GMperformanceparts.jpg (4742 bytes)      HARRIS PERFORMANCE Recommended 350 mods


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If you have questions or need recommendations, just email me at or call 336-471-2827 and I will be glad to help.

1. on the 85-89 MAF cars, removing the screens on the maf will allow more air through.  Be careful with the piece as its fragile and expensive.

2. CAM.  For a nice mild inexpensive cam, I generally just recommend using a stock LT1 Z28 94-97 cam and cut half the dowel sticking out of the front for timing cover clearance.  You can get these cams on ebay or for $50 shipped.   But for those who like to push it a little stronger the LT4 hot cam is a good choice for the MAF cars but I really like the competition cams especially the 8-304-8 and the 8-305-8.  These work nicely in the MAF as well as the speed density systems.   Just make sure your heads and valve springs are up to the task.  For the older 85 and 86 cars that still use flat tappet cams then run a comp cams 12-268-4 cam 1800-5800 rpm powerband.  224/230 duration @ .050" 477/480 lift.

3. Since all F-body 350 TPI's were automatics, once you change that cam the power curve will shift upwards costing you some of your low end torque.  Changing the stock torque converter to a 94 S10 4.3L converter will give you a 2200 stall for about $100.  This will keep a nice launch from the stoplight or drag.  A trans-go shift kit is always nice too. See for that.  Another common question for me is can I change the shift points on the transmission.  No the computer doesn't control the shifting until the 94 LT1 cars.   Typically readjusting the TV cable on your throttle body will cure most of those issues.

4. Gears.  2.73 gears should never have been put in a sports car and there are several of them running around out there and plenty Vettes with an even worse 2.59 gear.  I generally recommend a 3.42 gear for the automatics and 3.73 for the manual trans.  At least the 3.07 gear for the vette owners.  If you have converted to the 6 speed then 4.11 gears are usually the most popular.  They make a nice all around street gear.

5. exhaust.  Exhaust is always good.  I generally recommend replacing the whole thing from the engine back.  As long as nice mandrel bent pipes are used the brand isn't too important performance wise.  Long tube headers are a popular modification. But when you exceed about 12" of pipe from the head to the O2 sensor, you will have troubles getting the stock O2 hot enough for proper operation. This can be overcome by using a heated 3 wire O2 sensor for a 95 S10 4.3L V6 GM part number 25312179. Using a 3 wire for a 95 S10 4.3L TBI, wire the dark colored wire usually purple to the computer and the other wires to a ground and 12v ignition on HOT. A relay and a 10 amp fuse would be nice too.

6. Intake. The TPI setup works great on the 305 cars but the extra displacement of the 350 or 383 can cause it to quickly become a restriction.  I like the looks of this setup but I have not tried it.   The cost is about what I like to spend on an intake vs the high cost of a Holley Stealth ram, Accel super ram or TPIS miniram.  The need for the EGR valve for emissions legality will be a deciding factor on that choice.  I would go with a ram setup over just changing runners though.

7.  Injectors.  Once you get near the 300hp mark your going to need to think about injectors and the fuel pump.  LT1 24lb injectors and 26lb LS1 injectors can be bought on ebay pretty cheap.  Fuel pump.  I use the Walbro 255ltr GM universal $93 from for a lot of my projects.   If your going over 400hp then your going to need a little more injector.  But buying a larger injector than you need isn't going to add any more hp to your engine.

8. Heads.  This will yield the biggest gain especially on the F-bodies.   My advice on heads is get the most flow with the smallest intake runner that you can afford.  The larger the runner the less low end torque.  With TPI being very strong in low end torque and very weak in top end power, going with a larger runner in the heads will only cause the setup to be mismatched and power potential will drop. Now with a ram setup then you can run around a 200cc runner and nice big cam to make the motor RUN.

Also, check out the modified vortec heads from as they accept std intakes and flow better than std Vortecs.

NEW: Check out these edelbrock aluminum heads  which are 185cc with some good flow numbers which should make for a nice set of heads for the $900 for the pair.  Its as good a deal as I have found for aftermarket heads.  The procomp heads just don't seem to perform as well as advertised.

9.  Throttle bodies.  I usually recommend stock up to 300hp and 52mm for 300-350 and 58 for 350+.  Others opinions may vary but that is what I recommend.   Check out options from

10. Fuel pump, when you go exceeding about 320hp that stock fuel pump can be an issue.   change to a FPG001 from when you go exceeding 320hp and if your going all out and exceeding 450hp then go with a FPG002.

11. Crate engines.  If you motor has over 120k on it then a new crate engine may be in the works.  Herb builds some nice engines at reasonable cost and I have worked with him on nice fuel injection compatible setups.  He doesn't over estimate the power ratings for his engines and I have dealt with them a several times with some of their customers putting their 383s into fuel injected vehicles.