12 replies to this topic

[Brandon]

Need to find me a decent quality compression tester & leak-down tool.

General consensus on precision tools like this are 'avoid Harbor Freight, get the Snap-On if you're an engine builder & you've got a gold checkbook, Craftsman if you're wanting to verify things'.

Anyone have other thoughts/ideas on what brand and/or sourcing?

TIA!
Brandon

[Jim Boemler]

I've got a HF gauge, and it seems to work fine. There's no real magic to these things. It's just two pressure gauges with a standard orifice between them.

[Jim Drago]

Buy the one from longacre, it is pretty good.
Jim

[Keith Novak]

The thing with HF tools is their quality can be all over the map. Sometimes you get lucky. Sometimes you don't. I have a lot of their tools. They're the ones I don't care much about if they get rained on.

Definately get a dual gauge leak down tester. I bought a cheap single gauge Morosso that wasn't worth what I paid for it other than I could hear where things leaked from. I bought a Longacre that I like much better but I don't do much real engine work. They cost about $100 everywhere.

[dstevens]

If you want a quality leak down tool, get this....

http://buy1.snapon.c...ore&dir=catalog

You can get a good used one from evilBay or CL for around a $100. I can get one cash off the truck for about $200. So for the same price you can get a Longacre you can get the real deal used. Depending on location, of course.

If you want one that will work well for your chick car the HF, Longacre and OTC all are offshore imports. A few years ago a borrowed the OTC from Autozone, a team at the track has a Longacre and I bought the HF. Those three appear identical in function and I've tested my HF in the shop. Plenty close enough for what we do. It's a manifold that maintains a pressure and measures the leakage variance. It ain't rocket surgery.

[davew]

The Snap-on guy does not like me, I have had 2 MAC gauges over the last 30 years. One benfit to the expensive brands is that they come in a nice box. Since most people don't use the tools every day, they tend to end up at the bottom of a tool box, and damaged.

Dave

[Brandon]

Thanks for the helpful notes. Does our engine require any special adapters (that wouldn't come with either gauge - leak-down or compression) to fit down the valve cover hole?

Longacre, Napa, Matco, Proform, Craftsman...I'm off to the 't00bz for tools!

[wesmc]

all the ones I have ever used work or would work on your Miata.

[davew]

99% of cars use the same thread on the spark plugs. Most gauges will give you a foot long rubber hose to screw into the spark plug hole. I just saw a new version from Mac Tools, that has a threaded metal tube that screws into the spark plug hole. Sometime the rubber hose is a PITA to get started, this metal tube looks pretty cool for our engines.

Dave

[AJ Roderick]

I used one with the metal tube 2 weekends ago, much better than the hose. it was a nice piece i could switch between my gauges with.

[Gatoratty]

Buy a 14mm extension tube for OHC engines. Sears carries them and Amazon.

(null)

[Brandon]

Bought the Craftsman kit - nice set of adapters, extension hoses, plus a pressure-hold insert to be used while performing valve seal changes w/o removing the head.
Thankfully the numbers came back well within spec so no leak-down necessary (or so I think so).

Here's the breakdown of the cylinders & their pressure readings:
@~150* engine temp
(Dry)
#1 - 185psi
#2 - 185- psi (185 minus)
#3 - 183psi
#4 - 192 psi
(Wet)
#1 - 230+ psi (230 plus)
#2 - 226 psi
#3 - 232 psi
#4 - 228 psi

On the wet tests I did ~1/4 ounce of oil in each cylinder (turkey baster very handy: knew this needed to be as close to identical as possible).

The engine is a crate and was approximately 2 years old with ~500 race miles on it when I bought the car.
Since then, 1 season of HPDE & 2 seasons of races - ~8 races with 5-6 practice days each year. I've put nearly 3k race miles on it.

Good/bad/ugly on the numbers?

[davew]

Compression is only 25% of the answer, you need to do a leakdown to be sure.

Then a dyno test to see if the power is still there.

Dave