Will a .060 over bore cause overheating?

[Reg Evans]

I told a friend yesterday about my engine with the .06 oversized pistons in it and he said "OH NO....you're going to have overheating problems during the summer months" He says he never goes over .03. Says he has the cylinders sleeved if over that.

He's a retired chief ships engineer and was in charge of keeping the big ships shipshape.

[Plymouthy Adams]

I believe he is confused in his thinking concerning later style thin wall cast siamese engines..this will be a concern for overheating in these..for our old block..nah..notta...chances are this guy has had very little experience with the older cast blocks..

[Reg Evans]

Well...the strange thing about his comment is that he is an old Mopar flathead guy too. He has owned and worked on the old L-6's for 30 or more years.

Any one here have a rebuilt engine bored 60 over?

[jd52cranbrook]

Was told by more than one flatty engine builder that 30 was the limit on these.

[Young Ed]

I've heard from many that you can go .060 on these. Both of mine are only 030 over though.

[martybose]

My 230 block is 0.072" over, and has always run rather warm; usually in the 185 to 200 range. I have no idea of whether the overbore is a factor in this or not. The radiator is in perfect condition, there is no thermostat or bypass at all, and it heats up to 160 and over within a couple of blocks of leaving my house.

Marty

[Young Ed]

Not to steal Reg's topic but I've always heard no thermostat can actually cause it to run hotter because the thermostat besides keeping the block at a certain temp also causes a certain restriction in the water flow. And without it the water doesn't stay in the radiator long enough for it to function properly.

[Plymouthy Adams]

Ed is talking about proper heat transfer through the radiator by allow the water to stay in the block long enough to saturate with heat..lot of track racers will run without a thermostat but usually will place a restrictor in its place..

[Guardrail]

.060 over on one of these old flathead Chrysler products shouldn't be a problem. .040 over on a 327 Chevy is another story...

[Reg Evans]

OK....so far we have (3) OK's and (1) not OK.

Thanks for not straying to far from my little poll.

Anybody else?

[bob westphal]

I have know of old MoPar L-6s at .090 over. More power? Yes. More heat? NO WAY! I presently have a PJ running at .060 over and it runs at whatever the thermostat is set at, which happens to be 160.

[Young Ed]

Bob isn't that a 201? I've heard they have more meat to be bored out because of the smaller bore to begin with.....

[Plymouthy Adams]

I believe the earlier engines were also the same bore but different stroke..some 189 cubes at first entry..or thereabout..the redesign of the full water jacket in the introduction of 1935 model was external block design giving full circulation to the cylinder and moving the starter a bit further out from the engine and a bit lower..

somewhere I read an article that these engines can take a fairly good bore and be reliable...however my memory fails as to what place I did read this..

I need to start doing a better job of throwing this info into catagories within a folder for reference later..

NOTE...1933 release of the 6 flathead...

The valve-in-block engine displaced 189.8 cubic inches from a bore of 3 1/4" and a stroke of 4 1/8". With the standard compression ratio of 5.1

[Lou Earle]

George Asche has bored several to 100 with no problems except for now finding the slugs and rings

[jd52cranbrook]

Good luck,,,,,,,,,,,

[james curl]

My engine is bored .040 over and I drove from central Texas to Reno Nev. for hot August nights and on to Bonneville the first and second week of August and it ran 190 degrees while running 70 mph, at 60 mph it ran 180. I have never had a heating problem and run the original radiator. I have another set of .040 pistons to go into my original engine when it is bored.

[Reg Evans]

OK....so far we have (3) OK's and (1) not OK.

Thanks for not straying to far from my little poll.

Anybody else?

New tally from both boards.

(10) OK's

(1) Not OK

Since my friend is helping me with the engine swap I won't tell him of this little survey.

[Don Coatney]

New tally from both boards.

(10) OK's

(1) Not OK

Since my friend is helping me with the engine swap I won't tell him of this little survey.

Go for it

[Rodney Bullock]

My chevy 235 was bored 80 over and it never over heats or act up at 90 degree weather. My mopar has a rebuilt motor in it, The guy that sold me the car said it was 60 over, temp went up one time and saw the water sipping from around the out side edge of the head. I talked about it on this forum and the advice was to retorque it. I did that and it never got hot like that again. I think after some miles on your rebuild, you will have to retorque and your 60 over will not cause you any problems. Sometimes it's not the bore size but the head gasket and retorque, unless the gaskets are those that do not require retorque, proper care must be taken and proper break in.