Are these issues related? (long)

[Zmanco]

I've got a few issues right now that I fear may be related and need advice. Here's the background:

 

Rebuilt N42 with flat tops (.030 over) 15k miles ago

N42 head that was "cleaned up" including new valve seals (probably stock)

Reground cam 284/284

Initially ran with triple webers after the rebuild

Last summer converted to megasquirt fuel-only, recently added spark

 

Issue 1: when I had webers on it, I was able to run with 32-35 degrees of advance without detonation. Since converting to megasquirt, the max I can run between 4k and 5k rpm is 21 degrees. Above 5k rpm I can't hear detonation if I add more advance, but I'm not sure since the other noises are so loud. I can richen the mixture to ridiculous levels in that range, but can't go over 21 degrees. And this is on mild days (70 degrees F).

 

Issue 2: A few weeks ago I checked the oil and found it was down 2 quarts. This was only 1200 miles after I had changed it. Last weekend I was down 1.5 quarts after another 600 miiles. Granted, a few hundred miles ago I upgraded megasquirt so those last few miles have seen a lot of idling as well as pulls to redline. Still, the most I had ever lost prior was less than a quart from a 100+ mile track day.

 

Issue 3: Take a look at the spark plugs. A few look too white to my eyes. But I am used to tuning carbs, not FI, so maybe I'm just not used to clean plugs In any event, you can see there's oil on the threads on all. The area around the plugs on the head is clean on all but #6 (mild seepage from the valve cover gasket which I'll replace if/when I do the head swap).

 

There are no visible leaks. The exhaust does not have any tinge of blue when idling or blipping the throttle with the car stationary. In the last year I have noticed at times that after a high rev down shift, when I first got on the gas I could see some smoke out the rear view mirror. Also, on group drives, people said sometimes they saw a puff of blue smoke, but all said it was no big deal.

 

The oil in the engine right now is 10w30. Last summer and before I ran 10w40.

 

Today I ran a compression test on the engine (hot) and all were within 5 psi of 165.

 

I figure there could be any combination of the following issues going on:

 

a) With the N42 head and flat tops I'm at 10.3 CR which is probably too high. However, with the bigger cam and the fact that I'm at altitude (never below 5k feet), and the fact that I didn't have detonation with the webers, I figure that I shoud be able to run at least 30 degrees with megasquirt.

 

If oil is getting into the combustion chamber (it must be, right?) then that would explain why I can't run the full advance like I used to with the webers. In other words, it has nothing to do with carbs vs. FI, it's due to the oil consumption.

 

c) I figure the valve seals are probably in need of replacement, but given it doesn't smoke after a hot restart, I figure they can't be too bad.

 

d) I have a P90 head I picked up on ebay that I'd like to shave etc, but before I do anything, I feel I should understand the oil consumption issue. Of course, I'd change the valve seals before installing it.

 

Questions:

 

1) Is it plausible to see that much oil consumption from leaking valve seals? Or should I be suspecting the rings? But then why wouldn't the compression test have worse numbers?

 

2) If I ignore the oil consumption for a moment, does it make sense that I have detonation only between 4k and 5k regardless of how rich it is? Why would the detonation stop instead of remain at higher revs? Is that normal? It's not what used to happen when I had too much advance.

 

3) Could it be that I just need to run a heavier oil? Seems to me that going from 10w40 to 10w30 shouldn't result in this much consumption if the engine is otherwise healthy.

 

Ok, that's enough, I'll stop now and take a breath If you're still with me, thanks for reading all of this and I'd appreciate your thoughts and advice.

[woldson]

Most of that I can not comment on.

Have you checked coolent for the presents of oil?

That is just a huge amount of oil, considering no smoke and good compression. Hummmm.

Puddles under the car?

[Zmanco]

Coolant is clean, oil is clean too.

 

Reading my post again, I dawned on me that this is the first time I've run 10w30 oil in warm weather. I wouldn't think going from 10w40 to 10w30 would make that much of a difference, but tonight I changed the oil to castrol 20w50 as a test. I'll take it out tomorrow and see if there is a difference with how much advance I can run.

[Noddle]

Coolant is clean, oil is clean too.

 

Reading my post again, I dawned on me that this is the first time I've run 10w30 oil in warm weather. I wouldn't think going from 10w40 to 10w30 would make that much of a difference, but tonight I changed the oil to castrol 20w50 as a test. I'll take it out tomorrow and see if there is a difference with how much advance I can run.

