Hey i'm in the middle of switching from my TPI to a carb setup. i have installed a edelbrock RPM performer intake and a quadrajet carb. now what do i do about fuel? i bought a mechanical fuel pump that mounts on the block. what do i need to do now? remove the electric in tank pump. and if so what do i need to do will the sending unit work with out the pump?

Another issue i have is hooking up the hei distributor. i have a plug missing where is it in the engine bay and do i need to do some wiring?

 

You can either keep the in-tank electric pump and regulate it (after the mechanical, with a return), or remove it. Removing it won't affect the sending unit (I assume you mean the oil pressure).

The power wire to you coil will become the power wire to your HEI. You can get a connector that will hook up directly if you like.

 

The mechanical pump won't work on your block. For one, there is no pushrod to run it, and two, there is no provision on the stock cam to run it. You can either buy a 3 port bypass style fuel regulator and use the pump in the tank or you can pull that pump out and use an external electric pump. I would go with an external pump. The stocker is only so powerful. If you've got or plan on getting a motor that's going to make any power, the stock pump will be too weak anyway.

 

Okay, I'm a little slow. You mean the fuel gage sending unit.

Removing the pump won't affect the gage. You will need to put a piece of rubber hose or something, with a pick-up sock filter, to extend down where the pump pickup used to be.

I hadn't heard that L98's didn't have the fuel pump lobe. Later engines, yes. Guess that's something to verify before you get too far.

 

I'm looking at a stock L98 cam out of a '90 and it's got no lobe. Not to mention that behind the block off plate, there is probably no hole machined for the pushrod.

 

He'd better check his, then.

 

You dont need to drop the tank and pull the pump out, if you plan on using a mechanical pump. You have 2 fuel lines that go to the tpi coming from the driver side, a large line (supply) and a smaller line (return). You can use just use the smaller line (return), it extends into the fuel tank just as far as the supply line. This will keep you from having to drop your tank and remove the fuel pump, then extend the fuel line to make up for the missing pump in the tank.

Ohh, and some 305/350 blocks were machined with a mechanical pump provisions, it is easy enough to check. If there is a bolted on cover over where the mechanical pump goes, it has been machined. If no bolted on cover, plan on buying the by-pass regulator (it will save you a lot of time/effort).

 

You don't have to worry about the return line being too small? Will it still get the fuel to the carb with the right pressure?

 

The smaller line is fine for a carb., taken you are not hooking up 2 carbs, a dominator, or a nitrous kit. It was an easy solution I found several years ago when I did the same switch over from TPI to carb. I will mic the lines tonight, but what I remember is that the smaller line is about the size that a factory carb/mechanical pump fuel line should be (let me mic them first before taking that comment for fact).


As for pressure, you will not need a regulator with a mechanical fuel pump, it pumps the correct pressure for the carb. However, some aftermarket mechanical pumps do require a regulator, and if you stay with the factory electric pump, plan on using a by-pass regulator.

 

Not true. Factory size for carb'd engines was 3/8", V6 and V8.

Using the return line to suck fuel out of the tank is a bad, bad idea. Even if it "worked" for you.

 

so how can i find out for sure if a mechanical pump will work? i do have the plate where the mechanical pump would go.

 

If you have the plate there, that's a good indication that the block is machined for a mechanical pump.

To check the cam for a fuel pump lobe, stick a fuel pump rod in the block and check if it moves when you turn the engine over. You'll have to hold it up there, of course. One method would be to put it in, measure how far in it is, turn the engine over 1 revolution, check again. If it's the same in both positions, it doesn't have the lobe.

 

All of the blocks have the block off plate even if they've got an in tank pump all the way up to 95 or 96. What I've been trying to tell you people is that there probably is no hole between there and the cam for the pushrod AND there is NO LOBE ON THE CAM.

The return line will be too small even for a stock motor. Pulling the tank isn't a big deal. If you're this far into the conversion you should have no problem. I assume that if you're going through the trouble of this project, you'll be adding more power down the road. In that case you'll want to ditch the stock pump anyway and replace it with a good electric pump (255 or better) and a bypass regulator, or a decent external pump/regulator setup.

 

Wrong.....My 92 block (from factory) did not have a cover because it was never machined for a mechanical pump. The only reason that they would have a cover is if it was machined. The reason being is that when machined, oil would drip out of the engine if there were no block off plate. Ill post some pics of the 92" l98 roller motor (factory no block off plate, not machined) and a 87" 305 tbi (factory with block off plate, because machined). Just keep in mind that these engines/blocks were not specific to f-bodies. Trucks and some cars did not begin fuel injection until late 80's-early 90's and were carbed with mechanical pumps until then.


