Engine Stalling when Given Gas

[Hondanx250]

Here is my last Topic about the engine for Reference.

http://community.ratsun.net/topic/68708-engine-stalling-but-progress/?do=findComment&comment=1353242

 

 

Hey, I been messing around with this engine for awhile trying to get it to run right and a drive able car out of it.

I did a compression test All the cylinders are at 110.

 

I got the Car to Idle in Drive at 600RPM(Occasionally bogs down and dies). Have it at 8 Degress BTDC like the service manual says.

I installed a Weber 32/36 Kit. It seems to be  idle alright.

 

The Engine is Napz z20s. From a 1980 Datsun 510 A10 Wagon

 

 

This video was taken this weekend, I've gotten the engine to smooth out in drive and reveres.  Found a Vacuum line that was not plugged.

 

Anyways, In this video you can see a when i stick the car in drive or reverse and give it gas it cuts out. When you give it gas in Neutral or Park its fine.

Only backfires under load.

 

Ive adjusted the values, So should be correct there. Is it something internal? Should i go back to a stock carb?  Vacuum Line? I don't mind if i have to pull the engine out again and fix something.  Is the timing chain off?

 

I am lost and about ready to take it to a shop or have a mobile mechanic take a look.

 

 

 

Thanks

 

Oopps, Thought i posted under Engine Forum, If a Mod could move it. Or this page is fine.

[banzai510(hainz)]

I wouldn't take it to a shop yet.

 

is your distributor cranked all the way to one side to get it at 8degs?????????  to me just winging it, the dist if off and going out of time when your accelerate

 

idle misture could be better to get it smoother

 

 

never had a automatic myself so just a guess on my part.

[Hondanx250]

I wouldn't take it to a shop yet.

 

is your distributor cranked all the way to one side to get it at 8degs?????????  to me just winging it, the dist if off and going out of time when your accelerate

 

idle misture could be better to get it smoother

 

 

never had a automatic myself so just a guess on my part.

I put the timing gun to it, and it shows it at 8 degrees BTDC In Drive, The distributor Is more in the center. I could just play with it and see if it does anything.

[banzai510(hainz)]

if its close to center then I will assume its OK.

[racerx]

Have you checked for vacuum leaks?  Also when you did compression check, 110 is low, did you check when car was at operating temp.? did you use a screw in type of compression checker? did you make sure that throttle was wide open?  For vacuum leaks, spray brake cleaner around base of carb, intake, hoses while the car is in idle.  If idle goes up, then theres a vacuum leak somewhere.  Also what color are your plugs?  If too black then you can be running too rich and if too white then too lean, in between is the best.

[Hondanx250]

Okay.

 

So after thinking, And Trying to get it to run. With no Avail. Doing Steps over and Over. Reading and following everything. Can only get it to idle correct but once giving it gas it dies.

Spark plugs looked fine, Valves where adjusted once car was warmed up. Did not find any vacuum leaks

 

I can only conclude that the Timing chain is off a tooth?

[datzenmike]

Will it rev up slightly in neutral before stalling?

 

The idle circuit is simply the for idle and anything higher is going to need much more air and gas. I would say the primary jet is blocked or plugged with sediment. When the throttle is opened and more gas needed all you are getting is too much air and the engine stalls..

[Hondanx250]

It will rev up fine in Neutral and Park, Once its under load it will kill when you give it gas. You can kinda give it a little and move forward for like a second, but then it will die. Ill pull the carb off and give it a cleaning. Might of got some dirty fuel.

 

That why i say once its under load, the valves could not be opening and closing at the right time?

[datzenmike]

Valve timing is fixed no matter the RPM. Some newer engines have variable valve timing but only when revved up. The L series are fixed.

 

Sounds like your idle and maybe slow speed circuit are ok but the primary jet is plugged.

[Hondanx250]

Valve timing is fixed no matter the RPM. Some newer engines have variable valve timing but only when revved up. The L series are fixed.

 

Sounds like your idle and maybe slow speed circuit are ok but the primary jet is plugged.

 

Found one of the Jets Clogged in the float bowl.

[Hondanx250]

Found one of the Jets Clogged in the float bowl.

 

 

Do you know what the jet sizing are supposed to be at?

