Hey all you fellow lower-end rebuilt engine owners,

My question is what dome size did you use on your pistons and what compression ratio did you achieve? I'm looking to use a bigger blower and significant N20, so I'm wondering what size

dome I should be using.

Any suggestions are much appreciated....

Douglas

 

My .20 over Manley pistons have 8.4-1 compression or 8.4.5-1 compression...can't remember which and i am too lazy to look

 

Yeah, that compression sounds right, but there are at least 0cc, -9cc, -10, -11, -11.5cc, -15cc -17cc, -19cc, -25cc, -28cc dome pistons out there. Just look at:

http://www.modularperformance.com/

under pistons and you'll see what I mean.

Thanks

 

The owner of Modular performance had a voice in my engine build as he had some dealings with my engine builder at the same time mine was being built.
Mine is built for high boost aftermarket blowers and not nitrous,so my dish size is probably n/a for your intended future use.

Sal,at PSP would probably have an answer for you on dish size.

 

Um.......they are dished............not domed.

17mm dish w/pi heads is 8.90 to 1

 

..Dished... Good point, thanks Tim, I did put minus signs in front though!!!

 

I'm sweating it, as my builder says the 17cc DISH pistons I have will result in closer to 10:1, and Sal isn't available right now.

 

So Tim, what ratio do my 11cc domed ...opps,i mean dished pistons come out to with pi heads?

 

Have you changed the deck height, milled the heads, and are you using stock head gaskets? How many cc is the head? There's more to compression than just the pistons. By the way what pistons did you buy? You need a ~39cc dish I believe. We need more info .

 

[QUOTE]Originally posted by rscoleman
Have you changed the deck height, milled the heads, and are you using stock head gaskets? How many cc is the head? There's more to compression than just the pistons. By the way what pistons did you buy? You need a ~39cc dish I believe. We need more info . [/QUO

 

With the 17cc dish, that CR on the 5.4 is 8.5:1. This same piston on the 4.6 nets 10:1. The reason it's lower on the 5.4 is because the piston is .120 in the hole. Hope this helps .

 

Makes my day Sal!!!!!

 

 

I'll take Sal's word for it. Modular performance told me I needed a 39cc dish, which didn't sound accurate. Listen to Sal.

 

Use this:

http://www.modularperformance.com/compcalc.asp

Plug in 3.572 Bore
4.16 Stroke
44cc head
.040 Head Gasket
.120 Deck height
-17cc Dish

Result--8.83:to1.

Close enough for me......

Thanks Again Sal....