Here are the ‘very summarized’ results of how sixteen different pairs of heads recently performed on the 312 dyno mule.  A pair of the ECZ-C’s and C1TE-D’s was a before and after milling comparison which  jumps the number of published tests to eighteen.  The same carburetor, intake, headers, timing, and valve lash was used in all these tests.  The camshaft is a Crower Monarch with 0.450” lift, 238°@0.050”, ground on 110° lobe centers, and installed 2° advanced or 108° intake lobe centerline.    The intake manifold is an unported Mummert dual plane paired up with a 750cfm vacuum secondary Holley sitting atop a 2” oval opening carb spacer.  1.6:1 roller rockers are being used for all tests.  Total ignition timing is 38° BTDC.  For these particular test results, the headers are used with mufflers which helps to keep this particular information set comparable.  The degree or amount of porting when performed on the heads is not listed on this particular chart.

A special thanks goes out to those of you that donated heads, shipping, and/or funds to make all this happen.  For those of you that sent funds without any name(s) on the envelopes, an extra thanks also.  This testing has generated a plethora of information which is being put together for a series of articles for the Y-Block Magazine.

Next year hopefully some CNC ported Mummert heads, I think that is what I will need for a D/PP reacord.

Once again a great job. Thank you for all your time and effort.

Seeing the results of the cylinder head test and having facts and hard data as opposed to myth, urban ledgends and speculation makes me smile. Since I remember the day when the Yblock G heads were just the ones with the larger intake valves already in them and not the object of almost magical regard this helps to put it into perspective. In the case of the G heads maybe you really do not get what you pay for after all.

So don`t believe everything you hear. Pete

Thank you for running all of those tests on the different heads.  One comparison I see is the Stock G head was 5HP less and 9 ft/lbs more than a stock C1TE head?  I thought the C1TE heads would be alot worse.  I am in the process of changing out my C1TE heads for a pair of G heads on my 272.  Now I am wondering if it will make much of a difference in horse power/torque.  What do you think?

Im new but have been on the outside looking in for a long time.  I was wondering if the power curve data is available for this head test.  Im curious to see what rpm these max horse power numbers occur (also the torque).  In my opinion just the max numbers are a little misleading and don't tell the whole story. 

Thanks

In lieu of a bunch of graphs that get busy in a hurry, here’s a revised chart using a scoring format to gauge the overall performance.  While I've calculated the scores in the normal 2500-5500 rpm range, I've also included the scores for the 2500-3500 rpm range as this gives a better idea of the lowend torque values of the various heads.  This information was already compiled and comes from the in-depth article that will be in a future issue of the Y-Block Magazine.  The scores are calculated by adding together the average torque and horsepower numbers for the given rpm ranges, multiplying by 1000, and dividing by the cubic inch (322).  The table format in this instance with the scores gives a better overview than a crowded and busy graph.

I’ll add that the ported aluminum heads really shine on those engines that are built to accommodate them.  My roadster engine with the aluminum heads is now peaking at 520 ft/lbs of torque and that was enough to rip the planetaries to shreds a week ago at the Houston NMRA/NMCA race.  Lots of runs on that particular transmission so it wasn’t a total surprise when that occurred.  It’s just the first time I’ve done that kind of carnage with a Y-Block in front of the transmission.

The numbers i find most interesting are

g-stock heads out perform g-gh heads even though the stock heads are down by 12 horsepower.

g-mt heads out perform g-yellow brick heads with the g-mt heads being down 24 horsepower and 13 torque.

113-lp and g-mt score about the same with the g-mt heads being down almost 30 horsepower.

This is a good test but for me i have more questions then answers.  Also a lot of whys, how comes and what ifs.  I wonder on a stock 292 with a stock cam and intake how these heads would perform.  Why did the coae heads with the larger valves not do well?

Ted this engine is a 312 right.  You said to score the engine divide by the cubic inch (322).  Is this engine a 312 with a 60 overbore or is 322 a misprint.

Thanks again for the numbers and all the hard work-Greg

The dyno engine in this test is a +060 over 312 with the cast pistons still 0.025” in the hole.  Basically a stock rebuild other than the amount of overbore and a Crower camshaft.  More details on the rest of this engine are available at the start of this thread.

As a general rule, porting the stock heads will sacrifice some of the lowend torque values for upper rpm performance.  That has to do with the air velocity at the lower rpms slowing as the intake ports are either made larger or the port walls themselves made smoother.  The intake manifold becomes a serious player once head porting is done.  If the intake manifold does not flow at least as much air as the modified heads, then the intake itself will hold back the potential of the head porting.  And then the actual valve job is a player.  Subtle changes in seat angles can help or kill cylinder head flow which was part of the problem with the larger valves in the COAE heads.

If an engine is not going to be romped on where it sees 5500 rpms or more, then it starts to become a moot point to change intakes, carbs, cams, head porting or any of those other modifications that helps that seat of the pants performance feel.  Fuel economy is another subject though.  For those Y engines that rarely see over 3500 rpms, then the stock 1957 292 or 312 engines give a good basic blueprint for the best combination between efficiency and performance.  For those of us that want more performance, then head work is at the top of the list.

                                              Frank

Thanks for all of the great info. I see your on your +.060 312 mule you said that the pistons were stock .025 in the hole.  Were you using the Best Gaskets?  I have a 312 that looks like it will be .040 over. and stock G heads.  If  I keep it .025 in the hole and Best Gaskets do you think I could squeak by with a static compression of around 9.0:1?  Thank you.

I just picked up my first y block (I'll try to attach a picture). Its a 292, ECK block with ECL-C heads.  I know you did not test ECL-C heads, but do you know if they compare closely with another head you did test?  Thanks for the help.

As the ECL-C heads have the smaller sized intake valves, the best comparison on the HP chart will be to compare those to the C1TE and C0AE heads which have similar sized valves.  Without actually looking at the port sizes in the ECL heads which I suspect are smaller, that’s the best guess I can throw out there.

Just had a set of ECL-C heads donated to the cause that look to be runable without much work.  As soon as the exhaust tests are wrapped up, there are still some other cylinder heads left to run on the dyno mule so I’ll include the ECL-C heads in that session.  A quick look at those heads show that they’ve already had some port work performed so I’ll take that into consideration when doing the final tally.

Would that be a seeing ear? Chuckle.

Paul.  That was my observation also.  The dead stock G’s are very stout for everyday cruising.  I’ll add that even in the stock G castings there are some variances and picking out a ‘choice’ pair of G’s will make them look better than the average pair.  The quality of the valve job is a big player in all this also.  When performing port work on any of the iron heads, there is typically a trade off in the low end numbers in order to make them show significant gains in the higher rpms.  For increasing the overall performance, the best bang for the buck comes from raising the compression ratio by milling the heads.

Wayne.  The ECL-C heads that were donated to the cause measure out at 0.990” at the pads on one of the heads and 0.995” on the other.  And both of these heads look to have only been cleanup milled in the recent past.  Unfortunately upon doing a closer examination of these heads, the exhaust seats have been too heavily ground on to be of use without new seats being installed.  Due to the cost of fixing the heads without any future use for them other than a dyno test, the ECL-C heads will not be included in the next round of cylinder head testing.  That’s too bad as these heads have what appears to be some nice port work performed on them.

As an FYI, I have a pair of ECL- B heads off of a 1955 182HP Special 272 that measure 0.975” on both heads at the pads.  This pair of heads looks to be an unmolested set that have never been off the engine until I tore it down.   If I read the 1955 service bulletin correctly, the ECL-B’s were unmilled (1.000” pads) on the 1955 292’s and milled to 0.960” for the 1955 HiPo 272’s.