I have an engine block from a 1969 442. It is currently 400 cubic inches with a 3.870 inch bore and a 4.250 inch stroke. Can it be bored out to 4.125 inches so that the displacement will be 455 cubic inches. It would then be the same bore, stroke, and displacement of the 1970 442 engine (which I think used the same block) and I would be able to use the crankshaft that I already have. Just wondering if this is possible on the block I have without hitting coolant lines or running into other problems.

Thanks

 

personally I wouldn't waste time or money trying - just find a 455 or 425 block and you're already there - Crank / rods from G block 400 can be used in either to get 455 cid. - the walls will be too thin after that much of overbore on the G block .

 

Isn't it the same block used on the 69 h/o and 70 442? Were the walls too thin on those engines? Or is it a different block? Just wondering because I can have the block bored and machined almost free

 

.255" overbore removes over 1/8" of cylinder wall thickness.
I don't know how thick the cylinder walls are, but, I'm sure that doesn't leave much.
You could probably bore it out to nothing and not get 55 cubic inches.
I think the 455 crank has a longer stroke than the 400.
The guys on the ROP site can give you exact numbers and good advice.

 

While they are designed the same a 400 G and 455 F are not the same block. A 400 G block will not support that overbore, the cylinder walls aren't thick enough (not without sonic testing anyway). The stroke of a 400G & 455F are the same.

Like others said, buy a 455 block. You can usually get one for $100. All your other internals and heads will switch over.

 

i have always heard that the sand castings around the cylinders were the same between the 400 and 455, and that the G block would support that overbore as long as there wasn't a major core shift issue.


bill

 

Thanks for all the help. I know for a fact the 455 crank has the same stroke (4.250 in) as the 400 because I looked it up in a restoration manual, but what I'm worried about is the bigger bore to get the displacement. I am going to have it sonic tested anyways when it goes to the machinist, so hopefully I can bore it out that big but if I can't I'll just get as much power out of the 400 as possible. Looking at the block, it has over half an inch between cylinders, but I don't know where the coolant lines are or how big they are, and I also don't know much about how much room in between cylinders is mandatory. So the sonic testing should help whenever I get it done.

Thanks again for all the help

 

You can't bore it that big.I would do +.030 The only way you would get the bore size of the 455 out of that block,is if you gutted it,and put 8 sleeves in it.

 

Even if you could do it, at .030 a cut, that is 10 bores. The cost alone makes it not practical. As stated, blocks are $100, the machine work to bore that big would cost you much more than that. Plus the cost of the sonic test which you would not need on the 455.

 

Here's about every opinion on what you should and shouldn't do with your 400G block

http://www.realoldspower.com/phpBB2/...+bored+casting

Mine's sitting next to my furnace....

 

Back in the days of the old Chubecto list server, Chris Witt claimed to have seen a cutaway G-block that had outrageously thick cylinder walls. Obviously sonic testing is needed, but as others have pointed out, why spend the money when 455 blocks are inexpensive.

Now, having said that, I'd like to figure out a way to do it just so I have the correct G-block casting in my 69 442. In that case, it is not a cost-based issue.

 

They use the same crank - same part number.

 

I thought I remembered that Chris was talking about a 400E block

 

Well Joe,you could put 8 sleeves in it.
I know of a certain someone that uses 425 blocks,and sleeves them down,to make 67 400's for a stocker,making real think walls.

 

I (still) say the best way to keep an externally correct looking (i.e. G) block in a '68 / '69 car while about matching the performance of the earlier cars would be to use the rods and crank from a 400/425 and a high-comp 330 piston (only would need a 0.068 overbore). CI would work out to about 388.

It'd sure be differ.

 

Well, that post was in the early 1990s. Memory is a funny thing. I guess we could ask him.

 

Yeah, the way they do to the new Hemi blocks. I'm sure THAT'S cheap...

 

Then you could have a siamesed 400.

 

This is the quote from the FAQ on 442.com that I remembered from way back. It might not be the same thing you're refering to:

 

Well, memory is the second thing to go, and I can't remember the first...

 

Yeah, I mean so long as we're having wet dreams, why not use liners that take the bore out to 4.351.

Gotta say that I was in awe when I read about the shop that does that to the Hemi blocks.

 

I'm just reading an article from Bill Trovato on B/B olds engines and he quotes Oldsmobile big blocks have many shared features and dimensions. The bore spacing between the cylinders is the same as all Olds engines at 4.625. The main housing bores are all set at 3.189. Which would make you think that the cylinder walls on a smaller bore big block would have the meat in them to overbore to same dimensions than the bigger bore engines? The water jacket holes are I think in the same position on the 400 and 455 blocks.
Reading further he does actually say that you should check inside the water jacket from the deck and the freeze plug area as some blocks have thicker walls. Some blocks have more rust in this area and therefore have thinner walls. He recommends sonic testing.
In that Realoldspower forum they never really proved that the G block 400 ci could or couldn’t be over bored to a 455ci spec. I was waiting for someone to come back with a sonic tested 400ci B/B and give us the dimensions. I can’t believe that nobody on this forum has had a 400ci G block sonic tested and kept the figures.

 

They are doing the same sleeving with the new LS blocks as well.They gut them,and put 8 sleeves in.I was looking at some blocks with Bill Trovato,and came up with a concoction of using a diesel block,putting 8 sleeves in it,with deck spacers,and 4.350" siamese bores.Using that with my billet 4.700" stroke crank would put me in the 550+ cube range.It "could" be done,but you do NOT want to bore the block all the way down,or you will end up with a windowed-main block,just like the 403's. As long as you determine how low the piston travels,the is no need to go further.If Oldsmobile would have done this to the 403 blocks,the world would be a much different place today.

 

I am cleaning up the block right now and when I'm done I will have it sonic tested. I will put the results up here when I get it done in a few weeks or so.

 

Good on ya Red & Blue 442. We can then finally solve this mystery. Looking fwd to the results. This seems to be an issue which has been raised numerous times before with out a real satisfactory answer. It also seems that there are lots of people who would like to improve their 400ci engines performance but not necessarily change the original look of their engine (keeping it the stock look). I think most people understand that we will probably never have the performance gains that you would get with a 455ci. All we want is to get the best performance we can. Me, personally, whose 69 442 is mostly numbers matching (except for paint) would like to keep the original look but up the performance.
I think 400Hp+ is achievable without over boring.
Such as-
Headers
Jp 20-22 cam and accessories (lifters, R rockers, etc)
W30 carb or equivalent
Electronic ignition
Performance intake (paint it same colour as engine)

 

Yeah I wouldn't bore it out if it's numbers matching cause once you do there's no going back. Both my 69s are numbers matching but I have am extra g block out of a junker so I figured it'd be cool to build for all out power and put in one of the cars for fun, and then I'd still have to stock engine to go back to numbers matching if I wanted.

 

if memory serves...
i think it was Dave H. over at ROP that was saying they were the same internal sand castings.


bill

 

Find a 455 block. They are reasonably priced and I would not bore a 3.87 to 4.125. That is a bit overkill. Thats .255 overbore. Find a 455 or buy a rare but much more desirable early 400/425 that is all I deal with and they have a much better rod to stroke ratio including oversquare. RPM's are easier to achieve, only drawback is the cost to build them, depending on the cba and or lifter size.

 

This a pretty old thread. I guess "Red&Blue" did not get the info on the sonic check. I'm thinking he never did the engine either.

Gene