SUPER URGENT engine builder help.. Testing motor. PLEASE! - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

gotta240 · 11-04-2007, 01:39 PM

Quik rundown. I'm looking at purchasing an sr20 from a local guy. Guy seems super legit and honest. Said motor was overhauled 3k. miles ago while in japan(military guy). the motor has sat for 8 or 9 months since last run, and is still spotless. Checked all hidden nooks and crannies to find everythign spotless(meaning engine most likely was torn apart like he said).

I tried to do a leakdown test on it and had serious trouble. I removed all 4 spark plugs and started in cyl. 1 at TDC. Air would either leak from the intake or exhaust side. When we turned the crank enough one direction to stop the intake side leak, the exhaust side leak got horrible. When we turned the crank the other way to stop the exhaust side leak, the intake leak got horrible. I also heard air coming from the crankcase, but didn't seem quite as bad as intake/exhaust side.
I repeated the same process(with cylinder at TDC) for all cylinders to have the EXACT same thing happen. The leakdown tester litterally would read 100percent leak...meaning no pressure.

Am I doing something wrong? What else should i do(other than pull the head) to ensure the motor is ok? Does the fact the motor has no oil in it and has been sitting for 8 months matter THAT much?

Opinons? PLEASE!!! This guys is holding the motor for the rest of the day for me so i'm limited on time... thanks

racepar1 · 11-04-2007, 01:43 PM

You weren't on the right TDC. The crank rotates 720 degrees in a full cycle through the firing order you were almost certainly 360 degrees off.

gotta240 · 11-04-2007, 01:50 PM

If i were 360 degrees off then wouldn't the valves be WIDE OPEN? The valves were partially closed on BOTH intake and exhaust. Just a little turn one way sealed intake, a lil turn the other way sealed exhaust. If it were 360 out it would have taken a full turn to seal anyting..right? or am i all off?

Also, what is a reasonable leakdown number for a good motor thats been sitting for 8 months?

racepar1 · 11-04-2007, 01:58 PM

It goes: intake, compression, power, exhaust.
You had the engine right here: intake, compression, power, exhaust^
You need to be here: intake, compression^, power, exhaust
Like I said 360 off.

gotta240 · 11-04-2007, 06:12 PM

Thank you for posting complete and non-flaming replies.

Ok, one more q- Could it still be 360 off even though the timing mark was lined up with the marks on the crank pulley? Thats how we found the TDC on first cylinder... Screwdriver all the way up while cranking by hand, with the timing mark on with the timing mark on the crankpulley.

Also, it doesn't matter the other plugs are pulled...correct? Also, what are ok specs for a motor that has set for amost a year, but is in good shape?

racepar1 · 11-04-2007, 06:22 PM

The timing marks will line-up anytime the #1 piston is up. Having all the plugs out doesn't matter at all. An ideal number is 0 the only thing that might leak just because the engine sat is the rings so if it is leaking through the valves beware.

gotta240 · 11-04-2007, 06:28 PM

How much is "OK" for the rings since its been sitting so long?

Is there any other thing you'd recomend looking for in a SR you were going to buy? Thanks again. Don't know what the F you did to get all that rep but i just gave a posi.

RedtopTech · 11-04-2007, 07:03 PM

less than 10 percent leak down is good on any motor. With the motor sitting for a while just squirt a couple teaspoons of oil in each cylinder and rotate the crank a bunch of times. If you are under 15 percent it should be good.
when i built my motor i had 18-16 percent on all cylinders before the first startup. after 200 miles i had 12-10 percent on all cylinders and after 1000 miles i now have 8 percent on all cylinders. these are very good numbers. You will never find a motor with 0 leak down. When the engine is running the cylinder pressure is actually sealing the rings. cylinder pressure is MUCH higher than the 100 psi or so that you leakdown tester is providing. so static leak down will always show more than 0.

RedtopTech · 11-04-2007, 07:06 PM

also, these guys are correct. You have to be on the right stroke to test leakdown.

gotta240 · 11-05-2007, 08:43 AM

Ok, thanks a bunch guys.

