DustinP Posted March 5, 2009 Report Posted March 5, 2009 I'm running 21cc domes, FAST Racing dune/play port, bored .080 over, +4 timing in Kansas City around 900 ft. I tested my compression and Im at 175 psi. I heard 165 was cut off for race gas. Has anyone else had similar setup and what was their compression? Jeff thought this was high for my set up but didnt know why. He said to throw some octane booster in and I would be fine. Just wanted to get some other opinions. Has anyone else ran octane booster and at what compression. I am thinking of putting in 22cc domes so I can just run 91 octane. Any Ideas? Quote
AWR Posted March 5, 2009 Report Posted March 5, 2009 I'm running 21cc domes, FAST Racing dune/play port, bored .080 over, +4 timing in Kansas City around 900 ft. I tested my compression and Im at 175 psi. I heard 165 was cut off for race gas. Has anyone else had similar setup and what was their compression? Jeff thought this was high for my set up but didnt know why. He said to throw some octane booster in and I would be fine. Just wanted to get some other opinions. Has anyone else ran octane booster and at what compression. I am thinking of putting in 22cc domes so I can just run 91 octane. Any Ideas? 175 lbs. is pretty close to a stock exhaust height with 19's or 20's.i would definetly try 22cc domes.i would mix some race gas with punp before i would try octane booster.to each his own! ask FAST what your exhaust duration is????? Quote
bansheefreak Posted March 5, 2009 Report Posted March 5, 2009 might do a squish test.. you shouldnt have 175 with 21cc domes.. and you can run 110 with 175.. i do.. Quote
tidos76 Posted March 5, 2009 Report Posted March 5, 2009 something doesnt sound right. I about the same elivation as you and running 16cc domes and i'm ony 180. 21cc domes dhoulf be more like 150-160 if not less. Quote
spurdy Posted March 5, 2009 Report Posted March 5, 2009 something doesnt sound right. I about the same elivation as you and running 16cc domes and i'm ony 180. 21cc domes dhoulf be more like 150-160 if not less. I am running a 21cc custom cut 4 mil dome and am pushing 200psi compression. Lots of factors, exhaust duration, gaskets, etc. Kevin thought mine was high as well considering the porting he did. I have a new set of domes to check out. I run VP Red with no issues. SP Quote
DustinP Posted March 5, 2009 Author Report Posted March 5, 2009 I didn't really want to run race gas just because I didn't think the twice the cost for gas was worth it for minimal difference between running 21s with race gas and putting the 22s in. So I am willing to put the 22s in and run premium, but I just want to make sure everything is right and that the compression is what it should be and I am making all the power I can on premium. Quote
rubberneck Posted March 5, 2009 Report Posted March 5, 2009 I didn't really want to run race gas just because I didn't think the twice the cost for gas was worth it for minimal difference between running 21s with race gas and putting the 22s in. So I am willing to put the 22s in and run premium, but I just want to make sure everything is right and that the compression is what it should be and I am making all the power I can on premium. Check your squish. Also you might want to cc the head, maybe they were accidentaly mismarked??? I have never been a fan of octane booster. From what i have read and been told they do nothing to raise octane. From what i have been told they are solvent based products that serve to slow the burn rate of the gasoline down. It can prevent detonation, but can actually hurt performance. I would run race gas or lower compression. Just my .02 Quote
DustinP Posted March 5, 2009 Author Report Posted March 5, 2009 I will check the squish tonight and post it. If I go down to 22cc, that should be around 165psi what will be the power difference going down from 175 to 165. It should be minimal correct? Quote
bansheefreak Posted March 5, 2009 Report Posted March 5, 2009 you might try a diff compression tester too.. did jeff custom cut these domes .. if so you will have to have him custom cut 22cc domes to ..otherwise your compression will go down alot... Quote
GrMeyer Posted March 5, 2009 Report Posted March 5, 2009 Firehead is one to ask on fuel. But this has been done in the past and needs to be tagged. But As what everyone else is saying. my .02 would be to run avgas and mix it. here in Phx there is a gas station pump for 100 oct for $8.00 gal. or I can go to the air port and get 100ll for $5.00 But you need higher oct so you might want to get some new CC domes. Quote
TPhillips Posted March 5, 2009 Report Posted March 5, 2009 What's the difference between the av gas and 100 octane race fuel? I have heard of other people running the av gas before, but I am not sure why more people don't since its cheaper. Is there a difference or downside? Quote
sandman81 Posted March 5, 2009 Report Posted March 5, 2009 (edited) What's the difference between the av gas and 100 octane race fuel? I have heard of other people running the av gas before, but I am not sure why more people don't since its cheaper. Is there a difference or downside? this issue gets discussed like crazy on here. your gonna get so many different point of view. check this out see if it helps http://www.bansheehq.com/forums/index.php?...50&hl=avgas Edited March 5, 2009 by sandman81 Quote
GrMeyer Posted March 5, 2009 Report Posted March 5, 2009 100LL and 100oct. LL stands for Low Lead theres the diff be theres more to it then just that Quote
DustinP Posted March 6, 2009 Author Report Posted March 6, 2009 I put 22cc domes in it last night and it measured 157. I was told there is suppose to be 10psi difference per cc which should have put me at 165. The compression tester we are using is a snap on, before I used a craftsmen and it said I had 170 with the 21s. Can worn reeds affect your compression? My reeds were about 6ys old and seemed like they didn't have enough resistance. One of them was chipped where the bolt goes through. I put new replacement reeds in it last night(same time I changed to the 22s) I am lower than what I thought I should be. Quote
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