TRW flat top pistons...

Hozer 88GTConv · 03-25-2002, 07:10 PM

Anybody got any idea what compression TRW flat tops will make in a 306? Got a chance to get some in before a dyno run Wednesday.

Hozer 88GTConv · 03-25-2002, 07:26 PM

thinkin about 10 to 1 ish with TFS out of the box heads, 1.7 RR's and a B303. Anybody? Bueller?

Unit 5302 · 03-25-2002, 07:31 PM

Yep, they'll make it 9.02:1. By the way, I'm dead serious.

Didn't read your signature. TFS heads have a 61cc combustion chamber, that will make your CR 9.43:1.

Unit 5302 · 03-25-2002, 07:46 PM

Oh, here's why.

Stock E7TE. 64cc
TRW Flat top piston with valve relief. Valve relief = 5.5cc.
Total combustion chamber size 64+5.5 = 69.5cc

4.030"x3.00" = 306ci.

Cylinder volume = (pi)(r^2)(h)

pi = 3.14159265359
r = 4.030/2 = 2.015 x 2.54 = 5.1181cm
h = 3.00" x 2.54 = 7.62cm

(3.14159265359)(5.1181^2)(7.62) = 627.08cc

Now take cylinder volume divided by total combustion chamber size.

627.08cc / 69.5cc = 9.02. That's your CR.

If you really want to get technical, stock CR would be 8.89:1

Hozer 88GTConv · 03-25-2002, 07:56 PM

Sweet...

Hozer 88GTConv · 03-25-2002, 08:39 PM

I'm not sure these have the valve reliefs, trying to find a site with the info. I know I would be right on the limit with a b303 cam as far as lift/duration. But I am looking specifically for compression numbers without valve reliefs.
If that is the case, using your reported numbers and formulas which are accurate, compression would be 10.28 theoretically.
Thanks for a interesting reply.

Hozer 88GTConv · 03-25-2002, 09:03 PM

According to Summit, a deck height of 8.2" with a TRW L2488F piston ( yes it has valve reliefs) would yield a compression ratio of 9.98 to 1 with a 61cc TFS cylinder head combustion chamber.
All of this discussion is mainly for blower application consideration and I can have 'em in before my dyno run on Wednesday.

Ponycar_302 · 03-25-2002, 10:06 PM

Unit, thanks for the formula! I was wondering what compression ratio I had. This is my exact set up, except I use Windsor Junior heads (58 cc). Thanks again.

Unit 5302 · 03-29-2002, 11:08 PM

Hehe, I could have told you that you already had valve reliefs. It would be like running E7's with a B303 and 1.7's on an 86GT with stock pistons. Mmmmm, valves crunchy.

Sounds like they are a little different than stock replacements.

Ponycar_302, no problem.

Hozer 88GTConv · 03-29-2002, 11:14 PM

I apologize for not making it clear Unit about the valve reliefs. I knew there had to be some kind of relief, just not sure what cc effect it had. It is surprisingly difficult to find that kind of detailed information. It didn't even come with the pistons.
Still think my biggest problem is my TFI.
Great exchange of info, I think the cr formula is great. Should be on the tech page.

Unit 5302 · 03-30-2002, 09:35 PM

No need to apologize, just some tech advice flying back and forth across the computer.

03-25-2002, 07:10 PM	#1
Hozer 88GTConv Registered Member Join Date: Feb 2002 Location: Jacksonville, FL Posts: 706	TRW flat top pistons... Anybody got any idea what compression TRW flat tops will make in a 306? Got a chance to get some in before a dyno run Wednesday. __________________ 1988 GT Convertible 331 10:1 TW heads, GT-40 intake, MSD, TRW flattops, B Cam w/ 1.7's, MAC exhaust, 24's, 70 TB, 76 MAF, 3.73's, Pro 5.0, Koni's, Anderson PMS, Wideband 02, yatta, yatta... One week with new motor, two speeding tickets...joy

03-25-2002, 07:26 PM	#2
Hozer 88GTConv Registered Member Join Date: Feb 2002 Location: Jacksonville, FL Posts: 706	guessin' thinkin about 10 to 1 ish with TFS out of the box heads, 1.7 RR's and a B303. Anybody? Bueller? __________________ 1988 GT Convertible 331 10:1 TW heads, GT-40 intake, MSD, TRW flattops, B Cam w/ 1.7's, MAC exhaust, 24's, 70 TB, 76 MAF, 3.73's, Pro 5.0, Koni's, Anderson PMS, Wideband 02, yatta, yatta... One week with new motor, two speeding tickets...joy

03-25-2002, 07:31 PM	#3
Unit 5302 Registered Member Join Date: May 1999 Posts: 5,246	Yep, they'll make it 9.02:1. By the way, I'm dead serious. Didn't read your signature. TFS heads have a 61cc combustion chamber, that will make your CR 9.43:1. Last edited by Unit 5302; 03-25-2002 at 07:48 PM..

