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#5834306 - 11/22/11 Anybody familiar with old Chevy big blocks?
BillyGoatGruff Offline
Campfire Tracker

Registered: 11/17/08
Posts: 5874
Loc: North Central MT
I'm hoping somebody here on the campfire can help me out with this. Lots of guys on here seem to know a lot more than me, though that doesn't take a whole lot. Let me preface this by saying I'm mechanical, but I'm no mechanic. If I understand how something works, and someone can explain it to me I can usually get by.

Here goes. I've got a 454 that won't start. It was in a 1/2 ton '76 suburban I bought 9 or 10 years ago off a buddy in OR. It was obvious that it wasn't factory, but it ran. I always wondered why the crossmember under the fuel pump had a big hole torched in it.......

This past summer I bought an 84 3/4 ton suburban that needed an engine. It came form the factory with a small block, but the guy I bought it from had altered it and ran a big block. A buddy with lots of know how talked me into the project, and helped me get the motor swapped over. I had always wondered what the engine came out of originally, so while it was out I checked the engine code. After numerous online searches, I was able to determine it came out of a '75 Chevy car, but not which model. If memory serves it was rated at 315 hp, so I'm pretty sure it wasn't a hot rod. I was on a tight timeline to get it done before my buddy moved back to ND, and he wasn't able to help me much after the initial getting it bolted in. I got it all hooked up and it ran, but not great. I took it to a mechanic in town and they adjusted the timing for me, and evacuated the ac. (it had a front/rear ac unit and between fuel economy and room under the hood I plan to pull it all out). It ran great! Heck if I kept it to no faster than 60-65 and didn't have to fight much wind I could get 10 mpg!

Now for the whole reason I posted this. It had been leaking gas off and on from the fuel pump, and when I had it in the shop I asked them to replace it. But when I picked it up they said they looked for leaks, and since it wasn't leaking they didn't replace it. Last time they get my $. I didn't ask them to check it, I asked them to replace it. mad With my deer tag filled, and a little time on my hands I pulled it in my shop and figured I'd replace the fuel pump. Now I found out why the cross member was torched on the old ride. When I got a new fuel pump from Carquest, I told the guy I needed a mechanical fuel pump for '75 model Chevy car with a 454, but I didn't know what model. He gave me one (#40963) but it was too tall, and wouldn't fit on the block because the crossmember was in the way. So I took it back along with the old one and said I needed a short one "like this". He looked though his book and found one. I asked for future reference what it went to so if I needed another one I knew what to ask for. He said it went to a '69 Camaro, and I don't remember exactly what package, but I believe it was a higher performance one. (#40727)

I get it back and put it on. Truck starts and I let it run for a minute and call it quits. I head back out a week later and it starts, and I back it out without letting it warm up, riding the clutch just to get it out of the way. I then try to start it and pull it back in the shop and she won't start. She tries, and almost goes, but no. If I floor the accelerator while I'm cranking it put put puts, and sounds sooo close. But it won't take off. I let it sit for a day thinking I'd flooded it and when I tried to start it the same thing happened. I gave it a shot of ether in the carb and was rewarded with a fireball. eek I know she's getting fuel, when I crawl over the motor while the wife pumps the gas I can see gas squirting in the carb. I was going pull the gas line and stick it in a pop bottle to see if any gas came out while I cranked the starter (just to make sure I was getting fuel) but when I started to loosen the hose clamp gas squirted out. I figured if it's under pressure the pump has to be working.

I know there's more possibilities (coil/distributor/gremlins), and I could certainly be wrong, but it seems to me like the issue is fuel or fuel/air. I've checked, and though my google-fu is weak I couldn't find any specs for the second fuel pump to see if maybe it was a higher output.

1) If it were a higher output could it be the cause of my problem?
2) Is there another pump with the same dimensions that would work?
3) Even thought he pump fits, there's not much clearance between the output valve and the crossmember. Should I (and how hard would it be) to install an electric pump?

If anybody made it though the whole story thanks, and sorry for the long read, but I wanted to give enough background to describe all I could think was pertinent.

Jason

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#5834375 - 11/22/11 Re: Anybody familiar with old Chevy big blocks? [Re: BillyGoatGruff]
ken458 Offline
Campfire Regular

Registered: 03/09/09
Posts: 781
Loc: west coast of AZ
Did the fireball come out of the carb? If so, your timing is off.

