I'm nearing 1000 miles on a 406 Impersonator motor I built this winter.  The engine is almost identical to the one in the article.  It is currently using ~1 quart of oil per 200 miles.  This seems extremely excessive to me.  I spoke with the machine shop and they recommend I watch it for a while to see if it improves but they suggested it might be the valve seals on the new Vortec heads.

the short block is a '72 400 4-bolt with stock crank, 5.7" rods, KB 30cc D-dish pistons.  Short block was assembled by the machine shop.

the top end is a set of Vortec heads from Scoggin #### (the upgraded ones for over .480 cams), Edelbrock Performer RPM intake, new Edelbrock 750cfm carb.  Stock Vortec valve-train.  Comp 280 Magnum hydraulic flat-tappet cam.

I have a pcv valve connected to manifold vacuum and a breather on the other rocker cover.

The engine runs very strong.  Starts easily, doesn't smoke (which amazes me considering the oil consumption) and the spark plugs are not showing signs of oil consumption (the porcelain centers were bone white and the electrodes were clean.  The ring around the perimeter did show a bit of sooty black).  I haven't yet compression tested it.

Does it seem likely the new Vortec heads would leak so severely through the guides?  If the exhaust guides were leaky should I not expect to see much evidence on the plugs or during a compression test?

I've been closely monitoring my oil usage an recording amounts added and mileage.  I haven't seen any improvement.  What's my next step?

OM Gang

The insulators should not be bone white, this indicates either the fuel mixture is too lean or the spark plug's heat range is too hot.

Using a quart in 200 miles and not smoking doesn't make sense. Does this thing leak oil. That's a lot of oil.

What kind of rings, chrome at 1000 miles may not yet be seated. Incorrect cross hatch for ring type will cause problems. A smooth hatch on chrome may never seat the rings. A rough hatch on moly rings will wear them out quickly and you'll always have oil problems. Guys that hand hatch sometimes spend too much time in the cylinder, this tends to make the middle of the bore larger than the top or bottom. The ring rather than riding smoothly expands and contracts with the bore dia changes and can't get seated either against the ring land or the cylinder wall.

I recommend going to a colder range plug to see where they start to oil foul.

A general test that can be done with someone following you over a course where both of you can understand when your on it or when  backing off, cell phone these days I guess would help. Oil smoke on acceleration usually indicates it's getting around the rings. Smoke on decelleration is usually down the valve guides. Oil smoke is hard to detect from your rear view mirror, it takes somebody trailing the car to watch the pipes. Too much crankcase pressure will put oil into your air cleaner with the set up you have. Does the filter or housing get oily?

Bogie

Thanks 'Bogie.  I believe the white insulators were the result of too lean carburetion.  I've been running with the carb. jetted box stock.  I've since swapped needles for a 4% increase in cruise and 4% in power (1 step up in each direction) and will have another look at the plugs after a few miles to see if there is any change.  I'll experiment with colder plugs as you suggest also.

I do not know what kind of rings are installed - a quick phone call should answer that question though.

I'll try to setup a driving test with someone to follow.  I do not have the PCV connected to the air-cleaner; it is connected to the manifold vacuum port on the front of the Edelbrock carb.  I have a breather only in the other valve cover.  The old engine was tired and smoked significantly on start-up but, as you mentioned, I couldn't really see any smoke while driving (from the rear-view mirror).  This new engine doesn't smoke at all at start-up.  I've checked and re-checked under the engine and there is not an oil leak anywhere.

OM Gang

OK on the breaher set up, while doing my indoor speed reading I thought you wrote that the PCV valve went to the manifold and a breather went to the air cleaner. Since I live in SMOG check state, that's what I expect to see and therefore assumed, and we all know what ass-u-me really means.

Bogie

I'm now passed the 1000 mile mark.  Oil consumption is still high.  I've compression tested the engine.  All cylinders are between 168 & 176 (I did the test on a cold engine).  I don't know if these numbers seem low/high. They're all within 5% though so that seems good.  I am getting smoke on deceleration.  While I haven't performed the test with someone following me, if I decelerate from high rpm in second gear (auto trans) I can see the smoke easily in my side mirrors.  The heads are brand new from SD.  I purchased the upgraded head package

Upgraded Vortec head kits - features our high performance Z28 valve springs with light weight LT4 retianers, good for about 0.550" lift with a hydraulic camshaft.

