Edelbrock Performer intake and AFPR

americanmuscleman · March 24, 2003

Some of you all might have seen another post I put up where I popped a head gasket on my 95' Tahoe. I fixed that, and while I had the engine apart, I put an Edelbrock Performer TBI intake manifold on it, and an adjustable fuel pressure regulator. So far, I haven't seen any gain with either of them. I've adjusted the fuel pressure regulator quite a bit, with no noticeable seat-of-the-pants change in power. The intake manifold also feels just the same as the stocker.

I still haven't adjusted the fuel pressure regulator to the end of its limits, but so far, it doesn't appear to be effecting anything.

That rules out my thoughts that the intake and fuel pressure regulator could be holding my engine back. Now I just have to find out what it really is!

I also played with my timing quite a bit without much luck either. I think I've just figured out you can't make good naturally aspirated power with a TBI motor.

Oh well.

ByUBlue · March 27, 2003

Wow...I am completely shocked by what you said. When I modified my throttle body and put on the adjustable FPR...it made a noticable difference on my 93.

If you have the same TBI unit that I do, (which I think you do) I would recommend removing those ridges to free more air going in...I did this at the same time as the adjustable FPR...perhaps you have more fuel and are running rich now because of the same amount of air? Maybe the difference with my truck was due to more air and fuel both.

You can get a TBI on e-bay for $25 to $50, if you do not want to hack on yours...I think it would be worth it t find out...but then again, I am the guy who recommended you get the adjustable FPR in the first place.

There are several sites that walk you through removing the ridges on your TBI and opening and smoothing the top of the bores.

Proud to be an American!

americanmuscleman · March 27, 2003

ByUBlue, thanks for the ideas!

I'm shocked it didn't pick up any power either. At this point I'm trying to figure out what the deal is. I've always thought my TBI 350 should be making a lot more power than it does, and actually I think I'm making less power now than before I popped a head gasket.

I'm going to continue to play with the AFPR and see what I come up with. I've played with the timing quite a bit with no luck. I've been looking into adapting a TBI 454 throttle body to my intake and see how that works. Obviously my tuning is going to be off, but it would be interesting to see if that would help my top end power. I've heard of people doing that successfully.

I'm going to keep tinkering with it when I have time and see what happens. Thanks for the ideas!

ByUBlue · April 2, 2003

What is the duration on your cam? Many guys overcam these trucks. The computer is set to handle a certain duration. If you much over it, you bog your low end big time. Just an idea...

Also, how's your top end? Where does that 4L60e shift your truck?

I also have an inch and a half throttle body spacer on mine which helps a little with air intake speed...

One more question...with all you have on that truck...what's it run in the 1/4. Do you know? Will it take out a stock 5.0 on the street?

A couple other notes. I have heard of 454 throttle bodies working very well on these trucks. Seems like you have removed all other restrictions...but it would require a custom chip, and they still only flow like 575 cfm stock. I would talk to the guys at TurboCity about buying one that is already modified and take that intake to a machine shop to get it bored out. They have been working with these TBI setups for years and know thier stuff.

You can also put 454 injectors into your 350 TBI...but the problem is still AIR. Only so much can come through 2 small holes...yo9u can always get more fuel, but if your not sucking more air, you're not doing any good.

One more thing...you could lose the TBI entirely, drop about $1200 and put an Edelbrock EFI system on there. That is guaranteed to solve any fuel/air delivery restrictions...get better gas mileage too.

americanmuscleman · April 2, 2003

ByUBlue, my cam is a custom grind someone else made, but I think its around a 210/215 or so. I've tinkered around with quite a few cams in the past on different motors, and this is my best guess as to what it is.

My top end power isn't very good. Its better than a stock TBI 350, but its not even as good as a Vortec 350. It seems to peak at 3000rpm. My truck shifts at 4500rpm. I was hoping the intake would let the engine breathe better, but it still seems to run out of air.

I have a TD 1" throttle body spacer, I just don't have it installed. I do have a small injector spacer installed (like 1/4"), and then the Edelbrock intake is just a hair taller than the stocker.

I've never had the truck at the track because I know it wouldn't run close to a good time. I would get waxxed by a 5.0. I lost a race to my same truck with a Vortec 350.

I've heard another problem with TBI 350's is if you add headers or a free flowing exhaust (which I have both), your 02 sensor may not reach the 600 or so degrees it needs to be at to go into closed loop mode. One of the symptoms is the throttle response is real sluggish, which mine definitely is. My 02 in my truck is not heated, and they make a heated 02 for my truck, so that might be worth looking into.

I've been thinking about getting my truck dyno tuned by Ed Wright here in Tulsa. I'm starting to wonder if the tuning is off on my chip. My truck has always made great low end power, but the top end is non-existant. Once I get the distributor and fuel pressure set where it seems to like it best, I might go see about getting my truck dyno tuned. If nothing else, Ed could probably tell me what is my weak link (like not enough fuel or not enough air flow).

I've thought about the Edelbrock multi-port EFI system, but I think I would rather just spend the $3500 a whipple charger costs and be guaranteed to make a load of power. I've seen that guy that adapted an Edelbrock EFI system to a whipple charger on a TBI 350 and made something like 475hp with it.