In 1976, Chevy did put 454s in 1/2 ton trucks and suburbans (454 began in 1973), just not 4x4s. Last year for a 454 in a car was 1974, so your engine is likely the original to the suburban. I remember back in the early 80s I swapped in a 454 into my 1978 3/4 ton 4x4, and it fit like it belonged there, (because they did). I did not have any fuel pump clearance problems...my thinking is that perhaps your motor mounts are shot, or the motor mount brackets that bolt to the block are the incorrect ones (not tall enough). The fuel pump you replaced yours with shouldn't be the problem, especially if its pumping gas. I would work out the other "bugs" you seem to have; as I don't think you have a fuel devliery probelm, but perhaps a timing issue. Good luck.


Edited by ken458 (11/22/11)
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#5834383 - 11/22/11 Re: Anybody familiar with old Chevy big blocks? [Re: BillyGoatGruff]
woofer Offline
Campfire Outfitter

Registered: 01/02/03
Posts: 7959
Loc: VT...
How old is the gas? Bottle of dry gas may help. Sounds like some water in the fuel maybe? If you getting gas in the card should burp. Fireball says u got spark but maybe a tad off.. Pull the distributor cap and make sure it is dry and the contacts are free off schmeng.

If it ran before for a minute your fuel pump should be good to go.... That is enough time for the float bowls to require more fuel and it worked...

An electric pump is easy to install. Bout' an hour or less with proper stuff.... Bolt to fenderwell, pump and give it some juice...

Would look for some other reasons first though...

JMO

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#5834496 - 11/22/11 Re: Anybody familiar with old Chevy big blocks? [Re: woofer]
BillyGoatGruff Offline
Campfire Tracker

Registered: 11/17/08
Posts: 5874
Loc: North Central MT
Thanks for the help guys!

Yeah, the fireball came from the carb. The gas is new, or at least not in the can for more than a month or so. The VIN from the old sub says 350 I think. Was a 4x4 anyways. Wish I could find that blasted engine code, I wrote it down somewhere........
Now that it's out of single digits I hope to get out there tomorrow and pull the distributor cap and make sure the connections are clean. Shop is clean and dry with a new metal roof, but heat is via a wood stove. So that ain't getting fired up till the fuel issue is done. Pump would have been an easy fix, now I'm back to pulling out my beard. If all else fails I can come-along it onto my trailer and haul it to town, but if it's an easy fix I'd sure like to save the hassle. And learn something while I'm at it.


Edited by BillyGoatGruff (11/22/11)

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#5834767 - 11/22/11 Re: Anybody familiar with old Chevy big blocks? [Re: BillyGoatGruff]
walt501 Offline
Campfire Regular

Registered: 12/20/10
Posts: 961
Loc: Minnesota
Simple stuff, is there a fuel filter inside the carb? Most Rochesters had them there and you'd have to take the fuel line off the carb to get it out. It may be partially plugged. Check your cap and rotor. At least take the cap off and wipe everything off inside. This time of year moisture can build up inside the cap. Check your timing, but know that the distributor could simply be worn out. The gear that connects to the cam was notorious for wearing out. I believe the aftermarket still sells a brass replacement distributor gear. If you have fuel, then the only other thing is spark. If you have a volt/ohm meter, check the resistance on the plug wires. Remove the plugs and see what is going on there. That would also be a good time to do a compression test and see if there are any internal engine problems.
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#5834820 - 11/22/11 Re: Anybody familiar with old Chevy big blocks? [Re: walt501]
BillyGoatGruff Offline
Campfire Tracker

Registered: 11/17/08
Posts: 5874
Loc: North Central MT
Thanks walt. There is a fuel filter in the line before it gets to the carb (which is I believe a 4 barrel edelbrock). I can pull plug wires and check, and probably will, but I put a new cap, rotor, wires and plugs when I swapped it over.

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#5835036 - 11/22/11 Re: Anybody familiar with old Chevy big blocks? [Re: BillyGoatGruff]
ken458 Offline
Campfire Regular

Registered: 03/09/09
Posts: 781
Loc: west coast of AZ
If you find you need to replace the distributor or any electical parts in it, by far the cheapest way to go is get a NEW HEI from ebay. I've bought two so far, as something happened in my '86 Chevy 4x4's distributor, and rather than start replacing pricey electronic gadgets (module, etc.) I bought a NEW HEI for $48 shipped! Truck runs great now. They are always on ebay for that price.

Oh, forgot to mention that the HEI's come with new coil, cap & rotor, but no wires.


Edited by ken458 (11/22/11)
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#5835178 - 11/22/11 Re: Anybody familiar with old Chevy big blocks? [Re: ken458]
BillyGoatGruff Offline
Campfire Tracker

Registered: 11/17/08
Posts: 5874
Loc: North Central MT
Thanks for the tip! We're going into territory about which I know less and less. I did replace the distributor on my '92 chevy v6 once, but to do it again alone would be a real learning experience. It's not yet critical that I get it running right now, so I've got some time to tinker.

