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Join Date: Jun 2004
Location: North County San Diego
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Porsche Crest Smoking Engine

Hi Guys,

Looking for some advice and some ideas regarding my 2.4 engine.

It's official, she's smoking quite a bit during acceleration. Does this mean rings or valve or both? I pulled the plugs to get an idea of how many cyliders are burning oil and found that all were clean except the number five plug was pretty wet.

The engine is a 2.4 built from an aluminum case, weber carbs, solex cams and SSI. She runs quite well and revs high with a redline at 7200. I have been very happy with the performance and would like to just fix the problem as opposed to a complete rebuild - budget reasons at this point. I'm quite mechanical and plan on doing most of the work myself as far as pullng the engine and doning the rings.

What else do I need to know about this job, ie valves etc...?

Also, if I do come into a bit more cash to spend on her, is it a big deal to upgrade to 2.7 pistons and cylinders and what else would be involved with that conversion?

Any expert advice would be greatly appreicated. Thanks,
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Old 05-11-2005, 07:49 PM
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Open up your motor and look inside. May just need rings. Might need a valve job. Might need valve guides. 2.4 only about 34 years old. Hope the mains and rod bearings are ok. Intermediate shaft and bearings ok? Timing chains and tensioners? Cylinders and piston condition? Camshaft and rockers?
These are the issues we all deal with. Likely rings and maybe a valve job. But be ready to rebuild heads, replace cylinders and pistons, etc.
When you are done and the motor goes back in you want it to be great. Replace what needs replacing, fix what needs fixing, your budget will be fine and you'll be delighted in the end.
Enjoy the work ahead. After all, it's just another way to play with our toys.
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DOUG
'76 911S 2.7, webers, solex cams, JE pistons, '74 exhaust, 23 & 28 torsion bars, 930 calipers & rotors, Hoosiers on 8's & 9's.
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Old 05-11-2005, 09:16 PM
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Doug pretty much covered it all. It may be useful to do a compression and leak down test to see if you can isolate the exact cause of your smoking.
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Old 05-12-2005, 06:15 AM
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Thanks Guys,

The engine has about 50k on it and as far as being 34 years old, not quite sure if that's the case. The car is bit of a of a rebuild as this is not the original engine. I've had the car for approx 6 years and the only major bit of work I had done was chain rails as the block is a 67S aluminum and carrera tensioner aren't a bolt-on option.

Anyway, it will be fun to get into the job, but I just want my ride back so I can tear around the back roads of San Diego County again!
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Old 05-12-2005, 12:30 PM
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Andrew,

Your car has iron cylinder liners. They will most likely be worn and so you can't just re-ring it. You have a fantastic oportunity since you have a rare and strong engine case. Your engine would make a great candidate for a 2.7 or 2.8 rebuild. Your solex cams and carbs will work great on this engine. All you'll need is a set of 2.7 or 2.8 Mahle pistons and cylinders. You might be able to find a used set and re-ring them. These sets are nikasil and last a very long time. Your case will need to be machined for the bigger cylinders but other than that it should be a bolt on upgrade. This engine will have around 200-210 HP and much more torque at lower revs than the 2.4. Lucky you.

-Andy
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Old 05-12-2005, 04:47 PM
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Don't do anything until you do a compression check and leak down as Charles Navarro suggested above. Thats just basic 101 engine mechanics. Once done post results and reasonable suggestions can be made.

Note that even if you were planning to completely tear down the engine,it would still be usefull to have compression and leakdown info first.

Let me explain one reason why this info might be helpful.

Say the valves are good from a leakdown standpoint. Then you check dimensions on the valve stems and guides and they are well withing spec, result do nothing to the heads, saving big bucks as they will last for a couple hundred thousand miles of properly kept. Or maybe only ONE head has the problem, so just fix it, not all of them.

If the vaves are good and you only had 50K miles on it the entire bottom end should be good for another 150K miles, so don't take it apart, saving bokoo bucks. Maybe only one clyinder needs replacing and your good for at least 50k more miles. Maybe all the clyinders need replacing, but the bottom end should still be good for 150k more miles. ect......

Or maybe everythings shot and you got to plan accordingly.

Last edited by snowman; 05-12-2005 at 05:18 PM..
Old 05-12-2005, 05:00 PM
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Very good Jack, exellent advice. I will run the leak down soon and post the results.

Thanks Andy for the advice re: upgrading to 2.7 or 2.8. If the case needs to be machined to fit the larger barrels, can this be accomplished w/o opening it up?
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Old 05-12-2005, 07:04 PM
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Yeah, you'll have to open up the case a tad. I would recommend putting in the case savers first, then opening up the registers- there's less of a chance of doing any damage that way. Same trick we do with the vw mag cases.
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Old 05-13-2005, 09:34 AM
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Quote:
Originally posted by Eagledriver
Andrew,

Your car has iron cylinder liners. They will most likely be worn and so you can't just re-ring it...

-Andy
Hmm...I was just reading something the other day stating the opposite. I cannot comment either way. As far as iron goes, the wear properties should be excellent. Heat transfer....another story. If you do tear it open, and you do have worn cylinders you can always bore them to 85mm, and get custom JE pistons. (this might have been covered). But, the cheaper route is used P/Cs in good condition. I bought used 2.2T P/Cs for my 2.4T, and it's a nice engine for the street.
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Old 05-13-2005, 04:30 PM
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I say rings at least here. It takes a lot of volume of oil to 'wet' the sparkplug. Even severely worn valve guides will pass some oil; only bad or stuck oil rings/scuffed cylinders will pass enough to actually leave liquid on the business end of the combustion chamber. If only one cylinder is that bad, it will smoke considerably on accel.

At this point a compression test is a waste of time. The spark plug(s) tell the story. Plan on a top end rebuild / upgrade.
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Old 05-14-2005, 07:21 AM
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Thank you asphaltgambler. Good advice and kinda what I was thinking as well.
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Old 05-16-2005, 02:08 PM
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