TBI fuel pressure

[mouse]

I just wanted to see what everyone is running for fuel pressure on a small block TBI.

I just installed an adjustable regulator, and have turned it up to just under 13 PSI. After datalogging I see my BLM numbers are still a bit high at 800 - 1200 rpm (see below), and will probably bump the pressure up a little more. I will re-burn the chip to smooth out the mid range.

Engine specs: 350, .040 over silvolite pistons, 8.8:1 compression, comp cams xtreme energy cam, 388 heads with casting flaws removed, exhaust ports smoothed and 1.84 intake valves and bowl work for flow. Stock TBI intake and exhaust manifolds. Dual 2 1/2 inch exhaust. Stock TBI ignition.

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RPM \ MAP 20 30 40 50 60 70 80 90 100
400 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
800 0.0 135.0 133.0 0.0 135.0 0.0 0.0 0.0 0.0
1200 0.0 135.0 139.0 145.0 140.0 0.0 0.0 0.0 0.0
1600 135.0 172.0 158.0 157.0 146.0 135.0 0.0 0.0 0.0
2000 135.0 131.0 172.0 170.0 158.0 0.0 137.0 0.0 0.0
2400 127.0 0.0 0.0 0.0 0.0 134.0 172.0 0.0 0.0
2800 0.0 0.0 0.0 0.0 0.0 139.0 128.0 0.0 0.0
3200 127.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
3600 0.0 131.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
4000 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

 

[neverendingproject]

I think they recommended like 20 psi for my 383. Im gonna fire it up in the next few weeks so we will see.

 

[mouse]

I did some more tuning and was finally able to start pulling some rich BLM figures once I got the fuel pressure over 17.5 psi.

I am getting the tune pretty close. I am aiming for the "perfect" 128 across the board...

 

[MTBLAZER89]

quick question about this. Can you just buy an inline regulator? How is the pressure regulated stock? Will you see gains on a mainly stock tbi 350 with this upgrade?

 

[Cricket]

In stock form my regulator was set to 9.25 psi. After making it adjustable I bumped it up to 12. Never ran a scan on it.

 

[MTBLAZER89]

so you just replace the stock one with an adjustable regulator?

 

[southernspeed]

so you just replace the stock one with an adjustable regulator?

Yeah, there a few adjustable ones that replace the stock one in the TB unit. I use a Jet one. I bought a VRFPR but after reading that you need to mess about with different spring rates I gave up! Thet were designed for 454s so give too much pressure for a 355.
I've also drilled out the cap on the stock one and adjusted it that way before.

 

[Cricket]

so you just replace the stock one with an adjustable regulator?

Nope, I used the stock regulator but removed the limiter pin the factory installs to keep you from screwing with it.

 

[mouse]

I replaced mine with an adjustable, but the stock pressure regulator can be modified to adjust.

I bought one that could be adjusted without removing it from the truck...

 

[4X4HIGH]

Which brand or vendor did you buy from that it can be adjusted without removing from the truck? It looks like either the CFM-Tech or the Turbo city can be adjusted while still installed but i'm about to buy one and want to make sure beforehand.

 

[southernspeed]

I used a Jet one which can be adjusted with an allen key (or wrench...whatever you guys call it!!!)
I think the Turbo City one has a knurled thumb wheel adjuster doesn't it?

 

[RedBrute]

I gotta ask this only because I recently got an old style engine analyzer and have been looking at data on my '87 TBI Blazer. In road test mode my " Block Learn" numbers are always 108 to 112 and the integrator numbers (short term adjustments) are between 120 and 130. Now I always thought my engine was running on the rich side, but your post leads me to believe I'm actually lean all the time? By the way, I have no drivability problems or engine codes, I'm just trying to anderstand how the stock engine is running before I start any mods to it.Thanks for your time.