesting...like why is it that the big block Mopars, even the mild ones, seem to respond so well to throwing a tunnel ram on them???

Induction limited. Shows just how bad the stock stuff is.

Another eye-opener is doing a search on the various Mopar boards for quickest ET with stock, unported heads. Some pretty crazy times for stock heads.

Define 'crazy'. I've never seen anything that really surprises me. I think we should focus on the engines themselves, and not so much ET/MPH. A lot of variables get introduced when talking about the entire car...

Not argueing that the bigger heads aren't better, because I'm sure they are, just wondering how the small heads are able to perform so well on a Mopar.

I think 'perform well' is relative.

I just saw an ad for a crate LS3 direct from GM...the thing is completely stock as they deliver in their Camaros w/ the addition of a 219/228 at .050" camshaft (mild for 376 ci, yes?), and it's rated at 480 hp. Are there any examples of 383's producing this kind of power w/ such a mild cam? You can't hardly notice any lope in the idle.

- - - Updated - - -

Does the wider lifters not allow us more open time for breathing with all things being equal? Doesn't that explain why we can get away with less aggressive stuff, since the valves open sooner and close later? Of course, more airflow is a good thing, to a point, just two different manufacturers and two ways to get there. Basically, the chebby and fjord guys require bigger heads to keep up because their valves are open less time. Is that right, or am I off in left field? That would explain why our small valves keep up with their big ones, to a point..

The larger diameter flat tappet lifters don't influence open and closing events...they 'might' affect the ramps and how quickly the valve opens if taken into consideration in the lobe design.

If it takes 'x' amt of air to make *** hp...it seems there are two ways to do it. One is w/ small heads...and because of the small ports, the cam has to keep the valve open longer to move 'x' air. This is fine up to a point where compromises are made and camshafts create what I consider problems for street driven vehicles. Poor carb signal, raunchy idles, no vacuum for power brakes, potential piston-valve issues, etc. On the other hand, it seems big heads can be used w/ relatively small duration camshafts to move the same 'x' amt of air to make *** hp, w/ none of the potential drawbacks of a big cam. The advantage here is that to make more power, a simple cam change is all that's needed. W/ the small head scenario, the heads must be replaced or ported...both of which cost considerably more than a cam swap.

 

[67Satty]

Well, I'm not really looking to do a line by line rebuttal. But I think when you compare the big block Mopar to the big block chevy, it's pretty striking how well the big block mopar performs against it with it's much smaller valves and ports and I've always wondered why. Is it the larger diameter lifters that gives the big block Mopar an advantage? Is it something about the rod ratio? Some combination of both?

Now, I don't know much about modern Chevy stuff like LS3s, my eyes usually begin to glaze over when they are mentioned, but are you really wanting me to take a comparison seriously when you are comparing two motors with four or five decades difference in technology and manufacturing? You want to compare something with aluminum heads, block, fuel injection and close to 11:1 compression (what factory Mopar 383 came with anything over 10.5:1??? - most were closer to 9:1)????

Let's keep things a little bit realistic in the discussion.

How about looking at the F.A.S.T. cars, how is it that the 440 6 packs with their puny heads are able to be competitive?

As for your big heads and small cams are always better than small heads and a big cams, I'm not so sure. I think the bigger heads need a big enough cam to take advantage of what they have to offer. Whereas a small head (big block mopar anyway) motor will keep making more power even when overcamming by the conventional wisdom standards. It was proven by a test made by the Chysler engineers who took a bracket Duster with a stock bottom-end low compression 400 with iron heads. The kept putting bigger and bigger cams in it (ending with a .590, 312 duration) and it keep ET-ing better and better.

Here's one from my own experience of how a big head with a small cam didn't work out very well. My friend's 440 '70 Barracuda had Edelbrock RPMs and a small .484 lift MP cam. Let's say the Edelbrocks flow at least 280 cfm intake. This car with a 4.10 gear and less weight ran 2 tenths slower in the 1/8 than my Satellite.

My Satellite has a 440 but with smaller heads (stock, unported 452s - probably flow 220 cfm intake at best) but a bigger .534 lift cam. 3.91 gear and more weight but 2/10s in the 1/8 faster. So in this case, the small head, big cam wins over the big head, small cam.

