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Discussion Starter · #1 ·
Hi, my name is Marc and I am new to this forum. I have a 2000GT that I have been playing with for about 5yrs. It has a cobra crank, H-beam rods, 11 to1 notched pistons, comp 278 cams, stage 2 ported heads, valves, springs, long tubes, X-pipe, 75mm throotle body, stock pi manifold, AC delete, GMS cop, stock 5 speed, 430 gears, some susp. work, 3-1/2" in the front and 26"x10" drag radial in back. Car ran 1180's with a 1.60 60ft. I have the motor out, it was getting tired. I want to go to 12.5 to 1 and a 1mm bigger valve. Has anyone run that high in comp. and has anyone gone bigger on the valves:tip:
 

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Just go bigger on the intake depending on the flow of the heads. Usually any stock modular head, even ported, will have the exhaust flowing way more than the intake, percentage wise and that is why Hitech has the intake side of their cams with .050" more lift than the exhaust along with 4* more duration.
Going from 11:1 to 12.5:1 will not yield as much as when you went to 11:1 due to the actual percentage of increase. Also 12.5 is puishing it unless you run a large cam and the Comp 278 is that! How did you calculate the 11:1 compression? Meaning chamber size, gasket thickness, etc. The dynamic compression is what will allow or not allow the 12.5:1 if the octane you are planning to run is 93 octane pump. When does the intake valve close with the cams you have?
PS: Did the GMS coils add anything that was tested or even felt?
 

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Discussion Starter · #3 ·
4.6 Rebuild

Thanks for the repley, My motor builder did the block and heads. When I bought the pistons he assembled the bottom end for me and told me I was at about 11.1 - 11.5. He has my motor now, I have some scratches in th no#1 and 8 cylinders to deep to be honed. Yes it is tuned for 93 octane, but I think I had some bad gas and had some pinging, thats what he thinks.Now I think I am going to go 30 or 40 over and a little more comp. I have to buy new pistons anyway. I replace the cop's because I had one going bad, a little better throttle response at low rpm. did some other work at the same time so I really don't know.
 

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Kurt02GT ran over 12 to 1 Compression and it ran fine with 93 octane......its mostly in the tune as far as how much timing you run......but there is a threshold that you will need to run race gas.....not sure what that is yet....there is an 12.5 car that I know of that runs 93 octane and is fine........how much power did your set-up put down and what cams were you using?

"ED"
 

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Discussion Starter · #6 ·
The tuner got it to 336hp. 330tq. to the wheels, said he had it over 340hp. and had to take out timing, told me with race gas he could get 345 - 350hp. out of it. The car cracked the 11's after I did the shocks and upper and lower control arms. Coming out at 5000rpm. and shifting at 6500. the car pulls real good top end. I am running comp. 278 cams. Car ran 12.30 before the shocks and control arms (70-30 front and 50-50 rear)
 

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What type of MPH were you trapping in the 1/8th and 1/4....??

"ED"
 

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Discussion Starter · #8 ·
Hi, ED the best it went was 1.60 60ft., 7.628 @ 90.60 - 11.86 @114.7 , I was getting some wheel hop in the middle of 1st. gear, adjusted the pinion angle and added 1lb. to the tires. Went out and the driver side head gasket let go. That was why I pulled the motor and then I found other things going wrong. Hope to get it out by Sept. And shooting for 11.50's.
 
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