Attempted to tune SU Carburetors but still backfiring on intake

[Stanley]

Better question would be what type of braided hose to use. You'll need to figure out how you want to set it up and carefully measure everything in advance. That filter probably uses NPT fittings, so you'll need AN to NPT adapters, and an AN Tee fitting to branch out to the 2 carbs . The AN fittings won't make your car go any better, they are for safety, for racing or just a safer road car. They are much less likely to come apart in a wreck. I used AN fittings and cloth-braided (1000 psi rated) hose for a fuel pressure gauge in the cockpit, for safety. Sure, they look nice too. You'll also need AN banjo bolts, or NPT or metric with AN adapters if you want to take it all the way to the carbs.

No personal experience, but I've read some horror stories about using cheap stainless steel braided hose, like the stuff at PEP boys. If the rubber inside is crappy it will supposedly leak gas like a sieve after a few years, especially with fuel injection, so better get good stuff that can stand up to gas, heat, and ethanol. Maybe someone can suggest a good brand. There are some newer  braided hoses made with space-age materials like teflon. Fire-rated, USCG approved fuel hoses with fuel injection type hose clamps (needed because the hoses are thicker and more rigid) are a good compromise for safety IMO, somewhere between AN braided everything and ordinary fuel lines. Not as pretty as stuff from Earl's but way cheaper. I've got some cloth-braided covers from Wirecare on a few hoses mostly for looks.

If you decide on AN cloth or steel braided, I suggest you get your hoses and fittings and take them in to a company that makes up hoses for trucking, air-conditioning, etc. They can make them up in a few minutes while you wait, instead of you trying to figure out how to do it yourself without the right tools, and they'll have tons of fittings and stuff in case you forgot anything.

I like that filter, too.

[jalexquijano]

Quote

 

Well just replaced the pump with a Brand new Airtex 8012s! At first the car was still having problems on accelaration presenting some backfire. I pull the 6 spark plugs out and clean them with a brass wire brush and electronic contact cleaner. The car still lacked power and was backfiring at the intake of the carbs. Sincé i had 3 spare Brand new NGK BP6ES spark plugs on the glove box i replaced spark plugs 4, 5, and 6 (rear carb) and power came back. I did tightened all the screws of the braided hose that go to from the balance tube  to the vac brake booster.

 

Do you think this NGK spark plugs get so fouled that even after cleaning them, they become useless and you need to replace them???

Edited February 23, 2016 by jalexquijano

[siteunseen]

You have a hose that runs from the valve cover to the brake booster?

Yes, plugs get gas fouled and are no good.  I went through 6 a week on my speed boat when I was racing it. 

[Zed Head]

On 2/23/2016 at 6:30 AM, jalexquijano said:

 The car still lacked power and was backfiring at the intake of the carbs. Sincé i had 3 spare Brand new NGK BP6ES spark plugs on the glove box i replaced spark plugs 4, 5, and 6 (rear carb) and power came back. I did tightened all the screws of the braided hose that go to from the balance tube  to the vac brake booster.

Do you think this NGK spark plugs get so fouled that even after cleaning them, they become useless and you need to replace them???

Is it still backfiring?

[jalexquijano]

no longer backfires!!! runs great over 2000 rpms. the problem is between 1000 to 2000 rpms. Slight hesitation and back and forth shaking! Do you recommend getting the following pressure regulator so i can lower to 4 psi:

http://www.thezstore.com/page/TZS/PROD/11-2985

 

 

 

[jalexquijano]

On ‎02‎/‎14‎/‎2016 at 10:34 PM, Chickenman said:

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,

First of all i wish you a happy christmas and upcoming new year. Just to let you know the car is not stalling any longer but does oscillate its rpm from 950 to 700 after getting stuck in traffic jams or at traffic lights or just letting it idle in the garage. I think it should keep steady and just oscillate from 850 to 950 rpm. I did the following mods:

1. Remove the inline heat control manifold that comes from the intake wáter line from the system and plugged the line that goes to the main thermostat housing and plugged the wáter line that goes at the back of both carbs.  now the car takes 5 to 6 mins to warm up but at least it does not stall at long idles. 

2. Install 2 heat shield extensions covering the fuel bowls on both carbs.

Do you think i should look for a Nissan 160° thermostat so i can keep the Reading under 1/2 as on traffic jams it climbs to 3/4??

Please advise.

[Namerow]

23 hours ago, jalexquijano said:

Do you think i should look for a Nissan 160° thermostat so i can keep the Reading under 1/2 as on traffic jams it climbs to 3/4??

That's what he recommended (complete with an explanation), so no need to ask him again.  Now it's your decision whether you want to follow that recommendation or not.

[jalexquijano]

still looking for a Nissan OEM 160° thermostat. No luck yet.