Classic/Vintage engine.

[4v6]

Good evening Guy, I hope you're well.

I have been asked and partly volunteered to do a restoration on a rather old Audi or is it Auto Union? engine for an aquaintance and I thought I would share some of what I've found so far.

The vehicle is an Audi 60 Variant I believe, of 1968 vintage and the last of only two in Britain I'm told.

It's a four cylinder pushrod design of 1697 cc capacity with a bore of 80.0mm and a stroke of 84.4mm.
The compression ratio is quoted at 11.0:1 or 11.2:1 depending on the exact model.
Inlet valves are 38mm with exhausts at 33mm.
The cam timing is quoted as being:
Inlet opens- 6 deg btdc.
Inlet closes- 38 deg abdc.
Exhaust opens- 41 deg bbdc.
Exhaust closes- 5 deg atdc.

During the stripdown I've noticed amongst the worn items, some interesting aspects that I haven't seen before.
It has two type's of material for the guide's, one appears to be a copper based alloy of some kind for the inlet's, and the usual phosphor bronze for exhaust's.
More interesting than that is the design of the inlet port, it's quite unlike any I've seen.
It has a very flat entry into the head with no discernible angle of drop to it, it looks to be 90 degree's to the combustion chamber face.
The port is offset as it approache's the guide and diverts into a kind of ramp type affair or reverse helter skelter that according to the repair manual; "Automatically imparts a swirling movement to the mixture as it enter's the cylinder."
It does not look to be a nice design and as the engine produce's only 75bhp at it's best I would presume it to not be very effective.
I have yet to flowtest this head as that was never part of the restoration, although I am rather intrigued to see what the inlet port flow's and how the air actually move's through it compared to more modern design's.
Please see the attached photo's.

One item of concern I found was the camshaft.
It has suffered severe wear to its lobes due to water ingress and then having been run.
There's a rather deep lip been eroded into it by its follower which is terminally damaged.
The cam follower's are all damaged due to the same water ingress.

My question is: Could you recommend a course of action to refurbish the camshaft and replace the followers?
Although the owner is currently attempting to find stock of these very hard to find parts in Germany, I really need a fall back plan should he be unsuccessful.
I realise welding and regrinding could offer possible salvation, but I have no clue who or where could best carry out this kind of work, and your recommendations and advice are always ones to be listened to.
Many thank's for any help you may be able to offer.

I hope this is a post of interest to yourself and other's, I will post up the photo's of the finished engine and vehicle as it is completed.

Best wishes, Tony.

Complete engine. 40 years old.

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Valve guides showing differing materials.

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Inlet port showing offset and "ramp" on left.

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Inlet port viewed from chamberside showing "swirl" ramp.

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Destroyed cam follower. Corroded surface.

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Cam lobe wear/erosion.

day1 camlobedamaged (653 x 490).jpg (59.96 KiB) Viewed 7072 times

[Guy Croft]

I'm sorry I have not replied to this well-documented and interesting post - I shall try and get on it this week,

sincerely,

GC

[cos]

my advise would be to make steel cam copies by sending them to someone like Pipers, and the same for the cam followers. If you go down the steel cam route make sure you get the followers DLC coated.

[4v6]

Thank you for your brief response Guy, i look forward to your observations.

Cos, I have been in contact with a couple of the bigger known cam specialists', however I've been unlucky with one and had a partial response from the other.

The cam follower's can be custom made by a different company located in Coventry, however, they are going to be erm, expensive!

Piston's, bearing's and a gasket set have now been located so I am at least part way to the end result.

[Guy Croft]

The last time I encountered this kind of cam/follower wear in a pushrod unit was in the early 90s, a Lancia Flavia Sport, still owned by the notable leathergoods manufacturer Bill Amberg (as it happens).

I got the followers ground down to clean (I imagine there will be enough material to do this) - any firm with a magnetic base grinder can do this - and had them re-carburised and then Kent reprofiled the cam to get rid of the wear and I used top hat shims on the valve tips to take up the reduced follower and cam height so as not to mess up the rocker ratio.

