Well I appreciate the hope for possibly saving this engine...at least for now. A couple of rockers were surprisingly loose and the pushrod for intake on #2 was jammed up. Doesn't seem bent, but was just out of position somehow. I'll do a fresh compression test on those two dead cylinders tomorrow and see if adjusting all of the rockers helped anything. Looks like maybe a couple of intake valves aren't going down as far as others, so I think my next step is to pull the cam if it's still not cooperating.

I really appreciate all the advice! This is supposed to be a running project for my son, so if I can save this engine even if it's not perfect that would be awesome.

 

In case you’re not aware of the changes over the past couple of decades, the flat tappet cams aren’t used in any modern engine. So they’ve changed the oil formulations for less pollution. Getting rid of zinc, or more specifically ZDDP, has left flat tappet cams hanging out to dry in the wind.
So you have to be extremely careful which oils you choose. It has to say specifically that is for use in flat tappet cam situations.
Hopefully you were aware of that already, but just in case you weren’t, I figured I better mention it.

 

Hope it is as easy as put the push rod(s) back in place and all will be good.
But before you pulled the covers I was thinking if you have a air compressor you could put air in the 2 dead holes and see where the air was coming out.
Kind of like a leak down test.
Out the carb = bad intake valve
Out the tail pipe = bad exh valve
Out the oil fill cap = bad rings / piston / blow by

Once fixed you can still do that air test
Dave ----

 

Thanks everybody! We went through the valve adjustment procedure listed in the Haynes manual, replaced the very gummed-up spark plug in #8, put it all back together, and it purred like a kitten. I had already returned the compression tester so I didn't get any fresh readings, but it doesn't idle like it has a miss and isn't backfiring AT ALL anymore. Vacuum used to bounce wildly between about 8-14 while running...now it holds a steady 17. Still seems a few psi low, but it's so much better I'll take it at this point.

Of course, now we're running down some electrical issues with lights, but I'll keep digging or post that in another spot. Thanks again everyone...I thought I was in the market for a new engine just a couple days ago, so this group really helped me keep checking simpler solutions.

 

Hey, great news!
Don’t worry about the vacuum at this juncture either. The 17 is acceptable, though less than the 20 to 21 that we’d like to see on a stock engine. However, that may rise in the future for two reasons.
One is things might seal up a little better after you drive it for sometime.
But mainly, play around with the ignition timing. You might get a couple more inches of vacuum just by cranking in some more ignition advance if the engine tolerates it.

 

UNFORTUNATE UPDATE: After we got it purring like a kitten at idle and driving down the road, it made it about a mile before the backfiring returned. Re-ran compression test and cylinders 2 and 8 are still reading 0 compression. I ran a makeshift leak down test (where you take the Schrader valve out of the compression hose and listen/tissue test for where the air is escaping) and it seems on both cylinders that the leak is in the exhaust valve. At the same time, the compression on the good cylinders starts very low and gradually builds up over about a dozen compression strokes, which according to the Haynes Manual indicates worn piston rings.

All that being said, I'm thinking the inevitable conclusion is it's time for a rebuild/donor engine (unless someone on here can point to something I'm missing). I know it's burning oil (fouled plugs and smoke coming out especially on the left bank), which I was hoping was simply valve seals, but I'm now assuming it's the piston rings. So I initially thought about throwing rebuilt heads at it, but knowing the rings are also bad, that just seems like kicking the can down the road.

Any experience or recommendations on remanufactured engines? It's my 15 year-old son's truck (gotta love Idaho's younger driving laws), so I'm looking for a pretty stock setup...prioritizing reliability over anything else. I'm getting a quote from a local machine shop, and I've been looking at a reman from Powertrain Products Inc...anyone got experience or heard stories about their engines? I've also looked around for used donor engines, but there's nothing in the area that feels like it wouldn't be just rolling the dice on another unknown old engine.

In short, I guess I'm just looking for anyone who can think of something I'm missing before swapping the engine, and if not any advice on the best route to go for a non-show truck, rolling project for a young kid. Thanks for everything!

 

My reman long block 460 from ATK has been going strong for 14k miles. No complaints yet. I understand that their reman units are sold under many brand names and their main line of business is reman engines for the OEMs.

 

After another week of research, false starts, and some misleading suppliers, there is finally a reman engine on the way. Ended up going with Powertrain Products Inc. b/c reviews online were about 75% positive, and a rebuild at the local machine shop was gonna be $5-6K and 2-3 months. Talked with several other engine suppliers, and as cores become harder to come by, it seems their stock on hand becomes leaner as well. The only in-stock option was a '76 302 they had sitting on the shelf. I was hoping to get a replacement 351w to reuse all the tin/accessories, but I need to get my son back on the road so we can stop juggling 3 drivers and 2 cars.

All that to say, I think I have a handle on what can swap over and what can't. Am I correct in my understanding that the oil pan will not be the same? Also, does anyone have any good leads on an aftermarket 2-barrel intake for the 302. I can always junkyard or eBay a used OEM one, but I wouldn't mind starting fresh with an aftermarket unit...though I don't wanna upgrade to a 4 barrel carb at this point, which seems like the only aftermarket options I can find.

Thanks again for all your help, and I'll keep you posted once we get the swap completed and hopefully he's cruising down the road again.

 

Correct, they are different.
And I forget. Is yours a 2 Wheel drive or four-wheel-drive?
The pans are different between 2 Wheel Dr. and four-wheel-drive trucks as well. So make sure you get the correct pan and matching oil pump pick up tube for your truck.

Haven’t seen an aftermarket two barrel manifold in 30 years at least. Everything‘s four barrel, or four barrel with a two barrel adapter.
if you can find one, it probably wouldn’t be cheap. But you never know!

I have a two barrel 302 manifold from a 71. Wood bold write up, but would not have the same GR ports, and such as a 76 would have had originally. I don’t think anyway. But it would be awkward to ship I’m sure, depending upon where you are.

Sorry to bring this up again, but I never heard how you knew for sure it was a Windsor. But if you determined that it is, then the existing transmission and Bell housing will bolt right up to the back of a 302.
Most of the front accessories should bolt right on as well.
The imbalance factor will be the same 28oz. between the two, So no change in flywheel/flexplate is necessary.

Find out from the supplier what cam it has in it, Stock or replacement.
If they don’t know, you will have to determine manually, because the camshafts between 302s and 351s back then had a different firing order.
Not a big deal. Just something you’ll need to make note of before you do the final spark plug wire installation.