1962 overheating

[Phil A.]

A 1962 340 horse everything factory stock except was rebuilt with an 80 thousand overbore. A new dewitt radiator, distributor rebuilt and set to factory spects including timming, has all the shrouding, and the correct radiator cap and thermosat. It still gradually overheats, why? I think it's because the overbore is too much. Does anyone have any other ideas? Thanks Phil

[Jim T.]

Re: 1962 overheating

Since you asked for ideas, you did not mention the thermostatic fan clutch. Was you 62 overheating before the engine was rebuilt?
When does your 62 overheat, in city traffic on going down the highway at 70 mph?
Is your vacuum advance connected to full time vacuum?

[Mike E.]

Re: 1962 overheating

62 340 is centrifugal advance only, dual point

[Jack H.]

Re: 1962 overheating

Can you better describe 'overheating' as you use the term? What I'm getting at is some say their engine is overheating simply because the temp gauge reads higher than they expect it to read. That differs from a bona fide overheat situation where the rad cap pops and spews excess coolant...

[Paul H.]

Re: 1962 overheating

Have you confirmed that your gauge is accurate? IR gun is a nice tool to confirm your gauge accuracy. Lots of info in the archives in this often discussed topic.

[Joe C.]

Re: 1962 overheating

A 1962 340 horse everything factory stock except was rebuilt with an 80 thousand overbore. A new dewitt radiator, distributor rebuilt and set to factory spects including timming, has all the shrouding, and the correct radiator cap and thermosat. It still gradually overheats, why? I think it's because the overbore is too much. Does anyone have any other ideas? Thanks Phil

Are you sure it's a 327 block.
It's not a 283 block, is it?
I've never heard of a 327 being bored .080" over.
Are you sure that it's not .060" over?
Where did you get 4.080" pistons?

Is it actually boiling over, or is the temp gauge reading higher than you're used to seeing?
This issue has been beaten to death.
Check the archives and you'll find much on this subject.

[Phil A.]

Re: 1962 overheating

You can bore a 327 .080 over, however that is my concern because the cylinder walls have to be fairly thin. This is the original block for the car an 870 block. Jack, it's not the guage, it does spew over, and I have checked it with an IR gun. It will overheat in traffic and on the hiway. The fan clutch is new. This is the 6th C-1 I've had over the years and never had an overheating problem with any of the others. Thanks for all the suggestions. Phil

[Timothy B.]

Re: 1962 overheating

Phil,
I know you mentioned the correct radiator cap but does it hold the correct pressure, if not there will be boil over. If you checked temperature with a IR gun what reading did you get, how hot is it? If the 1962 distributor does not have vacuum advance then the more initial timing you can give the motor the better. Just be sure total timing (initial and centrifugal) does not exceed about 38 degrees.

[Jack H.]

Re: 1962 overheating

OK, you're confirming proper use of the term 'overheat' - it DOES boil over! Plus, when you added the fact that it overheats on BOTH the highway (in motion) as well as while stopped/idling, you've essentially ruled out the fan clutch. So, what's next?

Well, I've seen early SB's bored out to 105-over and NOT behave this way. So, I suspect it's NOT a case of having taken too much 'meat' out of the block (lower thermal capitance).

I'd go looking for small pressure leaks in the system (typically at the rad cap and/or hoses). Stant makes a nice analysis tool that if you don't have, you can get a competent local repair shop to supply.

The pressure checker has an adaptor that lets you install your existing rad cap, use the tools attached hand pump to exercise and verify the integrity of the rad cap. Plus, you can install it directly onto the radiator, in place of your rad cap, and monitor system cooloant pressure while the engine is running.

If all is well, you ought to see the system build and hold a pressure below the rad caps' pop point. When installed, you can also hand pump the system up above the steady state point to force & find small leaks at various hose interconnect points....

Plus, it's a good idea to closely eyeball the area of the radiator & cap where they interface to seal. Is there 'crude' present that can thwart the seal of the cap's rubber gasket to the neck of the radiator?

