Valve Deposits

[KNOT-RIGHT]

What causes buildup on the stem of intake valves.
I replaced my roller lifters and while I had the intake off I noticed port engine has some deposts on the intake valve stem looks like carbon or fuel sludge.
Starboard was much cleaner.
Engines run excellent and pull like you read about!! 40 hours on them.
Static compression test reveals 160- 170 each cylinder.
twin 540s gen 4 bowties
8.0 to 1 static
mooneyham 10-71,s
Lee intercoolers
15% overdriven produces 9lbs boost
Merlin cast iron full ported heads
Hardended seats
Ferrea Iconnel valves
Crane 741 Hydraulic roller
twin 850 barry grants
Ross Forged Blower pistons .010 Wall clearence
Speedpro rings gaped at .028
Jetted on the rich side.
What Causes this buildup on the intake valves?
Thanks in advance
Gerry

[KNOT-RIGHT]

C,mon Take a stab...
Anyone???

[paradigm shift]

Usually oil leaking by valve seals will cause build up. Intakes are prone since they usually run under vacuum. :rollside:
How much build up are you talking about? Any pics?

[Fiat48]

All I can think of would be valve guide clearance or valve seals.

[GofastRacer]

Yep, on the intakes I would say valve seals is the culprit, guide clearance is possible also!..

[Norseman]

Excessive valve guide clearance and / or bad valve seals.

[KNOT-RIGHT]

Didnt get a chance to grab a picture However I did inject a cylinder with air
and removed the spring. The play or clearence was compared to the starboard
engine and was pretty close. I hit it with brake clean and through it back together. I did notice the exhaust valves are slightly looser. The measurements was up and down and side to side. I thought it was Valve seals.
Through a set on it to be safe.
I never really liked the piston and wall clearence Ross wanted to run with these slugs. I thought I would be shooting dipsticks like arrows :rollside:
But knock on wood they ran Strong all season.
This is my first Blower build so Im second guessing.
Maybe Im splitting hairs I just found it odd that one engine had deposits and the other didnt.
The engines are pickled for the winter. Just for Sh@ts next year Ill leak it down. Maybe Blowby. The breathers vent into the arrestors.

[Tahiti350]

On a blown motor there won't be any vacumn to pull oil down thru the intake guide, if the valves are loose it will actually push fuel/air up the guide into the valve cover--Blowby, or oil thru PCV (if running one). Check inside the spark arrestor and the breather lines for any traces of oil. Could also be ring seal, or an intake manifold gasket leak (under pressure), again thru the breather tubes and spark arrester. One engine showing more than the other due to different machining or wear patterns, or a bad gasket. My .05 worth.
GaryB> Tahiti350

[Willis]

caveman,
i sure would like to know how your engine builder can get 170 psi on 250 rpm,
the blower don't pull that low on rpm's
Willis

[Havasu Hangin']

On a blown motor there won't be any vacumn to pull oil down thru the intake guide.
My blower motors pull vacum up to 2,700 RPMs, or so.

[KNOT-RIGHT]

caveman,
i sure would like to know how your engine builder can get 170 psi on 250 rpm,
the blower don't pull that low on rpm's
Willis
Im the engine Builder. Couldnt afford to do it any other way. :messedup:
If I had a engine builder I would just call them up and ask them.
This is why you see me asking the question here.
Would you beleave most of the info I get on the forums Helped
build these engines. (Scary aint it).
If I am reading your post correctly you are in dout of the compression #,s
with a crank no spark, Plugs removed, open throttles, standard compression check?
when I built the engines I did this test and recorded the #,s
2-158
4-164
6-160
8-164
1-164
3-169
5-165
7-169
After noticing the deposits on valves I rechecked the compression
and found all the #,s approx 3% higher (Ring Seat)?
When the season begins up here I will perform a leak down test.
Something I should have done from the start.
Gerry

[DansBlown73Nordic]

I wonder why you have so much compression? I think my motor with 7.5 to 1 is around #120. Maybe im wrong..... :hammerhea

[Tahiti350]

My blower motors pull vacum up to 2,700 RPMs, or so.
I stand corrected. I was speeaking more onspeed/accelarating, didn't stop to consider idle/off-idle/decell :rollside: . Thanks for the honest point.
GaryB> Tahiti350

[KNOT-RIGHT]

At Idle (900rpm) These engines have 12hg vacuum.

[Havasu47]

A cylinder head set up for a blower will have a little more guide clearance for the exhaust valve than the intake because of the higher temps that the exhaust valve sees. If you are using PC seals they are not a long lasting valve seal and carbon deposits on the intake valve is not surprising. Another thing to consider is rocker arm geometry. If it is not perfect it will push the valve stem against the guide and cause premature guide wear. You will only be able to feel it in the direction of the wear usually. This will also cause the seal (especially a PC seal) to let more oil by.
hope this helps