low compression, engine timing?

[allrice4g63]

So to sum it all up i did a 1g head swap on a 4g64 seven bolt. Car runs but im getting really rich numbers under mid and wot. I decided to do a compression test and cylinder number 1 was at 140, 2 was at 90, 3 was at 80 and 4 was at 140. So this brings me to my question..... Could my mechanical timing be off causing the exhaust valves to open in the middle two cylinder before it could build full compression. Like i said the car runs good but under boost my wideband pegs rich even with a hacked maf. Now to get to the story.... So if any of you guys know about doing the 4g63 headswap onto a 4g64 block you know the 64 block is 6mm higher and the dohc 4g64 timing belt has 154 teeth versus the 4g63 belt which has 153 teeth. So meeee being the broke ass i am couldnt afford the correct 4g64 dohc cam gears so the timing marks should line up like they are suppose to. You can use the 4g63 timing gears you just have to advance the intake and exhaust a half a tooth each to make up for the 154th tooth on the tbelt if that makes sense. OK so do you guys think having my timing off even one tooth or half a tooth cause these issues. No matter where i set my cas it still drops down to about 3-9* off timing under wot. replaced the knock sensor, coolant temp sensor is fine, tried two differnt style cas's. Really to be honest the only thing i can think of is the mechanical timing is off and the exhaust valve is opening to soon not letting those two middle cylinders build the correct amount of compression. when i did the compression test the motor was hot and i had all four spark plugs out. There was zero leakage between cylinders and what compression it did build it held it forever on the gauge. So can somebody verify my conclusions?

 

[viprez586]

Cylinder Leak Test - do it again, your loosing pressure somewhere - it just doesn't magically drop compression.

Listen at TB for leaking intake valve
Listen at tailpipe for leaking exhaust valve
Listen or look in coolant for bubbles/sound
Listen for bubbling through oil cap hole.

 

[allrice4g63]

Cylinder Leak Test - do it again, your loosing pressure somewhere - it just doesn't magically drop compression.

Listen at TB for leaking intake valve
Listen at tailpipe for leaking exhaust valve
Listen or look in coolant for bubbles/sound
Listen for bubbling through oil cap hole.

maybe im not losing pressure maybe its not building enough pressure because the exhaust valve is opening before the intake valve closes. so im only going to build SO much compression in a partical cylinder if the timing is off. Intake valve opens to fill the cylinder exhaust valve opens to release the air. I did a leak downtown test i can pressurize the cylinders and it holds the air forever. What i am asking can you mechanical timing being off cause one or two partical cylinders not to pressurize what they are suppose to due to the exhaust valves opening before the cylinder is full of air? you get what i mean?

 

[viprez586]

Yes, i understand. And its very likely that's the case. G'luck.

It holds pressure with the air fitting removed correct? (So no compressed air is being fed into the cylinder anymore)

 

[allrice4g63]

yes sir. it would explain why im so rich under boost and i have no power and would explain no matter where i set the cas it still pulls timing way back and would explain the compression and would explain why it runs better with a hacked maf. Everything points to my timing but it cant be off that much at the most its like 1 tooth. Do you think would tooth would cause this?

 

[kawgomoo]

your timing being off has nothing to do with a compression test.

the fact that the cylinders are not all even indicates bad something somewhere. rings, valves, head gasket etc. But since its two adjoining cylinders that are low, chances are its the gasket, deck surface or how you torqued it down.

How did you clean the head and deck surface? did you use any sort of rotary air tool?

Your center cylinders are low. More then likely its the head gasket. Did you torque it down properly? in the correct sequence? if you did the sequence backwards {outside to inside} you end up with a buckled head in the middle....and cylinders that dont seal.

if you use ARP head studs you cant use factory torque specs and you MUST use the supplied lube when pulling torque on the fasteners.

 

[allrice4g63]

i followed alldata for the sequence. I used oem head bolts. I used oem headgasket. I cleaned the deck surface with a razor blade and sandpaper. hmmmmm.......