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are they considered dish or dome
anyone know volume in cc's
I'm trying to figure compression and I need that info. I couldn't find in searching the web
Thanks in advance
Mike
dish with four valve reliefs should be 9.5 to 1 compression with the stock 58cc aluminum heads.I had a procharger on my 1989 L98 so I pretty much know all the specs. GMJR
dish with four valve reliefs should be 9.5 to 1 compression with the stock 58cc aluminum heads.I had a procharger on my 1989 L98 so I pretty much know all the specs. GMJR
Sorry, I should have been more clear, was looking for dome volume of piston. I found it at the web site I posted. Thanks for responding to my question
You might be interested in seeing the pistons in my '84 CFI engine:
(No dish)
That NHRA spec sheet lists my C.R. as 10.30, but my '84 factory spec book says 9.0. I don't trust the NHRA spec sheet! You may have noticed I'm 0.040 over.
Last edited by Hot Rod Roy; 12-07-2016 at 08:57 PM.
Yes you are correct as 1984 had forged pistons and your 1989 L98 had impacted cast pistons. Whether that's a hypereutectic or regular cast piston I can't say. But your pistons weighted 1.3 ounces which should help your balance calcs. Dish volume was not listed. But the most accurate method is to measure the volume with liquid preferably with the piston in the block.
GM parts direct says your piston part number was #10159424 but searching for the dish volume was unsuccessful. You may have better luck with more time to search.
Hope this can help milm0.
Last edited by cardo0; 12-09-2016 at 10:18 PM.
Reason: Stupid autocorrect!
Yes you are correct as 1984 had forged pistons and your 1989 L98 had impacted cast pistons. Whether that's a hypereutectic or regular cast piston I can't say. But your pistons weighted 1.3 ounces which should help your balance calcs. Dish volume was not listed. But the most accurate method is to measure the volume with liquid preferably with the piston in the block.
GM parts direct says your piston part number was #10159424 but searching for the dish volume was unsuccessful. You may have better luck with more time to search.
Hope this can help milm0.
i found site that listed the piston volume at 8.87 cc for l98 240 hp
with .051 head gasket I used, that puts CR at 9.6, but I had heads milled flat so I thinking that .041 is a closer number, putting CR at about 9.9
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Originally Posted by mlm0
i found site that listed the piston volume at 8.87 cc for l98 240 hp
with .051 head gasket I used, that puts CR at 9.6, but I had heads milled flat so I thinking that .041 is a closer number, putting CR at about 9.9
thanks
I agree it's tough to find the definitive answer....
12cc is the most common number I've seen listed over time in forums. OTOH, there's conflicting threads on the use of flat/dished pistons. When flat is cited 4cc is the number. When dished is cited, 12cc is the number.
Without looking AND IIRC, compression was bumped in the 1990-1991 L98s. Maybe a handful of late production 89's got the flat tops?
That said, 12cc is the number I think is most likely for the 89 dish. Not saying I'm right...just that it's been quoted a lot.
I also believe stock compression is either 9.3 or 9.5 -- depending on the source you read.
I agree it's tough to find the definitive answer....
12cc is the most common number I've seen listed over time in forums. OTOH, there's conflicting threads on the use of flat/dished pistons. When flat is cited 4cc is the number. When dished is cited, 12cc is the number.
Without looking AND IIRC, compression was bumped in the 1990-1991 L98s. Maybe a handful of late production 89's got the flat tops?
That said, 12cc is the number I think is most likely for the 89 dish. Not saying I'm right...just that it's been quoted a lot.
I also believe stock compression is either 9.3 or 9.5 -- depending on the source you read.
12-07-2016, 02:01 PM
L98 pistons