I'm running a comp 280 Magnum hydraulic cam (.480 lift).  To be honest, the heads shipped assembled and I did not take them apart to confirm everything was correct.  Maybe that's a mistake that will bite me.  Can you think of anything else, perhaps additional tests, that I should do before taking the heads off?  Or is there already enough info. to justify taking them into a machine shop for checking?

Thanks, OM Gang

I've been building a vortec 406 on paper for a while now, and those are the same pistons I decided to go with.  I noted that the pistons require a fairly substantial top ring end gap. I will occasionally use mine for towing. For towing (or power adders) KB recommends a .033" top ring gap for a 4.155 bore with those pistons.  

Do you know what end gap the rings were set to, or had?   It's just a thought.  If most of your smoke is coming from deceleration, then as Bogie said, it's probably your valve guides/ seals.  

What a bummer.

PS: Are you able to burn 87 octane without detonation with your combo?

<<Are you able to burn 87 octane without detonation with your combo?

To be honest, I don't know yet.  I have been running mid-grade (89) and it seems to be quite fine.  On a few occasions, when hot from creeping along in very slow, heavy traffic, I have heard a bit of detonation under heavy load/heavy throttle.  The problem may be my distributor though.  I cheaped out and purchased a Mallory HEI unit WITHOUT adjustable centrifugal advance.  The first one I got had 18-19 degrees advance in it which required 17-18 initial (total timing at 36).  I sent it back and the replacement has 21 so I'm still running 15 initial.  I think that may be just a bit much on a heavy Blazer with 33's and 3.08 gears.  I think I'd prefer 11-12 initial with 24-25 in the distributor.  That may also be the source of the troubles with my emissions testing.

As for the oil consumption, the machine shop that assembled the bottom end for me agrees with 'bogey as well.  Before I get too carried away they are suggesting I replace the seals on the new heads.  I haven't checked what type came installed on them yet, but hope to do so this weekend.

OM Gang

vello', I backed my initial timing down to 12 degrees today for another attempt at emissions.  I noticed a significant improvement in driveability and idle.  Acceleration at low rpm, high-load feels much better now too with no hint of detonation.  Unfortunately, my total advance is now only at 32 degrees.  I think a distributor with 24-25 degrees centrifugal advance would be ideal for my application.  I'd be able to run the lower initial and still have 36 total.  Once I get through my emissions test, and get this oil issue under control, I'll fill up with some 87 octane and post back my results.

OM Gang

 Thanks for your input. I hope new seals fix your oil consumption problem and I look forward to hearing about the 87 octane update. 

Have you talked to any tech people at Scoggin-deeky about your oil consumption issues?  I'm curious what they would say...

PS: once you fix your oil consumption  problem, you might try running some Marvel Mystery Oil (or some other similar product) through the fuel system.  The heavy oil consumption may have added some carbon to your combustion chambers, reducing your chamber CC size...    then again, the detonation may have been keeping it "clean"...    

Just a couple thoughts.

I sent an e-mal to SD customer service yesterday.  If I don't here from them in a couple of days I'll give 'em a call.

OM Gang

"vello', I backed my initial timing down to 12 degrees today for another attempt at emissions.  I noticed a significant improvement in driveability and idle.  Acceleration at low rpm, high-load feels much better now too with no hint of detonation.  Unfortunately, my total advance is now only at 32 degrees.  I think a distributor with 24-25 degrees centrifugal advance would be ideal for my application.  I'd be able to run the lower initial and still have 36 total.  Once I get through my emissions test, and get this oil issue under control, I'll fill up with some 87 octane and post back my results."

You may be right, but it may also be that the engine doesn't want that much timming.  My understanding is that Vortec heads tend to want a little less lead due to the combustion chambers and improved combustion process.  It's a thought.

I'm basing total timing estimate on the numbers from the Impersonator article.  I just rechecked and see they ended up at 35 degrees total and not 36.

OM Gang

I had a 355 with vortecs and it made it's peak power with 31 degrees full advance.