Attempted to tune SU Carburetors but still backfiring on intake

[Patcon]

92 degrees, not that hot and cars don' really feel humidity like we do. These cars sometimes don't cool well but that would be in 100+ heat. You have an ignition problem, a lean condition or insufficient cooling. You shouldn't overheat at those temperatures

[old guy]

I have not read every thing in this topic. But - are you still using ATF in the pots? I have a 72 bought in 2010

played w/it for years. Got serious and found mine would backfire cause I used too light of an oil in dash pots.

I'm now running 20w or 20/50. Lite oil allows the pots to rise too fast and/or too high. Too much air too little suction = backfire.

In one of these forums I found a drawing on how to set float height. Set mine and car runs great.

(Turn seat down 10 turns and get gas to just appear at top of seat).

[Stanley]

With fan shroud, aluminum radiator, new water pump and fan clutch, it shouldn't be overheating, at least due to problems with the cooling system. Are you getting a good flow of coolant through the radiator? It's easy to check.

Remove radiator cap and let the car idle. The thermostat should open at 160F to 180F. After it opens you should see a strong flow of water. If not, test the thermostat. Nissan thermostat is best. If the thermostat is OK, might need to flush the engine. Are you losing coolant? Do you have a coolant recovery system?

[jalexquijano]

With fan shroud, aluminum radiator, new water pump and fan clutch, it shouldn't be overheating, at least due to problems with the cooling system. Are you getting a good flow of coolant through the radiator? It's easy to check.

Remove radiator cap and let the car idle. The thermostat should open at 160F to 180F. After it opens you should see a strong flow of water. If not, test the thermostat. Nissan thermostat is best. If the thermostat is OK, might need to flush the engine. Are you losing coolant? Do you have a coolant recovery system?

i will tell him to check. I have a 3.0 0hm pertronix coil connected to a 1761 Petronix module. Ballast resistor is being bypassed. I dont think the coil is bad!  I will need to check the radiator coolant. How many degrees for the Nissan Thermostat? 160?

[jalexquijano]

92 degrees, not that hot and cars don' really feel humidity like we do. These cars sometimes don't cool well but that would be in 100+ heat. You have an ignition problem, a lean condition or insufficient cooling. You shouldn't overheat at those temperatures

Patcon,

 

Found this video and will follow his advice. No more spending money in wáter pumps or coils or whatsoever! This guy describes exactly my problem even though i differ from him regarding the fans. I want to keep the stock fan and the fan shroud.

 

https://www.youtube.com/watch?v=F6wGuYBiRLw

[Chickenman]

I'll give you a hand clap because you're finally on the right track. I was trying to lead you in that direction, but finally gave up out of frustration. Maybe it's for the best, as now you're finally starting to do some research and look for answers yourself, instead of being spoon fed everything and then spitting it back out!! Sometimes ya gotta throw a person in the deep end and let them sink or swim for themselves.

You made a very revealing post in one of your many threads ( months ago )  , that your car didn't stumble and die in the shade. That is a direct indication of fuel peculation and your first big clue as to what the real problem was...

The larger heat shield is an excellent idea, and the smart racers up here run full heat shield that actually follow the contours of the inner fender well to seal off any heat getting to the float bowls and carbs. Make it out of stainless steel sheet ( not aluminium ) SS tends to reflect heat not absorb it . If you really want to do a good job, make it a double layer of SS sheet with a sandwich of heat isolating matting between. If you really want to go Big School, use some Gold colored reflective foil on the sheet facing the exhasut manifold.

You could also take the exhaust manifold  off and have it Ceramic coated on the outside. That dramatically reduces the amount of heat that the exhaust manifold radiates. Ceramic coated headers would do the same thing. Even just sand blasting your exhasut manifold and painting it with WHITE or SILVER VHT Ceramic paint would work quite well.

The fuel hose re-routing will also definitely help, reroute the fuel hose/tubing  around the back of the firewall and cover it in Fire sleeve.