[Joe C.]

Re: 1962 overheating

OK, you're confirming proper use of the term 'overheat' - it DOES boil over! Plus, when you added the fact that it overheats on BOTH the highway (in motion) as well as while stopped/idling, you've essentially ruled out the fan clutch. So, what's next?

Well, I've seen early SB's bored out to 105-over and NOT behave this way. So, I suspect it's NOT a case of having taken too much 'meat' out of the block (lower thermal capitance).

I'd go looking for small pressure leaks in the system (typically at the rad cap and/or hoses). Stant makes a nice analysis tool that if you don't have, you can get a competent local repair shop to supply.

The pressure checker has an adaptor that lets you install your existing rad cap, use the tools attached hand pump to exercise and verify the integrity of the rad cap. Plus, you can install it directly onto the radiator, in place of your rad cap, and monitor system cooloant pressure while the engine is running.

If all is well, you ought to see the system build and hold a pressure below the rad caps' pop point. When installed, you can also hand pump the system up above the steady state point to force & find small leaks at various hose interconnect points....

Plus, it's a good idea to closely eyeball the area of the radiator & cap where they interface to seal. Is there 'crude' present that can thwart the seal of the cap's rubber gasket to the neck of the radiator?

Jack,

I think that the 283 and 327 used the same basic block castings, with small differences, but cylinder wall thicknesses were very close, if not the same.

283 has a 3.875 bore and 3.00 stroke
327 has a 4.000 bore and 3.25 stroke.

A .125 overbore on a 283 produces a 302.
A .125 overbore with a 3.25" stroke produces a 327.

So, since a 327 block is essentially a 283 with .125 overbore (and stroked). That is why there's not very much room left, to FURTHER overbore a 327.
Methinks .060" over is generally accepted as the safe limit, giving a bore diameter of 4.060". This would translate to a standard 283 block being overbored from 3.875" to 4.060", or total .185".

Joe

[John O.]

Re: 1962 overheating

Hi Phil

Make sure your thermostat opens. Is your water pump operating properly? I'm not sure if it's possible for the impeller to come loose. And here is one that happened to my used blazer I bought years ago. Had the same overheat problem, then found out someone put the wrong fan on and it was pushing the air out of engine compartment instead of pulling it in.

Good luck...John

[Duke W.]

Re: 1962 overheating

Jack,

I think that the 283 and 327 used the same basic block castings, with small differences, but cylinder wall thicknesses were very close, if not the same.
Joe

283 block castings used different molds/coring and came out of the mold with smaller cylinder bores than 327 blocks. Otherwise it would have taken too long to finish machine the bores.

I believe 327 blocks are considered "thin wall" and can't take more than about .060" overbore, and the walls should be sonic tested for adequate thickness if this much overbore is contemplated. Early 283s had thicker cylinder walls and some can actually take .125" overbore to 4", but I believe later 283 blocks are also thin wall and can't take as much overbore as early examples.

Duke

[Jack H.]

Re: 1962 overheating

The suggestions (don't go beyond 60-over) are basically safe & sane. But, I have seen traditional 283 blocks from the late 50's/early 60's bored out further (I mentioned 105-over) and still be 'streetable'.

On the 327, yes it's a different casting series and the basic question of how far one can go DOES relate to specific cast number! The advice given about consulting an EXPERIENCED machinest is well deserved. In the case of this thread 'someone' decided to take the 327 block up to 80-over, so that person should be standing behind the job...

I have a fuzzy recollection of a feature story about making a souped up 327 (www.roadsters.com???) where a '174 casting, 327 block from the mid-60 era was bored from 4.000 to 4.185 to create a 358 cu inch 'screamer'. I don't remember any comments in the story about how 'streetable' the resulting engine turned out to be (building for race competion is one thing and doing a street machine can be radically different), but if the block had turned into a 'Stanley Steamer' I'd have expected them to say so....

[Gerard F.]

Re: 1962 overheating

Phil,

If it's a carb car, check the carb for vacuum leaks, maybe you are running too lean.