993turbo

Actually the opposite is the case. The belt was overthightened, and over time made the cam snap. Fatigue. The damage to the belt and tensioner etc.. was a result of the initial cam failure.

And. No further damage to pistons or valves. All good.

993turbo

Im currently out travelling, but as soon as I return I will check 100% if an 84 E ROW S (S2) engine is interference or not.

I will put the intake valve on cyl 1 on full lift, place some light powder on the piston crown, then place the cyl head on the block. Then I will slowly turn the crank towards TDC. I will repeat the procedure for the exhaust valve.
I will then see if it touches or not. Washers will be used as spacers to simulate the tickness of a compressed head gasket.

Dennis Wilson

A loose belt can cause a jerking motion and a too tight belt can add additional strain on the cam. This coupled with the new low zinc oil, causing more resistance at the lifters, can and will break the cams at the weakest point, which is where the woodruff key is machined into the shaft. BTDT

Dennis

928FIXER

[QUOTE]I will put the intake valve on cyl 1 on full lift, place some light powder on the piston crown, then place the cyl head on the block. Then I will slowly turn the crank towards TDC. I will repeat the procedure for the exhaust valve.
I will then see if it touches or not. Washers will be used as spacers to simulate the tickness of a compressed head gasket. A true test of piston to valve clearance will need a solid style lifter installed as a hydrulic lifter can bleed down and not open the valves all the way.This is why 944's can break a belt on start up and not bend valves.

928FIXER

A true test of piston to valve clearance will need a solid lifter installed in the cam carrier.A hydrulic lifter can bleed down and not open the valves all the way.
This is why a 944 can break a belt on start up and not bend valves.

993turbo

Very valid point. This will be taken into account.

mark kibort

I think i posted the reality check here. the stock 85 euro pistons have a .175 valve relief. when we pressed down the valves on a euro head, thet touch the pistons at .3". so, if you have a .175 more valve depth relief with a euro 80-83 piston, then if you only have .475" cam lift, you will not have any contact, and that makes perfect sense. I measure a euro piston valve pocket, but I can tell by looking at it, it is very deep. certainly 2x .175" of the later pistons.
you dont need a solid lifter to test this. just take the test a few times and this will show you how much clearance you actually have!

mark kibort

by the way, that is worst case, if a cam breaks, there is littlle guarantee that any of the valves are at full depression. (probably very unlikely)

993turbo

Cheers. Great info. Do you have pics of the later vs. the earlier pistons?

Ohhh, BTW, have you heard of a fancy new way of making measurements? It's called the metric system.

karl ruiter

German car fans that live in former British colonies get pretty good at going back and forth. Hint: take inches* 25.4.

mark kibort

I do have a picture of the earlier pistos vs later. the ones on the "should I run the motor with the same rings on the pistons" thread, shows the euro pistons. Ill post the euro 85 pistons. shallow valve reliefs. same totally flat top piston, just thinner valve reliefs.

oh, i used inches, because most know what our cam lifts range from, so its easy to see if you will have interference or not. .5" is a racing cam. .3 to .4 is normal stock stuff.

mk

mark kibort

euro pistons have valve cuts of 9mm deep, exhaust, vs 11mm deep intake. vs the 4.5mm of the euro 85, and the 5 liter 2 valve conversions. so obviously, now you see that the early euro S engines are non interference. contact with euro S 85 is at .3" or 7.6mm valve depression and a 4.5mm valve pocket. so, even with make that valve pocket a euro depth, of 9mm min, you see that you would have clearance up to .6" valve depression. way more radical than any cam ever used on a 928 valve train.

So, all euros are non interference.

GlenL

'84-86 Euro piston...in 98mm!

993turbo

Cheers for the pict, howerver, there is a difference in the S ROW (euro) pistons from 84 to 86.

For the 84 model year, up to engine # 82E 00596 (manual) and 82E 06113 (auto) the pistons used had deeper valve pockets, similar to those of the 80 - 83 model year S ROW (euro)

Pistons in Engines from # 82E 06114 (auto) and 82E 00597 (manual) have smaller valve pockets...

993turbo

hehe, it was meant as a joke. I know very well how to convert.