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L67 engine block

I don't know how fast a l67 is with my setup... But this thing pulls hard and will screech the tires at 40 around 3/4 throttle (only boosting about 6lbs). Is that fairly normal or does that sound like the engine is putting out a little more power than normal (as the higher compression L36 will do with less boost).
 


It's real... If I take the s/c belt off I can beat on it with zero KR. And as long as I don't let the boost get over 5-6lbs the KR is at or close to zero. I'm seriously considering buying a 4.0 pulley for it... lol
 
A couple things to check IMO:

Catalytic convertor clogged?
DP 3"?
Compression ratio

I think you are on to something with the compression ratio. The L36 should be about 160psi and the L67/L32 should be much lower. Like the other guys said, have someone with tuning experience take a look at it if it appears to have the lower compression pistons.
 
I have ZZP's MPS

No catalytic converter. I have headers with 3" dp.
I'll try checking the compression on it sometime. I'm also thinking about closing the gap on my plugs a little... maybe .045 or so. They are gaped at .053 right now. Maybe that will help...
 
rolyat said:
Now has new fuel pump assembly and a known good ICM... same problem.

Is there an actual compression difference between a L36 with the L67 top end components? I know compression ratios are different, but what about the actual compression? Will it be higher? I really want to know if my car has an L36 lower end... I saw that a bolt was missing out of the transmission bell housing, which leads me to believe either the engine or trans was pulled at some time...
Click to expand...

CC's are both 64 cc.

The only difference in the bottom end are the rods, pistons, pins, balancer, flexplate, and cam gear.

Rico said:
A couple things to check IMO:

Catalytic convertor clogged?
DP 3"?
Compression ratio

I think you are on to something with the compression ratio. The L36 should be about 160psi and the L67/L32 should be much lower. Like the other guys said, have someone with tuning experience take a look at it if it appears to have the lower compression pistons.
Click to expand...

You cannot check compression ratio short of boroscoping both types of blocks or CC'ing the pistons.

The cam gear in a N/A block is 1* advanced. Not exactly detectable.

Compression test values are quite a useless figure considering ring wear and valve/seat wear would negate any differences.

rolyat said:
I have ZZP's MPS

No catalytic converter. I have headers with 3" dp.
I'll try checking the compression on it sometime. I'm also thinking about closing the gap on my plugs a little... maybe .045 or so. They are gaped at .053 right now. Maybe that will help...
Click to expand...

Closing the gap isn't the best way to solve this.

Have a known good ICM you can swap in?

When I first top swapped my car wouldnt run KR free past 2 psi until I swapped out the ICM for another unit.
 
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matt5112 said:
CC's are both 64 cc.

The only difference in the bottom end are the rods, pistons, pins, balancer, flexplate, and cam gear.



You cannot check compression ratio short of boroscoping both types of blocks or CC'ing the pistons.

The cam gear in a N/A block is 1* advanced. Not exactly detectable.

Compression test values are quite a useless figure considering ring wear and valve/seat wear would negate any differences.



Closing the gap isn't the best way to solve this.

Have a known good ICM you can swap in?

When I first top swapped my car wouldnt run KR free past 2 psi until I swapped out the ICM for another unit.
Click to expand...

Hmm. This argument has come up before. I think that 2 engines with the same exact cam profile and 12% difference in compression ratio would create pressures that are noticeably different, especially at cranking speed. I understand that that the NA cam is degreed differently (only 1% as you say) but the lobe separation is exactly the same...no? If the rings are bad enough to negate the pressure differences then the motor will probably need rebuilt anyway. Then you'll surely see what rods and pistons are in there.

BTW
CC'ing the cylinders at BDC is not that hard and may be an option for you.

Matt5112
I understand that you are probably much more experienced than I and if I'm wrong go ahead and beat me up. I'm learning like everyone else here.
 
Boy I wish my L67 was back in the GTP 'cause I have an L36 in the driveway. The curiosity is killing me. LOL
 
My compression tester wasn't holding the pressure, but it looked like the needle was bumping up to 145psi and maybe a little higher.

I just swapped the ICM and it made no difference.

I took off my ZZP plug wires and put in my brothers ZZP wires. It got rid of all the misfiring and gave me a noticeable power gain... due to the fact that I can finally put the pedal on the floor! There is still some knock (around 5*) at full throttle and higher rpm's. I'm thinking the ZZP plug wires are crap in general and I'll get some OEM replacements. I guess I just went from one bad set of wires to another and another lol. Maybe that will get rid of all the KR.
 


Does anyone have any recommended quality plug wires that aren't overpriced and will get the job done? Accel, Walker, ACdelco?
 


I went to oreillys and bought the lifetime Borg Warner's. Ready to get these sh**ty ZZP wires off my car and soak them in some gasoline... then watch them burn!!! I'll buy my brother a new set too. Lol
 
The new wires helped. I can go full throttle without any misfiring and the KR stays between 0-4* so it was definitely an improvement! I'd love for it to stay at zero, but this is the best it has been since I've owned the car so I can't complain too much.
 
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