AFPR or Not?

Frank Bokodi

Registered User
I have a project 93 SC. I will be running a bunch of bolt ons. I have SVO Roller rockers, MP raised top, 10% SC pulley, 190 lph fuel pump, 38 lb. injectors, 75 mm MAF, 75 mm BBK Throttle Body, Kooks med. length Cer. coated headers, and Big Dawg Exhaust. Can all of this work with stock computer and stock FPR. I am running out of money and I want to get the car on the road. I also don't want to make any mistakes. I want it to be right the first time. Oh if it makes any difference, it is .030 over with Total Seal Gapless rings, and mildly ported heads. If anyone can advise me that would be great. Also if anyone can shoot me some RWHP guesstimates, I am hoping for around 300 RWHP. Realistic? or NOT? Thanks all!
 
I would stick with the stock or a new stock replacement FPR. A lot of people have had problems with the aftermarket AFPR's going bad (Holley, Kirban, etc). Assuming that your MAF is "calibrated" for the proper size injectors, your car should run fine.
 
I just got mine back together with a set up similar to yours, the main differences are I'm running a big cam, fully ported heads, and long tubes. I have a tuner but I haven't got to using it yet but will have to soon. I've been burned by the aftermarket AFPRs also and have gone back to the old homebrewed Motorcraft AFPR that a elightened few knew about back in the days when there was no aftermarket linear AFPRs. It requires a little minor work but it doesn't leak. It's a good thing I did this and didn't go back to a stock regulator as my car won't even accellerate below 40 PSI and isn't right until 43.5-44. I tried to run it at 38.5 like stock because my idle vacuum is 11" and it bumps the fuel pressure high at idle, but at that setting I couldn't even rev it up in neutral without cuting out and backfireing.

I would get this unit and set it 43.5 like the 38lbs injectors are rated for in your case, I've never been able to achieve a save air/fuel ratio on a stock regulater, it would require computer recalibrating and that costs more than the AFPR. So again in your case I would get the regulator. At least this unit is under $100.

It's Motorcraft part# EOSY-9C968-A.
You have to drill and tap a 1/8" NPT hole into the housing (above the diaphram) and install a brass vacuum nipple to make it linear. Also the adjustment hex cap screw on the top is vented by a small hole that needs a dab of silicone to seal it. The OEM application is TBI and the vent is for barometric reference. Put the nipple on the pass side, not at a 90* but just past going towards the rear and it will clear nicely. Since it doesn't need a lock nut to retain a setting you can adjust it on the fly fairly easily. I drilled a hole into the cowl vent and use a allen wrench that reaches it to make adjustments a one minute job.

It would be bad for you to run lean and toast a new motor so don't take this for granted. Your system is calibrated for 38 lbs/hr injectors and they don't acheive that rate until they are at 43.5 PSI. If you can't afford immediate computer tuning then get this AFPR but not any other. The other will work but leak and cause other issues that though not as severe still piss you off. If you have any questions let me know.
Vernon
 
afpr, vernon........

Do you have any pictures of this mod you have done? This would be a good "how to" to post. If you could refer me to the article you learned from, I'd appreciate it.
mark
sohclx@yahoo.com
 
Frank,

I had the same problems Vernon mentioned with 38# injectors set at stock pressure. I had to set mine to about 44 psi or it would bogg if you gave it too much throttle.

I also had problems with the adjustable regulators leaking (holley and aeromotive) and now I'm back to using a stock one with a dyno tuned custom chip.

To answer you original question...yes an adjustable FPR will help if you don't have the cash for a custom chip or EEC tuner.

David

PS: I have a new in the box Aeromotive adjustable regulator I paid over $110 for and will sell it for $55. Let me know if interested.
 
Last edited:
Back
Top