So basically if the engine leaks more than 20 percent, there is NO EXCUSE for that being acceptable.. regardless of how long it has sat, oil/no oil, etc. Also, it seems there is no reason at all to use a compression tester if you have access to a leakdown tester... right?

this guy is telling me to just to a comp. test, but i dont think there is a point if the leakdown doesnt pass. right? thanks again for spelling this out for me!

steve shadows · 11-05-2007, 10:29 AM

looks like my help is no longer needed, good luck in the engine search

and be wary of anyone who says "the engine was rebuilt in japan with parts before it got here" unless a metal head gasket tab is sticking out of the motor and the lower oil pan removal reviels some shiny connecting rods

johngriff · 11-05-2007, 01:02 PM

hahah yeah, i might not be the best to ask for help on the weekend..

quick reference:

Intake stroke: Cam lobes facing "out" on cyl #1
Exhaust stroke: Cam lobes facing "in" on cyl #1

That will let you know what position the engine is in.

gotta240 · 11-05-2007, 08:47 PM

Thank both of you very much for taking the time to look in here and reply. Much appriciated.

And thanks to the guys above who beat these two to it! I just re-did the leakdown test with much better results! thanks again!

11-05-2007, 10:29 AM	#11
steve shadows Post Whore! Join Date: Aug 2003 Location: LA and OC Posts: 8,202 Trader Rating: (5) Feedback Score: 5 reviews	looks like my help is no longer needed, good luck in the engine search and be wary of anyone who says "the engine was rebuilt in japan with parts before it got here" unless a metal head gasket tab is sticking out of the motor and the lower oil pan removal reviels some shiny connecting rods __________________ Like Me on FaceBook !

11-05-2007, 01:02 PM	#12
johngriff Post Whore! Join Date: Jun 2004 Location: Long Beach, CA Posts: 4,103 Trader Rating: (4) Rides Gallery: johngriff Feedback Score: 4 reviews	hahah yeah, i might not be the best to ask for help on the weekend.. quick reference: Intake stroke: Cam lobes facing "out" on cyl #1 Exhaust stroke: Cam lobes facing "in" on cyl #1 That will let you know what position the engine is in. __________________ [email protected]

11-04-2007, 01:39 PM	#1
gotta240 Post Whore! Join Date: Dec 2005 Location: so cal Posts: 3,496 Trader Rating: (21) Feedback Score: 21 reviews	SUPER URGENT engine builder help.. Testing motor. PLEASE! Quik rundown. I'm looking at purchasing an sr20 from a local guy. Guy seems super legit and honest. Said motor was overhauled 3k. miles ago while in japan(military guy). the motor has sat for 8 or 9 months since last run, and is still spotless. Checked all hidden nooks and crannies to find everythign spotless(meaning engine most likely was torn apart like he said). I tried to do a leakdown test on it and had serious trouble. I removed all 4 spark plugs and started in cyl. 1 at TDC. Air would either leak from the intake or exhaust side. When we turned the crank enough one direction to stop the intake side leak, the exhaust side leak got horrible. When we turned the crank the other way to stop the exhaust side leak, the intake leak got horrible. I also heard air coming from the crankcase, but didn't seem quite as bad as intake/exhaust side. I repeated the same process(with cylinder at TDC) for all cylinders to have the EXACT same thing happen. The leakdown tester litterally would read 100percent leak...meaning no pressure. Am I doing something wrong? What else should i do(other than pull the head) to ensure the motor is ok? Does the fact the motor has no oil in it and has been sitting for 8 months matter THAT much? Opinons? PLEASE!!! This guys is holding the motor for the rest of the day for me so i'm limited on time... thanks

11-04-2007, 01:43 PM	#2
racepar1 Post Whore! Join Date: Jul 2007 Location: Simi Valley, CA Age: 42 Posts: 9,006 Trader Rating: (106) Rides Gallery: racepar1 Feedback Score: 106 reviews	You weren't on the right TDC. The crank rotates 720 degrees in a full cycle through the firing order you were almost certainly 360 degrees off.

11-04-2007, 01:50 PM	#3
gotta240 Post Whore! Join Date: Dec 2005 Location: so cal Posts: 3,496 Trader Rating: (21) Feedback Score: 21 reviews	If i were 360 degrees off then wouldn't the valves be WIDE OPEN? The valves were partially closed on BOTH intake and exhaust. Just a little turn one way sealed intake, a lil turn the other way sealed exhaust. If it were 360 out it would have taken a full turn to seal anyting..right? or am i all off? Also, what is a reasonable leakdown number for a good motor thats been sitting for 8 months?