Before I started modding my TBI 350, I originally planned to drop an LT1 in it. In hindsight, I should have done that. I made about 375hp with a 220/230 cam and headers through my LT1 on stock heads. I bet I couldn't get 375hp with a whipple charger through the setup I have right now! Hindsights always 20/20 right?

Thanks for the help!

ByUBlue · April 2, 2003

I guess my frame of reference is a bit skewed because I didn't modify this truck that much and it actually runs pretty well for a TBI truck.

I got this truck from someone else and it seems there may be some internal engine mods I don't know about. Of course, the positrac helps, and I think that I may have a higher stall converter too, but I don't know.

As far as LT1 vs a TBI 350...no contest there, but if you stroked the motor, and ditched the pollution control, and put a carb on it, you could hit that 375 w/o a supercharger. People have done it.

If you don't do anything else, put the spacer on...just make sure you loosen the bolt that restricts you from giving your fuel lines some slack...it can only help.

americanmuscleman · April 2, 2003

I have a buddy with an 89' SWB Chevy that has a bone stock TBI 350 with only exhaust... that could roast the tires through first gear and into second with wider custom wheels and tires on flat pavement. So, I know these TBI's can make some power... I just have to find where my power is hidding.

dj14901 · April 25, 2003

What fuel pressure are you running? For stock TBIs, the acceptable range from the factory is 11-13, which is quite a broad range. From what I've heard, any stock TBI (or one with a few mods) will run really well at 13. However, it looks like you have some more extensive mods that might require a bit more. I'd try backing your fuel pressure down to 13 and then bringing it back up in slow increments...

Hope that helps!

DJ

americanmuscleman · April 25, 2003

dj, thanks for the tip!

I've been so busy with work lately I haven't been able to post on here. I've actually been tinkering quite a bit with my fuel pressure and distributor timing. I've picked up quite a bit of power, and its idling a lot better in the morning. I've advanced the distributor timing quite a bit, and it loves it. I pumped up the fuel pressure as well, and it liked that too My only problem now is... now that I've done that, my truck is shifting too early now (4200rpm upshifts at WOT). I need to get this thing dyno tuned and bump that up to 5500rpm or so.

Anyway its running a lot better now

I still have a midrange missfire I'm trying to track down. I've eliminated a bad plug, bad wire, coil, and the cap and rotor. I'm looking into it having a worn out distributor. I know they can be rebuilt, and checked with an Ohm-meter. I just have to get some time to check it.

gmc4x4 · May 7, 2003

I am new to the board. I have a 94 chevy with almost identicle mods. My cam is 204/214 @.50...I also have the afpr and the edelbrock intake. My truck does exactly what you say yours did runs out about 3000. The cam should really come to life up there. Where did you eventually put you timing an fp to get it running better..Any help is appreciated....Thanks, Wayne

BadBowtie · May 7, 2003

I don't know if you ever thought if this, but I think the most restrictive thing on these motors is the heads, the aren't supposed to flow very well. I have never really looked into this, since its not something that I have the patience or money to change now, but might do in the future. Just something else you might look into......

-John

americanmuscleman · May 8, 2003

I am new to the board. I have a 94 chevy with almost identicle mods. My cam is 204/214 @.50...I also have the afpr and the edelbrock intake. My truck does exactly what you say yours did runs out about 3000. The cam should really come to life up there. Where did you eventually put you timing an fp to get it running better..Any help is appreciated....Thanks, Wayne

gmc4X4, I ended up advancing my cam about 4 degrees. My fuel pressure I'm not sure what it is. I don't have a fuel pressure gauge on it to check. I ended up just adjusting it by the seat of my pants. I got it where it seems to like it best, but I can't tell you what fuel pressure its running.

My top end seemed to improve the more I advanced the cam. I never advanced it so much that it "pinged" or anything like that, but I did advance it quite a bit. My idle got smoother, and the truck pulls harder all over. My shifts are also lower in the rpm which is nice. The bad thing is it lowered my full throttle shift point to around 4300rpm (as indicated on my tach). I originally thought it was 4200rpm, but it appears to be close to 4300. It used to run to 4600rpm or so.

Badbowtie, are your heads stock? When I took my stock heads off, and compared them to the Trick Flow heads I'm using... there was a huge difference! The stock heads ports are really ruff cast, and they have that swirling step in them that doesn't look like it promotes anything but maybe good gas mileage. The factory TBI heads are definitely a huge bottleneck.

gmc4x4 · May 8, 2003

I dont have the money rigt now to do heads so thats kinda outta the question. Anyhow on the timing.....You are advancing the cam timing or the distributor? I think you are doing the distributor. Thanks for the replies

BadBowtie · May 8, 2003

Yes my heads are stock, I don't have the funds to mess with them now. I have seen them apart, I didnt know that you were running aftermarket heads. I was just making sure that you didnt overlook them as they are very restictive.

How do you like the Trick Flow heads? Are they worth the money? I'm looking for more of a low end increase, I use mostly torque for pushing and pulling, seldom do I need top end horsepower. Thx

-John