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#5835728 - 11/22/11 Re: Anybody familiar with old Chevy big blocks? [Re: BillyGoatGruff]
walt501 Offline
Campfire Regular

Registered: 12/20/10
Posts: 961
Loc: Minnesota
Another thing to check is the plug wire connection at the plug. Most aftermarket wires, regardless of price, simply use a round crimped metal connector that after a few plug changes no longer has good tension against the plug. Easy to test for this, assuming your plug boots aren't frozen to the plugs, just wiggle the plug wire terminal at the spark plug. If you can feel that is not holding the plug tightly, that may be a big part of your problem. AC/Delco wires used a metal clamp with another clamp around the outside to maintain tension on the plug. They were the only brand of plug wires I'd ever use in my old '77 Suburban.
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#5841843 - 11/23/11 Re: Anybody familiar with old Chevy big blocks? [Re: walt501]
thetrio Offline
Member

Registered: 02/16/07
Posts: 21
When I was much younger, I did a swap of a 454 into a 75 chevy truck that had a 350.

From your description, I would guess a timing issue rather than a fueling problem. I would take the timing to Top Dead Center and then see if it starts. You do this by using using a very large socket that fits the fly wheel and move the fly wheel (clockwise) until the timing marks to line up at zero. Then you can check where your distributor is lined up to make sure that it is going to spark off the first cylinder. You should also check to make sure the piston is at the top of it's stroke by removing the spark plug and seeing or feeling the position of the piston.

We ended up with timing at idle around 12 degree befor TDC at idle if I remember correctly (been so llllooonnnnggg ago).

We ended up going with an electrical fuel pump to add more clearance to the cross member compared to the mechanical fuel pump if I remember correcly. The mechanical pump as you found out sits mighty close to the cross member / frame and our 454 had a lot of torque and got uncomfortably close to hitting it when hitting the gas and letting off.

The HEI unit is a great suggestion too.

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#5842247 - 11/24/11 Re: Anybody familiar with old Chevy big blocks? [Re: thetrio]
BillyGoatGruff Offline
Campfire Tracker

Registered: 11/17/08
Posts: 5874
Loc: North Central MT
More good help, thanks. I went out last night with the intent of pulling the cap checking for good connections and pulling wires and checking them. I said why the heck not and tried to start it, and I'll be darned if it didn't fire right up. So I took it out for a spin and she ran like crap, about died several times. Didn't want to idle, sounded rough too when it was running. After filling the shop with fumes, I figured I'd get after it again this weekend when I have time. If it is a timing issue I guess I'll have to take it in somewhere. I got the names of a few mechanics in town today.

And I'll definitely be exploring an electric fuel pump this summer, as the clearance is not confidence inspiring.

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#5842386 - 11/24/11 Re: Anybody familiar with old Chevy big blocks? [Re: BillyGoatGruff]
bethalhntr Offline
Campfire Regular

Registered: 07/26/11
Posts: 454
Loc: The Evergreen State.
Make sure and check for vacuum leaks, That could be your rough idle. Vacuum lines at the carb and make sure your carb bolts are snuged down good. Normally a chev will have a Quadrajet, If you have a carter afb there might be a spacer between the intake manifold and the carter, You might find the problem there. Best of luck, Deen.

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#5858937 - 11/29/11 Re: Anybody familiar with old Chevy big blocks? [Re: BillyGoatGruff]
Bull_Elk Offline
Campfire Regular

Registered: 05/03/03
Posts: 1140
I have an 85 3/4T Suburban with a 350 and about every 3 or 4 years I find myself changing the ignition module in the distributor. The first time it went out I was pulling a hill and I didn't think it would make it over the top. Took it to the dealer the next morning and because it cooled down overnight, it ran like a champ. They changed the module on a hunch and it ran great for a couple years until one day it didn't have the power to pull itself from a wet paper bag. Changed the module and off and running again. I've seen them act up when hot or just fail entirely. I carry a spare in the glove box with a phillips screw driver and a 1/4" nut driver. Depending on the vintage of your distributor, this could be an issue for you too.
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#5861979 - 11/30/11 Re: Anybody familiar with old Chevy big blocks? [Re: Bull_Elk]
BillyGoatGruff Offline
Campfire Tracker

Registered: 11/17/08
Posts: 5874
Loc: North Central MT
Thanks for the help and ideas guys. So now in the last couple days I got a fuel pressure gauge and regulator. I put the gauge in first and it read at 8 psi, which from what I've found is within the range it should be, but I figured I had the regulator so I tried it. I put it on wide open and it read over 9 psi and with it running I cranked it down to 6 psi, but no change. It still ran poorly. So I pulled them off and ran the fuel line directly from the pump to the carb again. I pulled the wires and cap, and I did find one wire that was all corroded up at the clip where it snaps over the plug. So I replaced that one and a couple others that were sitting too close to the headers with wires that had 45 degree booties. I also replaced the ignition module. One thing to note is that all 8 of the plugs were carboned up really bad, as in it wouldn't just wipe off on my coveralls, I had to scrape it off with a knife.

