Wrong Pistons?
#1
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Car: 1986 Monte Carlo SS
Engine: 1989 L98
Transmission: T-56
Axle/Gears: 8.5" 3.42:1 posi
Wrong Pistons?
The pistons listed below were installed in my L-98 shortblock. They were dead ringers for the pistons removed during teardown. However, I appears that I'm left with only 8.9:1 w/ 64cc heads or about 9.3:1 with the 60cc aluminum heads I'm using. With a .028" head gasket, 9.5:1 should be in reach. The machinist claims this piston is the stock replacement and would deliver 9.3:1 w/ 64cc heads.
350 Chevy 8.5:1 Pistons <products_view.php?id=4>
Dish hypereutectic pistons for 350 Chevy. 4-valve reliefs. 9.45:1@58cc. 8.9:1@64cc. Set of 8 Part #H423NP.
The piston below looks more like the one I'm looking for. About 9.9:1 w/ 60cc heads.
350 Chevy 10:1 Pistons coated <products_view.php?id=55>
Flat-top hypereutectic teflon coated pistons for 350 Chevy. 4-valve reliefs. 10:1@58cc. 9.5:1@64cc. Set of 8 Part #H345NP.
Here are the questions...
1) What is the CR of a iron-head L-98?
2) Which of these pistons more closely resembles stock L-98 units?
3) Is 4 or 5 points of compression going to make a noticable difference?
4) Do I need a new machinist?
Click below to find the list of pistons.
http://www.fastengineparts.com/products.php?cid=69
For background, I'm using ... Edelbrock Centerbolt Performer heads, Edelbrock Hi-Flow baseplate, partially siamesed SLP runners, 52mm TB, ZZ4 cam and Hooker 2050 headers.
Thanks in advance, and tips on the combination are welcome.
www.picturetrail.com/clutch_grabwell
350 Chevy 8.5:1 Pistons <products_view.php?id=4>
Dish hypereutectic pistons for 350 Chevy. 4-valve reliefs. 9.45:1@58cc. 8.9:1@64cc. Set of 8 Part #H423NP.
The piston below looks more like the one I'm looking for. About 9.9:1 w/ 60cc heads.
350 Chevy 10:1 Pistons coated <products_view.php?id=55>
Flat-top hypereutectic teflon coated pistons for 350 Chevy. 4-valve reliefs. 10:1@58cc. 9.5:1@64cc. Set of 8 Part #H345NP.
Here are the questions...
1) What is the CR of a iron-head L-98?
2) Which of these pistons more closely resembles stock L-98 units?
3) Is 4 or 5 points of compression going to make a noticable difference?
4) Do I need a new machinist?
Click below to find the list of pistons.
http://www.fastengineparts.com/products.php?cid=69
For background, I'm using ... Edelbrock Centerbolt Performer heads, Edelbrock Hi-Flow baseplate, partially siamesed SLP runners, 52mm TB, ZZ4 cam and Hooker 2050 headers.
Thanks in advance, and tips on the combination are welcome.
www.picturetrail.com/clutch_grabwell
#2
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Car: 1987 Camaro Z-28
Engine: 6.3L Victor EFI
Transmission: Tremec TKO 600
Axle/Gears: Moser 9"/4.11 Trac-Lok
9.8:1 is listed in the GM service manual for 90 Z-28. A half a point of compression won't make a lot of difference, certainly not enough to tear down an engine for. Your dynamic compression is what's important. That is determined by your valve timing + static CR. You can always install a .015" shim steel head gasket.
Last edited by Ricktpi; 10-24-2003 at 07:50 PM.
#3
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Car: 1986 Monte Carlo SS
Engine: 1989 L98
Transmission: T-56
Axle/Gears: 8.5" 3.42:1 posi
Just to be a little clearer, the shortblock is still on the motor stand. This is the time to make up my mind and change if it's worthwhile.
Thanks
CG
Thanks
CG
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Car: 82 Z28
Engine: Al LT1 headed LG4 305
Transmission: TH350
Axle/Gears: 3.73 posi with spacer
He propably used rebuilder pistons, which have a slightly smaller compression height from stock. This leaves the pistons lower in the bore, killing compression and ruining any quench you would want.
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