Combustion chamber size
 

I have a cylinder head dilemma going on here. I really like the trick flow TW series but I don't like the idea of having a 61cc combustion chamber. The only thing that I have found with a 58cc chamber are the GT-40x heads. But of course they $1250 versus the 1100 for the TF's. With the 3cc difference how much difference in Compression ratio are we talking? A stock bottom end. Also what would the power difference be? I have no plans whatsoever for a blower down the road. So I do want relatively high compression. Like 10:1. I do however plan on getting at least a dry 75 shot of N20. What do you guys suggest? I just can't make up my mind. I am using the trick flow street heat intake with the trick flow #1 cam.

Ask Mach1, he seems to know everything about everything.

Running 61cc chambers versus 58cc chambers, all other things being equal, will result in approx. .334 decrease in compression.

If you're not planning on adding any boost, I'd go for a goal of 10.5:1 compression. But that's just me.

Take care,
-Chris

Well, I was thinking that 10:1 would be a little better than 10.5:1 since I am planning on using nitrous. But if you think 10.5 is okay with nitrous, then I will consider it. What would the compression ratio be using 58cc heads? Thanks.

Good morning. When you add the typical space for the head gasket and the 4 valve reliefs in the piston top, and the the space above the top ring, 58cc heads on a stock bottom end will give you a 9.44:1 compression ratio.

:)

Take care,
-Chris

you could always mill the tw heads to raise compression or wait
and select pistons to raise it for your combo.

I thought about milling the trick flows, but I don't know the formula for calculating how much to take off in order to get the right combustion chamber size. I am a machinist, but I don't do auto machine work. Where I work, we do shut down and rebuild type work for other places. Anyhow, Chris could you be kind enough to share with me the formula you used to figure that compression ratio? Also, I didn't understand the 4 valve reliefs in each piston. There are only two valves per cylinder. Wouldn't the extra notches make me lose compression?

4 notches means the same piston can be used in any cylinder.

The formula is as follows:

Cylinder volume for a 302 is 617.78cc.
The space above the top ring, and the space for the 4 notches, is 5.5cc.
The average head gasket has a crushed thickness of .047", which equals 9.68cc.
Your combustion chamber size is 58cc.
Add them all together and you have total cylinder volume:

617.78 + 5.5 + 9.68 + 58 = 690.97cc

Now, you divide that number by the total volume above the piston, or

58 + 5.5 + 9.68 = 73.19cc

690.97cc / 73.19cc = 9.4407705:1 Compression Ratio.

:)

Take care,
-Chris

Thanks Chris, you are the man! After I posted that question about the 4 notches, I got to thinking about it. And I figured that 4 notches meant you could use it in any cylinder. That was the only logical reason I could think of myself. BTW, do you have a formula to figure on how much it would take to mill off the trick flows to get a 58cc chamber? I know that all heads are different in chamber shape. So of course this would only work for the trick flows. Thanks again.

A straight cut of .020" would reduce the chamber to approx 57.92cc.

Take care,
-Chris

D*mn Chris! It ain't the first time you've heard this and it certainly ain't the last. But we are very lucky to have you on our board. You da man!

I thought it would take a lot more than .02 to reduce the chamber size down to 58cc. I was thinkin at least .05. Now, if I cut .02 off the heads then I will have to have larger notches in the pistons. Right? I am pretty sure. But, Trick Flow says that the pistons don't need notching the way they have the valves set up. So, my question is, can I buy regular notched pistons from summit? Like I said in my first post of this thread, I am using the trick flow #1 cam. JIC, it is 275/279 with 1.6 rockers the lift is .499/.510.

Now you're crossing into territory I don't feel comfortable enough to advise you in. Try calling Trick Flow.

Take care,
-Chris

I am pretty sure that I am going to go with the windsor jr. heads because they have the 58cc chamber and 1.94/1.60 valves. They will accept a cam with a lift up to .560" Even though they are cast iron. Weight is not my concern, but weight transfer is. What do you think of what combo I have come up with.

Windsor jr cast iron heads mentioned above.
Trick Flow #1 cam.
1.6 rollers.
Trick Flow street heat.

