Hey Fellas, I was wondering if anyone could help me out with around about CP ratio figure on my motor. The Specs are as follows....... Speed Pro Forged slugs (the supposed 10 to 1 part #) They are .035 in the hole. The Head gaskets are .055 (crushed... I measured the pair I wasted last week). 70 heads. I'm not sure of the CC on them. I've unshrouded the valves quite a bit and opened them up some. This is where the guess work comes in. If I could get a figure on the stock CC'd head that woudl be great. I'm sure all and all, I removed about .5 or better on the combustion chamber. Thanks fellas!
Any Idea what the CC is for sure on the speed pro forged pistons? Figuring at 16cc gave me 9.6 to 1 That's with using 71cc as the combustion chamber size as well. Doesn't that seem a bit on the high side with the piston .035 in the hole and a .055 head gasket?
Aren't TRW's, and SpeedPro's the same thing? o No: I believe I was told that a while back. The information I found on heads said that 72's and 73's were 71CC....... I was basing mine off that since I've removed quite a bit of metal. It would be nice if they were 76cc. :grin: At this point, I'm not sure.
I found THE page for heads and their cc's. Looks I was way off and they should be 69 cc's. http://www.atlantabuick.com/CastingNumbers.htm Pistons are 24 cc's. If you remove the button and polish, that'll add another .5 cc, or a total of 24.5 cc's. Get's rid of a potential hotspot. Good luck. Phil
Hey Thanks again Phil, I didn't remove the button since it was balanced with them . If you go to this link and scroll down you can see a picture of my heads. Would you say I've removed at least 2cc's? Look at the back side of the chamber where I shaved that back all down at an angle so it slopes down even with valve seat. I also shaved bound the sides of the valves as much as could. http://www.v8buick.com/showthread.php?s=&threadid=26143&pagenumber=2
So.... figuring my pistons .035 in the hole, with a .055 thick gasket and .030 over 24cc dished pistons and 71cc chamber, it's looking like about 9.1 to 1 CP. I would have to say that's a lot more boost friendly even at the factory 70 head rating of 69cc's it's about 9.2 to 1. I'm more than sure I've removed more than 2cc's from each chamber but I think 2 is a good safe guess. What do some of you head guru's think by looking at picture of the chamber on the link above CC wise? Surley you have a better guess than me.
Rich, I don't mean to be a wiener, but unless YOUR comb. chambers are ACTUALLY cc'd, you are just guessing. I DO NOT believe the factory specs, ESPECIALLY after all these years of mods that have been done. IE: milling, valves sunk from valve jobS, chamber polishing, valve unshrouding, + factory casting variances = need to get a REAL measurement! If you can find a 100cc measuring buret somewhere and a piece of flat plexiglass, doesn't take long to measure.. Maybe your local machineshop?? Sorry Rich, I know you JUST torqued the heads on. just my .02 cents.
It's all good..... I realize this, I'm just after a fairly close educated "guess" from someone that's seen a lot of these CC'd and has a good "tape measure eye" :Brow: The heads are installed now, so getting an acurate measure is out of the question. In a worse case sanario, they would be 69cc (which they are not for sure.... even with being a little shaved. That would still put me at 9.2 which isn't to bad for boost
Rich, From looking at the pics of your combustion chambers, I would say they are 66 to 68 cc. I CC matched two sets of iron heads last week, and a set of alumiums and to run our zero deck combo at 10-1, it requires a 72 cc chamber. The alumiums actually go to 67-70 cc depending on the piston used, since we go around 10.25- 10.5 with those motors. That chamber is visually a lot bigger than yours. I have to remove the machining locator pad, and open and contour the walls up completely to the chamber edge. Accurate figures, beyond the chamber size, go like this. L2353 TRW pistons, with nub still in the middle, and no valve reliefs, are 23.5 CC. Using a 66 cc chamber, and your other specs, you could be as high as 9.5-1 compression. Good luck with the build. JW
Thanks Jim, That's exactly what I was hoping for. Even if it is on the smaller side like your stating (and I do trust your tape measure eye, you've deffinatly seen more of these CC'd than me) I've still dropped the CP with the thick gasket, and removing quite abit of materal at least .5 of a point. That should at least help with the boost some :grin: Thanks again for your input.
How new are your Speed-Pro slugs? If they are the old "true" 10:1's (2362P), then they are not the same as the TRW L2353 being sold today, as far as I know. The 2362P supposedly had a dish volume equal to that of the factory 10:1 piston (16cc?).
Just noticed from your pics you can barely make out numbers on one of the piston tops. Is is 353 or 362?
Hey Scott, I couldn't tell you for sure. I've already put the heads on and can't look. I took a peek at my pictures and couldn't make any numbers out at all. The only thing I have to go by is the TA part number from 5 years ago when they were ordered "1621A".
Upon zooming in and out on the original photo, it looks like the last number is a 3. That being the case, I would have to say it's the L2353. Rich
Well....... since the heads came off again, I CC'd them (just got finnished). Man what tedious work. I'd have to say worse than porting The Chambers ended up being 71 to 72 cc's. I'd have to say not to bad at all for an amature "eyeball" job. They are all really pretty close to each other. Figuring them at 71cc's, the gasket at .056 the piston dish at -23.5cc's and the pistons in the hole .035 it comes out to being 9.12 to 1. Pretty Blower freindly endeed.
