pre heater hose question

[DotSoon]

did some searching and havent found any info.... got my 720 with the z22 and noticed it doesnt have the pre heater hose from the exhaust manifold to the air cleaner.... what sort of problems would this make by not having the pre heater hose?  been a very long time since ive had a carb'd engine....

 

any input is greater appreciated

 

thank you

[darrel]

Summer time, none.

 

Winter, brings warm air up to the air cleaner, helps keep the carb from icing up provided the valves in the air cleaner are working properly.

[DotSoon]

Summer time, none.

 

Winter, brings warm air up to the air cleaner, helps keep the carb from icing up provided the valves in the air cleaner are working properly.

makes sense... still a bit chilly here in the mornings and it seems to take awhile for the little truck to warm up and behave.  guess ill get ahold of one and see if that helps.

 

thanks

[datzenmike]

For carb icing you need below 35F and very damp air. (freezing rain or cold and fog is perfect) Evaporating fuel absorbs heat from the air and will drop the carb to well below freezing. Moisture in the air will collect on the venturi as frost. It builds up and prevent gas from being sucked out. Your gas foot slowly goes down to the floor to keep up speed and then it slows down and stops.

 

At all other times the temp sensors keep the intake air mixed and at about 90 F. Then the air temp is consistently the same, the motor can be tuned for it and will run more reliably.

[LenRobertson]

The last time I iced up a carb was my L20b 200SX with stock Hitachi and air cleaner, but missing the hot air tube from the exhaust manifold. Conditions were about what datzenmike describes - just above 32F and a really wet snow falling. Engine ran increasingly worse until it quit completely. Fortunately, the heat from the engine melts the ice after a few minutes, and you can restart and drive a very few miles until the carb ices up again. It is a long, slow trip home. So the hot air tube is very important when Fall comes around, at least in cooler climates.

 

I've always wondered how a Weber carb with the open rectangular air filter gets along in carb icing conditions. I suspect they ice up just like a Hitachi. Someone recently posted the idea of running a tube up from the exhaust manifold and pointing it at the Weber air filter. That might work, but I have a feeling more hot air is needed than that to prevent icing. If I ever install a Weber, I intend to do the modification to the stock air cleaner to fit it onto the Weber, just to get the maximum hot air supply into the carb. Somewhere here on Ratsun within the last few months was a write-up on hacking the stock air cleaner onto a Weber. Maybe in the How To category.

 

Len

[datzenmike]

Good thinking Len.

[Sealik]

 

I've always wondered how a Weber carb with the open rectangular air filter gets along in carb icing conditions. I suspect they ice up just like a Hitachi. Someone recently posted the idea of running a tube up from the exhaust manifold and pointing it at the Weber air filter. That might work, but I have a feeling more hot air is needed than that to prevent icing. If I ever install a Weber, I intend to do the modification to the stock air cleaner to fit it onto the Weber, just to get the maximum hot air supply into the carb. Somewhere here on Ratsun within the last few months was a write-up on hacking the stock air cleaner onto a Weber. Maybe in the How To category.

 

Len

 

No difference between the Weber and Hitachi in this locale with some very cold temps.

That said...moisture is somewhat MIA...<.... icing is not of issue.

 

Running a 'winter' thermostat to keep under hood temps up ....should compensate.

 

 

[LenRobertson]

I found the How To I was remembering: http://community.ratsun.net/topic/10977-stock-air-cleaner-to-weber-mod/

 

Sealik - The pics you posted in that thread aren't showing up. Any chance you can re-post them somewhere so they will magically appear?

 

So far my recently rebuilt Hitachi is working pretty well, so I'll keep running it and stock air cleaner. But I've got a  dead 32/36 Weber and a carb kit sitting around here somewhere. I feel like I need to rebuild it and stick it on a Datsun,  just to see if running a Weber is a life changing experience. I kinda doubt it, but how do I know until I try it?

 

Len

[DotSoon]

seems like when i get off from working a night shift the temp guage isnt constant.  it stays really low but in the day time it seems to stay around 1/4 way warm.... if that makes sense.  would a bad t-stat make a bad reading?  guess it could be the temp sending unit or what not.   the heater warms up though so i dont know....

[datzenmike]

Well it's cooler at night but the job of the thermostat is to keep the engine at the same temp if you are -30 or 90F. I would change the thermostat for a new 180 or 185. The motor was designed to run best in this range. My Datsuns run about 1/3 of the way up in the 'run range'.

 

And spend $10 on one, don't cheap out or you'll have a $3 problem.

[DotSoon]

Well it's cooler at night but the job of the thermostat is to keep the engine at the same temp if you are -30 or 90F. I would change the thermostat for a new 180 or 185. The motor was designed to run best in this range. My Datsuns run about 1/3 of the way up in the 'run range'.

 

And spend $10 on one, don't cheap out or you'll have a $3 problem.

ok will do... ill get a pre heater hose and a new t stat. see if she wont behave better when its cooler out.

 

thank you.