HELP--Low compression on fresh build
 

Ok... I had a 2.3 and cracked my crankshaft so I decided to build a 2.1L, 4g63 block. After getting off the dyno and not being to impressed with the numbers I did a compression a test. I had 120 at 1,3,4 and 114 on 2, 10:5.1 piston. When the Pistons were installed we just did a slight hone and threw them in. I did a leak down test and had 1% at 1,2,4 and 3% at 3. I even bought a new compression tester to kinda cover bases. Has anyone on here seen this issue befor? Any input would be great!!!!
2.1LR
Ported head
R2 cams
FF 6466
E85

Anything?? Come on guys...

HELP--Low compression on fresh build
 

How did you build a 2.1L 63 block? Bored it out to 86.5mm, or.....? Did you check the cylinders for roundness and taper/straightness?

If you gave big cams your compression will appear to be low. In addition mivec seems to jack with compression a bit as well. My compression was close to 110 with kelford 282 cams. Once I went back to stock the compression jumped back up to normal. As long as it's nearly the same you are good to go.

That does seem low for a fairly high compression piston like that. How many miles are on the motor and how was it broken in?

Evo 9's have much lower compression numbers then Evo 8's. The service manual states 145 with a minimum of 92 and a variation of no more than 14 PSI.

Sorry for the delay fellas, been busy with work. Since we just did a light hone we weren't to worried about a real serious break in procedure. Drove it for about 50mi then threw it on the dyno :) I never knew mivec or larg cams could screw with compression but I'm only running r2's?? I decided to run it anyways since I have great leak down numbers 👍🏻

lol "only" R2'S.... That's a big cam. Duration is in between and the S2 and S3, with more lift than the S3's...