Oh yeah... and run a 160F thermostat for your climate. Not a 170F or 180F.  A 160F Thermostat will give you some extra over head in Traffic when the heat starts to climb in the engine compartment. Losing 10 degrees here and 5 degrees there all adds up. You just have to get below that tipping point.

Here are some links to Heat reflective matting, foils and heat sleeves that you should consider:

https://www.wirecare.com/braided-sleeving.asp#extreme-temperature

https://www.wirecare.com/products.asp?prodline=grf

 

Design Engineering Inc is a manufacturer of heat reflective materials for all forms of Motorsport. They have many products that you can utilize to eliminate your peculation problem.

http://www.designengineering.com/catalog/design-engineering-inc

Check out their heat and sound reflecting materials.

http://www.designengineering.com/catalog/design-engineering-inc/heat-sound-barrier

 

Make up some proper Custom heat shields, Ceramic coat the exhaust manifold ( Hell even just sand blast it and paint it with White VHT Paint ) , Re-route and insulate the fuel lines and run a 160F thermostat. By the time you get all this done, I'm willing to bet  you won't even need the electric fans.

 

 

 

 

 

[Chickenman]

Study these designs to give you some ideas on heat shields:

Edited February 15, 2016 by Chickenman

[grannyknot]

Chickenman, that looks like my old 84 yamaha FJ1100 only my carbs weren't that pretty.

[Chickenman]

Yeah.. it looks like a pretty sweet setup. carbon Fiber heat shield as well.

 

 

[Chickenman]

George : Get rid of that glass inline fuel filter ( Mr Gasket? ) They are terribly restrictive. There is a thread on these horrible things elsewhere.

They cause a big pressure drop and that can actually cause Vapor lock in hot weather. They act like an AC orifice valve.

Go back to the stock Nissan filter or put in a REAL high performance fuel filter. I've used a Fram HPG-1 on many race and street cars: You can run some Neoprene fuel lines from the HPG-1 and get rid of the steel tubing. That is one of the solutions covered. Or you could even put in proper AN style braided hose. That would be my choice. Summit ot Jeg's would be my vendor of choice for AN fittings. .

http://www.summitracing.com/int/parts/frm-hpg1/overview/

 

[jalexquijano]

Chickenman,

Thanks for all the wonderfull pieces of advice. My car was running nice the other day but i had to leave it at the shop for master cylinder and brake booster swap. Anyway, i just picked it up and driving it home the car he car had lost power and was backfiring at the intake. Mechanic said he did not touch the fuel mixture in any of the carbs as it had nothing to do with the brake system. I guess he could have left the airtex 8012s electric pump running at accesory. Even though the fuel filter is full as shown could the electric pump have damaged?

http://www.summitracing.com/int/parts/atx-e8012s/overview/

Are these pumps so frágile that if you leave them on for more than 30 seconds without turning the engine on they could damage immediately?? this will be the third pump i buy. This one lasted 6 months.

Do you recommend buying the same pump again and additional plastic fuel filter ro place besides the pump near the gas tank?

 

[jalexquijano]

On ‎2016‎-‎02‎-‎16 at 4:20 AM, Chickenman said:

George : Get rid of that glass inline fuel filter ( Mr Gasket? ) They are terribly restrictive. There is a thread on these horrible things elsewhere.

They cause a big pressure drop and that can actually cause Vapor lock in hot weather. They act like an AC orifice valve.

Go back to the stock Nissan filter or put in a REAL high performance fuel filter. I've used a Fram HPG-1 on many race and street cars: You can run some Neoprene fuel lines from the HPG-1 and get rid of the steel tubing. That is one of the solutions covered. Or you could even put in proper AN style braided hose. That would be my choice. Summit ot Jeg's would be my vendor of choice for AN fittings. .

http://www.summitracing.com/int/parts/frm-hpg1/overview/

 

okay i like this filter. Regarding the fuel lines, i would like to see potos of the the AN style braided hose. Can you provide some and how much feet of the braided hose shall i buy?