Hey guys, my car used to have TPI, a year ago when I installed my crate engine I decided to go carbureted and now currently run an AVS2 650CFM carb, originally with a fuel pressure regulator with the EFI pump but now with a block mounted unknown brand edelbrock copy fuel pump (running deadhead style). This car is my daily and around town it drives great, but when I try to get on it, I have absolutely zero power, the engine makes a ton of noise but the car isnt actually going anywhere, it actually makes more power when I have the throttle at 50-75% of the way which is super weird. I know this engine only makes about 300HP to the crank but I've owned and driven third gens that make a lot less and they have way more ***** than this thing, and I've gone over the ignition several times and made sure it has a decent curve so at this point I'm guessing it's fuel related. At first I ran this car with a fuel pressure regulator and the stock pump before I got it on the road, once it was on the road for about a week the pump died in the tank and I just left it disconnected, so the mechanical pump now pulls through the electric pump in the tank, before the in tank pump went, I remember having the timing set to 12 degrees initial (32 total) and having no isses at all but even since I went to the mechanical pump, I've always had to set the timing set to 4 or 6 degrees initial because anything higher and under WOT the engine would ping like crazy and pop through the intake, I'm guessing its running out of fuel at WOT and just going super lean from it having to pull through the dead pump. I never did a good WOT pull with the electric pump and regulator because the transmission wasn't set right so I wouldn't know how that would've performed but it sure did seem to run smoother back then and the times it did downshift it pinned me back in my seat. At this point I'm looking to just convert to a carbureted style pickup and run something like a M6626 pump or something similar that has a return line that isnt going to starve the engine at WOT. Any suggestions of good pumps or theories/advice would be greatly appreciated, thanks.

 

What a total BUMMER. Sorry to hear that. Oh well, if it's what you've got, you gotta work with it and make it the best you can.

OK, so there's the problem. A mech fuel pump can't "suck" through any kind of significant restriction. PUSH through, yeah maybe, SOMEWHAT, sometimes, a little; "suck" through, NO EFFFFFING way.

Explain to yourself (not necessarily to me, or to the users of the forum, butt to YOURSELF) how "set" "timing" is going to overcome your DEFECTIVE fuel system. Feel free to post up your logic you're using to convince yourself that twiddling the distributor is gonna overcome the BLOCKAGE in your tank. If you can convince yourself, then I'd REALLY like to hear how that works. Butt don't bother trying to convince me or anybody else until you've done the mental gymnastics and shown yourself TO YOURSELF to be a LOON.

Leave the distributor alone. Fix the fuel problem you know you have. Once that's done, if there's still an issue, come back and we'll talk about it. Meanwhile, you ALREADY KNOW what's wrong with your car, and it ISN'T "timing". It's FUEL DELIVERY.

At some piddly weeeeeeeeeeeenie minimal stock power level like 300 HP the STOCK block mounted pump is entirely adequate. Don't get all wound up in "Edlebrock" this and [part #] that. Just clear the tank obstruction and just hook up with AZ or PB or OR or RA or whereever and get the STOCK replacement FP for ANY carbed vehicle with a Chevy V8 a return line. Hell if you're REALLY scared that you won't get enough pump, get one for a big block in something; a 454 truck or whatever; doesn't matter, they're all the same, they ALL bolt RIGHT UP. Doesn't matter what brand, beyond making sure it's not sending your $$$ to the CCP or Kim Jong Un; if I were the betting kind (I'm not) I'd bet that there's only ONE mfr for ALL of em, and AC Delco, Carter, GP Sorenson, etc. etc. etc., let alone Duralast or whoever, all just buy it from THAT ONE source and put it in their box. Pay more attention to what's IN the box than to the printing on the side of the box, or for that matter, the "listed" "application". Doesn't matter what wrinkles are in the sheet metal it gets wrapped in or what stickers are on the side of said sheet metal; in 2024/5, if it's a FP for a carbed Chevy V8 w return line, you're good to go.

 

Just to clarify I didn't think that setting the timing was going to overcome a physical block nor did I ever say that. I wasn't even aware that there was a fuel restriction in the first place because I thought you can flow through electric pumps easily but I guess that's not the case and I'm just now learning this. I thought I had an ignition issue or something unrelated because when I backed off the timing the pinging stopped at the expense of the engine being a dog, which I didn't really care about since I don't race the car so it was never really a priority to me to dig deeper into it. Of course knowing what the actual issue is NOW I can take the proper measures to diagnose and correct the issue, theres nothing wrong with making an honest mistake and wanting to correct it. I just thought I should bring it up since it coincides with what I've been experiencing and would make a lot of sense for fuel starvation being the REAL reason which is clearly is rather than shotty MSD quality temperature change or fuel grade like I had originally assessed (I probably should've added that originally).

I've had hit or miss luck with the chinesium parts, but the carter fuel pumps I've bought seem to work out okay. Even edelbrocks parts have taken a STEEP decline in recent years, I've heard of people getting sand from the casting process still stuck in their carburetors and having to blow them out.

 

Yes, sometimes playing with the "timing" can sometimes cover up some of the symptoms of other problems. It's NEVER the right answer though. Put it back to where the motor runs the best it can and leave it alone.

Most electric fuel pumps are a YYYYYYUUUUUUUUUUJJJJJJJJJJE restriction when not operating. There's no way a mech pump can "suck" through one. That's gotta go away. Unfortunately it's not much fun to do, but That's Just The Way It Is.

Not sure whether you can still buy a fuel gauge sending unit (the name of the part that includes the pickup tube) for a carbed one of these cars anymore; you could try, butt the nearest you can get is 87 (that being the last year of carbs in these cars) but I have not the vaguest clue whether that would fit your 88 tank. Alternatively you could take your existing EFI pump "module" (the name of the corresponding part when an electric pump is involved) and try to fab something up.

A STOCK REPLACEMENT fuel pump with the return connection, for say 87 LG4, would be entirely adequate; and cause FAR LESS problems than any aftermarket one.

Yet another option would be to reactivate the electric pump, and use a 3-port regulator (pressure in, pressure out, return). Don't try to get away with a "dead-head" one (one without return), it NEVER works right.

 

another option is to use the '87 LG4 fuel pump which is low pressure and designed to work with the stock (style) block mounted pump WITHOUT a regulator.

it is a low pressure pump. the Carter P90070 'appears' to be a replacement for this. No guarantees on that though.

the factory upgraded the carbed fuel system to include the in-tank, low pressure pump to combat fuel starvation issues.

 

I just did the conversion today from the efi sending unit to the carbed one and I switched to the carter M6626 fuel pump (stock replacement pump for a 1987 lg4) and changed out the puny 5/16s fuel line I put in way back to the proper 3/8s size it's a night and day difference, I could immidiately see the difference off idle and especially at wide open throttle, now it's making the power I would expect from a 350, my engine calls for 10 degrees of initial which for my particular distributor is 34 total, I set it to that. Now there's no more pinging at wide open and buttloads more power than before! I also seem to be getting better fuel economy too, I guess that's just a benefit of doing to a return style pump. I noticed when I got to the fuel tank part of the job that the hold down and the seal was completely out of place, I don't remember leaving it open but it's good that I found it, I guess fuel was evaporating out of the tank into the air and causing a nasty gas smell when the tank was full.