Some thoughts on cams

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Some thoughts on cams

Post by IMPI » Wed Mar 05, 2008 8:05 pm

Whilst I dont claim to be an expert on cam selection here are some thoughts on the damn things
Rule 1 Dont overcam with 1600 gearing 5500 rpm in fourth means 200kmh approx
A cam with more duration means that there is a time when the exhaust and intake is open at the same time with the exhaust open and flowing exhaust first this means that fresh petrol is also sucked out the exhaust .... Lousy mileage results
For racing cars this obviously doesnt matter much but...
It also seems that not all Billet cams are of such great quality and wears out quickly It takes fancy metalurgy and compatibility between lifter and cam to make it last. For the 1961 beetle vw went to a nice light 2 piece lifter and stuffed up so many engines that the 61 was known for years as a dud Opel did the same on the early kaddets
For mild aplications I favour the stock cam and lifters just reground to about 270 degrees
When people talk about hardening the cam I know here is a story coming. The black coating on cams is called Parkerizing.
This was a method invented during the second world war to stop US guns from rusting. it is essentialy dipping the metal in a boiling acid solution which etches the surface and this microscopic etching retains lubricant well. the way cams are hardened is by the rubbing action of the cam against the lifter. (think of you bending a piece of tin the more you bend it the harder it gets before breaking.
The next important part on cams is the angle the lobe makes with the length of the cam IE the highest point on the cam is not parralel to the length of the camshaft (Almost like a pinion) The lifter is ground at the same angle and resembles a mini crown wheel. The rough etched surface from the parkerizing acts like the gear teeth and this results in the lifter turning as the engine is running constantly lubricating the surfaces and promoting long life. stop the lifter from turning and the cam is eaten away within minutes. Obvously ths constant turning hardens each surface until both are strong enough.This proces continues until the surfaces are so hard that small flakes start falling off (after hundreds of thousands of miles) and a regrind is needed.

Now if you assemble that new engine with these super high pressure titanium gold platet 1000000 rpm valve springs you dont give that poor cam a chance to self harden and life is typically short.
Some of the best in the business actually start their high performance engines on soft valvesprings and gradually increase tension to just keep the vaves closing at the chosen Rpm.
Hope this clears a few issues
Armand


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Re: Some thoughts on cams

Post by SUZIE » Wed Mar 05, 2008 8:11 pm

i learned something new, thanks IMPI
have nothing on the cards now, but have a red beach buggy in sight that I want

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Re: Some thoughts on cams

Post by eben » Wed Mar 05, 2008 9:16 pm

STICKY!

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Re: Some thoughts on cams

Post by Dawie » Wed Mar 05, 2008 9:34 pm

Thanks Impi.Had a camshaft reground and followers resurfaced,followers came back black,but cam is shiny silver metal colour.Thought it would be black.Havent put it in yet (standard 2L type 4). It came out of the engine worn and shiny colour.
Should this cam last? (Know must break it in at 2500 rpm).Paid R700 for the job at Mastercams, Cape Town.
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Re: Some thoughts on cams

Post by Dawie » Wed Mar 05, 2008 10:14 pm

Once read a US magazine where they were testing various items on a standard 1600 type 1. It had 1.4:1 ratio rockers at that stage, standard cam.They then fitted heavy duty hi-rev valve springs and the engine lost 8 percent power on the engine dyno! 4hp is 3 kilowatt,lots of extra energy wasted in valve train as heat,same as a geyser element! That is why it is good to use lightweight valvetrain parts.
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Re: Some thoughts on cams

Post by flatfourfan » Thu Mar 06, 2008 9:14 am

Awesome post. This just seems to back up with what we were talking about this weekend.

270 here we come..........

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Re: Some thoughts on cams

Post by Blitzkrieg » Thu Mar 06, 2008 10:34 am

Thanks for the the information!If I wanted to tune a Golf GTI and asked a certain reputable tuner for the same info, I would be accused of picking his brains :roll:

At least here we get good advice with no strings attached :wink:

I think for my mild 2,0 application, a 270 degree reground OEM VW cam would be sufficient :D The price is also not bad. . .
If it's too low, you're too old :twisted:

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Re: Some thoughts on cams

Post by flatfourfan » Thu Mar 06, 2008 10:37 am

This is actually the reason that I decided to go with van der linde. When speaking to sean, he wanted to know what my set-up was and said that we'll talk when I drop the cam off.

