Hey Guys and Gals, I have been talking with some 455 Buick racers about there combinations compared to mine. In specific COMPRESSION!!! My Stage 2 engine has 12.7:1 compression and is pushing my 2800 lb. car into the 9.30s. I am thinking there is room for improvement since these GSE guys are running in the low 10s at 3800 lbs. After talking with a few of the racers in this class it seems that I am down on compression compared to them. They are all up around 13.5:1. Has anyone out there made a compression ONLY change and gained HP and ET? Has there ever been any STAGE 2 dyno work done on compression comparisons? Any thoughts are appreciated!!! Thanks
I was once told that there was a 4% improvement by going up 1 full point in compression. Sounds like you could be leaving 25-30HP on the table!:eek2:
John, Talk to Bruce H., he should be able to give you some info from his dyno results after uping compression.
Compression For what it's worth, Bob G. at Performance Concepts once told me that he has never seen much improvement at anything over about 13.5 - 1 in a Buick 455 based motor. I think anything above that requires alot of R&D in combustion chamber shape, piston shape, timing, spark plug placement, etc. before any real gains are noticed. It's not uncommon for NASCAR (before the rule change) and NHRA Pro Stock engines to run 15:1 or 16:1. Have fun.
For what it is worth adding compression in a Buick race engine IS worth some HP, there is a cut off point though ,and it is in the area of 14-15: 1. Too much compression beyond that will rob HP at that point .You really need to get into correct deck and head surfaces, O-Rings and specific gasket installation methods and a correct torquing procedure on the heads, to run really high compression ratios. The resistance from too much compression creates resistance to the piston returning to TDC.Therefore you start to lose power. Kind of like when unburnt gases are on the back side of the piston creating resistance keeping the piston from travelling down and that is why a pump used to remove unburnt gases from the crank case can reduce this and give you HP. Too much compression makes it difficult on the top side. You must be careful with the pump too, as if it pulls too hard to fast, your wrist pins will run dry and hot etc.. as it will pull needed lubrication from parts if it is not set up correctly, and create oiling system problems.Taking oil away from need areas. And sometimes creates too much oil in other areas like the top of the motor , if not set up and installed properly.
Compression A good starting point with the Stage 2 race engines is 13-1. Our 13.0-1 Stage 2 made around 790 at 6200 rpm, with a solid lifter cam, SE heads with no o rings, and a vaccuum pump. The motor will make more power at higher rpm, but we didnt care to take it that high, as we achieved our torque goal of over 700 early on and packed it up. The pump was worth about 18 hp all the way up with 8". We will go up to 12" to 14", and will free up more power. The Professor says 14" - 16" is about as high as you want to go with one of these. In my experience, 13 to 13.5-1 is best for power and durability.
Yeah I'll say great cam !!! Good numbers for that combo too Jim. Best I have seen to date in a Stage 2 headed motor is 820 HP 6300 and 720 Ft lbs and that was with a 14:1 CR and decent solid roller cam.
Thanks for the information everyone!!! Now... how about talking to me about these camshafts????? I am currently running on off the shelf T/A 508S. What is the trick with these camshafts that are making 790 to 800 hp??? My engine has a very healthy set of Stage 2 heads that flow well into the 330s with very good low number? If you guys dont want to post any numbers here but are willing to talk with me privately I would appreciate it. Email me at .... Staged70Lark@aol.com Thanks
questions from a new guy How are you guys getting to 13:1 compression, and what do you have to look out for when building a motor with this much compression? I was thinking about this, and it seems like you would have to deck the block and the heads to get that high, and then how much valve clearance do you have when it's all said and done? At what point do you have to o-ring the block? Steve
Compression does equal power. Dont overlook the piston dome design. It is also crucial to efficient combustion. The more squeeze you have on the charge and the more efficient the combustion the more power you make. Steve, with off the shelf J&E pistons you must mill the block and heads to accomplish over 13:1 compression.. The Fel-Pro gaskets are good for about 12:1 and after that you are limited to either the performance gasket available from T/A or copper head gaskets. The J&E pistons have such huge valve reliefs that they normally have enough piston to valve clearance for most applications.
Jeff, 12:1 compression is paltry if you are looking for optimum performance. You are not tapping in to the potential that your engine combination could have.