 

"first time I've run 10w30 oil in warm weather" maybe this is why you can't run as much advanced, warmer weather, the air would be less dense than it would be in colder weather.

 

I'm no expert, but this may be a clue

 

Nigel

[Zmanco]

I had a chance to go out this morning (ambient is already above 70) and the detonation issue is better. I can run up to 28 degrees now before I begin to hear a little detonation. I suspect that may be the best I can hope for with the open chamber N42 head and flat top pistons.

 

Only time will tell on the oil consumption. But I would never have guessed that running 10w30 would make that much of a difference.

 

Has anyone else experienced this when running the thinner weight oils?

[z-ya]

 

Issue 1: when I had webers on it, I was able to run with 32-35 degrees of advance without detonation. Since converting to megasquirt, the max I can run between 4k and 5k rpm is 21 degrees. Above 5k rpm I can't hear detonation if I add more advance, but I'm not sure since the other noises are so loud. I can richen the mixture to ridiculous levels in that range, but can't go over 21 degrees. And this is on mild days (70 degrees F).

 

Have you verified the timing with a timing light? Just because you have 21 deg set in Megatune, it doesn't mean that that is the actual ignition timing. Verify that the timing you set in the timing table matches what you measure with a timing light.

 

Issue 2: A few weeks ago I checked the oil and found it was down 2 quarts. This was only 1200 miles after I had changed it. Last weekend I was down 1.5 quarts after another 600 miiles. Granted, a few hundred miles ago I upgraded megasquirt so those last few miles have seen a lot of idling as well as pulls to redline. Still, the most I had ever lost prior was less than a quart from a 100+ mile track day.

 

It shouldn't use any oil. I run multiple tack events on an oil change with a similar engine and I never see oil loss.

 

Issue 3: Take a look at the spark plugs. A few look too white to my eyes. But I am used to tuning carbs, not FI, so maybe I'm just not used to clean plugs In any event, you can see there's oil on the threads on all. The area around the plugs on the head is clean on all but #6 (mild seepage from the valve cover gasket which I'll replace if/when I do the head swap).

 

What are they gapped to? 35 thousands is good for your engine. Yes, they look a little light, but there doesn't seem to be a lot of oil residue on them.

[Zmanco]

Timing was verified with a timing light. (Note: it's pretty sweet to be able to create a custom advance curve based on rpm and MAP any way I want!) I found that the max advance I can run and not hear any detonation at all at any rpm is 26 degrees. It's less than I'd like, but as I said earlier, not surprising given the flat tops and open chamber head. Time to get going on the P90 project ...

 

I drove a lot around town today along with a bunch of pulls to redline on the highway. Total of about 75 miles with ambient temp pushing 90. So far I can't see any drop in the oil level. This is with Castrol 20w50.

 

Plugs are gapped to 0.050. I figured that with the MSD box and blaster coil, I could open it up some. Glad to hear you think they're ok.

 

I'm going to assume the main problem was the 10w30 oil. The brand was Mobil Clean 5000 (chosen because it was on sale). When I put it in towards the end of the winter, I figured that any brand name oil would be ok since they all meet the SAE standards and the weather wasn't right for any hard driving and track days. Perhaps it was mis-labeled and wasn't really a 10w30? In any event, I'll be a lot more careful about which oil I choose from now on.

[woldson]

Keep your eye on that oil level. That just dose not quite sound correct to me.

The heavy weight oil may leak/blowby?, a little less, but not that much.

[mobythevan]

It makes perfect sense that it detonates between 4k and 5k then quits, that says your engine flows the most air in that range. You should find if your VE table is tuned well that it is higher in this area, it is the engines most efficient range. You need to run less timing in this area. So your timing would dip between 4k and 5k then rise again above 5k. After reading the whole post it seems that you drove the car with the carbs in colder temps and now with the EFI in warmer temps. Where is your air filter located with the EFI setup?

 

On the oil comsumption thing I can only say that my friend was using oil like crazy and it turned out to be two things on his engine: 1. The turbo was leaking like crazy into the intake pipe and he had white powder on his plugs. His intake pipes/intercooler had quarts of oil in them down low. 2. All his pistons had broken ring lands, but he showed varying compression results.