Alright, from what I searched here, the combustion chamber volume on my NPI's is 49.77cc and 9.30:1. The NHRA stock car blueprints also attest to this fact. Here is the link
I have yet to actually get some plexiglass and a buret and check myself but the heads are back at school so it'll have to wait. Someone on a board i read said they were 52cc, but i think that is too big, that those are the cobra/mark 8 heads. Now the probe industries webpage
lists this info for compression ratio
Large Dish (-18.1cc)
42.4cc 47.7cc 54.2cc
9.00 8.23 7.80
Compression Ratio computed with .010 deck and .038 head gasket at bore +.125"
(weights and compression ratios are approximate)
Now I am looking for some gaskets that will be able to handle the boost I am going to throw at them, possibly upwards of 16lbs at the track with 103-octane+, and around 10-12 psi on the street, whatever amount i can get to run with pump gas. This means low compression pistons. I am looking at the std bore pistons.
My engine builder recommended Cometic head gaskets, http://www.cometic.com
,for MLS head gaskets but when i checked the webpage their listing for compressed height is only.030 and stock is .035. I also heard that the new ford GT and the 03 cobra get a four layer gasket instead of the 3layer that all the other 4.6's use and i believe that something like this would be best for my boost goals seeing as those cars are also s'charged.
Now when I go on the compression ratio calculator
and type in their calculations, i get 8.6:1. I don't know How to calculate it apparently. ANd when i type on .030 for the cometic head gaskets, i get 8.74:1. This isn't looking good. I need to get this compression ratio down. I should be getting lower than 8.23:1 seeing as i have 2 more cc's than the 47.77cc values.
Someone tell me if i am looking at this wrong. I need to keep the c/r at or well below 8.5:1. I would like 8.0:1 so i can run more boost on pump gas. I know i can just put race gas but that isn't cost effective for me as a daily driver. I can do that at the track and turn up the volume.
Any thoughts on how i may be calculating the c/r wrong?
Ideas on getting it down besides bowl work?
No, I am not getting rid of the intake swirl. I believe that JL said it was integral for efficient combustion. I may be wrong. I will need a dyno tune afterwards anyways.
Any help would be appreciated. Thanks.