As for cam and lobe, if the block is not machined for a fuel pump, it would make sense that they might not have a pump lobe machined on the camshaft. I especially believe this true for a roller-cam block; since these were always fuel injected motors.

 

From what I remember from the swap years ago, the return line was not much smaller than 3/8; but as stated earlier dont hold me to that as fact without me getting them mic'ed first.

As for that being a bad idea even though it "worked" for me. No idea is a bad idea unless it is proven to not work, or is unsafe to try. I used the return line years ago, on a stock 350 with performer 600 carb, performer intake, shorty style headers, th350 trans, open rear diff with 2.77 gears, and stoick size 15" tires/wheels. It worked fine for me, no fuel starving or carb problems. His setup is very similar to mine years ago, might as well call it stock replacement parts. That is why I mentioned what worked for me.

Why did I not use the supply line? Being a high school kid at the time, $130+ on a bypass regulator was out of the question. the pain of dropping the tank with fuel and every other thing in the way--no way. The return line was the other option, and it worked. If you are building a performance engine, by no means use that return line. I would even consider weather 3/8 would work for a real performance application.

Enough crying about fuel lines for now, the HEI distributor hook-up will not be present from the TPI electronic distributor with coil. HEI only needs one wire ran from a key controlled power source, the other side is for tach. You will need to check the harness with a testlight/ohm meter to find the key power wire in the current harness.

 

I'm sorry, I forgot that people on this forum know everything. Your car must be a real piece of work, especially with your "modified return line" Yeah, that'll flow enough fuel to make some real power

As for the plate, I've got at least a dozen roller blocks sitting here at the shop. All of which are machined for a block off plate but none of which have are machined for a FP pushrod.

 

Okay, enough of the food fight.

The return line is 5/16". That's the size of the stock supply line I had on the '57, which was okay with a mild 350. When the 396 went in, I upgraded to 3/8". I wouldn't purposely put/use 5/16" if the original line is 3/8", which the supply line on our cars is.

As for the block-off plate:
My personal exposure is limited. '87 LB9, fully machined, block off plate installed. '96 LT1 shortblock, no machining, no block off plate (although the block off plate mounting was machined) - basically a "no-test", because the engine was partially disassembled. '90-ish ZZ3, fully machined. '93 LO5, not machined, no plate installed.

I have heard of LTx cams not having the fuel pump lobe. I have never heard that any 3rd gen era cams did not have the lobe, but as we all know, the factory has done some really weird things over the years.

To the poor originator getting the email messages that someone has replied to your post: Check out your engine as described, and please, please get back with us!

 

ok i took back the mechanical pump and got an inline electric fuel pump instead. what do i need to do now to set that up properly? i read that i need to run some wires for a switch or something?

Second question is, where can i get a clip for my HEI distributor and what do i need to splice and soder?


Thirdly, whats the deal with the throttle cable. can i modify my old tpi setup cable or do i need another? and if so which one do i need. is there like a rule of thumb where i can use one off a like 84 camaro or something like that? any part numbers

 

The type of regulator depends upon the type of fuel pump. Most likely, the in-line you got can use a dead-heading regulator - which is good news, since they are the least expensive. A return style would still be preferred, but probably not necessary. You should be able to use the same power wire that went to the in-tank pump (which I hope to hear you say you will be removing). Alternative: Take back the in-line electric and run the in-tank with a return style regulator (why aren't you doing that, again?).

The power wire that was on your coil will now go to the "BATT" terminal on the HEI distributor. I have used simple blade-type sockets with no problem (that's what's on the '57 right now, for instance).

You may be able to coil the TPI throttle cable around, but any '82-'87 factory carb V8 cable will do the trick. No clue on part #, most people get them from the junk yard or donor car. A TBI cable will probably work as well.

 

aight, so how do i wire up this pump? i know where i want to mount it i just don't know how to wire it mainly cause i have no clue where the intank fuel pump wires are. do they come out of the tank to a easy place to soder them or just splice them together?

I apreciate the help on this even with my repeated questions. it's just that i can't get any facts on how to do this conversion. most things i read or hear are opinion that i later find out don't work for me. and all the write ups i find aren't that in depth.

 

Wire the fuel pump to either a switched ignition source or to a manual switch. I would personally tap into the factory fuel pump fuse holder. Any fuse under the dash that supplies 12v. with the ignition in the "on" and "start" position will work. Ground the "-" wire to the chassis.

 

Does the distributor drive gear have to be changed? I have read that roller cams require a special distributor drive gear or it will destroy the teeth on your roller camshaft.

 

your good untill you get a roller cam. then its only a matter of time till the gear on the distributor strips. thats what i've gathered from this site.