2.3 compression concern/problems

[Cesarlcase]

I did a compression test for the first time on my stroker since I bought it used, but with new internals, I saw everything in there from under the oil pan. Today, my results came as 120 across the board. The car was driven for a good bit but probably cooled down to 90 degree celsius over the coarse of the testing and i pulled the engine 20 amp fuse to do the test (not sure if that matters). Either way, here are my concerns, for one the obvious low compression. I was told the motor had after market cams in them and when the car was being put together, I had Aem true timing cams installed on them. So question 1: can these "aftermarket" camshafts not be timed properly causing low compression? Another reason I suspect there might be cams is just because of the high end pull especially around 5k it very aggressive as to where I thought it would be a bit weaker up top with the stroker.

Problem #2 I was suspecting valves seals initially because I have all the symptoms like oil on the header from cylinder two and the "morning puff" from the exhaust but with these results I'm not sure anymore :/

Idle vacuum is 16 steady.
No signs of blow by.
Idle is about 900-700 unstable Iac unplugged, failed.
Oil 10w 30 synthetic- should I use 20w 40
Battery voltage- about 12.1 12.2 volts
Car still pulls and is only on 10lbs atm

Any other info that could help please let me know.

I'm going to do a leak down test but that's a while from now, so some advice will help me expect the outcome. Please be knowledgeable,thanks.

 

[YZFR1]

If you are having doubts about it, your best bet is going to be to do a leak down test. But to answer your question, yes, aftermarket cams can make dynamic compression results to appear lower, especially if they weren't degreed. On the other hand, your idle vacuum doesn't seem to be too bad so i don't think you have too much overlap.

My brothers car has bc 280's with 10 inch/vac at idle and his compression results came out similar to yours. I haven't done a leak down test on his car yet though. Hope this helps somewhat.

 

[Cesarlcase]

If you are having doubts about it, your best bet is going to be to do a leak down test. But to answer your question, yes, aftermarket cams can make dynamic compression results to appear lower, especially if they weren't degreed. On the other hand, your idle vacuum doesn't seem to be too bad so i don't think you have too much overlap.

My brothers car has bc 280's with 10 inch/vac at idle and his compression results came out similar to yours. I haven't done a leak down test on his car yet though. Hope this helps somewhat.

Yeah, sometimes It's like 15psi at idle but no lower than that. Ooh well, that makes me feel a little bit better. Is his a 2.3 also and how many miles

 

[YZFR1]

He has a 2 liter with stock compression and close to 20k miles with a 35r.

My engine is a 2.3 with 9.0:1/s2's and only 50 miles on it so far. I'm seeing very similar vacuum at idle (15 in/vac) and my compression results so far are between 155-165.

 

[Cesarlcase]

He has a 2 liter with stock compression and close to 20k miles with a 35r.

My engine is a 2.3 with 9.0:1/s2's and only 50 miles on it so far. I'm seeing very similar vacuum at idle (15 in/vac) and my compression results so far are between 155-165.

Hmm... So do you think degreeing the cam would change the compression positively while increasing HP? I am going to get a leak down test sometime this month...

 

[YZFR1]

Degreeing the cams, especially aftermarket, just lets you know where they stand while being "straight up". For example, if you've machined both surfaces and install cams straight up, they can actually already be advanced from what the manufacturer intended them to be, while still being set as straight up. It just lets you know where you stand, a point of referance.

It's hard to say if degreeing them at this point would raise the compression or not, as it depends on where they are now in relation to that.

If i was you, i would buy a Harbour Freight $40 leak down tester. Forget about the second gauge that is on it, it usually stops working on the 1st or 2nd time you try using it but you don't even need it, just use the first gauge to take your readings from and calculate the % of leak down from it.

In order to get accurate readings from doing the LDT, what i would recommend is removing your valve cover, bring the piston up to TDC and make sure your valves are not already cracked open. That would depend highly on the type of cams you have in there. If some of the valves are already cracked at TDC, move the piston until both cams are on their "base circle" for the particular cylinder you are testing. This way you know that the valves are as closed as they can be. Hope this helps somewhat.

 

[Cesarlcase]

Degreeing the cams, especially aftermarket, just lets you know where they stand while being "straight up". For example, if you've machined both surfaces and install cams straight up, they can actually already be advanced from what the manufacturer intended them to be, while still being set as straight up. It just lets you know where you stand, a point of referance.

It's hard to say if degreeing them at this point would raise the compression or not, as it depends on where they are now in relation to that.

If i was you, i would buy a Harbour Freight $40 leak down tester. Forget about the second gauge that is on it, it usually stops working on the 1st or 2nd time you try using it but you don't even need it, just use the first gauge to take your readings from and calculate the % of leak down from it.

In order to get accurate readings from doing the LDT, what i would recommend is removing your valve cover, bring the piston up to TDC and make sure your valves are not already cracked open. That would depend highly on the type of cams you have in there. If some of the valves are already cracked at TDC, move the piston until both cams are on their "base circle" for the particular cylinder you are testing. This way you know that the valves are as closed as they can be. Hope this helps somewhat.

Great info man. I just hope It's a leaky valve or something minor,relatively speaking.


Just one more question to ask, my car shoots a nice puff of smoke after starting it in the morning, then it fades away to almost no smoke whatsoever until I start to drive and come to a light it would smoke a fair amount. No dipstick popping out even under full boost.Ive also noticed the smoke getting slightly worse over the course of the year,but no power loss. I know I need to do the leak down test, but could a valve seal or guides be causing this issue? Also, I was reading about having to retorque, arp head studs after a certain amount of mileage, think that has anything to with it?