I might be getting my car back from Helmut this weekend. Five weeks after my 944S belt failure, (see $5500 Head Job in the archives).

Just before the belt failed I had Brain Fade at the pump in Garberville and filled up with Regular Unleaded. I had filled up with premium two times before?? There was about 1/4 tank left of premium.

I know there are knock sensors that retard the timing if knocking is detected. Since I am essentially breaking in an engine, new rod bearings, pistion rings, reground nitrided cams, 15 new valves, some new cam followers and alot of money. I will not be driving the car hard. So I should not be pushing the DME to retard the timing.

My question is should I be concerned about the low octane in the tank. I plan to stay within 60miles of Arcata and drive back and forth until I hit 500 plus miles to take it back in for the re-tension. Then I will drive back to the Bay Area on Sunday. As I said I won't be driving hard but I will encounter hills and such.

I was thinking that I would refill with premium at 3/4 of a tank to improve the ratio.

Thanks, I have learned much reading the posts when I can.

 

You should do just fine . During the break in just don't let the engine lug down . By that I mean , don't be in 3rd gear at 20 mph forcing the engine to labor hard. Keep an eye on the engine temp on a new rebuild and change the oil more frequently for the first 2000 miles. That temp guage and pulling the dip stick out and feeling the grit in the oil will tell you more then any book will. Best of luck on your new car and enjoy.

 

Question: why did you replace only 15 valves? I mean, even at $90.00 per valve, another valve wasn't going to break the bank?!?

I think you should be fine with regular unleaded. You have to drive the car well below the max rev's while breakig it in anyway, right?

Just my $0.42,
-Z.

 

If your really worried about the octane, you can add some tolulene (spelling?) to the tank, check out racer x's page for more details on the "rocket fuel"

 

No sweat, I doubt you will knock, even on reg. unleaded as long as the gas is good.

 

Toluene, or zylene, A gallon or two of either should do it, assuming 5 gal of 91 octane and 15 gal of 87 octane, 2 gallons of either additive will bring you to ~90 3/4 octane (I don't go below 93 ). 500 miles should be way too early for a belt retension, I keep hearing 1500 miles on Rennlist but when I looked into it I found sources that said 2000 miles or 2500 miles. doesn't matter to me, My belts have been retensioned at least a half dozen times in the last 6000 miles

 

Add premium when you're down 1/4 tank.

 

Just lifted up carpet in cargo area and found wires back there. One wire is seems to be screwed into the body and I don't know where the other wire goes. Looks like the same wire and that they might have been connected at one time. Any ideas?

 

This goes to the heart of my disaster. My PO was a 944 newbee and only drove the car about 1000 miles, his PO owned the car a long time. The eBay ad said the head was rebuilt, valve job etc...(read cam chain tensioner failure) and that the next owner would not have to worry about the cam tensioner, (actually the ad said belts) for 60k miles. I emailed during the auction, asked about receipts and was told the guy autocrossed, owned a bunch of Porsches did his own work and was a good wrench blah blah bs bs.
What I think happend was the cam chain failure, expensive head weld repair including valve job with new valves, worn used cams, and the Porsche guy in Sunnyvale decided to unload the car. He did not do a good job on the timing belt, countershaft belts because the water pump bearing was shot, distributor rotor was very old and the idlers were well worn. So he scrimped on the front end.
The answer is the valve that survived, (how did that happen??, worn camshaft maybe?) was new and did not need to be replaced. If you are buying a new 16V ship it home and have the belts properly done no matter what you are told. I was going to do that at one time but was too hot to trot with my new toy.

 

I think the reason for bely retensioning is due to expansion of the block and head and 1500-2000 miles is assumed to provide enough time/heat cycles for the belt to stretch. I would agree that 500 miles is way too soon and you would probably want to maintain new belt tension for the first 3000 km so it could get set. The tension for a new belt is higher than for an experienced one.

 

if you re-tension the belt at 500ml, by the time you get to 3000 it will be way too loose, Porsche recommends re-tension at 2500ml to give the belt time to stretch, if you do it then you should be good for the next 15000 ml.

 

ok then I will drive it home 280 miles, drive for 1000 more, then go back up for a total of 1560miles to have Helmut re tension. He is including this in the current charge and I want to preserve his warantee.

Since the original failure was the counter shaft belt failing and dis lodging the timing belt I am concerned about the counter shaft belt. Somewhere I got 500 miles for re tensioning that belt. Is that correct?

 

How about just a bottle of regular old Octane boost available from PepBoys or Canadian Tire?

 

I think the sequences are the same. The balance shaft belt is less critical except for your experience of course. That is balance shaft worst case.

 

Octane boost... someone beat me to it. Either way you'll be fine.