So tonight with a new module, and good plug wires I tried her again. She fired up and idled, but didn't sound quite right. At higher rpm is sounded better/smoother, but at idle it wasn't a purr. I can't really describe it but it just didn't sound right. I took it out and drove it around for about 10 minutes and it just got worse, to the point it stalled. To get it to start I had to floor the accelerator and wait and after a few seconds the rpms picked up and I limped it back in the shop.

I think I've now exhausted all I can do with my limited knoweledge myself. A buddy offered to let me borrow a timing light, but I don't know how the heck to work on timing. When I pulled the cap off the connection points inside had a little buildup, but nothing that didn't scrape off pretty easy. The wires do look pretty old and it was a little rusty in there.

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#5862210 - 11/30/11 Re: Anybody familiar with old Chevy big blocks? [Re: BillyGoatGruff]
walt501 Offline
Campfire Regular

Registered: 12/20/10
Posts: 961
Loc: Minnesota
Do you have an exhaust back pressure valve? That's not the correct name, but I can't remember what it used to be called. Anyway, it should be located right where the exhaust manifold meets the exhaust pipe at the rear of the engine, usually on the passenger side. It looks like a spring with a weight attached, and you should be able to rotate the weight by hand. Its purpose is to hasten engine warmup, but if they become stuck they cause all manner of drive-ability problems. If you can't rotate the weight, try spraying some penetrating oil on it and leave it sit overnight.
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#5862238 - 11/30/11 Re: Anybody familiar with old Chevy big blocks? [Re: walt501]
BillyGoatGruff Offline
Campfire Tracker

Registered: 11/17/08
Posts: 5874
Loc: North Central MT
Hmm I'll check tomorrow, but I don't think so. I believe it's just headers straight back to the mufflers and tailpipes.

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#5862245 - 11/30/11 Re: Anybody familiar with old Chevy big blocks? [Re: walt501]
ken458 Offline
Campfire Regular

Registered: 03/09/09
Posts: 781
Loc: west coast of AZ
Originally Posted By: walt501
Do you have an exhaust back pressure valve? That's not the correct name, but I can't remember what it used to be called. Anyway, it should be located right where the exhaust manifold meets the exhaust pipe at the rear of the engine, usually on the passenger side. It looks like a spring with a weight attached, and you should be able to rotate the weight by hand. Its purpose is to hasten engine warmup, but if they become stuck they cause all manner of drive-ability problems. If you can't rotate the weight, try spraying some penetrating oil on it and leave it sit overnight.

I believe he mentioned that he has headers, which would eliminate the exhaust back pressure valve of the stock exhaust manifolds.

I would go on eBay and order up a $48 delivered NEW HEI distributor, and buy a new set of wires and spark plugs and install it. I bet that fixes your problem.
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#5862419 - 11/30/11 Re: Anybody familiar with old Chevy big blocks? [Re: BillyGoatGruff]
358Norma_fan Offline
Campfire Regular

Registered: 11/05/09
Posts: 918
Loc: Anchorage Ak
Originally Posted By: BillyGoatGruff


So tonight with a new module, and good plug wires I tried her again. She fired up and idled, but didn't sound quite right. At higher rpm is sounded better/smoother, but at idle it wasn't a purr. I can't really describe it but it just didn't sound right. I took it out and drove it around for about 10 minutes and it just got worse, to the point it stalled. To get it to start I had to floor the accelerator and wait and after a few seconds the rpms picked up and I limped it back in the shop.

I think I've now exhausted all I can do with my limited knoweledge myself. A buddy offered to let me borrow a timing light, but I don't know how the heck to work on timing.


Sounds like you might have a carb problem. It sounds like it's running rich and loading up, hence the having to hold the pedal to the floor then clearing up. Needle and seat may be worn or the floats are bad.

Highly recommend getting the timing light and checking to see where the base timing is, as well as making sure the advance is working. I don't remember what base timing should be off the top of my head, but a chilton manual will have it as well as instructions on how to check the timing.
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#5865348 - 12/01/11 Re: Anybody familiar with old Chevy big blocks? [Re: BillyGoatGruff]
tzone Online   content
Campfire Oracle

Registered: 02/23/04
Posts: 30617
Loc: MN
Bad plugs, wires, cap, rotor/points can make a motor do funny stuff.

