911 head bolts, lip on barrels

[theweaver]

Hi, I am new to this forum, and do not know if I should post my question here. Nevertheless,

Porshe 911SC 1980 3litre

I am in the process of rebuilding the top half of my engine, which has stood for 10 years, with 12 broken head bolts the engine has covered about 100k miles and my budget is now stretched after completing a full body restoration, and I was unaware that the engine was poorly!! It seemed to be running ok 8 years ago when I first bought the car!!

Therefore, the head bolts I have been supplied are the steel variety which I am told are satisfactory, but cannot find the reference in the forum

The standard Goetze piston rings are std, but I was expecting 'Ridge dodger ' rings to cope with the hardly noticeable lip at the top of the barrels.
According to Waynes book, some of the barrels can be honed, but I would like to know if it is satisfactory to hone the bores to remove the lip...probably a couple of thou, on my barrels

The no 2 ring within the kit is the ridge dodger type, having the rebate underneath, guess the question.

Wayne says to use Curil T for the O rings. What is this, as when using hydraulics, etc no sealant is, nor would be considered.


Your help would be most appreciative

[Flat6pac]

Welcome,
The Mahle P&Cs can be hones lightly KS cylinders are alucil and honing will ruin them and the general consensus is not to rering the KS Light honing is not to remove the top ring ledge.
O ring for the through bolts, grease well and keep the washers from spinning.
Bruce

[E Sully]

do I need to hone this?
Lots of opinions here.

[Wayne 962]

Originally Posted by theweaver

Wayne says to use Curil T for the O rings. What is this, as when using hydraulics, etc no sealant is, nor would be considered.

It's a good high-temp sealant that has worked well for me over the years. Actually, I've never really heard of any issues with it. I use it as an extra layer of protection when installing seals. There's really no downside...

-Wayne

[Walt Fricke]

Do you have a real ring ridge? Which would be the result of the cylinder bore wearing below its very top where no ring touches it?

Or do you just have carbon deposits down to the top of the top ring? I recently removed those from Nikasil cylinders with walnut shell blasting even though it seemed to be pretty hard.

I've never heard of ring dodger rings. It doesn't make sense to me to use anything other than the standard first ring in that position, and they don't have a recess. The recess has to be under the 2d ring for a reason as well, so inverting such a ring doesn't sound like it would work well for any purpose. Besides, the 1st ring is thinner, no? Anyway, I don't think you can find such a first ring for Porsche pistons.

And if your barrels are so worn that you need something like this to avoid the top ring from hitting a metal ridge, aren't the barrels too worn to reuse as is?

[theweaver]

Hi, Thanks for your comments.

That really is my question. Are ridge dodger rings available.?( google 'ridge dodger rings'

The lip in question is not a sharp ridge, but just a very small one, probably a couple of thou. New standard rings in the barrels produce the expected ring gap!! It is possible that standard rings may not cause any problems.
However, I wonder if the problem associated with using the old Alusil barrels, is just scaremongery encouraging owners to purchase over inflated priced parts.

If the engines are as robust as is said, then they should be capable of withstanding standard engineering practices. I feel that we are all being conned.
I suppose that you can expect these problems from chain saws that use the same technology, but they are not in the same price category.

Even the problems Boxters have with the engines is unacceptable.

No one has actually said what happens if you install new rings in the old barrels, as Waynes book mentions on several occasions that owners ,due to cost, re use their barrels, just it might smoke or may not last. This can be true of any engine rebuild. I would like to hear of examples of positive and negative results from anyone please. Also, I read on this site that someone was thinking about boring out the Alusil barrels. The material I understand is not just a coating, but goes the complete thickness. The coating is then applied afterwards. This coating can neither be that thick, nor can it last the life of the barrel, whatever that is.
My thoughts then, if that is the case, then this is poor design outright.

With modern engineering products for assembly, I think that there should be something like an oil or solution that can be applied to the barrels which would help with running in honed Alusil barrels.

