Jump to content
DanOKC

More Cam questions

7 posts / 713 viewsLast Reply

Recommended Posts

OK, I have a regrind cam with unknown specs, is there anyway for me to measure duration & lift at home ? All I have is cheap digital calipers.

Could a machine shop do this ?

All I can remember & this was from 20 years ago, I was told it was a copy of BMW 300 degree sport cam or 1800 tisa cam, I can't remember what they said.

Are these 2 cams different ?

He said something about taking a little off the backside, and I think that had to do with making a better idle. They were somewhat vague about it, not sure why. It was a local shop that copied a cam they took to them.

It did have a slight lope at idle, pulled like stink over 4K rpm, still had decent low end.

I think it’s in the 290 to 300 range, not sure & have a metric mechanic cam I bought used on this forum a while back, and another cam that came with a project car. Would be nice to figure out differences in specs between them.

Also, the duration spec on american cams is measured differently than the BMW spec.

duration at .050 or something for V8 pushrod engines ? vs what for BMW ?

Share this post


Link to post
Share on other sites

Unless they welded the lobes all they did was grind the base circle to get more lift. You can measure a stock and modified stock lobe and see about .02" difference. You can't get the wider duration of say a shrick 292 without adding metal to a stock cam if thats what your getting at.

If you have a spare head you can make a test stand with it, a cheap 1" travel dial indicator and a degree wheel you print off the net and tape to an old cd. Make light valve springs from the springs that hold the rocker arms so it turns easily by hand. You only need to do one pair of valves unless you want to check the accuracy or inaccuracy of the cam and do all 4 cyls. Mount the indicator so you measure the stroke of the valve. Set clearance as you would run them. No need to set at wide clearances as you will probably write down angle and lift every .01" or so because its so freakin cool to measure a cam yourself.

Share this post


Link to post
Share on other sites

uhh, if they ground down the base circle, there's some room for longer

duration. Not a 328, but some.

I have a low- lift long- duration on a stock blank, and while lift is like

.350", duration is well over 300 at 1mm.

As to measuring it at home, if it's in a head or an engine, a cheapo indicator

securely fastened to the top of the head and a degree wheel can give

you some meaningful numbers. This method's most useful for comparing

several cams, but if you're meticulous, you can get pretty darned close.

t

Share this post


Link to post
Share on other sites

Or if you are in Oklahoma City, I'm guessing buy your user name, try Kams Inc located. in your town. Any self respecting cam grinder has a Cam Doctor and would plot your cam for a nominal fee

Share this post


Link to post
Share on other sites

Theres no magic to this. Its just measuring valve opening amount to angle of the crank. The way i'm suggesting is easy, accurate and gives info to make a graph you can compare to any other motor. Measuring the cam itself and disregarding rocker motion just gives info to compare to another cam for the same motor. The guys at Kams Inc kind of told me this back in the 80's when I took a 2002 cam in for them to look at.

Dan i'm in Norman and have a spare engine dissasembeled but not clean and measuring tools if you want some help.

Share this post


Link to post
Share on other sites

Thanks to all who replied. I forgot I do have a cheapo dial indicator from H freight.

I have a few M10's on the back porch, couple have the head pulled, so I may try to do the

measurement myself.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.