[grivera]

I have the opportunity to buy a 421 that was machined about 5 years ago but then sat in a garage and never assembled. It comes with the Armasteel crankshaft, 76 heads, and a new set of .040 pistons. I assume the heads aren’t worth much- also, the seller said to give him what I think is a fair price.

These are the best pics I have at the moment, realizing it will need reinspecting, cleaning and possible machining.

1965 421 WG block, date code D85 (or D35)
1965 389/421 heads, 9778776, date code D85 (or D35)
Armasteel crankshaft 9773384
New .040 pistons - waiting on part number

[grivera]

Pistons

[tom s]

Those look like 428 pistons.Tom

[grivera]

Thanks - do 428 pistons have a different pin height or is it just the dish and valve relief placement as the difference?

[John Milner]

The pin height will be the same. You would just have to be careful about running much lift if you used the 76 heads as the valve angles do not match up with the valve reliefs in the 428 pistons. I would say .450 lift would be close to the limit with that setup unless you switched to the later model heads. I would think everything would be worth in the $1,000-$1,500 range.

[grivera]

Gotcha - so if they at 428 pistons, the engine would need a .067 over bore?

[b-man]

Standard bore size is 4.09375” for the 421.

4.120” is standard bore for the 428.

4.160” is +.040” for the 428 pistons so you’re poking that 421 .06625” over which seems excessive unless the block wouldn’t clean up without going that far over.

Those 428 pistons are okay I guess other than the pressed pins and heavy forgings that are kind of obsolete. I’m assuming you’re going to run later heads that match the pistons, the 76 heads aren’t really worth putting any money into.

That’s a $2000 bottom end as it sits, the heads are worth maybe $50.

Has the block been bored to match the pistons already?

[grivera]

Thanks Bart

The block was supposedly machined and ready for assembly by the seller’s dad who passed several years ago. Since I’m not with the parts, I can’t measure but will ask him to. Is it possible the pistons are for a 421 and just have a dish in them?
Also, I may not take the heads as I’d have no intention of using them.

[b-man]

Absolutely not 421 pistons. The valve reliefs are completely different on a 421.

The valve reliefs and dish shown are what forged 428 replacement TRW/Sealed Power 12cc pistons all look like.

Pictured below, 421 piston with large reliefs and a 389 piston with smaller reliefs. The 421 used deep valve reliefs instead of a dish to lower the compression and enable the use of the same heads as a 389. The deeper reliefs aren’t there because the 421 cam had more valve lift (.407”} than the cam the 389s used.

[grivera]

Thanks - I zoomed in - the pistons are L2257, .040

So now just waiting on learning the bore size on block.

Assuming bored to the 4.160 size, will that typically cause issues with a 421 block, like thin walls?

[b-man]

Originally Posted by grivera

Assuming bored to the 4.160 size, will that typically cause issues with a 421 block, like thin walls?

Not really because the 421 block has a pretty robust casting compared to the 389s. However that much overbore kind of diminishes the value to a certain extent. When I bought my 421 it was standard bore, and still needed to go 4.135” to make up for some dummy who messed up the top of the bore with a ridge reamer.

Plus you’re banking on the unknown machinist doing the bore and honing correctly for the supplied pistons which isn’t necessarily a slam dunk.

Just for reference I paid around $1500 for my ‘64 421 HO 45B manual trans 370 hp block, crank, timing cover and matching 9770716 421 HO/389 GTO heads back in 2011. Also came with the original rods, pistons and 421 HO 9770543 ‘L’ camshaft.

[steve25]

I am trying to find my notes from 25 years ago in regards to the valve to piston clearance deal, but here’s what I recall off of the top of my head.
Using 428 pistons in a 421 build with its original heads would allow .480” lift to be run.

On the other side of this a 421 with its original pistons and fitted with 67 and up big valve heads would only allow a safe .450” lift.

The first part of what I posted here is not carved in stone until I find my notes.

[blueghoast]

I would think that the condition looking at the pics I would say 500-1000.
For what's there. That's just me?

GT

[b-man]

For something that’s supposedly been machined and ready to assemble it’s sure looking dirty and rusty.

Assume all the machine work that’s been done will need to be redone. Also assume that since the machine work is no good those pistons will now be undersized for the new bore size.

I’m going to revise my estimate to $1000 only because the 4-bolt block is valuable, again probably close to max overbore already. The crankshaft looks pretty rusty and who knows if it will even clean up at 30 under. The pistons can be resold to someone building a 428.

A virgin 421 block and crank maybe double that, this one should be bought cheap and even then it’s kinda been ruined by getting machined and poorly stored afterward.

And now, his asking price for this piece of ‘gold’ ?

Exactly how bad do you want a 421? Might be better to pass on this one.

[tom s]

JMHO,I would pay $1000 for the block.crank and the 428 pistons and heads if I was in the market for a engine.Someone will want the heads.Tom

[steve25]

What year car might this motor be going in. Something 67 and up?

You might be better off building a 400 with 3” main stroker crank to get up to around those cubes.

[grivera]

It would have been as a spare block - I haven’t made an offer at this point. The seller did say the pistons in picture fit in the so we know it’s been bored to accommodate those.

[61-63]

Originally Posted by grivera

It would have been as a spare block - I haven’t made an offer at this point. The seller did say the pistons in picture fit in the so we know it’s been bored to accommodate those.

I wouldn't pay anything for it until I went over and measured the bores with a dial micrometer and visually looked the block over inside and out. I've had all kinds of claimed things said about engine parts I was considering and sometimes they are true and sometimes not. Memories are not always accurate including my own and here say passed down over time even less so.

[steve25]

I would also check it for sloppy lifter bores.

[blueghoast]

Originally Posted by 61-63

I wouldn't pay anything for it until I went over and measured the bores with a dial micrometer and visually looked the block over inside and out. I've had all kinds of claimed things said about engine parts I was considering and sometimes they are true and sometimes not. Memories are not always accurate including my own and here say passed down over time even less so.

I have taken blocks that look loike that and cleaned up good with a dingle
ball hone, It might be worth the lower price like Tom S said.

GT