Bore 4.030

Stroke 3.750

Deck height 0 with a flattop

CC relief 8

Gasket compressed .039

Gasket bore 4.125

Head CC 55

I get 12 to 1 here

WHere does my IVC event need to be to get 8.8 to 1 DCR? 65 or so degrees?



Thanks guys

David

 

Here is what I came up with using Pat Kelly's calculator. With a 5.7 rod you would need a IVC of 74.5 degrees ABDC for a 8.8DCR. With a 6.0 rod you would need a IVC of 74 degress ABDC. Hope this is what you are looking for. By the way using Pats calculator I came up with 11.95 SCR.

 

Woops 6 inch rod, sorry.


Is the IVC event of 74 degrees the actual number+15 degress?



Thanks
David

 

The actual number. Comp Cams uses the number at .006" lift as an example. Wait and see if you get other responses for back up.

 

David

I got 11.96 the way I do it

If you're talking about the Int, valve closing Number to achieve a running compression number. That would depend on the running duration, then I've found that if you close it too late - as in retarded back from its actual C/L, there is a point where the engine doesn't like it at all.

What I found out is that if you want to run pump gas it is better to use a 9 to 1 static ratio and create a custom cam/timing events that generate the cylinder pressure that you want.

Just my .02

Denny Schmidt

 

Denny, I have found it makes more power if you run more static and bleed some off with a bigger cam, 9 to 1 Compression??????????? these engines came from the factory with 10.0 to 1!!!


David

 

David

I know thats what they say they are. We have built about 12 of these Corvette Tuned-Port engines. The first one we did we made it 10 to 1 and the guy was back complaining about it making knocking noises.

We called the guy that makes the chips for us (Dave Emanual) and he saids to keep the car in the shop and send him the chip. He messed around with it several times and it got way better but never to our liking. From then on we always put the engines on 9 to 1.
We found this to be true for the Fords as well!!

Anyway thats my story and I'm sticking to it.

Denny

 

TPI is not reverse flow cooled, And a TPI is hard to make one run, What was his DCR? A/F ratio?


David

 

I don't know Dave Emmanual did all that for us.

Then you have to explain the Abbreviations so I can understand what you are saying.

Denny

 

TPI = Tuned Port Injection
IVC = Intake Valve Close
DCR= Dynamic Compression Ratio
A/F ratio = Air / Fuel Ratio

 

What's the difference between the TPI sequential and the LT1?
If you're talking about the reverse cooling then that's the reason you can get by with more C/R because you have to heat the water enough to get the same power level. Aluminum transfers the so fast that the BTU's of energy released into the combustion area are being used to heat the coolent rather than making power to push the piston down.

Here's an experiment one of you needs to try - take the heads to a powder coating place that can do high temp header coatings. Get them to coat the water-jackets of the aluminum heads - then put them back on your high C/R engine and see if you can keep it from pinging!!!

Here's somethin I found on the net - Buddy Rawls "Cam Truth" www.wighat.com/fcr3/

More info here too: ENDYN www.theoldone.com

Denny

 

Less heat in the head, less opportunity for detonation, WHich means more potential timing in the event and more power....The same way an Iron head motor and aluminum head motor work, ALum head can have up to one FULL point more compression over an iron head...more power...the LT1 takes it one step further in cooling the heads first from the top down...less hot spots, more even burn, more power.

When I teethed on 5.0 mustangs...the VERY first thing you did were put a 160* thermostat in and put the timing on 13* or 14/15* if it was winter time and pull the air silencer...those two mods alone were worth 3 tenths, Cooler engine, more timing, more power.


David

 

Denny if you do not know this you need to do more reading here and less posting.


So you are telling me that we get less power with the cooler coolant temps?

Relative to this whole compression and heat thing, can you tell me the EGT temps of your last high compression and low compression motor?

Have you ever done a head swap from cast iron to aluminum SCIENTIFICALLY and found a large drop in power due to the aluminum???? I know there is a magazine test done in the last year that showed that aluminum or cast iron have very little if not ZERO difference in power.

Hell if that WAS the case then the AFR "castings" that look a hell of a lot more like a block of billet would make more power due to all that casting holding the heat in there, but guess what THEY DON'T


Why would anyone want to reduce the amount of compression they can handle in a engine?

Why would you reduce the capabilities of the cooling system to do it's job?

Oh, and have you EVER powdercoated something before? There is no way in hell you could get even 20% of the water passeges covered with conventional powdercoating. Only way I can think of it is to pour straight powder into the passeges, and hope that it sticks to everything it touches. With the lack of a charge introduced into the powder it's not going to stick.

Bret

 

I deserved that

Yes we did exactly that when Brodix first introduced their heads - a copy of our ported turbo head from Reed Cams.

When everything is equal the alum head lose's power, it takes 2 points of C/R to get it back. We had the same difficultys when MOPAR made the swithc to aluminum heads for the Hemi's. Otherwise I wouldn't be so adament about the C/R issue.

Don't get me completely wrong I'm not saying that it can't be done - There is a company that specializes in doing the impossible with C/R - ENDYN - www.theoldone.com check them out. Larry Widmar says he can make a gasoline engine run with over 17 to 1 and has seen 23 to 1. I know that the 17 to 1 is truth because I saw the dyno results in some of the Ford Cup Cars. Now if he can get the 17 to 1 with racing gas what can he do with 87 octane.

Denny

 

So why does a GMPP 18° casting (364) make more power compared to a Brodix 18casting? They do a better job of cooling.

Denny, did you not read before I KNOW WHO WIDMER IS and HIS WORK, Smart guy. He has even done research with mulit material cylinder heads to use the material properties to their full advantage.

The problem that I have with the cast iron vs. aluminum theory that you need 2 points more compression to make the same power is about the combination. If I get 2 points more compression I can do a ton more things with the rest of the parts AND will make more power & torque (average). Maybe you saw this once with the old Hemi's but I've never seen an example today with the parts we use of going from a aluminum head to a iron head and reducing the compression 2 points and making the SAME POWER. Just doesn't happen.

Hell CHI makes Cleveland heads in Cast Iron how come one of the many Clevor combinations didn't do that in the EMC this year if it works so well? I mean they were mandated to 10.5:1 compression, and the ran 13:1 or more on pump gas in that contest before.

http://www.chiheads.com/cleveland_cast_iron.php

Bret