So I have this engine in my garage looking for a place to go. I'm thinking that it would be a nice fit in my Bronco whose engine is getting on in life [192K].

I purchased it a while ago site unseen [never again] and when I took it apart to see what I really got, I found some interesting things.

What I purchased was supposed to be a 5.0 with 347 Eagle rotating assembly, X-Cam and GT-40 heads with around 300 miles on the rebuild.

What I found was a 3.4 crank and 5.4 rods form Eagle, but 4.050 pistons from SRP (that makes 351!) a Z-Cam, 1.6 Scorpion rockers, and stock heads that have been worked to 1.9 and 1.6 valves.

Now I gues that crazy cam will be dumped in favour of something more appropriate of a slow *** truck but what about these .050 over cylinders?

Is is going to fall apart as soon as I step on it? I have had a lot of people say there is no way it will last, only a couple think it might. FMS catalogue recommends no more the .030 unless you have a siamese cylinder set-up (no cooling between the cylinders)

I would hate to dump the pistons and block and start again but what do you experts out there think.

I hear that some blocks are stronger than others but I know nothing about them. The pnumber on mine is E7TE-CA 6. So...we have a 1987 truck engine - but the CA 6 thing I can find nothing on...

Thanks for the help from a newbie!

 

Well you know its at its limits....luckily it doesn't fall in the low nickel content years but that has little to do with the thickness of the walls....which can only be determined by a machinist.

Draw back to an extreme overbore is overheating.

The real question is do you like to gamble?

If dropping it in and running it is not a big deal to you, then why not? Consider it a experiment and let the cards fall were they may. If you don't like to gamble and installing and engine is a hassle to you, then 302 blocks are plentiful and the cost of the block and new pistons might be worth your while to swap the rest of the internals over.

Flip a coin........good luck either way.

 

Called the FMS Tech line yesterday. As sson as I got to the .050 in the description the voice kind of went, "...oh really! That can be interesting."

He told me that since it will be used in a truck application then I may be able to get away with it. When I went on to say that I had 10.8 pistons he kind of reduced his opinion on the chances of success.

He said that you can generally get away with doing that to a B50 block or an A4 block that used to be sold in the early 80s. He said the otehr option would be to find a Boss 302 block, but to remember that you will have to use some special application lifters from someone like Crane in that application.

Bossind is kind of daring me/calling me names about the whole thing. I think I may finally cave and try to do it. I think we can do the change over in a weekend.

And if it destroys itself I know where to find some help to change it back!

 

Personally I would hate to see useful parts go to waste if their is any breaking, nicking, gouging etc. I'd err with caution and use what good parts you can, get a new block and build her right.

Sell your other parts, like your pistons on ebay and get some of your money back?

But post the success of this engine you got, its kind of got me intersted.

 

Don't think I can recoup enough money by parting it out. But I do think that I can get what I paid for it by selling it whole.

 

don't worry, i have a 90 302 bored .060 over. i didn't overheat. all you need to do is add an aluminum radiator and a good shrouded fan or electric fan. i recently took the internals out of that block since the bearings went bad and i am currently swapping blocks for a better 69 302 block. it is supposed to be as strong as a b50 block and has thicker cylinder walls.

 

For experimental purposes I have personally bore a 302 late model roller block block out to .125" oversize and sonic tested it. We found the walls to be at around .100 - .125" thick. Rule of thumb, (depending of power) .125" thick is min. So I would not worry about the oversize.

 

TMI


What components did you use with this block and how did the temperature look as it idled in traffic?

 

This was an experiment for a local race class. They are limited to 360 cubes and you can't stroke the engine, so we wanted to see how far the block could be bored. We bore blocks to 60 over a lot, I have bore SVO 302 blocks almost .180" over, but they are thick.

To answer your question, the block has never been assembled.

Here's my 2 cents:

1) A piston manufacture has more money than I do to find out what works. If they make an oversize, I'll bore it.

2) I have installed cylinder sleeves in blocks where the cylinder was completely gone, and they are a .125" wall sleeve.

3) I always hear people on the forums talk about over heating with over bore sizes. I don't believe it is from the overbore, I have bore many blocks in my life to a large size and not seen problems and yet I've seen guys with simple 20's and 30's over bore and have heating problems. I feel it's in the cooling system, ignition and fuel.

I am sure there are people who think I'm all wet, and I know, I don't know everything.

But I've been an automotive machinist for 20 years and just stating what I've seen. I'd love to hear some good reasons why a larger bore over heats.
I'm always willing to learn.

My 2 cents!!

 

I have nothing to offer other than word of mouth and horror stories but like you said, it could happen to any of them. Here is a link you may wanna check out, more importantly what the user KIM is saying:

http://www.corral.net/forums/showthr...ht=bore+safely

 

I bet the water passages where gonna be or are filled on your race engines as well.

 

None of these engines have water jackets filled.(FYI 1/2 fill on the water jackets and oil temps do go up)

Kim example is kind of extreme. A drill chip may be .010-.020" or so. compared to a 1/4" thick plate.

Try this, take a coffee can full of water and that 1/4" plate of steel, hold a torch to them same distance away.

When you go from a .030 over bore to a .060 bore it's only .015" per wall.

Again please don't get me wrong, I don't want to sound like I know everything. I would really like to see some good sound tests on this.

I see in some of these forums some people are trying to tell other people to throw their block away if it doesn't clean 30 over. To me that's miss leading and costing someone extra $$$$.

I have a good friend at JE Pistons, I'll shoot this idea to him and see what he says.

 

my belt came off on my 90 .060 over block and the temp got to 290 F for a few minutes. nothing blew or cracked. how's that for sound testing. lol.

 

Yeah I am aware filling the block will make it hotter, then again if you cut the coolant flow its bound to get hotter right.


And I also get the impression that if these blocks aren't filled, then you have faith in the structural integrity of the block to use such an extreme overbore.


I don't suggest people throw their blocks away, nor did you imply I did but I would like for them to be aware of the risks. Sure you block checked out fine but thats not to say another person will have the same experience.


I think you have made one excellent suggestion, when in doubt have it sonic checked.

 

TMI


Well I posted this question on another fourm with intent to learn something.

I have received a few generic posts that I would expect, then this one popped up after I mentioned you don't fill the .125 blocks and asked about over heating issues on anything over .030. What do you think?

This person is lying through thier teeth....

The late model thin wall blocks are not cast with more .250 cylinder material. With a little core shift there is less than that.

Put a .125 cut on that and your down to paper holding cylinder pressure....

Overheat isn't an issue, its the amount of cylinder distortion under pressure, and the lack of ring seal that is a huge issue.

Late model thin-wall stuff shouldn't be pushed more than .030 over, on real LOW performance engines then .060 is probably OK to keep a pump engine idleing.... .125... yea, thats why DART is building $1500.00 blocks.