Engine: How far can you bore a standard Stude V8 block ?

[BalkaRoo]

Well,
I may have hit a snag when I went up and had a talk to my machinist !
When he was talking to me on the phone he was talking about "oversize" he thought about .030 oversize pistons which I thought, "you beauty", but when I had a look at them they are actually flat tops in 3.655 size for the standard bore R3 304 cube engine. These pistons are brand new, never used, .093 oversize ! "come-on, Really"!!!!
Anyway, I "didn't" give him the go ahead to use them "yet", as I have read that a boring up to that is a "questionable" undertaking and the thought of taking that much metal out scares me to think about. What do you guys think, I don't want a high performance engine but I will admit the bragging rights to say "its got a 304 ci engine in it" is appealing even if it makes me look like a "complete d--k h--d" ! So, what do you guys think, can a standard full flow block be safely bored that far ! I also have to take into account that its 60 years old and could have some metal missing on the coolant side. He can sonic check the wall thickness, but I just thought I would run it past some of you who may have done it yourselves or at least heard about actual outcomes from some who have already done it. I have also read that the pre full flow blocks can be bored more successfully than the full flows, is that a fact, I have two 1962 type pre full flow blocks, would I be better off using one of them ?
Apparently, the engine these pistons came out of was and still is fitted into an Avanti, but with the performance cylinder heads fitted, the compression would have been too much for what the owner wanted to do, so it had dished pistons in the same 3.65 size fitted into the freshly bored cylinders. Obviously the Avanti owner had it done, but I don't know if it was successful or not. The engine guy I was talking to was involved with removing these pistons and fitting the replacement dished set and had forgotten over the last couple of years exactly which size they were when I rang him up out of the blue a couple of days ago.
The machinist didn't know if they were genuine made in the US for Studes or modified pistons as replacements, but looking at them they "look" like they are genuine ! Pin height is "exactly" the same as the dished originals !

Graham

[Bud]

I don't think it's a good idea to bore a stock block more than .060 oversize especially the later blocks that I understand can suffer from core shift issues and can have thinner spots in the casting. We tried boring a 63 R2 block to .140 oversize and hit water in a couple of cylinders so that wasn't good as sleeves were necessary to fix the problem. You are correct about a 60 year old block that could have a substantial amount of rusting which makes things even thinner. If I remember correctly Ford 292 pistons look like Studebaker pistons and will work but I believe their diameter is larger than Studebaker. This info comes from a guy that used to drag race a Studebaker and he said he was using 292 Ford pistons. Bud

[fastjohnll]

Check this out----- https://www.speed-talk.com/forum/vie...hp?f=1&t=37652

[Mike Van Veghten]

Graham -

Your best / safest bet is to have the block "sonic" checked.
This is an electrical meter that sends sonic waves into the metal and the meter will tell you how thick your existing walls are.

A good shop will check up and down every cylinder, at about 1" or 1-1/2" inch intervals, and at the 12, 3, 6 and 9 o'clock positions. This will give you a good map of each cylinder, and the wall condition.
You find the thinnest location. From that you know exactly how far you can safely bore the block.

The thinnest location for a non-supercharged would be about .13" thick (3.30mm).

Mike

[PackardV8]

Yes, .093" is usually safe and we've done several at .118"
No, not always. As you mentioned, there can be internal corrosion, core shifts, occlusions. One try opened a hole at .080"
Maybe, as MVV suggests, have yours sonic tested. On a full-flow, pay special attention to the areas nearest the oil filter adapter pad. Carefully visually inspect all the areas visible through core plugs and coolant passages. Even that is no guarantee, as a sonic test can easily miss a random occlusion. The good news is if there is only that one bad spot, the cylinder can be sleeved.

jack vines

[Buzzard]

I wholly concur with Jack.
I have 1963 R4 clone which was bored .093 for Jahn's Forged pistons and 12 1/2 compression. Here some 50+ years later, it is still very impressive with it's performance. On an NHRA track in the early 90's, it propelled my '63 GT Hawk to 14.6 @ 94 mph defeating a HIPO Fairlane in the next lane. (Seeing as it was in my windshield at half track, it still overpowered the Ford to the end). I was accused of sandbagging.
Go for it!
Bill

[Alan]

I have bored 1 out to 3 3/4" for 320 but I had to go through a few with a sonic tester to find one that would go out that far and leave .100" min wall.

[RadioRoy]

Are you considering this large bore just because the machinist found the pistons?

Wouldn't it be better to determine the minimum overbore that the block requires and then find some pistons that size?

[Bud]

I aggree with Radio Roy.It's been my theory that a block shouldn't be bored more than necessary to clean up the bores for an engine that will not be used for racing. Usually that will be .030 over and possibly .040 over if the cylinders are really worn. There are no more Studebaker blocks being cast so doing the minimum amount machining could mean that the block could be bored another time, saving the block and a bunch of money as sleeving 8 cylinders back to standard bore is not exactly cheap. Bud

[Hawklover]

Bill back in 1995 when I had my R-1 engine rebuilt at 97K miles I was told there was no need to bore the block??...........standard size rings were fitted and I have to admit that the car runs beautiful burns no oil and has plenty of pep. But till this day I question how an engine run for 97K miles could have no "abnormal" ware to the cylinder walls??? True, I have changed the oil every thousand miles since the cars purchase in 1966. LOL, still "burns" me that the "re builder" never changed the cam bearings..........but I do have excellent oil pressure. Go figure:-)

[PackardV8]

True, I have changed the oil every thousand miles since the cars purchase in 1966.

You answered your own question.

jack vines

[BalkaRoo]

Thanks Guys !
That is pretty much what I thought. I have been in a bit of a "quandary" about what to do here. In a way I agree with Roy, and in a perfect world it only needs to be bored .030, but these pistons are available "here" and "now" and I do have "spare" 259 blocks I can use if something goes wrong, or I can keep the original block with its original engine number and use one of them. I have a 64 Canadian numbered full flow block that has already been bored to .030 so I could use that, or I am seriously considering using one of the pre full flow 259 blocks I have ! You guys might think that's a silly option, but remember, my GTs are right hand drive and when built the oil filter would have fouled on the steering box so a blanking plate was installed on the oil filter base pad to redirect the oil, and a bypass filter was installed on the front filler tube in the same way the older cars did. I have read that pre full flow blocks give less problems when checking the number 6 and 8 cylinders around the oil filter area. Is this actually the case and is it only the case up until 1960 ? I have read on line that early blocks were less troublesome, but that site gave a date of 1960 as a cut off, whereas the pre full flow block went on for a couple of more years.

Graham

Edit,
By the way, would a 3.655 bore need different head gaskets to the 3.562 289 type (I already have a standard 259 - 289 gasket set ! )
Thanks,
Graham

[Hawklover]

You answered your own question.

jack vines

Thanks Jack coming from you I am humbled;-)

[Jeffry Cassel]

Would not go over 0.060" because there was a lot of metal there originally but it has been subject to 70 yrs of corrosion. Saw a 327 bored 0.060" with an impressive hole in the cylinder wall where it had blown thru the little bit or iron that remained. (No, I didn't do it!)

[PackardV8]

Would not go over 0.060" because there was a lot of metal there originally but it has been subject to 70 yrs of corrosion. Saw a 327 bored 0.060" with an impressive hole in the cylinder wall where it had blown thru the little bit or iron that remained. (No, I didn't do it!)

That's every obsolete engine builder's nightmare; a thin spot which doesn't show, but breaks through under the pressures of running.

jack vines