460 blowbye

[kbr577]

I purchased a 521 ford, the 460 block was bored and honed with plates, lifters bushed. the crank rods and pistons were installed by the machine shop that did the machine work, out of state internet deal. I put the cam and AFR heads and intake on it. I took it and had it dynoed , during brake in It was puffing smoke, blow bye out the breathers, it made good HP. The dyno operator really didn't have any advice. I put it in the car, took it easy for 50 miles or so, first time flooring it,it pushed the dipstick out and blow oil all over, it has no pvc system and the typical valve cover breathers. I did a leak down test on it but the test came up good. after a couple hundred more miles the same thing when you floored it. I pulled the motor, popped out the pistons and it seemed like the rings were stuck. So I took it to a good machine shop by me they checked the ring lands and cleaned them up, they checked the bores and they were straight, they honed it new rings and re assembled it, broke it in and the same thing a ton of blow bye. I've done a bunch of 460 based motor and never had this problem. Any input would be helpful.

[mag2555]

When you just had it at the shop I would have had them sonic check all the Bores , or have taken it to a shop that could!
What is the motors accutal cranking compression?

[DaveMcLain]

Are you sure you're using the correct rings for the pistons that are in the engine? Make sure that you don't have something like a .043 ring running in a 1/16th inch ring groove etc.

[kbr577]

I'm going to have the cylinder bores sonic checked this time, and the rings are right for the pistons. Thanks

[kbr577]

I think it was 150-170psi, I did it the beginning of the summer.

[mag2555]

How are you confirming that the rings are good for the Pistons as there is no guarantee that the ring grooves are machined right just because the piston manufacturer is saying what rings to use!

If you compress a compression ring all the way into its groove how much back clearance to you have and anything more then .004" of vertical clearance is no good in my book for the compression grooves.

[DCal]

I saw a motor once that the head gaskets didn't seal, real bad dip in the block surface. It pressurized the pan bad enough to blow the dipstick out also, but you have good leakdown. The other thing that bothers me is 'stuck rings' but how do you get good leakdown with stuck rings? let us know what you find because it difficult not having the parts to inspect in front of us.

[DaveMcLain]

Are you sure that the pistons are correct for the bore size and you don't have something like a 4.400 bore with a 4.390 piston? I've seen that done a few times.

[SupStk]

This is one of those cases where it could be anyone of a number of things. Guess if it was in my court the first thing would be a sonic test for wall thickness. 460 blocks don't have any sort of consistency. Was checking blocks I had on hand for an upcoming build. Two identical casting numbers ranged from too thin at standard 4.360 to being safe at 4.440.
If the pistons and rings are correct, my next concern would be honing procedure and assembly practices.
I do dyno work for other shops in the area. There's a couple builders, before firing their engines, its a sure thing they will blow oil and smoke out the breathers.

[DaveMcLain]

Another area to talk a look at is right past the bottom of the cylinder over on the main webbing side. Some guys don't bore the block deep enough and when you put in a stroker assembly the skirt on some pistons can hit in this area. I wonder if its doing that and then jamming the rings? it makes it a pain to hone the block properly too.

About a dozen years ago a friend and I put on the big Ford Block Summit event and I sonic tested over 30 production blocks in one day. If you're a 521 you're only at .030 over so I doubt you'll find a cylinder wall thin enough to cause any trouble. If you do check it test the area about 1 inch down from the deck where two cylinders are adjacent. I think .075 is about as thin as you want to be for hard running. I doubt you'll be that thin. It'll probably be closer to .100

[turbo2256b]

Leak down test or typ compression test dosent necessary prove the oil retention rings are working properly.
Different ring materials and honing grits may require different brake in procedures.

[MadBill]

But bad oil ring sealing wouldn't cause massive venting out the breathers and blow out the dipstick...

[kbr577]

Ok first off the piston rings were replaced, and the block was re honed. the machine shop that did the work is a very good shop and said even though the ring lands looked and measured good don't mean there flat. I just pulled the pistons out again and found one piston with the oil ring stuck in the grove. I pulled it apart with the intentions of putting new pistons in it, but also checking everything I can that might cause a problem, making sure the piston skirts aren't running out of bore is something I will look into, and new pistons for sure. Sonic testing the bores are only .030 over but that always doesn't mean anything, but the walls were straight. Thanks for the input and Ill keep you posted.

[hpetew]

Is it possible that the engine temp isn't hot enough to close the end gaps?

[bentvalves]

what is the I.D. of the valve cover breather?