I think that is the cam I want with those heads. The thing I can't get straight is the intake. I am thinkin that maybe the cobra might be a better intake. What I am looking for is a street beast with a lot of lower end torque. I am a stop light to stop light kinda guy with occasional visits to the track. Also, I am probably going to add a shot of nitrous. Don't know what size, but it will be a dry kit since I am a nitrous newbie.

Ideas and suggestions are appreciated.

I like the GT40, personally.

Take care,
-Chris

Me too, GT-40 heads perform so well I don't care what you do to them.

How ya been Chris?, been away awhile.

How's the dirt? still flyin' I'm sure, hey Chris, what effect does temperature have on dirt trackin'? do you have to deal with tire issues and suspension set-up with extreme temps or no?

My guess is hot weather would give you more traction because the track could be "bit" harder by your tires. Right or wrong?

Cold would make the track "harder?" thus slippery?

Later EECbreath!:D

I think he was talking about the intake manifold.

Anyway, why the GT-40 Chris? I already have the street heat. But if I was buying a new one, the gt-40 is $200 more.

I think the street heat will give me the most low and mid range power, but you know more than me. Which gaskets should I use? The ones to fit the intake or the heads. I assume which ever one requires less cutting. Thanks.

Hotter air temp usually means the track will dry out faster, and a dry track creates a condition known as dry slick. The best traction comes from a damp, tacky track. Put it this way; if the track tries to suck the shoes off your feet when you walk across it, it's perfect.

:)

Take care,
-Chris

Ieatcamaros-
I prefer the Gt40 for personal reasons. I try not to make specific parts recommedations or horsepower estimates. There are too many variables. You'll be fine with what you have.

~C

I understand that fully. Thanks for your input.

That's a good way to be, Chris. Just an easy way to start arguments with some people, even if the GT40s WOULD be a better choice :).

What is a recommended compression ratio to run if you plan on adding forced induction later? I'm trying to read and learn about heads so my decison won't be made with personal opinions from others, but I'm still pretty much in the dark.

82gt, I think this board has endured enough of your personal vendatta. Please stop already :)

Interesting. 82 GT sent me a private message apoligising for his remarks in the thread about selling a car, stateing that he tends to lose his head and that he was wrong, and then he turns around and pulls some crap like this?

Whats the matter with you anyway?

I guess he is another one to never be trusted. Is there any real, honest people left in America? Seriously....Im so tired of the "stab you in the back losers" out there, guess 82 GT is no different than the majority of people out there anymore. Maybe I just expect too much from people?

It really depends on how much boost you're planning on adding, Whether or not you'll have an intercooler, and what octane fuel you will have readily available. In general, I recommend 8.5:1 pistons as a good place to start.

:)

Take care,
Chris

If you took the time to pay attention to the date I made that remark, you will notice it was BEFORE I sent you the email.
I'm not going to fight with you on the boards anymore. PM me if you have more to say.
I apologize to the rest of you guys for the interuption with this thread.

Even outside of the forums, I've learned that YES! It is very easy to expect too much of people :mad:

I merely expect them to look around themselves when they drive, not let doors slam in my face, and to not walk out in the crosswalk when it says DON'T WALK YOU IDIOT!!! :D And alas...they cannot even accomplish this! Can you imagine if I expected them to be good people too??? Geez! ;)


Chris, thanks for the help, I don't even have my "wish list" planned out enough to be sure exactly WHAT my plans are as of yet. I suppose if I plan on running FI for sure, I should pick my blower before my heads?


Thanks, Belle :)

Ultimately, you will plan out everything before you make a single purchase. Unfortunately, 90% of people, myself included, aren't very good at this. ;)

You know the routine: Decide what you want the end results to be, and then figure out the best way to get there. I know that sounds over-simplified, but it really is the best way to go at it. Don't make any decisions until you have weighed out all the variables. Important factors to be considered are: power desired, drivability, cost, both for the build and for the drivability after the build, idle quality, efficiency, durability, and how service friendly you want it to be.


:cool:

Take care,
~Chris

Yeah, I think you hit the nail on the head. Especially if you live in NJ/NY area.

If you're looking for torque, dyno's have proven the GT-40 or Cobra will make the most low-end umph. It's hard to justify buying the GT-40 over the Cobra because of the price difference. The GT-40 and Cobra flow nearly the exact same #s. They both use the same lower intake design. However, neither of these intakes perform as well for upper-rpm horsepower as the designs from Trick Flow, Edlebrock or Holley.