11-04-2007, 01:58 PM	#4
racepar1 Post Whore! Join Date: Jul 2007 Location: Simi Valley, CA Age: 42 Posts: 9,006 Trader Rating: (106) Rides Gallery: racepar1 Feedback Score: 106 reviews	It goes: intake, compression, power, exhaust. You had the engine right here: intake, compression, power, exhaust^ *You need to be here:* intake, compression^, power, exhaust Like I said 360 off.

11-04-2007, 06:12 PM	#5
gotta240 Post Whore! Join Date: Dec 2005 Location: so cal Posts: 3,496 Trader Rating: (21) Feedback Score: 21 reviews	Thank you for posting complete and non-flaming replies. Ok, one more q- Could it still be 360 off even though the timing mark was lined up with the marks on the crank pulley? Thats how we found the TDC on first cylinder... Screwdriver all the way up while cranking by hand, with the timing mark on with the timing mark on the crankpulley. Also, it doesn't matter the other plugs are pulled...correct? Also, what are ok specs for a motor that has set for amost a year, but is in good shape?

11-04-2007, 06:22 PM	#6
racepar1 Post Whore! Join Date: Jul 2007 Location: Simi Valley, CA Age: 42 Posts: 9,006 Trader Rating: (106) Rides Gallery: racepar1 Feedback Score: 106 reviews	The timing marks will line-up anytime the #1 piston is up. Having all the plugs out doesn't matter at all. An ideal number is 0 the only thing that might leak just because the engine sat is the rings so if it is leaking through the valves beware.

11-04-2007, 06:28 PM	#7
gotta240 Post Whore! Join Date: Dec 2005 Location: so cal Posts: 3,496 Trader Rating: (21) Feedback Score: 21 reviews	How much is "OK" for the rings since its been sitting so long? Is there any other thing you'd recomend looking for in a SR you were going to buy? Thanks again. Don't know what the F you did to get all that rep but i just gave a posi.

11-04-2007, 07:03 PM	#8
RedtopTech Zilvia Member Join Date: Dec 2005 Location: Virginia Beach, VA Age: 40 Posts: 293 Trader Rating: (0) Feedback Score: 0 reviews	less than 10 percent leak down is good on any motor. With the motor sitting for a while just squirt a couple teaspoons of oil in each cylinder and rotate the crank a bunch of times. If you are under 15 percent it should be good. when i built my motor i had 18-16 percent on all cylinders before the first startup. after 200 miles i had 12-10 percent on all cylinders and after 1000 miles i now have 8 percent on all cylinders. these are very good numbers. You will never find a motor with 0 leak down. When the engine is running the cylinder pressure is actually sealing the rings. cylinder pressure is MUCH higher than the 100 psi or so that you leakdown tester is providing. so static leak down will always show more than 0.

11-04-2007, 07:06 PM	#9
RedtopTech Zilvia Member Join Date: Dec 2005 Location: Virginia Beach, VA Age: 40 Posts: 293 Trader Rating: (0) Feedback Score: 0 reviews	also, these guys are correct. You have to be on the right stroke to test leakdown.

11-05-2007, 08:43 AM	#10
gotta240 Post Whore! Join Date: Dec 2005 Location: so cal Posts: 3,496 Trader Rating: (21) Feedback Score: 21 reviews	Ok, thanks a bunch guys. So basically if the engine leaks more than 20 percent, there is NO EXCUSE for that being acceptable.. regardless of how long it has sat, oil/no oil, etc. Also, it seems there is no reason at all to use a compression tester if you have access to a leakdown tester... right? this guy is telling me to just to a comp. test, but i dont think there is a point if the leakdown doesnt pass. right? thanks again for spelling this out for me!

11-05-2007, 08:47 PM	#13
gotta240 Post Whore! Join Date: Dec 2005 Location: so cal Posts: 3,496 Trader Rating: (21) Feedback Score: 21 reviews	Thank both of you very much for taking the time to look in here and reply. Much appriciated. And thanks to the guys above who beat these two to it! I just re-did the leakdown test with much better results! thanks again!