Rebuilt engine "tight"??

Fred999 · 11:57 PM

My 2.0 engine has 300 miles since rebuild. It has the early sand cast aluminium casing. Since rebuild I have trying to address the issue of operating temps. It has been getting up to 210F. My mechanic has checked many things (so I will not provide a list).
Anyway, in checking out the engine the other day he found that while the crankcase would turn easily by hand when the engine was cold, this was not the case when the engine was warm. If he tried to do this after the car had been running at 190+ the crankcase was very hard to turn by hand. (apparently nearly impossible)

Not being very knowledgable about this, I have no idea why it is getting harder to crank the car in such a manner.

Could anyone tell me whether this represents a problem or not? Is there something that could have been missed in the rebuild?
My engine rebuilder said that the case wasn't milled or anything and to the best of his memory it was all within specs. (note: it was rebuilt a long time ago).
Oh, and also, after my mechanic checked the case and corrected a few things, etc the engine has no oil leaks and only leaked a drop or two a week anyway.

Fred

asphaltgambler · 03-02-2005, 06:06 AM

I dunno here ..............the guy said it would 'turn easily by hand when cold'?? Then very difficult when warm? That just doesn't make good sense. At 300 miles the rings haven't completey seated as well as a host of other metal to metal surfaces. I don't think that 210 is something to worry about unless after 1200 miles still runs warm.

Eagledriver · 03-02-2005, 08:08 AM

Just a couple of guesses. Does the car have mechanical chain tensioners? Maybe they're set too tight and are binding up the chains when the engine gets hot and expands. Maybe your mechanic is mistaking the higher compression feel of a hot engine for being "stiff".

-Andy

Fred999 · 03-02-2005, 11:53 AM

Eagledriver - you are right, the car does have mechanical tensioners. Thats a very interesting suggestion. I don't think we had thought of that.

Rot 911 · 03-02-2005, 02:42 PM

I seem to recall John Walker saying this is what happens when the cases are warped, but perhaps this was just in reference to magnesium cases. You might want to do a search of previous threads by JW.

Bobboloo · Bobboloo's Garage

It probably has to do with the motor expanding and no slack in the chains to make up for it.

If you measure the motors width when cold it is less than when warm. Even more so when using aluminum cylinders.

A warped case will induce drag on the crank whether hot or cold.

Why mechanical tensioners?

Fred999 · 10:11 PM

the tensioners are solid or "mechanical" on the advice of the engine rebuilder at the time (and I really wasn't in the position to know other alternatives). It was a long time ago - 1991, with the engine sitting since then and never fired up until 3 months ago. To do the carrera ones it requires the covers be remachined, etc. I got a quote to do that now and it was a whopping $2,700 AUD or $2100USD (labor and parts). Anyway, it is not uncommon here to use the solid tensioners on early 911s due to this issue. Also, if you ever want to sell it, going with solid looks original (I guess). Here, at least, the logic I have been told, is that other than a re-check and adjust every 10,000 miles, the solid ones are ok.

NevenM · 03-03-2005, 12:17 AM

Fred

This is going to be difficult to diagnose as you would have to get the engine hot and then pull the tensioners to determine if it is crank or cam. I'd be tempted to put in a pair of non pressure fed tensioners (certainly I not continue to use mechanical ones, they'll trash your chains way before the non pressure fed ones will fail)

I have a pair of new ones you can borrow if it will help (you pay freight from NZ)

Neven

Fred999 · 03-03-2005, 12:36 AM

Neven, thanks for the offer, but I think we should do some trouble shooting first. I guess, if it makes sense, we could just loosen the existing chains, (as the tensioner is adjustable), and then retest. If the crank still tightened up when we got the engine warm, we would know it wasn't the tensioner.

john walker's workshop · 03-03-2005, 07:48 AM

the early cases usually don't have a problem with the mainline getting out of true. have the guy pull the plugs when the engine is hot and see if it turns over better then.