I might be tempted to try the same route, ask Kent if they will take a look at the cam. If do-able great, if not proceed with Cos idea.

As far as heat treatment on the followers in this pushrod installation and if reusing the (reprofiled) cast cam, I would have a word with Nitrotec Services in Birmingham and ask them if it would be feasible. The process they use is much lower temp than nitrocarburising and thus will not tend to distort the followers as much (they can go oval).

That is the low cost way of doing it. As far as new followers are concerned it's just possible that Arrows may have some that are of same diameter that can be altered to suit. Agin, top hats can be used on the valve tips. Worth asking anyway.

And you are right about the swirl/flow head, it's flow characteristic will be very poor. Port induced swirl of course is now well-recognised as a 'robber' of performance in SI engines.

GC

[4v6]

Guy, many many thanks for that information, its alleviated a few headaches for me.

The followers; I have been in contact with Arrow but they're rather expensive so I think before I commit any further funds I'll do as you suggest and contact the firm you mentioned in Birmingham.
The valve tip shim arrangement is a new one on me to be honest as Ive not had a huge experience of pushrod engines, very good information once again.

I did contact Kent but they seemed less than enthusiastic regarding the camshaft, I am still waiting on a response from the other company.

I shall do a few flow tests on this intake port shortly and post the result here if you wish, just for interest, however i don't expect huge flow figures!
I just wish i could take a die grinder to it but the need to keep it original prevents me.
What a terrible itch.

Best wishes,and thanks for your time once again, Tony.

[4v6]

I wish to apologize profusely for not updating this particular thread earlier, it had slipped my mind completely.
The engine was finished in late 2008 and fitted to the vehicle shortly afterwards.

The engine I rebuilt in its entirety, including most all the ancillaries.
The water pump for example was simply not an available item any longer and had long been so but I still managed to track down a suitable bearing and seal assembly and overhauled it that way.
Most all the alloy parts i powder coated at home, the rocker cover, water pump and housings, inlet manifold and sump pan were all done in a welding rod oven i converted for the purpose.
A full set of Hepolite pistons ( packed in 1974!) were sourced as new old stock items as were gasket sets and bearings.
The only items I could not get from anywhere were the con rod bolts.
As these were torque to yield items I had to have them made as one offs and very expensive they were, however they fitted perfectly and gave me peace of mind.
Eventually it came to a point where the engine was finished and ready to run so I constructed a steel cradle assembly to hold this awkward shaped engine at the correct angle and ran it on the garage floor with an ad-hoc cooling and silencing system comprised of a 25 litre plastic drum full of water and connections made to feed the engine.
I dont think i would have won many popularity contests early on a Saturday morning for my efforts though.
I ran the engine up for a good 25 minutes at 2500rpm as the cam and lifters had all been reworked.
I have to say, it ran absolutely perfectly and smoothly and i checked the oil pressure constantly as i had also stripped and refurbished the oil pump.
The engine was then packaged up and collected before being refitted into its now refurbished bodyshell.

The car had a few local outings for testing and was eventually entered into the "Dub Freeze" event at Bingley Hall in Stafford last February (2009) where it took the award for best pre 2001 watercooled car.

I am thoroughly pleased to have been associated with the build and it was a pleasure to work on such a rare and unusual engine, helping to save it almost certainly from the scrapyard.

As ever, many thanks for Guys input and suggestions, most appreciated.

Finally here are just a few of the hundreds of photos I took whilst completing this engine build.

[Cousin Cleotis]

Fantastic work, I've been looking forward to an update on this project.

Who made the con rod bolts?

Thanks, Paul

[Guy Croft]

MODEL POST!


Outstanding work, superbly photographed and documented.

Brilliant, absolutely brilliant..

GC

[4v6]

Thank you Guy, i really appreciate your comments.

Paul, the rod bolts were made by TK Precision who only had one of the old bolts and my crude (in windows paint) drawing such as it was to go on.
They really are things of beauty in their packet and an almost exact copy of the sadly defunct OEM items.