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Debbie Harris's 1969 Grand Prix

2022 September
of the Month

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Bolt-On Mods for your 3rd Gen V8


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I wanted to share some info on the performance benefits of the BOLT-ON items I have installed on my 1991 L98 350. SLP had some very streetable parts such as the Siamessed Runners. These really made a difference from about 2,500 rpm to redline. Also their Cold Air Box was a huge improvement over where the stock location got its air from and there is a K & N filter inside. The performance computer chip seemed to make the low end punch really pick up. I don't know if the underdrive pully did help or not. The same with the adjustable fuel pressure regulator, its hard to judge how much it helps. The Air Foil may help somewhat, but not that you could notice anything.

The Edlebrock intake manifold worked well with the Runners as a package. Also the their TES Headers allowed the engine to pull right up to 5,200 rpm and I also had them coated inside and out about 12 years ago and they still have their silver finish and not a sign of rust.

There is an MSD 6A Ignition Box with a Blaster Coil and I must say it seems to work just by the fact that I can drive anywhere and when I wipe my finger inside of the exhaust pipes, there is not a trace of carbon buildup.

Another small item that really helps in the hot weather is installing a 160* thermostat along with a Hypertech 2nd fan switch that comes on when the engine reaches 176* and shuts off at 165*. These motors are heat sinks and this setup really keeps the temps down.

I did change the gears from 3:23 to 3:73 and I must say that unless you are renning drag street tires, there is too much low end torque and it lites up the tires easily.

For traction I have the Edlebrock tubular Lower Contral Arms and Panhard Bar. I makes a huge difference in the way the car leaves the line and also in the handling.

In the engine bay I have a Hotchkis Upper Struct Tower bar which took all of the hood cowl shake out of it. An IROC Wonderbar is also recommended.

Running Royal Purple 5W30 Synthetic Motor Oil keeps a very clean engine as well as adding several horsepower.

The spark plugs are AC/Delco Rapid Fire Platinum and it is a good idea to go with a top of the line plug due to the fact that changing plugs in the car is a REAL PIA.

I replace the blocked hood scoop plate with one that came off of a 1982 T/A H.O. where it has an open mesh. It lets out engine heat and every little bit helps in hot weather.

The exhaust is a BORLA 3" cat-back polished system with dual dual exhaust tips. By playing with the right side block off plate (most of the exhaust comes out of the left side) you can tune the exhuast note to your liking just be enlarging the hole.

In stock condition these cars ran about high 14's, but with all the mods it runs 13.8 on drag radials and around 14.0 with my Goodyear GS-C radials.

There is also a 1LE 3 1/2" aliminum driveshaft installed but hard to tell if it does help with 1/4 times.

One last item I would highly recommend is a set of subframe connectors. I have the Alston design which are welded on and it made the biggest difference in the way the car felt going over bumps. Gone was the shake and bang going over a rough rode and it made the car feel like it was a much heavier chassis.

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Have you seen any issues with low idle stalling (cold) / hesitiation at low idle (cold) or trouble codes generated from any of the these mods?

My '86 is essentially stock. I have an BBK 58mm throttle body (includes the air foil), an Edelbrock CAT back exhaust, and hogged out plenuim, a Accel stock replacement coil, fuel regulator, and K&N air filter. I own the SLP cold air kit but I don't want to do any cutting since the rest of the car is a survivor.

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I love the third gen car community. There are some real poineers there. I've read tons of thread over on thridgen.org about maf-only tunes and it's just mind blowing. There's a massive wealth of information there about tuning due to regular guys cracking the code.

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Have you seen any issues with low idle stalling (cold) / hesitiation at low idle (cold) or trouble codes generated from any of the these mods?

My '86 is essentially stock. I have an BBK 58mm throttle body (includes the air foil), an Edelbrock CAT back exhaust, and hogged out plenuim, a Accel stock replacement coil, fuel regulator, and K&N air filter. I own the SLP cold air kit but I don't want to do any cutting since the rest of the car is a survivor.

I have never had a single code pop up after any of the mods I made. The CAI box from SLP is one of the best mods you can do because the stock position sucks in hot engine air only, where as the SLP kit gets it from the inside of the front fender. You will have to move the canister from the passenger side, to the area next to the battery.

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I also tried a 58mm throttle body and the car LOST performance in the 1/4 mile, even though on the street it SEEMED to run better. The stock 52mm unit will work just as well even with the mods I have.

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Hmm. that's interesting to know anout the stock throttle body. I basically stole the BBK from a guy in Carlisle for $50.00, before used 3rd gen parts got stupidly expensive.

Yeah, I need to dig into the MAF stuff. Just pisses me off since I can't find a decent mechanicaround here that knows their way around a TPI motor. Granted, it is 25 year old technology but still, the basic principles are still in play today. I guess I need to spend soem time over at thirdgen.org. Thanks.
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