vettef6

Have very high oil consumption, so I took off the heads to look at the cyl walls. Wanted to take the heads off anyway to get them even more ported by LE.
All 8 cylinder walls look alike, intake same as exhaust side of the walls. Looks like piston slap to me and can't be fixed through new rings as I see it.

Engine has run about 4-5k miles.
These are forged 4032 SRP pistons with standard tension 1/16, 1/16, 3/16 rings with coated skirts.

Need some advice on this before I continue.

wrd1972

iTrader: (12)

Some vertical markings on the walls are normal and typically wont cause the oil consumption you are mentioning. Bad rings are the most likely culprit.

moehorsepower

iTrader: (3)

were these file to fit rings? I would pull the rings and check the end gaps...

fleetmgr

With that much scuffing in the cylinders, I'd say you have a pretty serious problem on your hands. What was your piston/cylinder clearance? You'll never get rings to seat over that.

WARDOG

Who did the machine work on your engine? What was the piston to wall clearances that you used? Those pictures defnately look like a piston slap problem. What kind of piston material are your SRP's?Are those made out of 2618 or 4032? 4032 has a lower silicone content (2%, avg.) and also has less heat expansion, 2618 has a higher silicone (12%, avg) content and requires a little more piston to wall clearence. The 2618's are used in higher hp engines (big boost, nitrous etc.) While 4032 pistons are more for street, road racing, etc, where piston to wall clearences are to be kept kinda tight.

4032- .0035 (coated skirt), .0040 (uncoated)
2618- .0040 (coated skirt), .0045 (uncoated)
These are my recomendations, soley based on personal experience.

WARDOG

My fault i just saw you running 4032

vettef6

To tell you fellows the truth, I bought this short block from Jason Short, moderator on this forum, a few years ago. He knows more about this short block build than I do.

BTW, the marks you see aren't that deep. Not that you think the walls are scuffed that bad. I will measure and see how much out of round the cylinders are.

JAKEJR

Here's my take on it: Is there corresponding wear on the pistons? If so, piston to wall is too tight. Wear's parallel to the piston skirt and cross-hatch is gone which tells me metal to metal; skirt to bore.

First, different pistons can require different piston to wall clearances due to their expansion characteristics when the heads are torqued in place and the pistons are exposed to the heat of a running engine.

Second, each piston should be mic'd and the bore it's to ride in should be honed to the spec for that specific piston. Although quality control has improved dramatically over the years, it's still best to mic each piston for it's hole.

Third, a deck plate should always be used when boreing and honeing a block to simulate the bore distortion the head bolts create when torqued down. In fact, one of the engine builders in my area has even created a heating procedure to run HOT water through the block as it's being bored and honed in addition to using torque plates. This mimics how the clearances will actually change in a running engine. His technique was featured in one of the mags along with the actual measurements which showed the differences with and without the hot water treatment.

Fourth, different cylinders can run at different temperatures, effecting piston expansion. So if a hole was honed on the tight end of the spec, that could be enough to cause what we're seeing.

So, based on what I'm seeing, honeing that hole, and any others can give you the clearance you need. Just take the parts to a shop that specializes on performance/race engines. Those shops tend to hold tighter tolerances. Not one that does, as its primary business, dealer warranty work. Custom paint shop Vs Macco. Honing will give your new rings a fresh break-in surface too.

Just my thoughts.

Jake

West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduation Day Parade 20 May 2010!!!

FASTFATBOY

iTrader: (23)

Did you do a leakdown before you pulled the heads? If not shame on you, would have told you what you needed to know.

What do you consider high oil consumption?

How many miles on that shorblock?

Fuel washdown issues at some point?

Pic of some plugs and pistons?

Those marks are normal with some miles.

vettef6

The engine has run about 6k miles.
Oil consumption is about 1 quart/300-400 miles.
No fuel wash down issues.
Pictures of pistons I'll post tomorrow.

At first I must say, I took off the heads only to have them shipped to LE for further porting and to get myself a SR cam. After the heads were off, I noticed the scuffing and then my oil consumption fell into mind. The engine otherwise runs great, starts immediately and has plenty of power. It's just not a street cam, it's not tuneable below 2300 rpm in CL.

I pulled the engine or what was left of it today. I will pull the pistons tomorrow. I don't know if I can get away with just honing the cylinders, probably not. If not I will have to look into buying new pistons. Really don't like the idea of going 4.040".

I think I found the problem. Jason Short had the block machined and supplied the pistons. I took measurements of everything possible. I noticed the clearance was below what SRP states it should be. Since this block was freshly honed and the pistons were as good as new, I never paid too much attention to the clearance. I thought the shop knew what it was doing, so who am I to say they are wrong. Looking at the notes I took, here is what I found:

Hope you can see the chart. Only two meet the specs; one is way to low.

SRP Piston 4.030"
piston skirt 4.0280

clearance should be 0.0025--0.0035
Cyl. 1
top 0.0015
middle 0.0019
bottom 0.0019
Cyl. 2
top 0.0015
middle 0.0019
bottom 0.0019
Cyl. 3
0.0015
0.0021
0.0025
Cyl. 4
0.0015
0.0015
0.0021
Cyl. 5
0.0011
0.0019
0.0023
Cyl. 6
0.0015
0.0019
0.0019
Cyl. 7
0.0015
0.0019
0.0019
Cyl. 8
0.0017
0.0023
0.0025

FASTFATBOY

iTrader: (23)

It does apper to have a slight taper wear issue in the cylinders.

What crank rod and piston are in it?

James Montigny

iTrader: (13)

Did you happen to try a leak-down test before you took it apart?
I'd be curious to know how that turned out and which direction air was escaping.

vettef6

The clearances I showed you above are after honing, not now!! It shows very clearly that there was NOT enough clearance to start out with, and I don't have piston slap but insufficient piston to wall clearance.

I'm using 6" rods with a cola crank and SRP 4032 pistons.