i have a 305 tpi engine in my 1987 Transam
i want to add K&N airfilter and TPI airfoil.
How much HP will i gain ?

Cor, The Netherlands

 

Vand, did the same thing recently to my GTA. You can notice some improvement, but it is not huge. As far as the horsepower improvement is concerned, I always take what the manufacture states and divide it in half. I would guess, no dyno information available, that the improvments added approximately 10 hp total. Good luck.

 

You will notice a little seat of the pants increase. The biggest difference will be sharper throttle response.

 

I have these on my car too, you might notice a little difference, but like mentioned above the engine will probably respond a little better and it will breath a little better maybe resulting in better times. 10-15 hp but probably no more than 12. If you want to try and make a nice difference add some sort of cold air induction, modify your MAF relocat the MAT and you would feel some nice gains, and all can be done for a reasonable price. Good luck.

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87 GTA 350 L98
K&N filters, beefed up TH-700r4, Accel Manifold, Ported Plenum and Runners, Fuel Press. Regulator 49.5psi, air foil, modified MAF, SLP cold air box, Hypertech Thermomaster chip w/160 thermostat, MSD 6AL and Blaster 3, B&M shift kit & megashifter, Moser Ford 9in Rear with Richmond 3.50 and locker, Edlebrock TES headers and Cat Back,Hotchkis setup in rear, Poly suspension and Koni in the front, relocated MAT, bypassed IAC, 300 lbs lighter

Fastest ET's
Stock-0-60 6.8, 1/4 15.0 @ 94
Best-0-60 4.7, 1/4 12.8 @ 112
Norm-0-60 5.2, 1/4 13.2 @ 108

 

The more mods u do the more they will work with them.

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Looking For:

87 IROC-Z28 350 TPI
The car I want.

84 TRANS AM 305 H.O.
Another car that would be OK to own while I still look for the IROC-Z!!

 

You'll notice more with the K&N. Not much with the air foil.

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'88 IROC TPI 355, '69 truck 4-bolt, fully balanced, 9.75:1 compression, fully ported '70 truck heads(for now), Harland Sharp 1.6 Roller Rockers, Comp Cams CS 252AH-12, ported '86 TPI converted to speed density, Crane AFPR, Flowmaster 3in. exhaust, Edelbrock TES headers, all emissions equipment is still intact, plan on burning my own chips, many more mods and parts on the way as time and money permits =(
Best E.T. with TBI 305: 16.11 @ 82mph
Haven't been to track with new motor
If you have any questions on converting from TBI to TPI email me at jdkchevy70@yahoo.com
In memory of Dale Earnhardt, I'll miss cheering for that black #3 on raceday!!!