352 to 390 conversion / Wall thickness

[swissranger]

I would like to change my 352 to 390. I have learned that the bore has to increase from 4.00 to 4.05. Due to this the block should be sonic tested before machining regarding the wall thickness. Thanks Keith and Chris for this advice.
Does anybody know minimum values for the remaining wall thickness?

[willowbilly3]

.125 thousandths on the thrust side for any serious peformance. For a street engine you shouldn't have to sonic test to bore .050, never hurts to be safe tho, I guess.

[cobraF100]

Willowbilly is right about "you shouldn't have to" check wall thickness when your only going .05 over but there are a few blocks out there that wouldn't even take that bore.....Hell there are even 428's that are standard bore's and WILL NOT take a 30 over Bore...
Most of this is due to "Core Shift" Bad molds or Bad Cast

So what it comes down to is """Peace of Mind""" because most place's only charge $100.00 for a Sonic Check,and thats Money well spent on any build.

Just my again.......

[swissranger]

No problem, I would spend $100.00 for the sonic check. The problem is that both machine shops I asked today about sonic checking, do not use this or an other method to check the wall thickness. Due to this I will search for a company which uses such a system maybe for other things, like checking sheet metal or tubes. This is the reason why I would like to know the minimum wall thickness.

Thanks a lot for your very competent hints.

Roman

[cobraF100]

Ok,,,I'm going to try to help you find a Shop that will do this for you...

I know your not in the US but what are some big Towns close to you over there?
I'm going to post this Question over at the FE forum after you let me know some towns around you and see if anyone knows a shop over there to help you out.

If you would like Email me Directly at :
cobraf100@yahoo.com

[68F250]

Personally I'd just bore it and go. A lot of 352's have had this done with no problems. Ford put the overbore spec at .060" for the 352 and .040" for the 390. Yes, a lot of 390's cast after '66 won't go that far due to core shift but I've never heard of a problem with a 352.

[muchtomydelight]

You'll need a minimum of 0.130" wall after boring to prevent overheating as a general rule of thumb. The machine shop you take it to should know or be able to find out. If they cant, find another machine shop. But you should be able to safely go .050 over with no problems.

[willowbilly3]

Just as a brain fart, I don't think it is as critical to sonic test your 352 block as it might be for a 390. If you have a 390 block it might actually be a 352 that has already been bored .050.
Anyway we rebuilt a bunch of engines before sonic testing was commonly available. I have never had it done. If the service is available and it will make you feel better by all means do it. Just knowing if you had another build left in the block would be great. But I also would just bore it. I have never seen a bored FE that the stock cooling system couldn't keep properly cooled. I have seen sbc boilers, many.

[muchtomydelight]

from the factory! The 400s were aweful about that I hear.

[swissranger]

Willowbilly3, could you please explain what's a sbc boiler? Is there maybe Chevy included?

Roman

[muchtomydelight]

chevy 400s had very thin cylinder walls which led to overheating and boiling coolant.

[cobraF100]

swissranger,
Haven't herd from you in a while.

Well I was looking for a Block for my Truck and herd something that I'd like to ask you.....

Did you get a 428 Block for that Truck?
If not then there's another guy over there with you that did;said he has an Old Ford Truck..