He didn't have enough cam for his bigger better flowing heads (at least 70 cfm more flow) for it to matter or take advantage of the better flow. Maybe torque curves and mid-range power is what matters when moving these heavy cars quickly from a stop?

I think something like a Victor like you are talking about would need a cam of at least .575 lift to make the most advantage of the extra available flow. Once your getting into that amount of lift, that's not going to be some 228 @ .050 duration cam, that's going to be more like 240-250 @.050 minimum unless you get something custom ground.

So yeah, the bigger heads are better for making the most peak HP - but only if the rest of parts are matched to take enough advantage of what they can do.

 

[Herr_Poopschitz]

Now, I don't know much about modern Chevy stuff like LS3s, my eyes usually begin to glaze over when they are mentioned, but are you really wanting me to take a comparison seriously when you are comparing two motors with four or five decades difference in technology and manufacturing? You want to compare something with aluminum heads, block, fuel injection and close to 11:1 compression (what factory Mopar 383 came with anything over 10.5:1??? - most were closer to 9:1)????

Let's keep things a little bit realistic in the discussion.

I'm not sure what's unrealistic about it. An engine's an engine...different specifics, but they all do the same
thing...some just do it better than others. The question is why? Not all LS engines have Al blocks, and I've never known there to be a power advantage to using one at these moderate hp levels. LS engines make even more power w/ a single plane and a carb, so FI isn't a consideration. 383's can be built w/ higher compression, and have aluminum heads available. The question is what can be done to make more power, not a comparison of two engines built as delivered from the factory from different eras. What can we learn from the newer stuff...maybe to apply some of the principles if possible?

How about looking at the F.A.S.T. cars, how is it that the 440 6 packs with their puny heads are able to be competitive?

Purpose built race cars.

As for your big heads and small cams are always better than small heads and a big cams, I'm not so sure. I think the bigger heads need a big enough cam to take advantage of what they have to offer. Whereas a small head (big block mopar anyway) motor will keep making more power even when overcamming by the conventional wisdom standards. It was proven by a test made by the Chysler engineers who took a bracket Duster with a stock bottom-end low compression 400 with iron heads. The kept putting bigger and bigger cams in it (ending with a .590, 312 duration) and it keep ET-ing better and better.

Yes, assuming the timing events occur at the right times, more power will be made in either scenario. What compromises must be made in each, esp for a car seeing time on the street? It appears camshafts of equivalent sizes will make much more power in an engine w/ what are conventionally thought to be ‘too large of a head’. Have you also noticed that in some racing classes, superior heads require a weight penalty?

Here's one from my own experience of how a big head with a small cam didn't work out very well. My friend's 440 '70 Barracuda had Edelbrock RPMs and a small .484 lift MP cam. Let's say the Edelbrocks flow at least 280 cfm intake. This car with a 4.10 gear and less weight ran 2 tenths slower in the 1/8 than my Satellite.
My Satellite has a 440 but with smaller heads (stock, unported 452s - probably flow 220 cfm intake at best) but a bigger .534 lift cam. 3.91 gear and more weight but 2/10s in the 1/8 faster. So in this case, the small head, big cam wins over the big head, small cam.
He didn't have enough cam for his bigger better flowing heads (at least 70 cfm more flow) for it to matter or take advantage of the better flow.

There’s not enough information here to draw any kind of conclusion.

Maybe torque curves and mid-range power is what matters when moving these heavy cars quickly from a stop?

I’m trying to understand what you mean by this. HP is nothing more than a byproduct of torque and rpm. I would say that getting the engine into its powerband quickly and keeping it there would be the most effective way of accelerating the mass of the car. That’s torque converter or clutch slippage though, which is a drivetrain issue, not engine. Making the most avg hp in the powerband is the concern, where the powerband consists of maybe a couple hundred rpm past peak to as low as the engine rpm falls back to between shifts.

So yeah, the bigger heads are better for making the most peak HP - but only if the rest of parts are matched to take enough advantage of what they can do.

Did you read the DZ vs Boss article I posted a link to? Those big ports seem to do pretty well at making low end torque. I think the goal w/ any build is to match components to achieve a set goal, yes?