NevenM · 03-03-2005, 10:00 AM

Fred

No prob, 210F is pretty normal in traffic esp in summer, the other thing to check is if it gets stiff as the cylinders heat (before the crankcase is hot) then it could be a piston/ring probem

Where are you in Victoria?

Neven

cstreit · cstreit's Garage

Definitely pull the plugs before checking... As mentioned I suspection tensioners... Could be too tight either from the collapse collars or something else. Also are you using a non OEM piston like the old JE's? Could the piston be scuffing/expanding?

911mot · 911mot's Garage

Does the starter sound lazy or struggle to crank it when hot?
Maybe it just has real low compression when cold

Bobboloo · Bobboloo's Garage

Chris, He has the solid tensioners.

Here's a jpeg of the safety collar. The picture is with a 901 tensioner as opposed to the 930 tensioner which is the better way to go with the later style idler arms with bushings. Which by the way shouldn't be overlooked as the idler is just as important to the equation.

Fred999 · 03-04-2005, 03:56 AM

I will find out more tomorrow.
NevenM: it appears that there are two schools of thought with these early small engines in regard to temps. Some people say they should run btwn 180-200F while other say warmer. It would appear that the early temps experienced by these cars were probably not the best as Porsche both put an oil cooler duct in the alternater shroud and a front cooler with no displacement increase between '67-'69.

Cstreit: The pistons are Mahle - purchased from Porsche. Since the rings are not seated yet, it doesn't seem to have high compression that its fighting. A compression test the other day gave 125-135 all around. That probably has more to do with the S cams.

911MOT: it starts like any carbed car does when hot - nearly straight away if left for a short time but longer if it has had a little time to cool off. It turns over fine, and I think the delay in firing up has more to do with the Webers.

911pcars · 03-04-2005, 11:44 AM

Your last post has me thinking it's perhaps a starting system issue. If the engine is very difficult to rotate by hand, the starter will reflect this as well (difficult to crank), but you say it starts okay (longer cranking when warm). Are you sure your tech said he tried this with a wrench on the pulley?

Sherwood

Fred999 · 03-04-2005, 05:48 PM

I saw the car today and walked through things. Based on talking with my mechanic, the tightness isn't out of the ordinary and is more a function of being such a fresh engine. So, I probably overreacted. It is true, it doesn't catch or anything when turned with a wrench, just a little tight.

Actually we have the engine out of the car at the moment due to the temp concerns. We decided to change the original alternator shroud and change the fan pulley size. My mechanic located and installed a later T shroud (repainted red) that has the grey tunnel bit for the oil cooler. The original shroud ('67) had virtually no room (or minimal) for air to be pushed down over the cooler. The new fan, combined with the higher fan speed, should cool the engine more (our hope).

I would be curious to know if other people had also "upgraded" their shrouds from early cars to ones with the cooler duct and what results they got.

Fred999 · 03-04-2005, 06:10 PM

I saw the car today and walked through things. Based on talking with my mechanic, the tightness isn't out of the ordinary and is more a function of being such a fresh engine. So, I probably overreacted. It is true, it doesn't catch or anything when turned with a wrench, just a little tight.

Actually we have the engine out of the car at the moment due to the temp concerns. We decided to change the original alternator shroud and change the fan pulley size. My mechanic located and installed a later T shroud (repainted red) that has the grey tunnel bit for the oil cooler. The original shroud ('67) had virtually no room (or minimal) for air to be pushed down over the cooler. The new fan, combined with the higher fan speed, should cool the engine more (our hope).

I would be curious to know if other people had also "upgraded" their shrouds from early cars to ones with the cooler duct and what results they got.

Fishcop · Fishcop's Garage

The later shroud definitely makes a bit of difference to getting more air over the cooler. Adding an additional cooler will do you no harm either.

Cheers

NevenM · 03-04-2005, 10:33 PM

Fred

What were your termperature concerns (how high did it go)

Neven