IC 392 Max Stroke?

V

Vaughjw

New member
Hi,

I'm a new guy here my name is john vaught. I have been searching the internet looking for different solutions to rebuild my ic392 and I have some questions that I can't find the answer to.

(1.) what is the most you can weld and offset grind a 392 crank before it starts hitting something? I.e. Block, cam and heads?

(2.) if one was to offset grind the crank a large amount and then use destroked pistons would there be any negative side affects.(don't really want to go this way I'm just curious)

I have 16 "e" style pistons and it would be nice to reuse them they all look really good but I need to get my compression up a bit because I would like to get a little more performance out of the engine because its going in a 1973 Scout. So I thought about having the crank stroked to accomplish this because it's cheaper to have that done than it is to buy custom pistons, and the additional displacement would be nice as well.

I really don't want to remove any metal from the block or heads that I don't have to.


Thanks.
 
Last edited:
vaughjw said:
Hi,

(1.) what is the most you can weld and offset grind a 392 crank before it starts hitting something? I.e. Block, cam and heads?
Click to expand...
To many variables to give you an exact number but with stock rods you would be safe @ 1/4" stroke increase. Above that you will need to check cam to rod clearance. You need pistons to go that much. Rod beam to barrel clearance will need inspection for interference.


vaughjw said:
(2.) if one was to offset grind the crank a large amount and then use destroked pistons would there be any negative side affects.(don't really want to go this way I'm just curious)
Click to expand...
Any stroke change will require a re-Bob and balance of all rotating assembly parts. The small stroke change for effective zero decking is quite small so clearance won't be an issue. Always assemble the engine to verify there is no interference.


I have 16 "e" style pistons and it would be nice to reuse them they all look really good but I need to get my compression up a bit because I would like to get a little more performance out of the engine because its going in a 1973 Scout. So I thought about having the crank stroked to accomplish this because it's cheaper to have that done than it is to buy custom pistons, and the additional displacement would be nice as well.


Thanks. [/quote]
 
Robert kenney said:
Any stroke change will require a re-Bob and balance of all rotating assembly parts. The small stroke change for effective zero decking is quite small so clearance won't be an issue. Always assemble the engine to verify there is no interference.
Click to expand...

Cool this is what I was after I'm planning on getting everything balanced anyway but I want to get the crank altered to get to my deck to zero to raise compression.

I measured the piston to deck clearance when I tore the engine down but I didn't write it down....I think it was .030 to .035. I didn't think it was important at the time.

So my thought was to take the stroke to 3.716 - 3.726 to take the piston up to a zero deck.

Is this a faulty thought process or will this work?

Thanks
 
You should measure the deck height (both sides), rod length and piston compression distance. Then calculate your position as it is now. Your ideas are sound.
A 392's stock stroke is 3.6563. To zero deck .035 in the hole will require .070 more stroke or .035" of crank pin center line shift. Total stroke at that point will be (as you wrote) 3.726 in theory. Dry mock the short block and verify the out come before commiting to the final assembly.
 
Awesome.

I just hate to deck this block that much it looks perfect no wear at all, strait deck and heads. I was also worried that if I decked the block or heads that I would run into valve train geometry issues and intake fit issues.

P.s. Is it acceptable to grind the slag of of the oil drain back ports/holes in the lifter valley area? Is it bad to clean the slag off of the gear drive and distributor area as well? It looks like someone just punched a hole in the thin cast iron in those areas it's not a clean cut.
 
That is fine. It is a good idea to deflash blocks. Not necessary but can't hurt. Just don't create any new gouges/ grooves that can be stress risers and possible crack/fracture points.

A point on stroking and not reducing the recipricating masses on v8's, many times weight needs to be added to the counter weights by the use of mallory (heavy metal). That can be costly depending on severity.
 
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