03-25-2002, 07:56 PM	#5
Hozer 88GTConv Registered Member Join Date: Feb 2002 Location: Jacksonville, FL Posts: 706	One word... Sweet... __________________ 1988 GT Convertible 331 10:1 TW heads, GT-40 intake, MSD, TRW flattops, B Cam w/ 1.7's, MAC exhaust, 24's, 70 TB, 76 MAF, 3.73's, Pro 5.0, Koni's, Anderson PMS, Wideband 02, yatta, yatta... One week with new motor, two speeding tickets...joy

03-25-2002, 08:39 PM	#6
Hozer 88GTConv Registered Member Join Date: Feb 2002 Location: Jacksonville, FL Posts: 706	P/N L2488F I'm not sure these have the valve reliefs, trying to find a site with the info. I know I would be right on the limit with a b303 cam as far as lift/duration. But I am looking specifically for compression numbers without valve reliefs. If that is the case, using your reported numbers and formulas which are accurate, compression would be 10.28 theoretically. Thanks for a interesting reply. __________________ 1988 GT Convertible 331 10:1 TW heads, GT-40 intake, MSD, TRW flattops, B Cam w/ 1.7's, MAC exhaust, 24's, 70 TB, 76 MAF, 3.73's, Pro 5.0, Koni's, Anderson PMS, Wideband 02, yatta, yatta... One week with new motor, two speeding tickets...joy

03-25-2002, 07:46 PM	#4
Unit 5302 Registered Member Join Date: May 1999 Posts: 5,246	Oh, here's why. Stock E7TE. 64cc TRW Flat top piston with valve relief. Valve relief = 5.5cc. Total combustion chamber size 64+5.5 = 69.5cc 4.030"x3.00" = 306ci. Cylinder volume = (pi)(r^2)(h) pi = 3.14159265359 r = 4.030/2 = 2.015 x 2.54 = 5.1181cm h = 3.00" x 2.54 = 7.62cm (3.14159265359)(5.1181^2)(7.62) = 627.08cc Now take cylinder volume divided by total combustion chamber size. 627.08cc / 69.5cc = 9.02. That's your CR. If you really want to get technical, stock CR would be 8.89:1

03-25-2002, 09:03 PM	#7
Hozer 88GTConv Registered Member Join Date: Feb 2002 Location: Jacksonville, FL Posts: 706	Deck height? According to Summit, a deck height of 8.2" with a TRW L2488F piston ( yes it has valve reliefs) would yield a compression ratio of 9.98 to 1 with a 61cc TFS cylinder head combustion chamber. All of this discussion is mainly for blower application consideration and I can have 'em in before my dyno run on Wednesday. __________________ 1988 GT Convertible 331 10:1 TW heads, GT-40 intake, MSD, TRW flattops, B Cam w/ 1.7's, MAC exhaust, 24's, 70 TB, 76 MAF, 3.73's, Pro 5.0, Koni's, Anderson PMS, Wideband 02, yatta, yatta... One week with new motor, two speeding tickets...joy

03-25-2002, 10:06 PM	#8
Ponycar_302 Registered Member Join Date: Feb 2002 Location: Pennsylvania Posts: 120	Unit, thanks for the formula! I was wondering what compression ratio I had. This is my exact set up, except I use Windsor Junior heads (58 cc). Thanks again. __________________ I'm sofa king we tall did.

03-29-2002, 11:08 PM	#9
Unit 5302 Registered Member Join Date: May 1999 Posts: 5,246	Hehe, I could have told you that you already had valve reliefs. It would be like running E7's with a B303 and 1.7's on an 86GT with stock pistons. Mmmmm, valves crunchy. Sounds like they are a little different than stock replacements. Ponycar_302, no problem.

03-29-2002, 11:14 PM	#10
Hozer 88GTConv Registered Member Join Date: Feb 2002 Location: Jacksonville, FL Posts: 706	Apologize... I apologize for not making it clear Unit about the valve reliefs. I knew there had to be some kind of relief, just not sure what cc effect it had. It is surprisingly difficult to find that kind of detailed information. It didn't even come with the pistons. Still think my biggest problem is my TFI. Great exchange of info, I think the cr formula is great. Should be on the tech page. __________________ 1988 GT Convertible 331 10:1 TW heads, GT-40 intake, MSD, TRW flattops, B Cam w/ 1.7's, MAC exhaust, 24's, 70 TB, 76 MAF, 3.73's, Pro 5.0, Koni's, Anderson PMS, Wideband 02, yatta, yatta... One week with new motor, two speeding tickets...joy

03-30-2002, 09:35 PM	#11
Unit 5302 Registered Member Join Date: May 1999 Posts: 5,246	No need to apologize, just some tech advice flying back and forth across the computer.

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