Overhead-camming a Type 1 engine

[Jadewombat]

OK, it's not a new idea and has been done several times since the mid-70s, most notably 911 components have been used. There have been maybe 2-3 dozen total OHC VW air-cooled flat-fours over the years (with T1 or T4 case) and maybe handful of these engines are still in use today.

So why bother? Why not just "Subaru" it. Stronger case, components, etc. Also heavier and a bit more complicated.

With the engine swap, radiator, harness, overflow tank, piping, etc. there's no way a Subaru powerplant would ever weigh what a T1 fully dressed would (~250-300lb for a 1600--40hp, 1200s were only 196lb).

So enough about that.

The 911 parts still aren't getting any cheaper after all these years and the rocker arm design Porsche is basically unchanged since the early-60s. The 911 crossflow head design and hemi-chamber do work and definitely have added some serious hp to those engines that have been converted, but still having the cam sit directly over the valves and cam followers (like the Rabbit, Golf, Jetta design etc.) should be better to gain and maintain higher revs.

viewtopic.php?f=1&t=59308
viewtopic.php?f=15&t=97336
http://www.thesamba.com/vw/forum/viewtopic.php?t=437199

So here's the idea, use a T1 cam out at each T1 head above and inline with the valvetrain. As you can see here (again, thanks Pile!) the cam lobes line up with each valve. Use a piece of flat, rectangular aluminum stock which could be CNC'd and machined to hold hydraulic lifters and cam bearings. This old dual-port head and cam were generously donated by Kar Parts here in Houston. http://karparts.net/ I got some measurements on a T4 hydraulic lifter also. There's a cup and port on the bottom of the lifter where the pushrod would sit and something would have to be used so the end of the valve would touch this cup.

I have a few questions (of many I'm sure):

-There's no valve gap on a later T4 2.0 engine. IIRC it's 1/2 turn more than "0" gap at the rocker arm. In simple terms, how does the hydraulic vs. mechanical lifter work then and why is the valve gap needed for mechanical lifters?
-More importantly, is this a good choice of using a T4 hydraulic lifter vs. a Golf ('85 and later) hydraulic cam follower?
-Anyone have a measurement on a Golf type cam follower?
-What grade aluminum stock would be good to use for this/machining, etc.?

If none of this is feasible, then there's no point in trying to go to the next two stages, oiling/sealing the head and belt drive. Thanks in advance.

[Piledriver]

This would be for a racing engine turning ~8-11K, under that the VW valvetrain is well developed and perfectly capable with the right components.

This might be cost effective if the engine lives mostly over 7K for extended periods.
(road racing) The more radical cam profile possible may provide some advantage.

A hydraulic lifter is designed to take up the slack without keeping the valve open, although it is extremely likely to at very high RPM*, which is where a OHC ACVW is planned to live.
(*AKA lifter pump up)

A mechanical lifter NEEDS a small, well controlled amount of clearance or it will burn valves or beat things to death.

I still suggest the 2.3 Ford style rocker arm OHC setup (or similar) as superior for this by nature high RPM app, as well as for engine width...
Later version had roller rockers, with the roller on the cam.

The cup-over-cam Golf style setup WOULD probably be easier.
Most of the very high RPM setups I have seen use rockers.

The ultimate goal here is not to use it with stock heads, but racing heads like 910s or CEs.
The stock head would be for proof of concept.

One other advantage for racers is you could potentially swap cams in a few minutes.

[wreck]

Instead of the lifters , what about buckets and shims like a lot of OHC engines( Like Pile suggested ) .run the lobe straight on the valve. not as complicated and less weight .tappet adjustments are a pain on a T1 head the exhaust port is going to cause issues .I can't see the point to do this kind of work on a VW head . I think the main reason people have gone OHC is to use a better designed head .

