High RPM Driving

[Benz Dr.]

A couple of thoughts about exceeding your previous rev limits:

Make sure you have full oil pressure at hot idle. High RPM's will take out rod bearings if everything isn't in good order and low oil pressure at idle is a good sign that everything is worn.

If you haven't taken your engine over 3,500 in 25 years I would be very careful doing that. Engines wear the way you drive them and upper cylinder wear follows that pattern. You could suddenly find  the upper piston ring squeezing up against the ring ridge at the top of the cylinder resulting in a cracked ring.
 I've seen where high speed and prolonged driving actually broke a couple of rings due to upper cylinder taper. The ring will break about 15 - 20 mm  from the gap and then start to flop around until it turns upward coming out in the combustion chamber. You would likely have to sleeve the cylinder/s to repair the damages.

All of these things tend to happen on higher mileage engines with little to no known service history. If you have a fresh rebuild then you should be OK. If your car was driven by an old lady or has been sitting unused for years I wouldn't take it up past 3,500 RPM while shifting or driving until I was sure it was in good running order.

[ghenne]

One piece of advice I heard when my 230SL was still fairly new: don't push in the clutch over 5000 rpm. There are only 3 main bearings, so the driveshaft can flex under these conditions. Get the rpms down before pushing in the clutch.

The 280 SL engine, with more bearings, does not have this problem.

[cydways]

i had the head off just last month doing the gasket and cylinders had excellent wear and minimal carbon build up. 99k km on the OD and i run premium fuel with a high zinc 20w50 Valvoline oil. from everything i can tell this engine is happy with those speeds on a daily bias for long periods of time. weather was about 80 degrees in the day with coolant temp staying the same as shown.

but yes, its loud! i am used to that though.

[Benz Dr.]

Actually, they have 5 main bearing and the 280 has seven but you're close enough.

[Baybear]

I'm with Michael on this one. Just got back from the Fairway Club event at Pinehurst, NC.  Screaming at me at 4000K  +- 500 rpm, but wife managed to talk with daughter for 1.5 hrs. with no problems.
Will

[114015]

One piece of advice I heard when my 230SL was still fairly new: don't push in the clutch over 5000 rpm. There are only 3 main bearings,

Actually, they have 5 main bearing and the 280 has seven but you're close enough

You both fine Gentlemen are so right !

3 bearings plus five bearings sums up to eight divided by you two Gentlemen results in four main bearings each, which is absolutely correct. 


Four bearings on my one 230 SL engine and four on the spare engine. Thus 8 in total.

Best,

Achim
(MBfourbearingsenginecollector)

[Benz Dr.]

Well, I was half right - sort of. 

[zak]

Based or your expert advises I did some hi rpm hi way driving today- about 40 miles at 4500+ rpms and my 250 SL drove like a dream- engine temp low and constant at 190 C.
I even hit 5000 rpms at toll booth take offs and no smoke whatsoever.
The engine was singing!
thanks.
jz