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Re: Some thoughts on cams

Post by Bugger » Thu Mar 06, 2008 3:09 pm

That is why Different strokes for different folks

My 316 T4 cam was in a twincarb 2.2 and was a perfect match for my driving style at the time then sold the bug and the new owner did not enjoy the bug with the wild cam and changed it to a billet C35 and was very drivable

For my 2.3WBX that Im planning to build for my DC I want more torq and a open range and got a W120 which will have nice pulling power for towing the race car behind
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Re: Some thoughts on cams

Post by forcecooled » Thu Mar 06, 2008 6:42 pm

Try and stick with tried and tested # grinds, or copies thereof . as soon as you get into the custom cam issue the chances are that you will be disapointed with either to little or too much of whatever the cam was expected to do.
VDL make some fantastic cams, but how many street cams have they ground for flat 4's?
I am not saying that they do, but most tuning and development shops think that A/C vw's are sh1t, and a dont really have a good idea how they really work and breathe, and you might have to spend huge $ to buy other goodies to get the system to work properly.
I wonder if you can get a cam ground by a top development shop here for any less really than what a brand new billet cam, dual thrust bearings and a good set of new followers imported from from the US might cost you?
Import the stuff Gary, at least you will know what you are getting, and its new with good wearing surface treatment
Remember on a new OHC car changing the cam if its not what you expected it to be is not really a big job, but changing a cam on a flat 4 is a real ballache, especially if you dont have to strip/remove the motor for any other reason !
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Re: Some thoughts on cams

Post by IMPI » Thu Mar 06, 2008 7:50 pm

The reason why the cam is still shiny is because of the gear is made from either aluminium or magnesium and the acid used for parkerising eats the soft metal. Brand new cams and lifters from vw came shiny from the factory.
The easiest way to know that your type four isnt eating its lifters is to make a mark (white paint) on the edge of the lifter run your engine for a while and remove pushrod tubes rockers and pushrods check that all lifters have been rotating If you are unsure just remove each lifter and check if the wear is circular.
Whilst I would generally agree with the statement that VDL wouldnt care about aircooled cams I found them to have a bussineslike approach and they are not burdened with the collective american past Which says that this and that is such and basta. Even Jake Raby a well known us type four Guru publicly stated a few years ago that type fours cannot be turbo charged until a few South Africans and swedes started proving the opposite To his credit he now offers turbo cams.
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Re: Some thoughts on cams

Post by flatfourfan » Fri Mar 07, 2008 8:33 am

After speaking to VDL the first time that I called. Sean said that they have done a few 914 cams off a 2.0 and are familiar wth the 86 grind. As Armand said the reason I'm going with VDL is that they are always looking into new ways to skin a cat.

Buying a cam from the states for now is a no-no, almost R2000-00 compared to R350-00 to have mine cut. Armand and myself have spoken about this a lot over the last few months and I believe that this is the best option for now. I know guys with VDL cams who have over 100 000kms on their rids with cut VW cams, nothing wild, kind of like what I'm doing.

I would like the engine to be ran for a few thousand kms first and then strip down to check the internals anyway. I don't think that there is anything wrong with a 30 year old cam that's still 100% condition.

My whole head build is 100% custom anyway, so once the cam is done, doing the rest won't be a major issue.

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Re: Some thoughts on cams

Post by forcecooled » Fri Mar 07, 2008 10:18 am

VDL do excellent work-- - just wondered what grinds they have for T1 and what the specs are
I must give them a shout sometime
!00,000 kms in a T1 cammy engine is some good going - must have belonged to a granny that lived far from the shops!
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Re: Some thoughts on cams

Post by Bugger » Fri Mar 07, 2008 7:46 pm

VDL actually got more than plenty specs on cams than you might think
The cam that was done by Sean and i used it in my moms WBX that was done in 1993 and dome 250K defnitely shown wear
But thats good now just a reface and cool

With all the develepment work they have done with Group n and SATCARS and and and they can actually put any grind you want on a cam split inlet and Exhaust

Garry do you want to borrow my W120 when you go there cos that is basically also close to what you are going they can copy it if they do not have it for futher revf(and I just said they can do almost anything :D )

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Re: Some thoughts on cams

Post by forcecooled » Fri Mar 07, 2008 11:34 pm

Now, there's an offer. You are going to get a copy of a tried and tested formula in a W120 !

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