[Jadewombat]

OK, thanks. I think I understand better now the hydraulic lifter. One thing that didn't dawn on me before is with no rocker arm at all there won't be any ratio to select (aftermarket) and push the valves further in. The stock valve spring is a hair over 30mm diameter, meaning if the head is to be serviceable through the cam follower bore it would need to be 31mm or so and the T4 lifter at 24mm would be too small. The width of the lobes on the cam are 15mm each and the stock tappets are wider than that IIRC--so they rotate in the case I'm guessing and diameter of the cam follower is not too crucial as long as it is centered, correct??

I agree guys, this is not putting a man on the moon or anything and this is not ideal as far as performance. But yes, the goal is to start small and simple of apples to apples comparison of a stock pushrod 1600 motor vs. OHC and I think there's a lot to be learned in the process. Rocker arms would be a lot better as far as space considerations and performance options. However...cam-on-cam follower-on-valve worked so well for VW in the FWD cars, Audi also, a lot other manufacturers, and Porsche somewhere along the way.

A T4 head would be better as far as head design with the crossflow, exhaust etc. What would be ideal is a 4 cams, 20 valves, variable valve timing and direct-injection but that ain't gonna happen any time soon and I think there are some benefits to opening up the power band from 4000-5000rpm range to at least 6000-7000 (or infinity and beyond??)

Thanks for the input, it's invaluable to me. I'll either pursue this with a machinist or put my mind to rest once and for all. (Probably not though)

[Piledriver]

Throwing out another very badly broken variant on the idea...
It wouldn't be a 20 valve but a modular Ford 6.2L heads are 115mm bore spacing. (SOHC Big block For a Truck. Really)
112mm T1, 124mm for T4 IIRC.

115mm is probably in the workable range for either, I suspect starting with uncut cases you could offset the bores a bit to match if needed. Steel side plated cases with through bolts would be ~mandatory to match the stud pattern and probably to keep it all together.

You'd probably need to start with a pair of these due to the head stud pattern and cam drive, sadly looks like there is a left and a right head, although they may be based on the same casting and machined different at one end.
I wonder if they'd bolt on a 427 or 429... EASY 700 HP under 7K RPM. NA.
I think a set of 62mm ITBs would look nice on this.

4" (4.020 stock) or better bore would be required, as it has canted valves, dual plugs, and the intake valve is 2.1"...
... and somehow the chambers scream "Super Cobra Jet" at me.

I'll guesstimate 400HP would be easily possible, with some port work given enough motor between them...
Normally aspirated.
How much boost could they take? Probably more than any VW block could deal with, but Autocraft...

I'd bet money the ports can be made to flow well north of 350 CFM if desired.

The logo is the name of the website:This is the 6.2L top view
The assembled heads don't look all that tall, but this is a big mother...


Almost makes me want to buy a truck.

[Jadewombat]

I see what you mean now. Those Ford heads are purty...how would you deal with the water passages that would normally mate up to the block? Weld them closed at the bottom then tap two ports at the sides for water (or oil) cooling?

I think this is the size of the Golf/Jetta lifter:

>>Specification:

Size: outer Diameter:35mm
Height:26mm
Product certification:ISO/TS 16949:2009
GB/T 19001-2000 idt ISO9001:2000
Warranty: 12 Months
<<

and I like the idea of a lifter already designed to sit on top of the valve and not have to use a shim with the T4 lifter...however, the distance between the valve springs is only 11mm. Meaning if the cups are 35mm OD, then that would leave a little less than 6mm of meat between the lifter bores. Should be enough though since they'll be lubricated by oil, right?

[Jadewombat]

Now that I think of it, those Ford heads would be ideal for use on an Oxyboxer (T5) since they already have the water jackets. It's a shame VW never (commercially) made a OHC flat-4. It seems to me VW got fairly close to trying something higher tech. with the Vanagons, but never really pulled the trigger on it and just raided the parts bin of T1 parts??

[Stripped66]

...and just raided the parts bin of T1 parts??

I'm doubting that VW's stock-pile of T1 rod bearings and rocker assemblies were the motivating factor behind the wasserboxer...

[Jadewombat]

...and just raided the parts bin of T1 parts??

I'm doubting that VW's stock-pile of T1 rod bearings and rocker assemblies were the motivating factor behind the wasserboxer...

