Any One Using Spearco Front Mount Conversion?


Active Member
Aug 20, 2001
I ran the Spearco setup for 4 years. I really liked it and went the time in my sig very untuned (black smoke everywhere) on pump gas and street tire. The problems I've seen is the small elbow adaptor at the back of the manifold and the plumbing on mine was only 2.25" which should be fine for a 12 sec or slower car. My car also would not idle with the Spearco and big turbo. It idled ok with the stocker. There's a member here who has no problems with the big turbo and Spearco that I can't explain. I had to end up moving my throttlebody from before the turbo to right before the intake man. The IC will definately get you into the 11s.

The turbomotion kit is just that, a kit and the modified stock IC coupled with the much better intake is going to give you a bigger gain.

When I first got the IC, it was my only mod other than a K&N filter. Nothing else, not even a fuel pump. I went 13.9@ 101mph at only 13psi boost, again street tire and pump gas.

The only reason I upgraded is I want to hit the 10s and I don't feel the Spearco and small plumbing would take me there.
V2 and Spearco setup

I have one of the few V2 setups created for usage with the Spearco front mount. IMO I don't think the smaller piping is really an issue - the motor is only going to consume the amount of flow allowed by the smallest opening of the intake tract (the throttlebody). This has been debated time and time again... and usually leads to an arguement of theory.

The piping of the Spearco setup is approx equal to the inlet size of the throttle body. If you install larger piping it is argued you will see more flow. I believe our motors will never see the rpm required to make this theory stand as correct. The inlet flow of the stock throttlebody is good into the 10's on the '86/'87 cars.
The Spearco intercooler is a definite improvement over the '87 intercooler IMO... larger inlets and outlets as well as being moved to the front of the radiator.

It's all relative IMO. The drawback of the Spearco setup is the routing of piping to the '84/'85 throttlebody location (the stock location mounted on the turbo itself).

I have all the pieces sitting in my garage :) I really wish some of you guys would step forward and try Jay's setup. IMO it is worth 140 to 150 horses as a bolt on.
I agree with you Louie to a degree. I don't think the plumbing will hold you back up to the high 11s and the IC itself is a definate improvement over stock. Here's where we disagree: The TB IS the biggest SINGLE restriction like you said. Just like the turbo is the single biggest exhaust restriction. But you still gain hp from a DP and exhaust, right? If the turbo makes 15psi backpressure and the DP and exhasut make another 5psi, you have 20psi. Improve the flow after the restriction and it's still going to have less resistance. Why run a 3" DP when the up pipe is only 2"?
I'll offer more insight...

The '84/'85 crowd hasn't invested (as a whole) in some of the newest technology to come down the pipe. The stock intake is also part of that "breathing" hurdle. The '86/'87 cars do not suffer in this area. So the air enters the throttlebody and then gets compressed into the intake at 300+ degrees (less if it is intercooled) to reach the next stop gap - the stock GM created abortion - the '84/'85 intake.

I stand by my observations of the first sentence. I talked with Jay at length about our group. Let's be honest and face it... for most part besides myself, BFH, (and a handful of other guys) a majority of the '84/'85 owners are in the 17 to 25 year old group and they have other obligations (survival is probably the biggest obligation). I purchased the V2 setup... and what does it do? It sits on a garage shelf next to brand new ATR headers, an Accel Batch DFI system, and other accumulated stuff. Oh well... I'm fortunate that I can spend money on a whim for my hobby.
I hope in time many of the rest will get to that point in their life that they can too. :) Someday I'll also have the free time to go hand in hand with my "parts collection hobby." (Isn't collecting stamps cheaper?)

I don't think the 2 1/2" piping (or is it 2 1/4"?) is the real issue here. The 3" downpipe is part of the end process only as a result of reduced resistance to the internal forces within the turbo itself. The big picture? I assume we can debate and debate this one - until we drop big dollars on a stage 2 motor that will spin 6,500 rpm I doubt we're going to find an answer that won't have some room for further debate.
i like my spearco.

my car idles good and spools up quick.

my piping is 2.25".