Premature Valve Guide Wear

[Henry Schmidt]

Originally Posted by BURN-BROS

What valves did you use?

My thoughts exactly. If the replacements were Intervlave, there is a chance that the valve stems are machined improperly. (very rough radial grooves). We see this all the time. They are usable but they must be polished before installation. We use the same tool that we use for polishing cranks.

[VFR750]

I'm not sure of the source of the valves. They were fitted and honed.

I appreciate the info. Yes, it looked like there are radial lines on the stems. I will keep and eye on this.

What I have noticed over the past 200 miles is a significant reduction in start up smoke. Actually very little. I'll be keeping a eye on the smoke and oil consumption.

[Lapkritis]

As I look at the picture again, it looks like the valve head/neck is right against the guide. Perhaps the wear is due to diameter being too great or guide not seated far enough from valve seat. Dimensional interference... Rather than exclusively poor surface finish. Further along the stem to the spring end doesn't have the same heavy wear.

[VFR750]

7/24/15 update.

About 750 miles on the breakin. While startup smoke has greatly diminished. Consumption has not gone down that much. Easily >1qt/1000 miles.

Pulled LHS carbs off and still seeing oil pooling on the valves. Looks the same as the earlier pictures.

So I'm somewhat on the fence on pulling the engine.

[VFR750]

https://youtu.be/E7zdQ6eQxvQ

Here is what my puff on start looks like. I'm thinking the rings are ok. But I'm dumping oil into the engine on start and it's quenching the spark just as the engine tries to start.

Plus I am burning 1qt in 500 miles. Best I can tell it is being sucked past the valve guides on the decel. I ran down a very long straight hill in gear and could discern a light grey cloud down the middle of my lane.

Btw. When I started this thread I was getting a huge, fill the garage with smoke, kind of cloud. I think that was the rings. And after some very aggressive driving, the huge cloud went away. I am treating that as rings not seated. And now they appear to be seated.

High oil consumption and puffing on start are the current symptoms.

[Lapkritis]

My first start after winter storage for 7mos might look like that... Seems quite excessive for a regular start.

[VFR750]

Another Video. Far worse than 7/31/15 start.

Actually more typical than the last one. I normally see a large residual cloud. Now I know exactly what it looks like. Ugly.

https://youtu.be/TfJrK-d1utY

The only part of my engine rebuild that leaks, is inside.....

[Lapkritis]

Do you have access to a bore-o-scope? Harbor freight has them cheap. What I would recommend is another prolonged parking period (3 days seems to be plenty) and a peak into each cylinder before starting to see how much oil might be leaking by the rings vs. leaking by the stem seal. The intake valve closed cylinders should have less oil in the cylinder than say the intake valve open with all else equal, to nail down the stem seals/guides instead of piston rings.

...and maybe a leak down to confirm rings are seated.

[VFR750]

Would oil be coming back through the intake valve and wetting down the inside of the head intake runner?

Or is that valve guide leaks?

Just drove around a bit and got tanked up with gas. Pulled into the garage, shut the engine down and immediately pulled the LHS carb off. And found a coating of oil inside the intake ports.

Wet, shiny, light brown oil. Wiped off. Heads were really hot too! Ouch.

No puddle on the valves yet. But I can see where there will be, once all that oil makes it's way down due to gravity.

[Lapkritis]

What do you have for cams? You can get intake reversion.

Nevermind, I see your note earlier:

"WRT the cams, I have a custom DRC cam. DC-20/19 with 110 lobe center, timing set per John at 2.4mm. I have DRC valve springs.

There is more duration and overlap, such that both valves are open at TDC. This is not a CIS compatible cam.

I expect there is reversion. Does reversion make it harder to seat the piston rings?"

It might be worth a call to John to discuss your port sizing WRT the cam choice if everything else checks out (stem seals, rings etc).

[VFR750]

I'll post some pictures tonight but here is what I know:

Right after shutdown, pulled the LHS carb and found 1,2 &3 the intake ports and top of valves are wet with clean oil.

Oil wipes off with a paper towel. Does not evaporate. Means it's not fuel.