As for myself, I do not intend racing my car around a track, nor thrashing it anywhere, just a weekend car to cover a few thousand miles each year, on a manageable budget. No I do not a flat cap!

Readers please do not respond with sarcastic quips, as I feel that keeping a 30 year old car on the road is a joy, and not something which should bankrupt an enthusiast. Plenty of enthusiasts are running these cars on a budget, otherwise there would be no necessity for these forums!
Alternatively, too many 911s are destined for the breakers.

Obviously, what I have spent on the car so far would have bought a very nice alternative sports car that is not broken!

The brigade who just do things without real questioning should, I think, be asking these questions.

With a car of this age and technology, I can understand the problems with age and water on the body, engine problems do not seem to have been a priority with Porsche, ie use this head bolt or that bolt because water might splash on it, causing it to break, etc.

Yes, I also understand that it is a Porsche I own, duh!!

[Walt Fricke]

Well, grousing won't help. You are neither the first nor the last Porsche 911 owner to grapple with the Ausil issue.

Have you measured your bores with a bore gauge? That ought to be the first step in deciding the state of wear of your cylinders. There is a tolerance spec for that. I'd be surprised if it is as high as two thousandths (your estimate of ridge depth). And it would tell you if the ridge was due to bore wear below it, or carbon on top of the wall. Bore gauges are not all that expensive, and of course any machine shop ought to be albe to do it for not too much $.

If you are worried about the ridge (which won't interfere with installation of the pistons), remove it. You don't have to hone the whole cylinder to do that. There are ring ridge removers for Detroit iron, and I'd suppose one of them would work as well here.

Me, I just bought a new set of Nikasils when it became rebuild time. Saved the cylinders and pistons. Don't know if any use will ever be made of the pistons, but the cylinders went to US Chrome, which machined and Nikasiled them for a race motor with J&E pistons.

If you can't find the answer by searching posts here about Alusil (lots of them), you could contact US Chrome to see if they can re-Alusil.

But under no circumstances would I fuss around with rings which had an inverted notch on their tops. That just does not sound like a good way to go with a 911, even if it is possible to find such rings (which I doubt).

[theweaver]

Hi, Thanks for your positive reply.

It is probable that the bore wear is less than a couple of thou, but that is a conservative esimate.
The lip is not carbon, but this ever so slight wear which I can easily get measured accurately, should it be necessary.
In reality, I am enquiring of anyone who has had real positive and succesful experience of honing and polishing the bores and re ringing these barrels., without having this coating applied.
I do not know of any engineering shop in this locality who could do this work of re coating the bores. Some I contacted were unable to replace me the valve guides.
I managed to do them myself.

As far as I know, the Alusil is the full depth of the barrel, and ought to be capable of this realatively simple procedure.

I think that these automotive shops would hone me the barrels.

Thanks

[Walt Fricke]

Well, do a search here for Alusil. You'll find explanations as to what it is and what can be done for it. Maybe it has to be acid etched or something after any honing. But you don't want to install pistons in bores which might be too large for them - that's not a very good way of rebuilding something. You might be better off just putting it all back together.

What were the leakdowns before disassembly, and where were things leaking?

I don't know where you live, but in the US anyway it is not hard to send something as small as a box of pistons out to have work done on them.

[bh912e]

For Alusil cylinders all you need to do is to wash them with soap and water. I use the scrotch brite side of a dishwashing sponge. Apply soap to sponge and lightely scrub the barrells.

As for the carbon buildup on top of the barrells just soak the top of each cylinder in clothes detergent over night, probably a 1/4 inch of detergent in a dish/ bowl. This will break up the carbon ring and allow you to wash it off using the dishwashing sponge.

After the final cleanup of the cylinders just apply some motor oil to the cylinders/ pistons/ rings and insert. Of course before this check all ring gaps, on both of my builds the oil rings were on the tight side. Also stagger ring gaps. Both of my alusil re ring jobs had no smoke or excessive oil consumption.

Have fun!

[theweaver]

Hi Thanks for your reply. That is exactly what I have done, following much reading on the subject. Hope everything will work ok