BAD-HABIT

I have a SBC late model roller engine with factory lifters and Comp Cams Roller Tip Rockers. I seem to be getting exessive blow-by. I am using Keith Black Hyperkentic pistons and Dana moly rings. I only have 4 hours on the new motor. During the first hour or so I thought I had a fire or something going on back there! Smoke was really coming out of the breathers. Now it's not quite as bad. I did away with the valve cover mounted breathers and went with the stock hoses to the air cleaner. After about an 2 hours of running between 3-4000rpm's I noticed about a teaspoon or so of oil around the upper lip of the carb and it was seaping over the sides. The inside of the carb also had a slight film on it. Is this normal. I called my builder and he said give it 10 hours and it should be normal. Is this correct? I guess with a new motor and all Im just a little concerned with all the mess from the breathers making my restord engine compartment and engine filthy.....
What's everyone's thought on this? Is it too early to tell at 4 hours?

"Bad-Habit"

Blueman

You should not have that much smoke. You did get a cast ring with a moly set correct. Also alot depends on the finsh of the cylinder walls it should be a high finsh for those moly rings. I don't guess there is any way you could have run lean or detonated the motor is there. Does it run smooth. Let us know how it turns out.

Vinny P

It sounds to me like there is a problem here. There should not be that much smoke let alone oil coming into the carb. If you pull the hoses out of the valve covers (with the engine hot) do you see a trail of smoke pumping up through the holes? Do you know what the builder set your ring end gap at? Do you know what the piston to wall clearance is? If this was my motor, I would run a leak down test to see if any cylinders has excessive leakage. That will tell you right away if pressure is blowing past the rings. Good Luck.

BAD-HABIT

Well I also think this is not "normal". But what I want to know is if this thing progressivly gets better should I worry before I get to 10 hours? I mean what kind of damage might I do? The piston clearance is .002 I belive according to my build sheet. I have a 90 day warranty on the short block. I purchased the short block from Jasper. I had a local builder assemble the heads etc....I went thru Jasper's Performance shop not there regular shop. I custom ordered the 4 bolt late model roller block and had a comp cams roller cam with keith black pistons installed.

"Bad-Habit"

Vinny P

Well I can't think of any damage that you can do although motors that suck up oil tend to detonate easier. Make sure that your timing is not too far advanced and it should be o.k. I suppose if your engine builder says to let it run for 10 hours, then maybe you should do it. After the 10 hours, run a leak down test and give him the numbers. If they are bad, then he should stand behind his work. Personnaly, I think that he either didn't put the correct finish when he final honed or the ring end gap is too large.

BLOWN 1100

F3LS
It is my opinion you definitely have a problem,
it is not normal to have noticeable blowby on
a new overhaul. At normal temp engine should
be broken in within one hr. Let us know what you
find.
Loy

blue thunder

What are you using for oil during your breakin period. I've heard sya that dino oil should be used, not synthetic.

BT

BAD-HABIT

Well after speaking with my builders ass't I Found out that instead of assembly lube he likes to use STP! I guess he coated the cyldr walls and the entire valve train.....His assn't told me that he personally dosn't like it for the simple reason it burn's easily and tends to leave deposits..He thinks that some or all of my blowby is from the stp. Well Ive got 5 hours on the motor and yes I have about 50 percent of the initial amount of smoke so hopefully im headed in the right direction. I used 10/40 for the first hour and have switched to straight 30wt now. I plan on changing to 15/50 Mobil One at 15 hours as long as my symptoms subside. An interesting note though...On Mobil One's site they say that it is ok to use Mobil One to break in a motor. They say that the early (60-70's)synthetic's had problems in this area. And that all that is fixed and that the rumors still exist. To prove their point they state that BMW,Porshce,Corvettes and Vipers come from the factory with Mobil One........Some one suggested a "leak-down" test. How is this done? I will keep everyone posted thanks

"Bad-Habit"

excaleagle42

i had a 97 z28 ss and it came from the factory with mobile 1 oil in the engine, rear, and richmond 6 speed. i just broke a pair of engines in with synthetic. runs good.
also, it's important how you seat your rings. part throttle cruise, to full throttle for a few seconds about ten times if you have some blow by. moly's can be a pain to seat. like other guys have said, your builder hopefully had an aggressive cross hatch pattern on the cylinders.
keith blacks have a higher silicone content and don't expand as much as regular pistons so you can run tighter ring gaps. i'm sure your builder knows that so they probably just need to seat. i agree about the stp being too thick and not helping your rings seat. regular motor oil in cylinders is best. just my opinion but i think when all the residual stp goo is off your walls, it will be fine.
fran

Vinny P

I mentioned the leak down test. I am a firm beleiver of this test being an accurate way of determining the condition of the internals of a motor. You asked how to do it, so I will assume that you never did it before. So, I will start with the basics. First you need to get a leak down guage. Next you need some form of compressed air at the boat. Pull one spark plug out, get the cylinder to T.D.C. screw the guage into the plug hole. Add air pressure , your guage will tell you how much pressure to regulate it to. Then just read the leakage guage. You want zero leakage but that never happens, anything under 10% is usaully o.k. Do this for all the cylinders and compare your findings. If 1 cylinder is way higher than the others, then you know there is a problem there. Also, you can hear where air is escaping. Put your ear on top of the carb to determine if you have an intake valve leak, and listen by the breathers or oil fill in the valve covers to check the rings, tail pipes to check the exhaust valves. It is better to pull the manifolds or risers to check the exhaust valves, because it would have to be a big leak to hear it at the tail pipes.