Dial Indicator w Magnetic "arm" base or deck bridge?
 

I'd like to be able to use a CHEAP dial indicator to be able to fairly accurately measure how far down the hole my pistons are AND to be able to more accurately measure ACTUAL top dead center when degreeing in my cam.

I'm unclear on whether I can use a magnetic base with the arms on them like this:
Or whether I have to use a deck bridge like this:

My understanding is that the kind with the arm is useful for more tasks than just measuring how far down the hole the piston is and when the piston's at TDC.



Thanks,
Adam

The magnetic base is the better option ONLY if you get a good one. Try Craig's list. I got a name brand one for cheap. The cheap ones on Amazon move and wiggle way too much. If you need to go cheap a bridge and using a piston stop method is the most economical accurate method.

I have several of the arm versions, much more versatile and cost effective. Not sure the brands of mine as one is super old and others have no markings but were not cheap when bought them(not too expensive though).

A bridge is best for measuring deck height. But you can use a magnet if it's real steady in the arms. It takes a little care to measure. best to be right over pin..but you can also measure 90* to it by rocking piston all the way down and then all the way up and splitting difference.

For degreeing cam you want to use a piston stop to get true TDC and a very steady dial indicator to measure lobe movement.


For general all around use...I use these flex type. Easy to setup and work well vs all the pivot arms.

https://www.bing.com/shop?q=ball+joi...03B0BD5FDDBB18


JIM

There is also a vise-grip base indicator mount. Harbor freight cheapie.

I have a magnetic type base from HF. IMHO its extremely difficult to work with, But better bases are $$$$$ so balance it against how often your going to use it. I'll be trying a flex arm style next time around.

As any toolmaker, machinist, and operator will tell you cheap and good quality measurement tools really don't go hand in hand. If you are going to work on your car you will find a quality 0-1" indicator and a good mag base will pay for themselves over time. I only use Starrett, I think they have been one of the best for the past 100 years or so but I have the cheap ones tool. There is a big difference- I have a couple of those mag arm bases but the magnetic pull is weak on them all compared to my push button Starrett. The Chinese indicators have weak springs in them and often loose position without you knowing it. The few that had all broke in short time, the last one I have I use for a travel indicator for rough lathe work.

I would spent the money and get a good used set of ebay, they are always on there or I can sell you the fancy looking arm base sitting in my cabinet the past 5 years taking up space.

Adam,
Let me look at my mag base setup and get back to you. I'm at work right now. I had no problems checking my flywheel with my setup. Worked great and I think it's just what your're looking for. Decent performance and not too expensive.

I used Starrett mag bases daily for 30 years but now very much favor the Noga base.

I'll agree on the weak bases, you need a nice solid mounting surface. The hardware is sketchy at best, I have hard time tightening down the knobs...even after lubing the threads. But as Adam said, I'm never going to use it more than a handful of times so there's zero reason to buy something high end.

There're a bunch a youtube videos comparing Chinese dial indicators and other measuring devices to high end U.S. made and Japanese instruments. The imports are just as accurate. One guy compared spring strength and the import was actually stiffer than the high end model. I've check the accuracy of my 'Chinese' measuring tools and they're dead on....

I truly believe you get what you pay for, if I were a professional I'd have a set of high end instruments and tools. But I'm just a garage mechanic with one project car, entry level, but accurate instruments will work just fine.

This is what I have and it works fine for light duty work.
https://shop.harborfreight.com/media.../3/63663_I.jpg

https://shop.harborfreight.com/media.../3/63521_I.jpg

I found these pictures on Harbor Freight but I don't think I bought them there as it came in a kit and these are listed separately on HF.