I have an 89 conv w/15000 miles. The car is basically stock, so I decided its time to do some upgrades. I'm going to install air foil, K&N with cut lid, TPIS long tube headers, hi-flow cat, and Borla cat-back. What kind of realistic horsepower and torque gains should I see with this? This will basically blow my budget for the year, but are there any other things I should consider while doing these upgrades? Thanks.

 

Id say realistically 30-40 if not a few more. Personally, Id save my money and not get the airfoil. I guess it depends on how good a deal your getting but Id only pay 15 bucks at most for one personally. The headers and cat and catback are really going to make a difference and you are going to LOVE the sound of those Borlas. I am dropping some Borlas in my 66 TPI truck this weekend . . . I cannot wait.

 

Save the money on the air foil. The K&N filter isn't a bad idea with the open lid but don't expect any major seat of the pants increases. Also don't expect much from the cat-back other than sound pleasure. The headers are where your power is going to come from. Then you'll only be looking at 10-15 in an otherwise stock application.

 

up to about 30hp

dont waste money on the airfoil.

 

i gained 28 chp with my exhaust, give or take a hp or two......

 

Thanks for the info. I'll the the advice about the air foil, and let you know how the rest goes.

 

The TPIS headers are next on the list for my '89 convertible. You may want to consider changing gears when the budget permits.

 

umfan, you will experience a noticable kick in the pants & quicker revs with the removal of the pre-cats and addition of LT headers. the rest might net you 5-7chp.

the horrifically restrictive L98 exhaust greatly benefits from a freer flow. imho for the L98, LT headers are the perfect beginning of a family of mods.

i would open up the intake next, by at least going with large tube runners & aftermarket intake manifols such as the TPIS BigMouth or Accel --- this is assuming you wish to retain the stock look as well as the amplifying the characteristic L98 low-end torque slam.........of course better breathing up top won't be increased all that much - you should get good power to the upper 4,000 RPM range rather than low/mid 4000 RPM range. at this point you'll most likely want your chip recalibrated.

last step for L98 350cid is the venerated SuperRam plenum & runners + LPE 74219 cam + either porting to your stock heads or getting aftermarket, something that nets in the neighborhood of 240-250 cfm intake @ .500" valve lift. oh, more chip reclaibration here, for sure. you'll be slamming into the next gear at about 5500-5800 RPMs and saying bye bye to most any ricer of other goofball that dares mess with you.

i aint there yet, but getting closer.......

 

ive had skepticism about that airfoil myself, does it do anything at all?

 

It reduces the weight of your wallet. I'd hold out for a larger TB if you are going to get remotely serious. one of my friends was considering getting one, and instead used silicone, and made his own. then paintied it cast grey. He never told me about it until he took his air cleaner off at the track one day, and I saw it. I said "I thought you said you werent going to buy one of those". His reply "I didnt. Push on it a little bit" It looked pretty good in there, but there is no gain if the motor is not pulling more air than the TB in stock form is flowing. Its basically like this. It smooths out the air going into the TB, but what good is that if there is enough going in already. The air is just going to become turbulent once again as it is heading into the runners.
Dont waste your money.

 

I have done tests on the air foil and you will only pick up flow above 100 mph.The kinkey tube infront of the throttle body breaks up the air to much.
I would go with the K&N, becareful the L98 does not like to have air rammed into the stock manifold, the engine computer can not increase fuel or air to compensate for the increase.
The engine will humm nice but will not pull or create power .
I would say forget the mufflers and install cut outs.