TPITuned Port Injection discussion and questions. LB9 and L98 tech, porting, tuning, and bolt-on aftermarket products.
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The engine is a stock 355 TPI from a 89 GTA. The engine and 700R4 are in a 88 Jeep YJ. This is a BAR approved smog-legal swap. I want to stay CA smog legal.
I would like a little more performance but don't want to sacrifice low-end performance and want to optimize torque from 1000 to 5000 rpm. I desire to achieve at least the 440 lb-ft of torque that Scoggin Dickey claims for their vortec TPI motor.
To do this I am planning head and cam replacement. I think I want to keep at of below 180 cc port volume to keep the intake velocity up for good low-end torque.
I see my choices as either the vortec or bow tie vortec head and a vortec TPI base. Or AFR 180 eliminator heads and extrude honed stock TPI base. Clearly, the AFR approach is more expensive but not a whole lot more.
I will be running custom made stepped, long-tube, 2-1/2"merge-collector headers with AIR fittings. Probably 1-5/8" to 1-3/4" although I will also consider 1-1/2" to 1-5/8" as torque and low-end are what I'm trying to optimize for. I know they are not quite smog-legal, but they might have an exemption number.
It is likely that I will run a single-pattern Mike Jones camshaft. I have been very impressed by 1989GTATransAm's thread on his 228/228 Jones camshaft. The AFR has better exhaust flow so maybe a single-pattern cam lends itself a little more to the AFR heads. The exact cam will be selected once a decision is made on which heads. I also don't mind paying for a custom grind if that is what is required. Also, I will change pistons to up the compression ratio if it is required to optimize the system. I am willing to run 91 octane but would prefer to optimize for 87 octane. Might have a hard time getting good gas in Mexico.
Which head/TPI manifold combination would you select and why?
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Last edited by sol_searcher; 07-09-2008 at 05:47 PM.
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