Dynoed the GSX last Saturday. It made 275HP at the wheels which equates to about 350HP at the crank. Seems a little low for a stock 455 with stock heads, TA headers, 3" exhaust, TA C110 cam Mallory Ignition with Access spark plugs, stock plugs, and 800cfm carb from John Osborne. Air/Fuel mixtured looked about right. I have not checked the timing. Running on 91 octane gas. Any suggestions on how to get more power out of the car? I have a SP1 intake I can put on the car. I think the car should make at least 380 or 390 at the crank given the exhaust and cam. Mark Macoubrie
Mark, The heads are the secret, port them with the larger valves , the alum intake and it will come alive !!! Bill
Try checking the timing #'s for some "free" horsepower.o No: This would be the first area I'd start. You can sometimes get some pretty big gains here.. Of course the cylinder heads can always use some work!:Brow: That's an awful small cam for headers and 3" exhaust. You might consider using something like TA 212 or 310. But I'd call TA if you think a cam change is needed. Some light head porting, a little bigger cam, SP-1...:TU: :grin:
Mark, One word....... NOS. Well I am not sure NOS is a wordo No: Actually your question needs to be narrowed down to be a bit more specific. 1. Are you looking for more HP without spending $$$$? 2. Are you looking for more HP spending just a little bit of $$$? If your not looking to spend any money then your choices are limited. I would look into how the distributor is curved or carburation. Running the car a bit on the lean side will always make a bit more HP. Remember.... Leaner is Meaner!! If your spending some $$$ then I would look into cylinder heads and a larger carb. An engine is nothing more than an air pump. The more air you can get in and out the more HP it will make. If you go the route of cylinder heads then MAKE SURE the person doing the heads knows cylinder heads. Dont go the cheap route when it comes to heads. Good Luck John
I'll second the timing comment. I picked up 35+ hp on the dyno, changing from 30* to 36*. Good flowing heads are a must. Currently drawing .338 cfm (intake) out of my Stage 2's. Good porting DOES make a difference! :TU:
I'll go with timing too, get that curve in early and run plenty of initial as well.....mucho power here to be found, it just takes time to get the right curve.
Hey Mark.My engine was dynoed with 35 total timing.In MHO you could use more cam and some bowl/port work on your heads.Check out my earlier post if any of my info can help you some what.Later,Tony.
Short Version- "Best I can do without spending cash" Long Version- I want the car to be the best it can be with whatever it has on it. 350HP may be the best this can be but with a stock rating of 350HP I was thinking the exhaust and headers and cam should have added some HP since the came was good for 30HP, headers for another 30HP and 3" Exhaust a few I think 380-390 should not be out of reach. I am not a great tuner so thats why I am asking if this is realistic or are my expectation too high? I do understand that everything needs to work together to make the most possible. A setup needs to compliment all of its parts to make it run. Ultimately I would really like to go to Aluminum heads and build a 500+HP motor but since that cost more then I want to spend right now I am looking at how to get the most out of what I have. I will work with the timing. I am also isntalling an MSD-6A and Taylor plugs (Parts I already have) this winter. That may also help out. Mark
Hold on Before you start making a bunch of changes, run the car at the track and see what happens. Dyno's are relative.
Just my .02 - If you haven't done it already, change all of the lubricants to synthetic. Mobil 1, Royal Purple, Redline, etc, all make products that are more than adequate for your HP level. I would go with a synthetic engine oil around 10w-30, synthetic ATF, and synthetic rearend lube. I will guarantee you will se a HP increase. You can get even more HP by going to a 5w-30 or even 0w-20, but that will probably have adverse effects under everyday driving. While true that headers and big exhaust will add HP, the other side has to be upgraded also. Take your intake off and clean up the ports with a die grinder. It would also be nice to port match it to the heads. Just don't take alot of material off. Then make sure your carb is jetted right. That will take some trial and error to get it right. As others have said, play with the timing also. It's the combination that makes HP. Hope this helps. Have fun.
Mark, You have a nice motor. G & G built it. Give chris a call at G&G if you need any details. You have: John Osborne qjet TA dialed distributor curve (twice) TA cam Headers Degree'd cam Hyper Pistons 23cc Balanced, .0015 on rods and .002 mains honed oil passages rebuilt rockers backcut valves small valve heads The problems you are having will more then likely be ignition timing and spark energy. This is where its always popped up when we built it. It barely ran when it won the autorauma, bad coil. I still don't think its getting a good current source. Darryl replaced resistor wire I believe but you may want to check that.
Thanks everyone for the information. I will continue to work on the car. The motor does seem strong. I think it was built well. The car is also been very nice except for a few minor things I will continue to work on. I have a MSD 6AL Ignition, Billet Distributor, and Blater 2 coil I am going to install this winter. Maybe that will help. Thanks for the info on the engine. I did not know all the details. I am also going to but a K&N filter on the car and take the the stock air cleaner all. We ran the car with the stock intake and then ran the car without the air cleaner lid and it picked up quite a bit of power. Mark
Remember that those HP ratings were GROSS. No accessories, air cleaner, max tune. Maybe one out of a hundred pulls hit that number, so that's what they used. I'm also sure they didn't care about the engine on the dyno and whomped the snot out of it too. I'd guess 310HP is more realistic. Whicjh makes about 230HP rear wheel. 45HP gain with headers and mild cam, good carb and exhaust. Your output may be nice, but the input is suffering. Porting the intake (or at least just port matching it) will help. Read Greg Gessler's article in the new Hot Rod. He tells you everything you need to know.
Just as a reference, I had my '70 GS455 on our chassis dyno at Mallory. The engine is stock except for a Mallory ignition and a set of headers. Rear wheel horsepower peak was 251 hp. I had a mid 11 second AMX on that same dyno and it only made 370 rwhp. A '56 Chevy with a race only 427 that ran high 10's only made 425 rwhp. The point is, don't be surprised when you only see 225-275 rwhp from a fairly stock muscle car engine; we see it every day. We like to call our dyno the "Humblizer". You wouldn't believe how many people think they have at least 500 hp and only dyno at 300 or less rwhp.
