well, i cant figure out the issues with my sbc with vortec heads

[01maroonz71]

long story short....

i bought the truck back, and the guy i sold it too had vortec heads installed. truck still had edelbrock 1406 carb i put on it when i installed the crate motor 10 years ago. he obviously installed a different intake, but had the same crappy headers on it.


fast forward to this year, i bought it back, as im pulling it on the trailer the guy said it has sat with old gas in it for a while, and that it doesnt like the gas in it.

it was almost empty, so i filled it up with fresh gas and some sea foam. drove great for about 20miles, then it began, thing runs like hell now. i just rebuilt the carb, installed new plugs, wires and headers. timing is set to 12 at baseline, with the dizzy unhooked. not sure on what the advance number is. even at idle it fluctuates a tad and as soon as you rev it, it sounds awful.

im not real sure where to go next. any ideas?
thanks so much

 

[paratrooper307]

First, check all the easy stuff. You never know what a previous owner has done. Make sure all your work is good, if different problems appeared after what you did that would be something to track down.

Fluctuates at idle--could be a lot of things, from a vacuum leak, to timing chain, to valve issues. Get a vacuum gauge and based on its behavior you'll be able to rule out problems like leaks, valve issues, and blocked exhaust.

Pull off the valve covers, check for loose rockers, bent push rods, broken springs, and evidence of wiped cam lobes.

Look at the old plugs. Their color and condition can point to potential issues.

Can you elaborate on "sounds awful"? Are we talking top end noise or bottom end noise?

The fact that it ran fine for 20 miles and then started acting up is suspicious, as if the seller was hiding a problem. Good luck!

 

[1-ton]

When it comes to a top-end job, if the PO did not have a clue what he was doing...he could of screwed-up a lot of things. Which is why he sold it back to you because he was in over his head.

 

[01maroonz71]

the sounds awful thing sounds like it's pinging. sorry, should have been more clear.

the ignition system is the original one that was on the truck when i bought it before i put the crate motor in. the distributor/coil im sure is probably tired/wore out, so im going there next. im going to get an HEI distributor, but im not sure that what i have now isn't one.

can anybody tell me what type of setup this is?

i literally pulled the distributor out, and dropped it in the new crate motor when i swapped it all those years ago.

i do not think it's an HEI setup b/c i had to crimp on the points style connections on my accell plug wires when i put the new headers on.

also, shouldn't my 83 have come from the factory with an HEI setup?

thanks so much

 

[paratrooper307]

An 83 would have come with an HEI setup from the factory. That isn't an HEI system, and probably worth changing because of age. Do yourself a favor while you're in there, and clean up those vacuum lines and butt connectors/quick connectors on the wiring, those will just be headaches down the road.

Pinging could mean advance issues. Vortec heads don't need a lot of timing. Vortec heads also require self-aligning rocker arms (or machining). If they weren't used, the pushrods won't clear and will make noise.

 

[diesel4me]

Might check to see if all the plug wires are on the right plugs...
1-8-4-3-6-5-7-2...clockwise rotation...rookies often mix up the firing order...
I have seen quite a few chevy's with the #5 and #7 wires crossed and on the wrong plugs..

 

[dyeager535]

Could also have used the wrong plugs. See that a fair bit with the vortec heads. Wrong plugs will have bad results.

 

[paratrooper307]

Might check to see if all the plug wires are on the right plugs...
1-8-4-3-6-5-7-2...clockwise rotation...rookies often mix up the firing order...
I have seen quite a few chevy's with the #5 and #7 wires crossed and on the wrong plugs..

If you mix those two up it'll run, but it will get worse as you rev and pop and backfire. Ask me how I know...

There's really only so much that could be wrong. Time to sit down with these suggestions and start eliminating potential causes. That's the frustrating thing about buying someone else's problem.

 

[JoshHefnerX]

just start w/ the basics, fuel/air/spark.

HEI started on 70's trucks. My 77 had one, my 80 has one. so yours should have one.