400 Block question..
 

I have a 1973 400 bare block.....

A local shop has expressed interest.....but declined because the original main caps are not there.....

I have another set...but said shop they would have issues line boring it without original #1 and #5 caps....

Is this block junk...or are we missing something..?

Any input is appreciated

Kinda worthless with the original caps missing.

Had the almost same thing happen with a 455 block I bought that supposedly was 4-bolt main, before I knew anything about block codes. It had 4-bolt caps alright but they weren’t original to the block, turned out to be a 2-bolt block with 4-bolt caps slapped on it.

Shop couldn’t handle the job right and ended up with a nightmare that I won’t get into here, and the #1 & 5 caps were still original.

Blocks missing the caps especially all 5 are pretty much worthless at least to me and plenty of other people. A nice 2-bolt 400 block with the original caps still intact is worth building up to around 600 hp, one without any caps is pretty much just scrap iron.

It’s junk, I think your shop knows their stuff. If it was the last 400 block in existence it might be worth doing something with…..but it’s not.

great thanks...

Anything can be fixed.

Whether or not it’s economically feasible is the question.

Locating all 5 caps properly and line boring by any competent shop won’t be cheap, probably about the same cost as buying 3 or 4 good used 2-bolt 400 blocks with the caps still intact. Getting that rear cap to properly hold a main seal in decent enough alignment with the crankshaft is a big issue.

Ok....on to plan B

That shop contacted me wanted a 400 bare block....

I have a 74 400 core with 4x heads,,,crank rods pistons,etc...

I'm not interested in taking it apart...

What would be a current fair selling price to ask..?

Maybe somewhere in the 400 to 600 dollar range.

Also depends on where you’re located.

The crack-prone 4X heads don’t add much value but maybe if they’re looking at rebuilding it stock they’re worth having.

I'm guessing they have everything they need for their build but OG block was not useable...

I have a 428 that had a problem with the rear cap. I brought the block and a 455 rear cap to a machine shop and they were able to make the other rear cap work. They pulled the dowels in the block, ground the donor cap, located the donor cap, drilled/installed very slightly larger dowels in the block/cap and gave the rear journal a line hone to size the bore properly. So far so good on that engine. I do believe the thrust cap causes some problems when trying to use different caps than what came on the block. Adding different caps to a block is doable but it is expensive and really needs to be done by someone with experience with Pontiacs.

Is it std bore ?
Might be worth getting some aftermarket caps. But its a problem. If it were just the 3 center caps it might be worth getting some program Engineering billet steel or Milodon ductile iron caps.
But that rear one is very expensive from Program Engineering and then you have machine work.

I got a RA V block missing all 5 caps,5 billet caps and line hone got it done.Just numbers in a check book.Tom

Well said, Tom. I have align bored over one thousand blocks, most of which were missing one or more main caps. Unless you are using aftermarket caps ( nearly all of which are undersize to allow for fitment) you are pretty much going to have to have multiple sets of OE main caps to find ONE set that will actual fit close enough to align bore the main saddles.

It really depends on the skill of the machinest and the equipment being used.

Having the 1 and 5 caps does make the job easier. So does having buckets of used caps to match up.

I definetly wouldn't discard the block with no caps if all else is good with the block.

Of course a RAV block missing the caps is worth putting numbers in a checkbook to fix.

Exactly what were those numbers Tom, for inquiring minds? To give folks a real-world idea of the actual damages involved with bringing a block back to life missing all the caps.

If i owned that ‘73 400 block without any caps I’d give it to the first person who would pick it up.

That includes the scrap man.

I have all the main caps except for the rear main from a 73 400 block.
You can have them if you want, just pay shipping.

Bart,I have to go back and see what 5 billets caps were from Butler.I remember that was the big nut.Tom

I did the same thing. Sent a 1970 4-bolt 400 block to a machine shop for a sonic check. They went out of business and lost all the main caps. I only retrieved the block back. I bought all 5 mains from Pro-Gram Engineering. My engine builder installed them for $550 at the time. It was used on 4.125 stroke / 4.165 bore combo that made 699.9 hp at 6900/7000 rpm. This before the aftermarket blocks. were the norm.

"Just numbers in a check book. Tom" :)


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Full set $730 plus tax and shipping now.Tom

Recent block I had done for a friend not necessarily done in order listed.

Block was Baked and tumble .
Squared
Mag
Sonic tested. Thinest spot .180
Pressure tested
Lifter bore brace installed
New Cam bearings installed
Bored .030 over
New freeze plugs
Oil galley front plugs taped for threaded plugs installed
Line bore checked.
Rear oil Galley rear plug oil drilled for Distributor oiling.
Oil restricters installed.
Thank god it didn’t need steel caps and a line bore
Total cost $2700.00 including $300.00 cost for block. I can see why buyer past on 73 block.

For me if your not interested and doing all this, I’m not interested. Can you imagine doing all this but never having block pressure tested. Your talking 50 year old blocks and who knows their history.

Aftermarket caps ? Use larger diameter dowl pins already mentioned.

https://butlerperformance.com/c-1459...owel-pins.html


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Labor to make the block happy with the caps probably cost at least that much as well.

So not easy to make the decision to save an orphaned 400 block when by the time the caps are ready to go and you still haven’t paid to finish the machine work completely you’re about halfway to the cost of a nice strong aftermarket block.

Just because you can doesn’t mean you should.

Not every Pontiac block is worth saving.