Problem with Newly Built L20b

[510SSS]

Hey guys, I just finished putting my motor together and damn has it been tough, but I learned alot. I finally think i have everything dialed in, but something is not right and I need your help. Here's the problem, it's a L20b stock pistons with .020 overbore, 8 LB OS Giken Flywheel, u67 head portmatched to 1.5in SU manifold, Lightly Ported Exhaust Ports, 280zx Intake and Exhaust Valves, Dual SU Carbs just rebuilt by Z therapy, Shorty Header, 2.25 in exhaust system, Matchbox Dizzy from 1979 620. The thing is every time I rev it it starts to sound like a Loud Tick/Rattling, that ramps up with engine speed. I tried to adjust the valves several times without much change. I have tried .08 Intake and .10 Exhaust and I have tried .06 Intake and .08 Exhaust cold noise quieted a bit on idle. I am wondering with the larger valves and exhaust will this effect how I should set my valve adjustment? I also do not have much play in my distributor to adjust ignition timing, could this be pinging? Maybe because of the lightweight flywheel the SU's are going lean because they cannot keep up with the quick revs? Would a different needle be needed perhaps? Thanks guys, I really wanna get my car back on the road and have already spent too much to start over now.

[DAT510]

Hows your oil pressure?

[bananahamuck]

You should adjust the valves HOT ,,, it might not help,  but i adjust cold to get it running then adjust at full running temp.

 

lots of specs at link below

 

http://olddatsuns.com/

[510SSS]

As far as my oil pressure I am not sure because my gauge is broken, however I do have a Nissan Comp Spray Bar system hooked up, with the cam oiling holes not plugged. Could this cause a problem? I have a KA24E High Output oil pump installed new, but perhaps this is still not enough to keep up with the dual oiling system?

[bonvo]

so you did all this to it and have a stock cam? if not the valves are adjusted differently

[510SSS]

Yeah the cam is a stock u20 cam.

[dattoboy70]

could it be chain rattle? did you put your timing chain on correctly?

[510SSS]

I think it is on correctly it is exactly centered on the bright links of the dimple, I do remember one of my bolts on my tight side guide being a little bit stripped could this cause the noise?

[dattoboy70]

alot of slack in the chain can cause the noise.

[dattoboy70]

pull your valve cover off inspect it. that would be the easiest thing to do before you start with other things. or use a stethoscope to see where the noise is coming from

[510SSS]

It sounds like it may be coming more from the rear of the valve cover, chain seems tight, Im starting to suspect low oil pressure.

[EricJB]

OK lets back up a bit. First of all I hope its a typo, and you didnt really adjust your valves at .100  and .08. It should be .010 and .008. Make sure you are on TDC for the cylinder you are adjusting.

 

Take the valve cover off and pull the sparkplugs. leave the ignition off and put a starter button on the starter. Put a oil pressure gauge on it even if it is a cheap POS threaded right into the block. Spin the motor over with the button and watch for oil on the valvetrain and for the gauge to move. Dont fire it up untill you have pressure. The timing chain is hydraulically tensioned. No oil pressure, no tension. Good luck.

[banzai510(hainz)]

hopefully you seen this

http://vimeo.com/19077890

 

olddatsuns.com the tech section

 

you Prime the oil pump before start up?????????

 

I also do not have much play in my distributor to adjust ignition timing????

You put the oilpump/dizzy spindal in and timmed it correctly at TDC? rorot is at #1 exactly with center of timming plate R---Center----Advance.

 

 

I cant see how its going to lean out to much with no load on it. But IM only guessing

[510SSS]

Yeah Ive seen your video many times, thanks btw couldnt have built it without you. I think the dizzy spindal is at 11.28 position, I triple checked it. Would low oil pressure cause a loud metallic sound that increases on revs? I bought the correct pedestal and timing plate so I think it is correct. What should be the correct ignition timing for an l20b with SU's 12 degrees? 14? which way would the dizzy be turned to achieve this setting?

[darrel]

Hey guys, I just finished putting my motor together and damn has it been tough, but I learned alot. I finally think i have everything dialed in, but something is not right and I need your help. Here's the problem, it's a L20b stock pistons with .020 overbore, 8 LB OS Giken Flywheel, u67 head portmatched to 1.5in SU manifold, Lightly Ported Exhaust Ports, 280zx Intake and Exhaust Valves, Dual SU Carbs just rebuilt by Z therapy, Shorty Header, 2.25 in exhaust system, Matchbox Dizzy from 1979 620. The thing is every time I rev it it starts to sound like a Loud Tick/Rattling, that ramps up with engine speed. I tried to adjust the valves several times without much change. I have tried .08 Intake and .10 Exhaust and I have tried .06 Intake and .08 Exhaust cold noise quieted a bit on idle. I am wondering with the larger valves and exhaust will this effect how I should set my valve adjustment? I also do not have much play in my distributor to adjust ignition timing, could this be pinging? Maybe because of the lightweight flywheel the SU's are going lean because they cannot keep up with the quick revs? Would a different needle be needed perhaps? Thanks guys, I really wanna get my car back on the road and have already spent too much to start over now

.020 over pistons?

 

[EricJB]

.020 over pistons?

 

Ya I saw that too, but didnt think it was possible that one could make a mistake like that. I've seen wrong bearings used, but not pistons. Talk about piston slap though.

 

Did you fill the oil filter before install? Did you prime the pump?

[Dawa]

^was wondering the same thing and assumed he meant .020 over pistons/rings.

[racerx]

if no stetascope, then use a long metal bar or pry bar or long screw driver and cup end to your ear while touching valve cover area where you think noise is coming from and compare with other side of valve cover and should notice a difference.  Also should install a oil pressure gauge, specially with ol cars like ours.  Good luck..

[hobbes_the_cat]

Would low oil pressure cause a loud metallic sound that increases on revs?

YES. Put an oil pressure gauge on that thing. All that work and no gauge to check oil pressure is crazy. Don't run it anymore till you put a gauge on it.

[datzenmike]

it's a L20b stock pistons with .020 overbore,

 

Need to know about this!!!!

 

 

Would low oil pressure cause a loud metallic sound that increases on revs?

 

Yes low knocking sound like a muffled hammer on the side of the block sounds like a rod knock. No oil will pound the bearing(s)out. Don't run this until you get an oil pressure gauge on it to be sure. I've seen rods installed and one gets forgotten and not torqued.

 

When you turn key to on the red OIL light lights up???? to test the bulb... start and it goes out? This would indicate you have at least 8 pounds of pressure.

[510SSS]

Thanks every1, I'll gonna hook up an oil pressure gauge to it and see what my pressure is. Hopefully i didnt damage my engine. Also yes my pistons are matching overbore as well. .020.

[banzai510(hainz)]

remember the block threads are 1/8 BSP.

 

 

soem places sell a 1/8 BSP to the more common 1/8 NPT which most kits come with.

[racerx]

you may want to consider getting a sunpro or similar that has oil, voltage and temp. gauges.  MIne has all 3 and it's good to know these things, specially on old cars.

[banzai510(hainz)]

sunpro is cheap!

VDO or Steward Warner and these are already outsourced in Maylasia I trhink already. I would get the electronic one that uses a x ducer so a oil line dont break.

Autometer also

But be honest find the knocking first as It might be too late already.

 

sure its not just a loose alternator mount rattling around?

[510SSS]

Yeah I remembered to prime the oil pump. I will double check the alternator mount to see if that is it but I think i have them all torqued to spec. I think i am gonna try to completely delete the spray bar system, and see if I run it with just the cam oiling holes then perhaps the oil pressure will increase.