I didn't mean it as a motivating factor. Plenty of VW parts wound up in other cars (914, 924, 944, etc.). My point was VW had the technology and funds and option to make an OHC engine (especially in the mid-80s) but the only major thing they did was make it watercooled. In fact, I'm about 99% sure VW did make an OHC engine somewhere along the way, but it's in a VW museum somewhere and or something we'll never see. But it doesn't matter anyway.

I went to two machine shops here in Houston today. The second was a race shop referred by the first one. There wasn't even a sign at this place so I figure they don't advertise. I spoke with one of the guys and he was halfway interested in the project, but I got to thinking after I left this is probably not the way to go. Not in the sense that they wouldn't do good work (they had some insane, sick V8 stuff everywhere) more that with all the work involved I'd be making at least half a dozen trips over there if not more and I don't want to waste their time with a pet project like this.

I'm going to shoot for getting my own setup. The price, size, and usage of small CNC machines has come down considerably the last few years. 10 years ago a CNC machine was nearly untouchable as far as price and size. Now a small setup is $3000-4000. I have a few other things on the horizon I need to have done on a lathe also.

http://www.bonanza.com/listings/Sherlin ... fgod1REHpw

[Piledriver]

We have a few of those little Sherlines at work, great for certain things...
Great if you are building RC sized model aircraft/RC car parts or clocks/watches, or stuff at those scales.

They sadly aren't large enough to do much of anything at full scale, particularly for a car.

You need a lathe that can swing at least 7" and chuck 5" to be reasonably useful.
The small one HF sells allegedly has a 7" swing but the largest it can chuck is ~3" if that.

A 10-13" swing is a good size, but a real one will weigh ~more than your car.

A WOOD lathe would almost be more useful, just don't expect to be cutting any steel or iron.

The little mill setups can be somewhat more useful in that size range, but their accuracy is iffy and cutting speed is mediocre.Still best for RC car-scale projects.

You can pick them up used for a fraction of that from folks who bought them thinking they were generally useful and discovered they were doorstops for most uses.

You can probably get a real Bridgeport in ~working condition for that or less, but expect to pay a rigger 1K to move it.
Don't have anyone who doesn't move heavy machinery all the time even touch it.
It's a specialty.

[Jadewombat]

Yeah, I've seen a lot of the behemoth machines about 10 or so years old selling for a few thousand on CL, but I don't have space for that. The aluminum plate would be about 10" wide by 4" tall by 3" thick. The Sherlines wouldn't quite handle that though? Thanks for the info.

[Piledriver]

Yeah, I've seen a lot of the behemoth machines about 10 or so years old selling for a few thousand on CL, but I don't have space for that. The aluminum plate would be about 10" wide by 4" tall by 3" thick. The Sherlines wouldn't quite handle that though? Thanks for the info.

Maybe.
I'm sure there's a website where Sherline users hang, it would be a very good idea to put the question to someone that has one before dropping serious $$$ on it.

[Bruce2]

. The aluminum plate would be about 10" wide by 4" tall by 3" thick. The Sherlines wouldn't quite handle that though? .

The Sherline could handle it if it was 1" wide by 0.4" tall by .3" thick.
Please don't waste your $ on a Sherline, they are only good for super tiny projects.
A previous employer had one, plus a full size lathe. The only time I used the Sherline was when the parts were so small, the real lathe had difficulty holding the workpiece.
The Sherlines are not very rigid, so they are CRAP for accuracy.

[Piledriver]

When it comes to lathes or mills, given a choice, you really want the 50 year old 2000 pound hunk of iron.
There is still absolutely no substitute for mass/rigidity when it comes to accuracy.

[Jadewombat]

OK, thanks guys. Will go mechanical and manual for a while.

I looked at a few of the videos users have posted of little projects. Some of it seems pretty neat, but yeah the pieces were pretty small. I have some round rod I need to make some spike center caps for my rims at some point, and a couple of other things. I'll keep watching CL, if there's a unit the size of a Coke machine that would work instead of a cargo van sized CNC unit.