How to determine cam specs from an existing unmarked cam ???

[mtnmankev]

This may be the challenge of the decade.
I may need to replace the cam in my 383 stroker,, but it's been 20 years since it was assembled and the original paperwork is long gone.
If the cam I have been running doesn't have any markings to ID the maker and model, is there a way to determine the lobe separation and duration ?
Measuring the lift is no big deal, but there's a lot more to cam performance than just that, and I want to duplicate the cam performance I have been getting from the engine.
I asked the local machine shop and they told me all they can measure is the lift.

 

[Blue Ox]

Dial indicator and a degree wheel.

And a lot of patience.

 

[mtnmankev]

I'm about a third of the way there.
I have a dial indicator.
Need a degree wheel and some detailed instructions.

 

[Blue Ox]

Well, maybe a quarter. You'll probably need some graph paper too.

What you're going to have to do is measure lift at the pushrod while turning the engine. Set the dial indicator to zero on the base circle, then when the pushrod starts to lift you're going to record the lift measurement in relation to the degrees of engine rotation. Plot the intake and exhaust measurements against degrees on a graph and you'll end up drawing a picture of the cam lobes and their relationship to each other.

If you have Excel or a similar spreadsheet it will do the drawing for you.

 

[mtnmankev]

Thanks, Derek ...
I will get a degree wheel from an online source.
I am running Linux on my computer, so no Excel, I will have to see if Linux has a similar program.

 

[mtnmankev]

I found a deal on a comp cams wheel on fleabay, ordered it.
I guess I will need to fabricate some sort of bolt-on pointer to use it, shouldn't be too difficult.
Now to do a search for a Linux program for a spreadsheet, roomie said he had heard of one a long time ago that was designed for MS and Linux both.

 

[Blue Ox]

A piece of coat hanger attached to a random bolt will work for a pointer. The spreadsheet is just for convenience. You can still play connect-the-dots on graph paper.

 

[Rusty Nail]

can't

 

[mtnmankev]

Can't what ??
Enquiring minds want to know.

 

[75gmck25]

Very easy to find Open Source (free) spreadsheet software for Linux.

I use Libre Office, which has multiple apps like MS Office, and Libre Calc is the spreadsheet. Libre Office also has a version that runs on windows, so it’s also a good choice for that platform. You can save your files in the open office format, or in Microsoft Office format.

Another great cross platform (both Windows and Linux) app is Handbrake for video files. You can shoot video or pictures and use Handbrake to reformat and compress it for YouTube, email or other places where you want to post it.

Bruce