[datzenmike]

Generally around 100, probably very high 90s. I do have a 107 (from a local  truck L20B) in my 710 but I'm at sea level. Last spring I had 99 in it for a 3,000 mile trip and got the best mileage inland at higher elevations in the mountains than at home. The 107 definitely has more power at sea level than the old 99 that was in it. The original jeting may have been for Nevada, where the car is from. Average elevation 5,000 ft.

 

 

Have a care if you have the secondary jet out. They will interchange. The secondaries are around 160

[Hondanx250]

Okay, I should of wrote them down. But i think the range highest was 170 and the lowest was 120 with i think a 140.

[datzenmike]

I'm assuming a stock Hitachi carb. Remove the 12mm covers and (I ground down a bladed screwdriver) reach up inside and unscrew the jets. You have a Z20 engine? Primary is farthest from the valve cover.

 

The 12mm jet covers (Black) are at the bottom in this picture.

 

 

The jets are in those two gas covered holes but unscrewed from the under side.

 

Primaries are around 100 secondary are around 160. A 120 sounds rather large.

[Hondanx250]

The carb is a New Redline Weber that is supposed to be for this vehicle. Yes engine is a Z20 engine

[datzenmike]

Then you need a weber expert.

 

Anything else that's non stock that we should know?

 

Did it run before the carb change or the same?

[Hondanx250]

It ran before i rebuilt the engine. Pulled the engine due to one of the cylinders reading low and wanted to learn how to rebuild a engine. Ended up one of the cylinders had a shorter road. Installed engine.  Ran with the old carburetor back and forth in the driveway.

Swapped it out with a Weber and been having this problem since.

 Everything else is stock.

[Doctor510]

Please, what is a "shorter road"?  Webers usually bog if the idle jets are too small or the idle bleed holes are plugged.  Yeah, I know it was new in the box, mfg dirt, clean it.

 

30 years worth of wisdom.   "Never enough time, never enough money, if it comes in a box, it's wrong."

Dave Weber, Malvern Racing

[datzenmike]

Z20s had 152.5mm rods and flattop pistons. Some PO must have replaced it with an L20B rod 149.5mm. Compression would have been non existent on that cylinder and would have vibrated ??

[Jesse C.]

Looks like you first need to rebuild the carb before going any further. Make sure everything is clean and where it belongs before you start changing things. 

 

Who know, it might fix the problem.

[Hondanx250]

Got the Engine Running and Driving back and forth in the driveway after cleaning the carburetor.

 

 

Pretty sure i have a Rod Knock going on now though.  

[datzenmike]

Rod knock is when the bearing clearance is excessive for several reasons. With too much clearance it's difficult to contain an oil film between the rod bearing and the crank. Without oil there is no hydraulic 'cushion' when the piston is driven down suddenly when the cylinder fires. The rod and bearing slam into the crank and there is a definite knock sound like a muffled hammer blow on solid metal.

 

Generally louder under load and gets softer, even silent when you let off of the gas.

 

In early stages much quieter progressing to MUCH louder. This can take from seconds to months depending how hard it is driven.

 

Once the rod begins to knock it never gets better. You can somewhat reduce the noise by running very thick oil but it will get worse.The bearing shell can wear down or just like forging metal can be pounded flat to razor thinness. When there is enough clearance, one bearing shell can ride up over or under the other and block the oil supply. If driving slow enough you will hear a squealing sound and shortly after the engine will just seize and stop. The heat of friction (from lack of oil) melts and wends the rod to the crank. Naturally at high speeds, high RPM, this can happen so fast the rod will weld to the crank but the crank cannot stop so the rod snaps off, rotates around and punches a hole in the block or pan. Sometimes the crank will break.

 

If caught soon enough, I mean really soon you might get away by replacing the rod bearing. This will reduce the clearance back close to normal. If nothing else you can save the rod and the crank.

 

 

Now for the good news. There's a good chance that you are mistaking excessive valve clearance for this. Valve noise is more of a loud clicking sound that a knocking sound. Here's the difference... valve clearance noise is the same volume no matter how hard you are driving it, even at idle. It will increase with engine speed but not get louder or softer.

[240zness]

Good little topic, except for some poor grammar

 

I own a z20 powered car, appreciate the info. I know d*** about the engine but seems like the short 'road' could cause the bearing to get beat up..?

[Hondanx250]

Good little topic, except for some poor grammar

 

I own a z20 powered car, appreciate the info. I know d*** about the engine but seems like the short 'road' could cause the bearing to get beat up..?

 

"Rod" I replaced it with a z20s rod.