With all that carbon build up, it sounds like it is a timing or fuel problem. When you had the timing adjusted the first time, it may have helped, but with the mixture of carbon, bad wires, and crusty points, it may be wigged out again.

I'm far from an expert on this stuff. It sounds to me like you're checking the right stuff.
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#5865608 - 12/01/11 Re: Anybody familiar with old Chevy big blocks? [Re: tzone]
BillyGoatGruff Offline
Campfire Tracker

Registered: 11/17/08
Posts: 5874
Loc: North Central MT
I'm going to dive into the carb this weekend. Never looked in one before, always thought they required voodoo to understand/work on. But heck, I'll learn something, probably quite a bit, and if I can get her cleaned up and maybe rebuilt it'll help. I won't get the timing light from my buddy for a couple weeks probably so I'll do this in the mean time.

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#5866928 - 12/01/11 Re: Anybody familiar with old Chevy big blocks? [Re: BillyGoatGruff]
northern_dave Offline
Campfire Oracle

Registered: 09/29/04
Posts: 30982
Loc: Minnesota
I'm sorry I haven't opened this thread until now. Tzone brought it to my attention.

Please leave your timing and all ignition related items and adjustments alone. Don't go chasing gremlins that aren't there.

You have a fuel problem. I saw it from your first post and every post you have made since your initial post confirms it.

You are flooding, plain and simple.

Your black plugs, the sluggish running, the heavy fumes, having to hold it open to clear the cylinders to get it to start.

Rich, rich, rich.

You have gone down the right path on your own with fuel pressure gauge and regulator, this tells me that you also suspect a fuel issue.

Mechanical pumps like you have installed usually aren't going to give a problem with overpressure that will overpower your float unseating your needle and flooding your carb.

I do like around 6 PSI myself for a street application where your engine is sucking it's air through a carb.

Overpowering your float with too much fuel pressure is the first suspect and possibility. It's more common in cases where an IFI set up with elect fuel pump has been replaced with a carb but the guy is still running the old efi pump.

Do you have an edelbrock 4 barrel like you spoke of earlier? looks like an old Carter AFB?

does it look like this?



This one pictured has an electric choke, does yours have that or is it a manual choke?

here are a couple other possible carbs you might have on your big chevy.

holley:



this is a rochester quadrajet:



Please tell me it's not that ugly sumbich you have on your engine....

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#5866982 - 12/01/11 Re: Anybody familiar with old Chevy big blocks? [Re: northern_dave]
northern_dave Offline
Campfire Oracle

Registered: 09/29/04
Posts: 30982
Loc: Minnesota
Check your engine oil too gruff, pull the dipstick and see if the level is high, smell it and see if it smells like gas.

If your old pump was leaking they can leak into the engine and put fuel into your oil. It's a diaphram that causes leaky fuel pumps, if the diaphram cracks then fuel leaks through to the dry side of the diaphram. Usually there is a weep hole on the dry side that allows the fuel to leak outside of the engine but gunk or other things can cause it to basically have "internal bleeding" as in, the gas leaks into your engine block instead.
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#5867182 - 12/01/11 Re: Anybody familiar with old Chevy big blocks? [Re: northern_dave]
ken458 Offline
Campfire Regular

Registered: 03/09/09
Posts: 781
Loc: west coast of AZ
great suggestions northern dave. But why the hate on Q-Jets? wink
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#5867214 - 12/01/11 Re: Anybody familiar with old Chevy big blocks? [Re: ken458]
northern_dave Offline
Campfire Oracle

Registered: 09/29/04
Posts: 30982
Loc: Minnesota
Shortest answer I can provide is... I'm a Ford guy lol!!

That being said... I actually had a Q-jet on my 360 ford in my plow truck until just recently.


Q-jet in all honesty is a remarkable fuel delivery device, it stands far out from the croud of conventional jet and power valve metered carbs.

But, it can be a love hate relationship. High maint IMO.

If gruff does have a q-jet, I'd suggest running that fuel pressure in the 3-5 psi range, no more than 5.

I'd also suggest he look at the float first as the plastic foamish floats are kind of notorious for becoming saturated and not being able to close the needle. The needle has a wire clip that has to be installed correctly as well. it is very common for q-jets in particular to have this spring installed incorrectly. Also the welch plugs often leak in these carbs, it was common for them to be installed and also JB weld sealed on rebuild to help prevent leaking.

We'll let gruff come back with an ID on his carb before I go dishing out too much trouble shooting though.

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