High lift cam

[AUTO]

Hi im going to start rebuilding my my engine for my karmann beetle its been in bits for some time and was originaly intended for my bus, its a 1641 with a scat c35 cam its one of the milder ones, so my question is will the cam work ok with the stick shift gear box, it is the later one with improved gear ratios and park
cheers phil 
 

[Bookwus]

Hiya Phil,

You should be fine.

Do understand though that the clutch is the weak link in the AutoStick drivetrain.  Luckily it is buffered by the torque converter so you should have room for increased horsepower.  The general consensus (and this is not cast in stone by any means) around here is that the stock AutoStick system ought to be good to handle up to (approx.) 90 hp.

What are you planning to use for carburetion?

[AUTO]

Hi bookwus thanks for the advice
Times are hard at the moment so im going to go pretty much standard and use what i already have, allthough it was originaly a 1600 single port i have some newish twin port heads already fitted with the uprated springs for the cam, and also a standard twinport manifold, as for the carb i do have a newish brosol H30/31 i dont know if you think it will work with this setup ? the only other carbs i have are old original  1500 ones
also convertables don't have as many cooling vents so i will be fitting a type4 oil cooler and i have already modified the doghouse fan to suit,  im thinking of makeing a cool air scoop under the car with pipeline up to the rear of the fan housing, but im not sure if this would be wise or not ?
any way thanks again cheers phil 

[Rick]

Hi Phil
I would check with SCAT to seee if the duration and lift will allow enough vacum  to be generated from your engine. The more aggressive the cam- the less vacum your engine generates. Obviousily with a standard shift this is no problem, however with the AS you need the vacum. I hope this helps you.

Rick

[AUTO]

Thanks rick i'll have to look in to the vacum problem
but im not sure any one will have any info on this subject
if its not some thing most vw tuners are concerned about
any way we will see
cheers phil

[68autobug]

I have seen autosticks with twin carburetors..
I don't think You will have any problems with the cam...
as the vacuum tank holds enough vacuum for about 10 changes...

so it should be full of vacuum all of the time...

I really don't like cams with heavier springs
I prefer ratio rockers...  less strain on the camshaft etc...

cheers

LEE

[AUTO]

 
Thanks for the info some very good points
but i have now found out it is a c25 cam which is closer to stock compaired to the c35 so i think it might have a chance of it operating the servo on the gear box the duration [degrees] of this cam is 272 im not sure what a stock one is but i think im going to risk it and fit it would ratio rockers effect vacum?
cheers phil

[greenghia]

Hello Phil,  Creating vacuum for the servo is no problem with a modified camshaft as vacuum is most effected at low rpms with a performance cam, just rev it up a couple of times and problem solved.  The most likely problem will be the vacuum signal to the control valve which as you know controls engagement of the clutch. The signal is very picky and will probably require a lot of experimentation to get it right, if you ever do.  I have read somewhere that people are using dual carbs and getting the signal from a vacuum balance line between the carbs (metered somehow).  I don't think they were running a non stock cam with their setup though.  Keep us updated as to how you finally get it worked out as the question comes up pretty often.   I hope you find a way to get it done!

[AUTO]

Hi thanks for the info
I can see why twin carbs would need conecting to produce the same amount of vacum as a standard manifold but im a little worrid that the control valve is very picky i hadn't realised that, i dont want to have to do this twice is there much scope to fine tune it to work and if so how ? 

[Bookwus]

Hiya Phil,

Hmmmmm........I'm not sure that control valve is all that picky.  I'm thinking that Lee or Sean might be able to give you some idea of the operating vacuum requirements for a control valve.  As Lee has already mentioned, the AutoStick system incorporates a reserve vacuum tank which is "charged" as the engine is in operation.  This reserve could work as a "surplus" in the event actual engine vacuum was low at the time of the shift.  Honestly though, I'm thinking this entire vacuum issue is not going to be a factor for you.  However, take that as an opinion from a guy who, although he has owned an AutoStick for the past ten years, has no hands-on with a moderatly "built" engine.

Oh, and another thing............I'm thinking that the picky reputation of the control valve may well be linked to shift action vacuum hose connections and not the operating vacuum hosing.  The shift action hosing (the small 3.5 mm from the control valve to the carburetor) needs to be hooked into THE correct vacuum port on the carb.  If it is not (and many are not!) the driver will experience very abrupt shifts.  Drivers going with a dual carb setup have to figure out not only where to hook up their operating vacuum hosing but also where (and how) to hook up the shift action vacuum hosing.

And while I was keying in that least sentence, another thought crossed my mind.  Other folks have used "performance enhanced" engines with an AutoStick set-up.  I believe Sean knows of somebody using an engine well over 2000 cc with an AutoStick.  If it will work for them, it should +certainly work for you. 

[AUTO]

Thanks mike
I think im going to take the plung and fit the cam ? but if any one has any other reasons
for or against  fitting this cam i would be happy to listen so i can make the right choice
but i need your views soon im going to be assembling the engine tomorrow
Thanks every one for all the advice so far
cheers phil   

[68autobug]

Hi
I would stick to the standard cam and add ratio rockers, which will still open the valves more than standard

Problem: control valve vacuum - I had this problem for nearly 3 years before I fixed it...
I am using a Non standard carburetor and the port in this carburetor had way too much vacuum
[the port was designed for vacuum advance distributors]
I took the port out of the original carburetor which was blocked with old gas.... Yuck..

I placed this port pipe.. about 20mm long with large hole in one end and very small hole in the other end
so it joined two pieces of vacuum hose together..

Now this did work -but the clutch servo really clunked into action every time i touched the gear stick..

On the other hand - if this small vacuum hose is disconnected from the carburetor -
it will take up to 8 seconds [or more] for the clutch servo to engage...
[Not good once You have pulled onto a busy highway...lol]

but, with too much vacuum, the system still works..
with the clutch activating VERY very fast...

the main problem with this, was the noise it made when selecting Low or reverse in parking areas
outside the supermarket....  lol

Now with the pipe in place where its supposed to be

My Autostick is driving like a new one....

cheers

LEE

http://community.webshots.com/user/vw68autobug

[AUTO]

Thanks Lee
I didn't get chance to bolt up the engine today just the crank
so i have changed my mind again and took your advice i don't
want to have to rebuild it again, do you think the twinport heads
will be ok and what about that brosol carb ?

[68autobug]

I would say yes to both questions..
What distributor are you using?
You will need one with Vacuum advance , if you have a 009 distributor...

Twin carburetors would give You more power
and sometimes better economy too..

plus you can use them with a 009 distributor...

Cheers

LEE

[AUTO]

Hi Lee
I have an old vacuum advance taken from a semi auto beetle but im not sure if it works but i'll give it a try
im also going to try the brosol H30/31 as i just want to get it running with out spending a fortune as next on my list of things to do is the gear box overhaul i eventualy got a new clutch disc from evw i couldn't find one over here  so i might need to  picking your brains soon 
cheers phil