60 over 68 302 block, over heating issues?

Overheating issues are more likely the more you bore the block.
However, every block is different and problems are not gauranteed.

You can have the cylinder bores sonic checked for thickness thoroughly to get an idea, but that costs.
Personally, I would steer clear, but you may not have as many available blocks over there...
Good luck

My 1968 "Heche in Mexico" 302 block was bored 0.060 over and stroked to a 352 cubic inch motor (now in a 1966 Mustang). It's producing around 450 hp according to similar builds. I'm using the stock 2-core radiator, but everything else has been upgraded (5-blade flex fan 1" away from radiator, fan shroud, high flow aluminum water pump, high flow 160 degree thermostat). It runs warm, but does not overheat.

I would have upgraded the radiator, but this was a last minute motor switch and will be removed sometime during the summer.

It is a general rule not to go more than .030 over for performance applications. This is not true in every case though: it depends on core shift during the casting process. Some blocks have very thin walls while others are more forgiving. Personally, I would not buy any block that couldn't be fixed with a .030 overbore. You might consider a new block from Ford if used ones are that hard to find there. Then you would have a std. bore and be able to rebuild years down the road with no worries.

i would upgrade you radiator and make sure the block does not have scale(sp) built up in the water passages, when and if you take it to a machine shop make sure they wire brush the water passages.

I think you would be ok, as long as you are getting a FAIR price for the block... Any chance you can have a machine shop do a quick inspection to make sure it is useable before purchase?? 0.060 will be less forgiving with a knicked cylinder or hairline crack etc...

BTW - I run a .060 302 without significant cooling problems (do have an electric fan + al radiator though!)

ratio411 said:

Overheating issues are more likely the more you bore the block.
However, every block is different and problems are not gauranteed.

You can have the cylinder bores sonic checked for thickness thoroughly to get an idea, but that costs.
Personally, I would steer clear, but you may not have as many available blocks over there...
Good luck

Click to expand...

This is it in a nut shell. Have seen some blocks that can't go .030 over. Seen a few here at .060. You need a COMPETENT machinist that can tell you if it can take .060 over.

Bosscat said:

Thanks for the input. It is pretty cheap, for here. A stock everything351W rebuild runs around $2000.

I plan on running a Mark VIII fan, with a 3 core alloy rad. I guess I will go ahead and buy the block, and throw the dice.

Click to expand...

If it does have a problem, you can always sleve it.

I think cylinder wall stability is a more reasonable concern than overheating. Thin-wall castings are just that, thin. When you add possible core shift during casting with thin walls to start with, trouble is possible. I've run .060-over blocks in the past with no problems, but in my area, 302 blocks are just too common to do that anymore. I think people hear "sixty thousandths" and think it's some huge number and panic. Look at it this way, a sheet of paper is typically .003" thick. If .030" is generally considered a safe over bore, then the step to .060" over is only 5 sheets of paper per side more than that. If your block is sooooo think that taking .015" per side is too much, then it was probably just an accident waiting to happen anyway. I say measure every bore to ensure it's the size the seller is claiming and go for it.

I have bought a 94 stang with a 302. The motor has been bored .60 over. I bought it broken, but not from over heating, one of the valves got bent and the piston beat the hell out of it and you can guess the rest. Well, had a sleeve but in and honed it. i was able to save the head as well, the shop were I had taken it tig welded it and machined it out. Thank god because the heads are AFR, can't remember what series. With all the stuff on the motor I have match in the Summit catolog the guy that had it spent some dough. 302 .60 over BBK cold air intake with mass air flow sensor. Edelbrock manifold upper and lower if that sounds right,AFR Heads,Tremic Racing 5 speed,Headers can't tell what brand they are,303 cam not sure what series,Had DSS pistions but I am getting a new set,The guy I bought it from said that it had a high volume fuel rail if there is such an animal, and it had the red injectors have heard that the color means something and have heard not,MSD coil. However to make sure I am going to upgrade the water pump and oil pump, as well as the radiator. Along with a performance t-stat. I thought about going gear to gear timing on it as well. I am new to this tearing down and building up. I have read and read but you can't ask books questions, so I am also new to the forum. I am assuming that there was no over heating issues due to the fact that its a 94 and two owners since the mods. I hope that is a sign that the block is a good one. The machinist said the reason for the valve issue was oil flow. I have read that when you sup up the horse power its a good idea to also upgrade the oil pump like the shaft especially, due to higher torque and the shcok one twisting. it was in one piece,but it crossed my mind that the supply was less than the demand because of the horse power. Well any input would be helpful..so here i am lay it on me.

they will run a little warmer, but can still be managed. i would want it sonic checked because most 302 blocks at that bore size are a little thin,which is obviously what causes them to run warm, but can also compromise ring seal.

Well I have decided to stroke my 302 .060 going out with a bang, going for broke. I got my summit catolog and there is a kit, now just have to raise the money.

I'm not a very good mechanic. My dad owned a garage so I learned a lot by just being around him. When I was pretty young my dad built a 302 boss, now I don't know all the specifics on it, but I know he said it was bored out 60 over and he said he took a jeep radiator cut the ends and a little extra off, welded the ends back on. I'm 45 years old now and I was pretty young when he built it. No more than 10 years old. He raced it really hard know he even beat a motorcycle. We still have it. Same engine.

going .060 with a 302 block is a hit or miss deal. if the cores didnt shift during casting then you are fine. if not then you will have thin spots that will cause excess heat to enter the cooling jacket, and possibly overheat your engine if your cooling system isnt set up to handle the extra heat. but as pointed out that isnt the biggest issue. the thin spots create an instability in the cylinder bores, and while they wont cause problems in the short term, medium and long term you may find cracking from those points.

if you get the block for a cheap price, i say take it to your favorite machine shop and have the block sleeved back to factory specs. that will eliminate any question of thin wall issues.