Compression tester

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Model T Ford Forum: Forum 2016: Compression tester
Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom Donahue on Saturday, December 24, 2016 - 09:59 am:

First let me wish all a very Merry Christmas! I am interested in getting a compression tester, does anyone have any recommendations of brand, model and where I can purchase it? I've seen Harbor Freight sells one, does anyone have experience with that brand? Last, am I going to need any adaptors in order for the tester to fit a Model T's spark plug threads? Thanks again to all who help me out on these newbie questions. Now I need to run to the bakery to get a pie for Christmas dinner. Will check in later!


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Saturday, December 24, 2016 - 10:27 am:

Look for one that has a little button below the gauge to release the pressure and a 14 mm spark plug connection on the engine end.

With such low compression, you need a screw in and a tight fit.

You will still need a 14 mm to 1/2 inch pipe thread plug to screw on the engine end.

They all have 0 to 300 pounds pressure gauges.

The most accurate area of any gauge is the center third or 10 to 200 psi for most gauges.

You can remove the gauge from the kit set and install a 0 to 100 psi gauge for greater accuracy, as most original engines will read 35 to 45 psi, which is in the red area of a 300 psi gauge.

Here is a modified for Model Ts Sears Tester.

Tester

Harbor Freight has a larger, easier to read sprayer gauge for about $20 that is ideal.

Gauge

Sears has a compression tester kit on their website for $26.99 now.

Description Item # 00902171000P Model # CP7827

CP7827 Compression Tester Kit.

•Measures cylinder compression to accurately diagnose engine condition •Tester has 14-in high pressure flexible oil and grease resistant hose •Compression tester has external pressure release valve •14mm and 18mm ends fit most spark plug openings •1-year warranty • A 5% restocking fee will be applied to this item.

Harbor Freight has several for about the same price.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chad Marchees _____Tax Capital, NY on Saturday, December 24, 2016 - 10:36 am:

Tom, I have no experience with Harbor Freight compression gauge. However, my experience tells me that their gauge would probably be fine. Gauges like that are merely good for checking differences across cylinders, rather than being super accurate on the readings. Meaning that if you have a good cylinder at 55PSI and the harbor freight gauge shows 50 psi, it will still be fine as you want to get readings for comparison across the 4 cylinders. My gut feeling is that the Harbor Freight ones are probably no better or worse than the old Cal-tool or similar brands you used to by in the auto parts stores years ago, I personally would not shy away from them---I would still check your local auto store though, pricing might be similar or better.

As far as adapters, a quick peak at the HF testers reveals there hose end is straight thread with o-ring---and then you use the appropriate included adapter (14mm is the common modern adapter). You can get around this in a T if you buy a set of the 14mm x 1/2" MPT plug adapters from the usual T vendors.

You may also want to check your parts stores for a tester, theirs may have a hose that has a 1/4" male pipe thread (MPT) which you can then go to the hardware store and get a 1/2" MPT to a 1/4" FPT and screw the hose right into that (which is how mine is set up).

You could also as a last option go to a shop that makes custom hoses and have them make you a specific hose to fit your tester and that already had the proper 1/2" MPT thread on the opposite end.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chad Marchees _____Tax Capital, NY on Saturday, December 24, 2016 - 10:42 am:

James makes a great point I missed, in that you do need a smaller scale gauge to be more accurate. 300 psi is way to much, mine goes to 200 psi but I use it on more than just T engines. If you could find a 0-100 gauge you'd be in the money, but most modern gauges won't go that low.

Again, you could visit a local hose maker / Hydraulic shop and have a purpose built gauge and hose that may not cost more than the HF testers.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Saturday, December 24, 2016 - 10:44 am:

I've got a Mac tools compression / vacuum / fuel pressure test kit. You can pick one up used on eBay for $20 - $30. I went to Home Depot and bought a 1/2" NPT to 1/4" NPT adapter for $1 to screw the quick disconnect nipple in to.



Here's a photo of an identical kit to mine on eBaay right now:


Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert Brough on Saturday, December 24, 2016 - 11:18 am:

Langs's sells the spark plug adapters in a set of 4, but if you order just one, they will sell it to you. That's what I did and used my $20 tester from AutoZone to check both my Model T and my 42 Ford jeep. Works great and I was pleasantly surprised at my 40 to 45 psi readings across all 4 cylinders on the Model T.

Auto parts store will rent you a tester, but it was the same price to buy one and have it around the garage for future use.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chad Marchees _____Tax Capital, NY on Saturday, December 24, 2016 - 11:33 am:

To still further add,

Here are three gauges that would work. From left to right, Quality tire pressure gauge (0-60 psi), Fuel pressure gauge (0-100 psi) and a Compression gauge (0-300 psi). Any one of these could be used as they will hold pressure and there is a button to release the pressure.

Obviously the smaller range gauge would be better. The tire gauge I bought off Ebay, here is a similar one, cheap at $22 and free shipping too:

http://www.ebay.com/itm/Longacre-Analog-Tire-Pressure-Gauge-0-60-PSI-w-1-Year-Warranty-PN-50417-/360710933522?hash=item53fc0c0c12:g:ntEAAOSw9mFWGHL4&vxp=mtr

Also pictured is the 1/2" MPT to 1/4" FPT adapter (Home Depot)




(Message edited by Chad_Marchees on December 24, 2016)

(Message edited by Chad_Marchees on December 24, 2016)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom Donahue on Saturday, December 24, 2016 - 11:42 am:

Great information fellows. Just so I'm sure about what I'm reading, I need 1/2" male thread to go in the spark plug hole correct? Then an adaptor would need a 14mm female hole for the compression tester. Did I get that right? So checking the web there seems to be a large number of inexpensive options. All would need a smaller range gauge, but that shouldn't be a problem for me. I can even get it calibrated to read accurately at work. So all I would need is to know I've got my understanding of the reducing adaptor correct.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Saturday, December 24, 2016 - 11:51 am:

Most of the compression testers use a standard air chuck quick disconnect so that you can screw the spark plug adapter into the engine, then snap the tester hose in place. That's why you buy the $1 adapter from Home Depot as shown in the photos posted by Chad and I. It allows you to screw in a standard air hose nipple (1/4" NPT) to fit the T plug hole (1/2" NPT).


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chad Marchees _____Tax Capital, NY on Saturday, December 24, 2016 - 11:58 am:

Tom, yes as Royce has pointed out.

If you buy the 0-60 "tire gauge" (which will function just like a compression gauge) as I posted above, and all you need to get extra is the adapter from Home Depot or hardware store.

I guess my link did not go through, but search Longacre 0-60 tire gauge. Longacre makes quality race car grade items, and their gauges come through with an outer rubber protection shield to protect in case of drops. Total cost for gauge and adapter would be under $25.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom Donahue on Saturday, December 24, 2016 - 02:51 pm:

Thanks guys! Have a Merry Christmas!


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