I have a 350 4 bolt main the year is 1974, it's tired and needs a rebuild. I have a few questions. I'm not sure if it's bored out, but I will take the block to school and find out. Assuming it's the stock bore is this rebuild kit any good?
http://www.summitracing.com/parts/SU...-000/?rtype=10
I'm not sure how much more power a 350 has over my 305 H.O, I've never driven a car with a 350 in it. I'm not looking for tons of power but I would like it to have a little "oomph" in it. Any parts I should be looking for?

Also, if it's not bored out what is a good amount to do? 30 over? 40 over?
Also, what's the hardest part of an engine build? I've never done this before but I would love to learn how

 

The correct amount to bore it is whatever it needs to get the cylinders round again.

There's nothing "hard" about building engines.

 

I personally would not put a 350 in my car that is bored more than .030 over unless it is strip only or I've got the cooling system from hell. Others can do as they wish. I will never fight cooling issues even a little bit and I use the a/c and it gets HOT down here.

Ymmv

 

The amount of overbore makes absolutely zero difference to cooling.

 

The size of cam made a difference in my 355's cooling but not the bore.

 

Ok

So rate of transfer of heat through thinner metal is the same as for the thicker metal?

 

The more you bore it, the hotter it will run. and get ready for hard turning over when it's hot!

 

The odds of a 1974 motor still being stock bore are so slim as to be quantum mechanical. If I was the betting kind, I'd bet a paycheck (especially if it was somebody else's) that it's been bored.

Measure everything before buying anything.

Get your machinist's opinion on whether it will clean up before it reaches .060" over. That's pretty much end-of-life UNDER THE BEST CIRCUMSTANCES for those older 70s blocks with their astoundingly crappy quality control. And, it only gets worse over time, as corrosion eats away at the water jackets from the water side of the metal. Alot of em won't even go .060" any more without starting to seep water.

Remember, you're dealing with a motor that's almost 40 years old.

Next, check to see if it has The Starter Problem, wherein the starter bolt pattern is too far away from the crank (about a third of blocks from that era have this... they must have had 3 machines that gang-drilled the holes... makes the starter NEVER work right, and make that horrible grinding ganshing sound you can hear from a quarter mile away); The Lifter Bore Problem, wherein the lifter bores don't point straight at the crank; The Bell Housing Dowel Pin Problem, wherein the BH flange isn't registered correctly on the crank, such that the centerline of the crank doesn't line up with the centerline of the transmission, which makes it EAT pump bushings; and so on.

If there is ANY HINT WHATSEOVER of any of these Problems, DO NOT waste a dime on it!! You will be throwing your money away. Evidence you can see includes wear on the flex plate teeth (if it comes with one) right out at the tip of the teeth, lifter bores with deep scratches near the bottom, or other inexplicable odd wear on anything. Classic indications you get from the story that comes with such a motor are, you buy it, and the seller gives you some kind of mealy-mouth mumbled excuse about how he's selling it even though it's freshly rebuilt and only has 200 miles on it but his wife wanted something with better gas mileage; it had "too much power" and he was scared of it; and other such .... tall tales. When you hear stuff that defies belief like that, it means, the owner is SICK AND TIRED of fighting something he doesn't understand what causes it and can't find what's wrong, and he just wants to wash his hands of it and make it a Next Owner's Problem. If you heard ANYTHING even remotely dimly faintly near a hint of a whiff of a glimpse of a clue of ANYTHING LIKE THAT, proceed WITH EXTREME CAUTION, because most likely you only think you have a block but all you really have is some scrap iron.

As cheeeeeeeeeeep as MUCH BETTER 350 block cores are, no sense in taking any unnecessary risk. 96-2000 ones with roller cam setups - and most important, NONE of the infamous Problems - can be had for $100 or so.

 

You can't even measure the difference. Coolant temperature is about the rate that heat is transferred into the coolant in the engine and removed from the coolant at the radiator, not the rate it travels through the cylinder walls.

The thickness of the cylinder walls of two random stock blocks can vary more than the amount taken off on a rebore, and nobody notices.

Boring has zero effect on temperature.

 

What he said ^^^

 

Not true. This can be measured. But not with one temp probe. Take an engine new std bore, measure water temp and temp of air coming out of radiator. Bore it and do the same at the same water temp. Everything else being equal including ambient conditions. Have to do this over time because the thermostat should stay open more if more heat is going into the coolant. If you have a thermostat that stays wide open all the time then you don't have enough capacity in the radiator (or maybe your pump is not flowing good).

That is what effects the coolant temp - true. And the amount of heat that is transferred to the air (thru radiator) had better be more than is transferred to the coolant through the cylinder walls, heads, etc. These systems were not over designed to any great degree - if they were no one would have coolant issues to the point where we were buying high flow pumps, searching for the "ultimate fan", and buying aluminum radiators. And yes the higher horsepower engines will generate more heat causing the need for the above.

This is not true. You want more heat to go out through the exhaust - not transferred through the cylinder walls.


Very very true. I believe that some std bore may also have cooling issues if raised the horsepower. Some bored .060 may never have cooling issues.


Again not true. It may have no effect that you notice if it is a good block to start with. But t is higher than zero.

I do believe you can get a good machine shop to check wall thicknesses and you can make an informed decision to bore or get another block. Else you are rolling the dice. As cheap as blocks are (and I have a spare std bore in the garage) I will not bother with that.

Now all that being said, I do not have the proper equipment to set up an experiment to measure this nor the time/money. I am just basing this off of experience trying to cool equipment in an industrial setting and other peoples opinion. So, since I do not have the hard data, all of the above is IMHO, ymmv. In my experience I have noted issues with cooling in engines that were bored more. Granted I don't change engines out as much as my underwear.

But after doing a search on the internet the number of people saying it does affect cooling from their experience far out ways those saying it does not. That is also not conclusive.

I may be wrong, I just don't think so. It would take hard absolute conclusive data to make me put an engine in my car bored more than .030 over. It is not worth the need to have to pull it out and find another and I'm sure not going to put the cooling system from the space shuttle in there. I try in all my modifications to not cause a problem where I cannot use off the shelf parts. And I will not drive a vehicle that is on the ragged edge of cooling.

For those people that don't mind fighting this, not a problem, I did it myself back in the day. I just choose not to anymore. I like driving the car, not working on it all the time or throwing money at it.

Note that I do not give advise one way or the other - only my opinion. I sure wish someone would do this or find the data where others have. If it comes up effectively no difference then I could use blocks longer

Someone could design the proper system to diagnose cooling issues.