69 N.O.X. RATT

A few days ago I took the heads off my motor to have a little porting done on them. I noticed the intake valves were covered with deposits. I thought this was odd since the motor is all new with only 5,000 miles on it. When I took them to the porter (Bob McKray) I asked him what he thought about this. He told me it was relatively common in big blocks, and this is why.

Bob said that it is not uncommon for oil to be pulled through intake manifold gasket from the lifter valley. He said most types of gaskets are susceptible to this except Fel-Pro's. I went home and checked my old gaskets and sure enough it had a little oil residue through the bottom side of it where it would be pulled into the intake runners. Bob said the fix to this was to use Gaski-sinch around all the intake runners on the head side. He said that the very smooth surfaces on the head to intake mating area can make it worse.

I thought this would be a good tip, I have never heard anyhting like this before, and those deposits would difinitely cut down on flow to the heads (Less hp :cuss )

Jughead

Thanks for the tip John. I'll keep that in mind when I get to that stage of my rebuild. I've used Gascacinch before and found it to be a great sealer.

Len :chevy

J Z06

Wow, nice write up. I never used fel pros. I will try that next time,if and when the intake is off. :cheers:

LT1driver

great tip, i will be pulling a manifold soon and will use felpro and your tip. :cheers:

LD85

:thumbs:

Lt1er

If you had enough leak to suck in oil mist. did you also notice that your jetting was a little bigger to make up for the equivolent of a vacuum leak?

I always use Fel-Pro. One of my motor buddies showed me how to install the intake gaskets to ease future changes or manifold removal. He uses that red spray permatex on the head side only and glues the gasket in place. Then he smears a lite coat of red lithium grease on the manifold side.

He pullled off an intake that had been on for a couple of years and it lifted right off once he pulled the bolts. I've fought intakes stuckon so hard that you had to pound a pry bar into to break the intake free.

The real beauty of the grease idea is he doesn't even have to replace the gasket. Which is a big plus when you pull the intake quite often.

VetteLS6

I would look for other causes of the oil getting there...A "properly seating" manifold with correct torque specs should have a good enough seal that the compression of gasket wouldn't allow oil to pass into the intake port. It is common practice to not use the front/rear rubber gasket to help with the sealing that you descibed, instead a small bead of Hi-Temp RTV. Did you have the heads milled previously, this would be a avenue to have improper angularity in the mating areas on the manifold. Also, on another note some of the after market manifolds can be machined thicker in the base and have seating troubles in the BBC as well. Has the block been decked? This could be another source. It seems that the above fix is cheap way to cure a more costly mistake. :nono:

Hank

Pulled the heads on my 502 today and there was (!) oil visibly pooled in the intake ports, down around the valves where they seat. And evidence of oil in the intake ports (wet black walls) and black deposits on the piston tops.

This engine ran great, no blue smoke, light oil consumption (as far as I remember -- rarely had to add a quart).

Thanks for the tip,
Gerry

VetteLS6

What prompted you to pull the heads if the 502 ran great and used no noticable amount of oil? That ever happened to idea if it works dont fix it? :smash:

backtrail69

wow

marky mark

Great tip, thanks!

I pulled my intake to discover that the #6 exhaust lifter and cam lobe had gotten into a fight (neither won, I also lose). But I noticed that all the intake valves have this black and slightly oily soot covering their bases. Car did not burn oil. I thought it might have been oil pulled in by the PVC valve. Also, when the shop installed my engine they lifted it into place via the carb mounting area in spite of the fact that I had installed two "lift tabs" like the motor originally came with. I felt that the strain of lifting that much weight (427 + 4 spd) might have caused the intake manifold to lose some of it's sealing abilities. I noticed that the vacuum gauge never gave a reading that didn't keep moving up and down a few degrees either.I think that the intake block "fit" might also be the culprit. Intake was milled slightly I think. I did use fel-pro gaskets with the exhaust crossover blocked out. They looked o.k. upon removal though.
Just some thoughts. Thanks for the info, I thought it was just me!


[Modified by marky mark, 3:30 AM 1/4/2003]

VetteLS6

Food for thought....Valve Guides and poor valve seals could also cause oil to leave deposits on the intake valve stems...this doesn't occur on the exhaust valve because of the positive pressure during the exhaust cycle of the engine. One point of observation here is that with good manifold gaskets and no wicking, seeing oil deposits on the intake valve stems would have me looking at the seals/guides.
Larry :lurk: