Quick Question: 4ag hicomp motor - Toyota Nation Forum : Toyota Car and Truck Forums

hachi_slow · 03-23-2004, 07:08 PM

What's the compression on the jdm smallport hicomp motors? Want to know what numbers I'm looking for when checking out an engine. I know it's above 200 but how high?

|PuNiSh3R| · 03-23-2004, 08:21 PM

Could be 10 or 11:1... I ain't positive which one.

hachi_slow · 03-23-2004, 08:26 PM

The compression ratio is 10.3:1 but I want to know what numbers (lbs/sq in) on a compression check it should be.

toyotaspeed90 · 03-23-2004, 09:02 PM

i can't seem to find it right now.... i saw it on club4ag (tech reference somewhere) and the lowest it shouldn't be below is 150lbs.......

hachi_slow · 03-23-2004, 09:05 PM

I'm getting readings of ~230-240 psi dry test. Wet test I get the same, except for cylinder #2 which shoots up to ~260.

Piston rings fried?

|PuNiSh3R| · 03-23-2004, 09:24 PM

All cylinders good except #2.. shot rings

hachi_slow · 03-23-2004, 10:53 PM

Pretty much what I was thinking...nice project to start the spring off with.

Not planning to take the engine out of the car though...I'll just go from underneath. This should be fun.

|PuNiSh3R| · 03-23-2004, 11:18 PM

lol.. could pull engine out just as easy.. either way shouldn't be to hard to drop 1 piston.. could do it with just pulling the pan.. although, you will need to hone the cylinder.. may need to take engine to machine shop if there is bad scoring.. all depends.

hachi_slow · 03-23-2004, 11:21 PM

Yeah...just gotta wait and see. Thanks for the help |PuNiSh3R|.

hachi_slow · 03-24-2004, 01:55 AM

Actually...doesn't high compression indicate carbon build up? When I took a look at the spark plug in #2 there was a lot of it. Couldn't I just decarbonize the cylinder head?

I'll figure something out.

project trueno · 03-24-2004, 05:02 PM

do a leakdown test on cylinder#2, and listen through the PCV.