Thread: gmpp 290 hp 350

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Hi All. New member here.My son and I purchased a gm 290 hp crate engine and installed it into a 1988 s15 shortbox.TCI street fighter th 350 trans, TCI saturday night special convertor,new summit dist,new edelbrock 1405 600 cfm carb new waterpump,corvette rad etc.The problem we have is it smokes like its burning oil on the passenger side bank.The only thing not new is intake ,it is a crosswind intake from e-bay.I pulled the plugs looks like #4 is the culprit.The engine runs strong lights the tires easily,antifreeze stays up no other problems.We have about 300 miles on it now.I marked #4 plug and the fouling is only on one side of the insulator,and is facing the intake valve.We followed the break in procedure exactly.primed oil system etc.I have pulled intake once and replaced gaskets ,thinking it was sucking oil from valley,but seemed to be fine.Runs with 15" vaccum at idle,is this normal.I will try and post a picture of the #4 plug.I have no warranty as was over one year before we got it running.Hope you guys can give me some ideas.

thanks.

Originally Posted by s15

Hi All. New member here.My son and I purchased a gm 290 hp crate engine and installed it into a 1988 s15 shortbox.TCI street fighter th 350 trans, TCI saturday night special convertor,new summit dist,new edelbrock 1405 600 cfm carb new waterpump,corvette rad etc.The problem we have is it smokes like its burning oil on the passenger side bank.The only thing not new is intake ,it is a crosswind intake from e-bay.I pulled the plugs looks like #4 is the culprit.The engine runs strong lights the tires easily,antifreeze stays up no other problems.We have about 300 miles on it now.I marked #4 plug and the fouling is only on one side of the insulator,and is facing the intake valve.We followed the break in procedure exactly.primed oil system etc.I have pulled intake once and replaced gaskets ,thinking it was sucking oil from valley,but seemed to be fine.Runs with 15" vaccum at idle,is this normal.I will try and post a picture of the #4 plug.I have no warranty as was over one year before we got it running.Hope you guys can give me some ideas.

thanks.

Have you done a comp. test yet?

ok thanks will check that

How long did this motor sit before firing? What break in proceedure did you do? It doesn't look that bad. I do have a question about what oil you're using. I'm gonna start a fire storm here (which usually is a good thing for the builder). I prefer not to use Paraphenolic oils ever, especially on break-in runs. I like the rings to heat sink for a half an hour after shut down. And I always am concerned about the rings collapsing if they sat too long on the crate before purchasing the unit. Was this an "M" motor or a reproduction unit built by a person and maybe sat a while before you bought it? Valve guide on that cylinder could have a problem. More than likely, A ring in that cylinder is not sealing (oil control or a compression ring). Give us a bit more info on your build so we can look at it from a different perspective.

This is a gm crate engine bought from a gm dealership,If you mean M as in Mexico yes it is.I have my suspicions it sat for a long time before we bought it as he gave us 500.00 off.I used quaker state 10w30 and gm oil supplement as per instructions with engine.When i got it i used an priming tool on a drill ,pulled valve covers and and and pumped oil till it came out all rockers and turned engine over with a wrench,as i was priming it.It took us awhile to gather parts before installation,so immediatly before starting we primed it again.When we started it in the vehicle we kept it at 1500 to 2000 rpm for the first 20 mins.We then drove it with varying throttle not exceeding 4000 rpm.

I'm sorry about the mix-up. "M" motor was a VIN designation for a crate motors rated at 290 HP and very popular for GM usage. When I said paraphenolic oils it was referring to parafin based oils such as Quaker State, Pennsoil and some of the Castrol Entry level oils. I also had a thought about Teflon additives which should never be used during break-in running. It will give you the same fits as you are experiencing right now.

well maybe ill change oil again and hope for the best what oil do you recommend

I'll tell you to run Valvoline.....Let the firestorm begin...... I trust it from years of use.....I would love to hear from the other guys here who have vast experience on their choices of oil. How long did the motor sit before usage?

You're not going to find a non-synthetic oil that isn't parafinic, napthenics can't pass todays API test procedures. I don't think anyone (motor oil producers) has not used parafinics in at least 30 years.

That spark plug is perfectly normal. Newer heads have moved the plug closer to the exhaust valve. Radiant heat from the exhaust valve cooks the carbon off and leaves the insulator white. The black spot is just shadowed from the radiant heat.

yeah, it is oily.... bad choice on oil for a break in.... i ussually use castrol HD 30
when i do break ins, the more the spread on viscocitys, the more additives in the oil to hold it together.... i'm not even a big fan of castrol but their HD30 is much cheaper than the shell rotella

^^^^^^^^^^^^^^^^^

Originally Posted by DennyW

Sorry Bob, I still go by this matto:

3 more words on break- in:
NO SYNTHETIC OIL !!

Sorry Denny,
If you reread my post you'll note there is no advocacy for synthetic at break in. Merely the comment that virtually all non-synthetics are parafinic. Also note that I don't advocate for a brand of oil either, years ago I learned enough to know that's generally a waste of time.

Man, Denny, now I'm gonna have a brain overload headache for the rest of the day................keep up the research....when my head get's back to a size I can deal with, I wil reload your links and reread......We luv ya man.

Is he running power brakes ? depending on where he is pulling vacuum from he might be pulling oil from a faulty master / power assist unit and fouling the plugs nearest the vacuum port. The vacuum line to the transmission would also be suspect in my mind. Easy to troubleshoot, just disconnect and see if smoke stops. or if there is obvious signs of fluid in the vacuum lines.