Has anyone successfully bored a 318 to 4.04?

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Captainkirk

Captainkirk

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Has anyone successfully bored a 318 to 4.04?
Or will you 'hit water' if not properly done?
While 340 blocks are becoming rare to find these days, seems like a simple solution.
 
I think with the amount of 360's floating around it would be too costly to sonic check several 318 blocks to find a useable one. There is a company (i can't remember who) who made a bearing insert to use the shorter stroke 273/318/340 crank in a 360 block.
 
I bored a truck 318 to 4in, probably could have gone the extra 40-thou, but yeah I reckon the bores would have been pretty thin.
 
Depends on how long you need it to run for, I guess.
 
You could always sleeve it (like with a loose woman)...
 
There are rumors of thick wall casting 318 that were the same core as a 340 block.
I don't know anyone that has done it with a 318 block.
 
The cost of sonic checking and machining would probably get you close to a usable 340.
 
Captainkirk said:
Has anyone successfully bored a 318 to 4.04?
Or will you 'hit water' if not properly done?
While 340 blocks are becoming rare to find these days, seems like a simple solution.
Click to expand...

Are you in need of a 340 block? I'm in southern WI just across the boarder
 
This is a age old topic, its been done for years, like rusty said. I was told about it many years ago by some guys who roundtrack raced mopars in the mid 70s. After they used up all there 340 blocks, they found some of the early 318 blocks thick enough to bore to std 340 (4.040) bore size. HOWEVER, they were thinner than a 340 at std bore, and these guys blew up a ton of motors including the one I saw, which had a split cylinder wall. Keep in mind, a max bore 318 block will be much weaker than most std 340 blocks. Thick, straight cylinder walls make power...........318 blocks also have shorter, weaker main caps, although that can be corrected.
 
krazykuda said:
You could always sleeve it (like with a loose woman)...
Click to expand...

I was going to ask that question when I opened this thread. Can you put a 4.04 sleeve in a 318 block? Can you bore the sleeve to 4.07? Next question. Is it worth it? Bore helps a lot in the down force when adding more square inches of piston surface but we're talking a 4% increase in the 340 over the 318. Can we go directly across the board and say that the power gain is proportionate to the increase in surface area? If a 340 has a 4% larger bore than a 318 can we say that we get 4% more HP with all things being equal? That's a difference of 300 HP or 312HP respectively. Is it really worth it? Truth be told I've done my last 340. I'll save all the 340s I run across and sell them to someone that thinks they need a 340.
 
Leadfoot said:
I was going to ask that question when I opened this thread. Can you put a 4.04 sleeve in a 318 block? Can you bore the sleeve to 4.07? Next question. Is it worth it? Bore helps a lot in the down force when adding more square inches of piston surface but we're talking a 4% increase in the 340 over the 318. Can we go directly across the board and say that the power gain is proportionate to the increase in surface area? If a 340 has a 4% larger bore than a 318 can we say that we get 4% more HP with all things being equal? That's a difference of 300 HP or 312HP respectively. Is it really worth it? Truth be told I've done my last 340. I'll save all the 340s I run across and sell them to someone that thinks they need a 340.
Click to expand...

Add a 4 inch crank, make it a 390- ish engine, give it 250 + cfm intake port. Sweetness.
 
I did a 318 truck block to 4.0" with a 4" crank. The block was offset bored by Brian at IMM engines. There was plenty of meat to go 4.040. It was 402 CI. I installed a gear drive on that one with a pretty big HYD flat tappet cam. I sold the short block to 68GTCONVERT.

I have another 318 Truck block sitting in the corner of my shop.....
 
Mad Dart said:
I did a 318 truck block to 4.0" with a 4" crank. The block was offset bored by Brian at IMM engines. There was plenty of meat to go 4.040. It was 402 CI. I installed a gear drive on that one with a pretty big HYD flat tappet cam. I sold the short block to 68GTCONVERT.

I have another 318 Truck block sitting in the corner of my shop.....
Click to expand...

OHHH .... That's good info...
 
Mad Dart said:
I did a 318 truck block to 4.0" with a 4" crank. The block was offset bored by Brian at IMM engines. There was plenty of meat to go 4.040. It was 402 CI. I installed a gear drive on that one with a pretty big HYD flat tappet cam. I sold the short block to 68GTCONVERT.

I have another 318 Truck block sitting in the corner of my shop.....
Click to expand...

By chance, a casting number of the block, Mad dart?....
 
Leadfoot said:
I was going to ask that question when I opened this thread. Can you put a 4.04 sleeve in a 318 block? Can you bore the sleeve to 4.07? Next question. Is it worth it? Bore helps a lot in the down force when adding more square inches of piston surface but we're talking a 4% increase in the 340 over the 318. Can we go directly across the board and say that the power gain is proportionate to the increase in surface area? If a 340 has a 4% larger bore than a 318 can we say that we get 4% more HP with all things being equal? That's a difference of 300 HP or 312HP respectively. Is it really worth it? Truth be told I've done my last 340. I'll save all the 340s I run across and sell them to someone that thinks they need a 340.
Click to expand...

You can resleeve a block to the maximum allowed area. The overbore allowable is dictated or dared by the wall thickness. A 4% increase in bore size does not equal a 4% rise in power.
Roughly speaking, on the small blocks, a .030 overbore is about 5 cubic inches. Bore size dependent of course.
 
price out what it will cost to sleeve and finish 8 cylinders and you will figure out real fast a good 340 block is STILL cheaper. possible, yes, practical, probably not.
 
.................I have had a few 318s bored to 4.04.......but nowadays just bore it .030 and stroke it............kim.............
 
I have been wondering about this too. I have a set of 4 inch flat top pistons for a 360 that I want to use in a 318 to duplicate HotrodDaves super duper mpg 318 build. Would it be safe In a Daily driver or would the 9.5:1 compression crack a cylinder?
 
replicaracer43 said:
price out what it will cost to sleeve and finish 8 cylinders and you will figure out real fast a good 340 block is STILL cheaper. possible, yes, practical, probably not.
Click to expand...

This ^^^^

Sleeving blocks is for repairing damaged cylinders. It doesn't increase cylinder wall thinkness, as most dry sleeves are .125 thick at the most.

page 14-15

[ame]http://www.mellingcylindersleeves.com/Portals/8/pdf_catalog/Melling%20Cylinder%20Sleeves%202014%20Catalog%20pages%201-40.pdf[/ame]
 
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