Poly heads on an LA block

[patrick28]

My saga of restoring a 63 Power Wagon continues, and the machine shop tells me that the original 318 A series block I gave them is shot - but the poly heads can be salvaged. I read all the time about people putting Poly heads on an LA block, but has anyone here done this? Any gotchas to look out for?
By the way, I understand that it may be cheaper and easier to start from scratch with a brand new engine, but the reason I want to keep the poly heads is that rebuilding the engine is why I got the truck, and it'd be cool to keep at least some of the original engine.
Thanks!

[dodgeboykim]

Get yourself onto some Sweptline Facebook groups. A 318 Poly engines are out there.
As for the A heads onto an LA Block, I can't comment on that.

[PwrWgnDrvr]

Too bad you're on the opposite coast. I have a dozen poly's stashed here....LA's too.
As for the heads, I tried that once about 15 yrs ago. There are several machining issues that make it way less than simple, so I chose NOT to do it. Some of those are water jacket ports that don't line up and the biggest problem is the pushrods are angled away from each other. That causes half of them to hit the block so they don't line up with the rocker arm. A lot of grinding on the block may give clearance to solve that, but I wasn't up for that effort. Especially not knowing how much extra metal there is in that area. So, find someone who has done it and get precise details before trying it.
btw - what does "salvaged" mean for your heads? Typical valve job and hardened seats is an easy $6-800. That may not be worth the money w/o doing an entire engine?

[patrick28]

Great info, thanks! He quoted me $4k all-in to get the engine back in running shape, un-assembled. His comment was that the block was pretty wore out, so he needs to do everything. He quoted $1k just for the heads - like you say, hardening the seats, valve job, etc. My problem is I picked up the Power Wagon cheap mostly to get my hands dirty with tearing up an engine and learning - I was hoping to not have to put so much money in it, especially since I'm not really a collector. The other factor is how hard it is to work with Polys - my next headache would be finding headers. Having said that, I'm not really interested in just dropping a crate engine in, either. Is $4k a fair price?

[PwrWgnDrvr]

Maybe $1k is current price for head work - I don't know having not done a set in the last decade. $3k for block work seems insane. What does that include??? All my rebuilds have been in the $1000 - $1500 max for parts and machine work including flywheel and clutch parts, but Ive never had to bore a block or buy pistons. Of course, I do all the assembly myself.

[Series1Utiline]

$1k for grinding the valves, changing the seats and grinding them and, resurfacing the head is (per costs in my area) quite high unless he's doing more than what I've listed.

I have $400 in machine work on mine but in addition to resurfacing the gasket surface, I had them cut the heads for larger valves that I provided for my application, they added new larger seats, machined the valve spring pockets for the new springs I provided, and added new positive pressure valve seals at my request. The valves I used have a necked down stem and are stainless for my blower application so that added another $400. The springs and retainers were another $120 so that all totals $920. I spent another $350 on new rocker shafts, valve adjusters with locks and having my rockers bushed. My total is roughly $1300 but that included a lot of labor and parts most of which you likely wouldn't need or want in your application.

There is a fellow on the east coast that sells a steel adapter that allows you to run Gen III Hemi (shorty) headers on a poly. I made adapters for mine that mate Ford 302-351 (full length) headers to my poly.

Pick up another block and keep going on the poly!

[Conductorblg]

The poly head is what makes this motor different. If you're thinking about going to the LA head anyway and worried about the cost, do yourself a favour and find a running LA or Magnum motor. Looking into the engine compartment, LA heads and matching intake will make the two engines visual twins and only very slightly different from a Magnum.

What is "wore out"? Unless there's been a catastrophic failure or the block is cracked it's likely rebuildable. These engines predate "thin wall casting" and most poly engines will take a considerable overbore. Perhaps even .090 or .100. Even 1/8" is not unheard of, although sonic checking the block before going to any of those extremes would be advised. Shouldn't be any more difficult to do one of these than a LA or magnum motor.

Find the right set of pistons to put a 4" crank intended to stroke a 318 or 340 LA motor in the basement and we're talking 400 cu in at .090, 402 at .100, and 408 at 1/8" (.120). Throw in the right camshaft (even a reground), add a little head work (oversized valves, perhaps porting not unlike what has been described in this thread if you can afford it) and you'd be amazed. The 290 HP 318 in the 57 Fury is not the reason why Chevrolet and Ford came out later with high performance motors using staggered valve heads. A 400+ HP poly motor is more than do-able.