Oil film covers almost entire inside surface of the port.

A small puddle developed over time as the oil sank to the lowest point.

Intake valve shaft is now (900 miles) very polished, verses what it looked like at 400 miles. I can see clean, smooth surface, because it is now a mirrored surface on 75% of what I can see. Some roughness remains.

From what I can see, there is no oil sitting in the #1 cylinder, when I look through the open intake valve.

So the most reasonable scenario is oil being pulled past guide seals during the idle (max vacuum) intake stroke, and then impacting the closing valve causing it to rebound and spray up into the intake and soaking the runner.

Idle fuel flow is not enough to wash it away.

Seems reasonable to me. Comments?

[chris_seven]

I would expect maximum vacuum to be at relatively high engine speeds but with a closed throttle.

I would think that at idle you should have around 17-20 in Hg and over 25-28 for a short time when you snap the throttle closed at high rpm.

I would have thought that the majority of seals should be able to deal with this amount of pressure quite effectively providing they they are not worn.

Both clearance and surface finish of the valve/seal will have an influence .

Ra for most valve stem seals should be between 0.10 and 0.25 microns.

If the surface is too smooth wear of the seal occurs as there will be insufficient lubrication and if the finish is too rough the valve will abrade the seal.

The positive type stem seal should have a small groove in the top of the seal that keeps a small amount of oil against the stem and allows a very small film of oil to lubricate the stem.

If there is oil puddling onto the valves then either the guides or the seals are excessively worn.

Either the guides were opened out too much or the surface finish of the stem was poor but is seems to me as if it needs to be 'fixed'.

[VFR750]

This is what the #2 intake looked like 10 minutes after engine shutdown:


I wiped some of the oil off with a paper towel, and this is what it looks like now:


What's amazing is how much oil is spread about inside the intake runner. It glistens with a heavy coat of oil.

All intakes: #1, #2, and #3 looked this way. #1 was open when the engine stopped. I've looked in through the open valve, and can't see any oil on the cylinder bottom.

[VFR750]

Originally Posted by cgarr

Your cam is not that high a lift, if you can find out what the installed valve guide height is? On higher lift cams sometimes you have to shorten up the guide otherwise with the valve spring compressed it can hit the valve seal and destroy it, I don't think that's your problem unless the guides were set way too high?

This is an interesting comment. I'll take a closer look when I get a chance. It might explain why all valves guides are leaking.

I'm running DRC racing springs with the steel retainers.

The upper spring retainer is very deep-cupped and uses a large staggered spring height. The installed height specs are also taller than many other springs. I think 39.5mm. But that would only apply to the outer spring, not the inner one.

Maybe this was something missed during guide installation?

[cgarr]

Did you get the valve spring seats that should have come with the springs? I just installed a set of these and if you use the stock spring seats there is no way you can set the correct height when using the thinner spring seats for those springs must be set to 39.5

[VFR750]

I bought the kit with the steel retainers. Included all of the required pieces. I have the old springs, seats and upper retainers in a bag. Keepers were reused.

Just checked!

[Cairo94507]

This is upsetting for sure. I hope you are able to accurately diagnose the issue and correct it so you can enjoy your car w/o the oil consumption and smoking. I have to think it is the valve guides.

[Henry Schmidt]

Over the last few years, we've seen some valve guides that sit too high when installed. With the higher lift cams, the retainer hits the valve stem seals and that interference destroys the seal in a very short time. Usually an issue with intake valves not exhaust.

[VFR750]

Henry. Thanks. I'll try to confirm how much lift I'm really getting at the valve, and try to measure the gap between the retainer and the seal.

Engine coming out.....

[VFR750]

Interesting fact: number 4 intake valve has a big oil puddle.

Can't say anything about 5 or 6. No 5 intake was just closing. And no 6 was just cracked open. Both were open just a tiny amount. If there was oil, it would have drained out. So no definitive answer.

I can say this problem is 100% certain on 1-4.

Something is not right. It makes no sense to be an issue on four seperate heads.

Heads are going to be reworked and it will get figured out.