compression too high after overhaul??? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

feito · 11-04-2012, 10:56 PM

we just drove the first 100 miles and did the first oil change on my little bros stock ka. We check everything ourselves and everything seemed withing specs so we just went with std rings and bearings. Got the head (and cover) resurfaced at one of most reputable machine shops in town (miller's in San Antonio TX) and lapped the valves at home. we used ebay npr rings and clevite main/rod bearings. I also took care of deleting all the useless crap...
When we first finished putting everything back together we ran a compression test and everything checked at around 160 across the head. Now after a hard break-in, and 100 miles, doubled check the compression numbers, and they are as follows: 217-224-220-220. Isnt that too high even for a resurfaced head?
BTW engine runs good
And i'll whore it up a bit in here:

GroundPerformance · 11-05-2012, 01:15 AM

Was the replacement pistons flat or dished top? You could have put in a KA24E pistons.

feito · 11-05-2012, 01:51 AM

we reused the old pistons, all that was replaced on the bottom end was rings and bearings.

91ka24 · 11-05-2012, 05:16 AM

Possible that a valve is stuck open? Although u would think it would run badly. You could get a vac gauge and hook it up to the intake mani, see how much vac your pulling. If the needle starts bouncing rapidly that will tell you that you have a valve train prob.

Croustibat · 11-05-2012, 05:39 AM

err... he is saying he has TOO MUCH compression, meaning no valve stuck open ...

Now either the compression test tool does not work, or the headgasket is too thin, not compensating for the head skim. Either run high octane & a modified to fit timing /fuel map or change the headgasket. If you drive it like that, it is likely your engine will det to its death.

shift_down · 11-05-2012, 07:18 AM

Rev up the motor and listen for detonation, but stop once you hear it (you will most likely hear it). If you dont, then its possibly a bad compression tester. Do you know for sure that the tester is good?

feito · 11-05-2012, 08:26 AM

I just ran a compression test with the same tool on my recently adquired s30's l28 and everything checked good at around 170 so i believe the tool is good. So u guys think the head was shaved a lot bumping the comp up so much? They did tell me hoe much was removed but i dont remember what it was smh.. Also, is it still too high for a warmed engine?

GroundPerformance · 11-05-2012, 05:53 PM

That is fairly high. But since the rings are new and most likely still in the break-in phase give it some miles and dont run it too hard. Just curious what did you gap your rings to?

11-04-2012, 10:56 PM	#1
feito Nissanaholic! Join Date: May 2007 Location: Texas Posts: 1,948 Trader Rating: (1) Feedback Score: 1 reviews	compression too high after overhaul??? we just drove the first 100 miles and did the first oil change on my little bros stock ka. We check everything ourselves and everything seemed withing specs so we just went with std rings and bearings. Got the head (and cover) resurfaced at one of most reputable machine shops in town (miller's in San Antonio TX) and lapped the valves at home. we used ebay npr rings and clevite main/rod bearings. I also took care of deleting all the useless crap... When we first finished putting everything back together we ran a compression test and everything checked at around 160 across the head. Now after a hard break-in, and 100 miles, doubled check the compression numbers, and they are as follows: 217-224-220-220. Isnt that too high even for a resurfaced head? BTW engine runs good And i'll whore it up a bit in here:

11-05-2012, 01:15 AM	#2
GroundPerformance Zilvia FREAK! Join Date: Oct 2008 Location: Socal Posts: 1,477 Trader Rating: (44) Feedback Score: 44 reviews	Was the replacement pistons flat or dished top? You could have put in a KA24E pistons. __________________ SoCal KA24DET/KA24ET Owners << Join the FB Group >>

11-05-2012, 07:18 AM	#6
shift_down Zilvia Junkie Join Date: Sep 2012 Location: Tulsa Oklahoma Age: 31 Posts: 313 Trader Rating: (0) Feedback Score: 0 reviews	Rev up the motor and listen for detonation, but stop once you hear it (you will most likely hear it). If you dont, then its possibly a bad compression tester. Do you know for sure that the tester is good? __________________ Ka24 t3/t04b + Z32MAF + 550 subys + Walbro 255 + enthalpy Tune + 91 octane

11-05-2012, 05:53 PM	#8
GroundPerformance Zilvia FREAK! Join Date: Oct 2008 Location: Socal Posts: 1,477 Trader Rating: (44) Feedback Score: 44 reviews	That is fairly high. But since the rings are new and most likely still in the break-in phase give it some miles and dont run it too hard. Just curious what did you gap your rings to? __________________ SoCal KA24DET/KA24ET Owners << Join the FB Group >>

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11-05-2012, 01:51 AM	#3
feito Nissanaholic! Join Date: May 2007 Location: Texas Posts: 1,948 Trader Rating: (1) Feedback Score: 1 reviews	we reused the old pistons, all that was replaced on the bottom end was rings and bearings.

11-05-2012, 05:16 AM	#4
91ka24 Zilvia Junkie Join Date: Sep 2010 Location: Oklahoma city, ok Age: 32 Posts: 414 Trader Rating: (11) Feedback Score: 11 reviews	Possible that a valve is stuck open? Although u would think it would run badly. You could get a vac gauge and hook it up to the intake mani, see how much vac your pulling. If the needle starts bouncing rapidly that will tell you that you have a valve train prob.

11-05-2012, 05:39 AM	#5
Croustibat Nissanaholic! Join Date: Aug 2011 Location: France - Toulouse Age: 41 Posts: 1,851 Trader Rating: (0) Feedback Score: 0 reviews	err... he is saying he has TOO MUCH compression, meaning no valve stuck open ... Now either the compression test tool does not work, or the headgasket is too thin, not compensating for the head skim. Either run high octane & a modified to fit timing /fuel map or change the headgasket. If you drive it like that, it is likely your engine will det to its death.

11-05-2012, 08:26 AM	#7
feito Nissanaholic! Join Date: May 2007 Location: Texas Posts: 1,948 Trader Rating: (1) Feedback Score: 1 reviews	I just ran a compression test with the same tool on my recently adquired s30's l28 and everything checked good at around 170 so i believe the tool is good. So u guys think the head was shaved a lot bumping the comp up so much? They did tell me hoe much was removed but i dont remember what it was smh.. Also, is it still too high for a warmed engine?