Discussion in 'Engine & Transmission' started by rstucke, May 10, 2021.
there are a number of types of guides
here's a few
cast iron (not used in vw air cooled)
Silicone brass Aluminium manganese (STD)
Phosphor bronze (marine bronze)
High leaded tin bronzes contain the most widely used bearing bronze alloy C932 (also known as SAE 660). Widely available and somewhat less expensive than other bearings alloys - it is known for its unsurpassed wear performance against steel journals.
Valve materials are very varied, but essentially there are three groups. The first is the old-style standard road spec, second up-rated standard road spec, and lastly race spec. The material types for both road spec valves are both complicated and irrelevant. All you need to know is that the early types had plain finished stems and seats because leaded fuel was very kind to them, the up-rated (or modern) ones have chrome-plated stems with triple-material heads giving a super-hard seat area - both to improve longevity, especially in later years where unleaded fuel is used.
Unleaded fuel is the problem largely because of the 'high-drying' solvents used in it. These are extremely abrasive, cleaning away any traces of normal lubrication - such as engine oil. Material mis-match between valves and guides will cause galling leading to seizure of the valve in the guide, exaggerated by unleaded fuel. So which valves do you use with which guides?
With bronze guides
you can use any type of valve material you like. The earlier standard road spec valves that have no surface-treatment on the stems will wear out quite quickly though - especially on the more modern manganese/silicone-brass alloys as they are very hard.
Which bronze? Your choice, anyone can get a decent engineering shop to manufacture valve guides from any material. The high lead content bronze material might be what Davids' engine builder did, who knows but there is a case.
As for valve seats
high chromium or cobalt cast alloy
Stellite, chromium, cobalt, tungsten and nickel alloy blah blah blah
Name your poison, this is why some engine builders advertise ulp hardened heads. They have chosen the combination of materials they believe are better than the 70's ulp standard (more diverse materials available now)
I'd have jumped on this earlier
but I left my computer at the w/shop last night and went on a bike ride today
Some of you guys are living in the past.
But basically a type 4 head will run unleaded satisfactorily without modification ?.
yes, but longer lived by more exotic materials (maybe)
I think ( as Barry pointed out) that the yanks ran unleaded ( assume in quantity) from early 70s and the yanks were biggest market for vw (?) hence motors would have been dictated by such.
While we are off topic ,
Might do another thread picking your brains on a modified ( slightly) type 1 ( specifically a type 3) motor build list.
My daughter's has a knock, and hopefuly lasts till I clear the yard of other jobs , but I intend to rebuild it myself.
Again living in the past
Pm with the knock and info any time
maybe, but I drive an old car
I agree that there are different and some newer materials for valve guides to what VW used, and some of these are/maybe better, but the following comments remain true
No one that is running unleaded fuel in their kombi and using stock VW heads or unmodified valve guides in their replacement heads is going to have valve guide failure due to running the unleaded fuel
There was no need, as in @David H case, to pull down a healthy motor to replace the valve guides. His mechanic was certainly “up selling” for his own gain. Different story if the motor need to be rebuilt anyway.
The point of this tangent was all from the original statement by @David H that the engine failure in the picture of this post was due to running unleaded fuel with stock heads.
That is not true and no one should be running out and handing over wads of cash getting their valve guides upgraded.
Anyway...............never let facts get in the way of a good story...........
Hey Rick....has ceramic ever been considered for valve guides ?
You are absolutely right
GeneBerg.com Parts Catalog: VW Air Cooled Heads for Unleaded Fuel - FYI
I'm just relaying what's out there
and what some engine builders believe is better and what some part suppliers sell (mostly crap)
For example take AMC Heads. Do they use the same spec materials that VW used in their type 4 Heads. No
They have stainless steel valves instead of hard chrome and tri-metal exhaust valves (a no no according to Gene Berg). They use unspecified brass/bronze guides.
so some engine rebuilders recomend the heads be modified before installing in the engine.
Problem when the guides wear out is VW never specified the metallurgy of the guides (that I'm aware of), so unless you buy nos parts your back to the best choice from a long list of materials that are compatible with ulp.
The layman is just told the heads are built for ulp
Excellent info Rick.
I was just curious as to how much extra @David H paid, what he specified to be done, and what was actually done, to upgrade an engine already able to happily cope with unleaded, to the “unleaded upgrade”?
Do you really want to do this, do you not understand What I'm trying to say, let it go
anyway moving on
Pulled the heads apart
here's the culprate
Funny, problem only on one side yet evidence of similar on the other but previous (covered black, not shiny), guides don't look like they've been replaced.
When the bottom end is apart I'll decide 1800 (same crank) or 2ltr (crank I have spare) either way new bearings and if necessary line bore.
If its trash down there there'll be some parts for sale and this thread will end
Think I'll risk suggesting that doesn't come under the classification of " work hardening" ??
Was not a 'healthy motor' @Barry. Just part of the normal maintenance process as it had low compression & needed a rebuild. Just one of the many engine overhauls a million km's in a 76 Sopru would get. All done by the one mechanic@Barry.
& thanks @rstucke for the explanations.
Motor is apart
Bottom end and cases good but will be machined.
heater boxes repairable, tinware, fan and housing good, spare pair of carbies
I measured the cylinders and turns out it's a 1700
I fooled myself because the cases are factory replacements, they come with an engine number comprised of a vw symbol and a C, the rest is blank.
Aparently you transfer the engine number to the new cases and destroy the old ones. The numbers were never punched in.
I'm wasn't sure the RMS would wear the above but checking with a friend who was part of the rebirthing task force, he didn't think it was a problem as long as I used the original number. Will get an official answer when the time comes
I guess the rebuilder was relying on the number on the fan housing (which I never took any notice of)
When I saw the shorter stroke I assumed 1800 (1700 & 1800 are the same)not realising the jugs were a couple of mm smaller.
This will be a spare bottom end with a 2ltr crank and cam (not sure weather to use a STD or a C25 torque cam) . I'll sell it down the track.
The rest of the stuff will be used on another 2 motors I'm re-conditioning, One to sell and one for me.
I'm starting another thread and all 3 will take shape in that.
Found similar when blue slipping my son’s lowlight.
Engine case did not have a number…..it was a factory replacement and not stamped.
Fella was reasonable and said as long as the number matches the (expired) rego papers , he’d leave it at that.
He could’ve insisted on a die test to ensure that a number hadn’t been machined off the case and the engine rebirthed.
It was pretty obvious that it wasn’t …..but he could’ve been a dick.
A good set of number stamps can be handy…..
I've got those
They came with an OHP trolley ?
no I actually bought them, with most things in my w/shop
Separate names with a comma.