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Heads and oil consumption!!

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DjD

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Discussion starter · #1 ·
Looking for some input. My 383 with about 4000 - 5000 miles on it is burning 1/2 qt in 500 miles. The leak down was less than 5% in each cyl and compression is about 185lbs in each cyl. We pulled the heads and disassembled them. The back of each intake valve was loaded with oil crud. There was .003 clearence between the valve stem and the guides with no unusual wear. The seals looked fine...

Any thoughts?
 
#3 ·
Yup, oger's right, pulling oil past the bottom of the intake gasket. Could happen when you deck the heads and use a not perfectly matched gasket. Also if the intake runners are large and the mating surface at the bottom of runner is small a slight mis-alignment of gasket can open up a way for oil to get it.

Luck, Kevin
 
Discussion starter · #4 ·
No sign of oil leaking past the intake gaskets. Could too small of a cam with the Sportsman II heads cause some kind of inversion? (or is the word reversion?) The cam I have has .465 lift 221 dur @ .050 (Isky 21271)
 
Discussion starter · #7 ·
I guess World Products feels for a race motor .003 is acceptable maybe even perfered. The guy doing my heads said he felt it excessive for a street mill. I just got a call from the machine shop, the heads are done.. Looking for any other possible issues before this thing goes back together. Jody and Scott - how did the seals look?

Thanks for all the quick replys!!
 
#8 ·
Dennis,

The seals looked great. The guy who did the heads is someone I trust and a professional head porter. He said the guides used in the Sportsmen II, Iron Eagle, Victor Jr, etc. aren't very good, even though he likes the heads themselves. He claims they use a softer guide which eliminates a siezed valve but gives high oil consumption. He prefers to use a better guide and set them up correctly. All I know is that when he finished the heads besides a bunch of hp from the port work they used NO oil after that. My consumption was about exactly what you're getting.

The seals can't control that much clearance and will pull oil, especially on the intake side under deceleration (high vacuum).

By the way, he also said they go away in as little as 150 miles. Mine only had a couple hundred miles on them.

Jody

[This message has been edited by Camcojb (edited 10-04-2001).]
 
Discussion starter · #9 ·
Thanks for the input Jody. I hope guides are the resolve! Bill K posted some info for me on the Chevelle site that will have me checking the rings before it's all bolted back together...
 
#10 ·
.003" stem clearance is way excessive for a starting point on a new engine; production spec is .001"-.0025", with .001"-.0015" preferred. Starting at .003", especially with soft guides, is a guarantee of excessive oil consumption. Doesn't matter much 1/4-mile at a time, but it does for a street-driven car.

------------------
JohnZ
'69 Z28 Fathom Green
 
#12 ·
Keep us up to date on the reworked heads and resultant oil consumption.
thx
joe c.
 
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#13 ·
Dennis, I know you have an oil pressure problem you've talked about. Any chance the lifters are passing too much oil to the valve covers and flooding the valve guides?
The anti-pumpup type lifters were notorious for squirting oil a foot when valve covers were off!!

I'd grind the drain back passages and open up the head gasket area where the oil drains back from the heads.
David

------------------
Check my web page for First Gen Camaro suspension info:
David's Motorsports page
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67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer
 
Discussion starter · #14 ·
David - thanks for the lead in!! The shop that built the engine has been insistant that everything is covered by warantee. They have reworked the heads and went through the lower end to resolve the low pressure problem. The engine went back in and the oil pressure problem is still there. Don't have any idea if the head work resolved the oil usage as I didn't get 10 miles on it before they yanked the engine again...

The shop thinks the lifter bores are too large. The block is "Made in Mexico" and several of the guys the shop deals with have stated they have seen it before. The theory is that oil leaks out between the bore and the lifter causing low pressure readings at idle but allows the pressure to build under RPM!! (BillK - you have any input?) The bottom line is it's all coming apart and a replacement block may be in the works! They're dangling a 400 block they have in the shop in my direction!!

I'll mention the anti-pumpup lifters on monday... thanks all!!
 
#15 ·
There is a welch plug in the oil passage just above the oil pump. Check that it is in there, sometimes it gets removed for a block overhaul and not replaced. I have read if it is left out it can reduce oil pressure. I don't see how as it just diverts oil through the oil filter and back. Leaving it out would bypass the filter not dump oil.
Check the cam journals too, might be undersize. If the lifers are not put back on the exact lobe they were run on before, you might have cam problems like a flat cam.
If the builder didn't keep them in order, get a new cam.
I had a cam lobe go flat and little strings of metal shavings got in the oil pump relief valve, making it stick.

I've heard on the net the Mexico blocks were cast from pretty good material, don't know for sure.
If the 400 block is not bored and honed with a block torque plate, pass on it. I had one with a .040" overbore and it had 65% leak down one year after I put it in. It was a mass produced rebuilt engine.
David

------------------
Check my web page for First Gen Camaro suspension info:
David's Motorsports page
First Gen Suspension Page
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer
 
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