New Member
Jun 7, 2020
Burke Va
Hey Guys,
So I have a forged 347 currently running N/A with a 9.5-1 Compression ratio, E303 Cam, 30 lb/hr injectors, and a 190 L/hr fuel pump in my 89 Lx. I was told the motor was built for boost (hence the low compression ratio and cam). I am told it had a supercharger but the prev owner removed it because he could not figure it out with the old ecu (a chipped A3M)(he was not the engine builder). I purchased the car with intentions of boosting it and this past summer I installed TerminatorX and currently have no issues with the car and the motor runs better than it ever has with Holley Efi. Originally I planned on saving up for a Vortech v3 Si-tuner package priced at $3800, but the more I look at that price, the more I look at alternatives. I just had an opportunity to purchase a functional DB-11A Powerdyne supercharger and mounting kit for $1100 (yes I've heard some horror stories). It is completely stock from Powerdyne (2.93" pulley estimated at 5-6 psi Max). Now obviously I have to upgrade my injectors, Fuel Pump, and MAP sensor (currently using the 1bar) but an idea I had is to purchase this used kit and run it after I upgrade those components in preparation for a 9-10psi setup but only run the stock powerdyne setup in it's normal 5-6psi range. Then, when I have more experience and the money or if the supercharger fails earlier than expected I would get the Db-11A supercharger rebuilt by either superchargerrebuild.com ($890 with the billet impeller) or 928 motorsports ($1400 with a billet impeller and a few other goodies they claim makes their setup better) for more CFM and get around 9-10 psi with a 2.7" pulley (assuming no slippage). I would also pay a professional to send me a tune for each setup as that would be the safest option. So my main questions are if anyone sees any major flaws with this plan? If someone has advice on Holley compatible injectors (high impedance) that won't break the bank and run safely at 10 psi (I wouldn't want to go over 85% duty cycle so that my ecu has correction room incase of issues)? And Lastly if any one has experience with either supercharger rebuild company and recommendations on one or the other.
Thanks for helping a newcomer to this forum (didn't think the Welcome Wagon would be ideal for this post)!
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What block do you have? The factory block is the weak link and becomes iffy at anything over 500 HP. Depending on your heads, a boosted 347 can get in the iffy zone very quickly.
Your plan seems well thought out, and as long as you've got aftermarket support for the powerdyne, I see no issue going that route. Vortech is always a good bet since they've been around forever, and have a good upgrade path should you need anything more than an S-trim. I do have a personal preference for Vortech, and an S-trim will be great on the street at the boost levels you're wanting.

There are quite a few injector manufactures that'll get the size you need (around 40-50-ish, depending on HP levels and if FMU will be used) in high-impedance.