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Discussion Starter · #1 ·
Hello. Does anybody in this forum have a clue about what the problem with my tripower engine is??

The engine, 390 C6ME block has been bored .30over, had crank checked and polished, new pistons installed.
The heads has had new stainless steel 428 valves installed along with comp. cams springs and a lunati camshaft, 270 H, to give it a bit of "Character".
The intake is a ford tripower manifold with 3 2BB Holleys, the exhaust is double 3"" with cast iron shorty hedders, the dizzy is mallory dual point with mechanical advance ( wich shortly will have a pertronix modified and installed.)

The damn thing backfires, and i have tried everything imaginable, compression test, another advance curve, another distributor, running high ignition, running low ignition, turning the mixing screws up and down, it still backfires through the carb, and only through the rear carb.

The symptoms are as follows, it starts right up, when you hit the gas it hesitates, fires through the carb, it has trouble reving over 3000 rpm.

Any ideas?? or will i have to replace the tripower with something more less "exotic"?? I have read somewhere that these tripower setups were notorious and known for backfiring, and many had their setups replaced on the factory warrenty, and if this is the case, i would gladly be without the hassle.

Thankyou

The dane.
 

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make sure floats are properly adjusted, Float bowl not cracked, carb bolts to manifold are tight & gasket is good, Jets are cleaned & same jets in all carbs, All carbs properly adjusted,replace power valve it's probably shot by backfires. You can't just go turning screws up & down. Have a fire extinguisher handy when adjusting float bowl level. soak all carb gaskets in trans fluid overnight..Makes them reusable...
 

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I'm not very familiar with the Ford set up but I've tuned a few multi-carb engines.

The most common cause of a hesitation (hence a back fire) is not having an adequate accelerator pump shot. Look down the carb throats at the amount of fuel delivered by the accelerator pump(s), with the engine off of course.
A vacuum gauge is your friend when tuning the carbs.

Post a couple pictures of your set up.
 

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Discussion Starter · #4 ·
I Have fire equipment in car and beside me at all times . A must when you are tinkering with an engine, but thankyou for pointing that out.

btw I usually adjust floater hight using a ketchup bottle attached to the feeding hose. makes adjustment easier and you are not bended over a rotating fan.

I´ll try changing the power valve.

Thankyou.
 

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What about the timing chain being off a tooth or the cam is designed to be run with 4 degrees advance at the timing chain.Basically did it do this with a different intake set up ?
 

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With a backfire through carb I would normally suspect a timing problem first. Just as phantom pointed out.. But if it's just 1 carb on a six pack & the same carb every time. I would suspect the carb... Just my train of thought.. The size jets you should use are the ones that will get you the best performance..You're going to have to try different ones. WE used to change our jets regularly depending on whether we were racing or street driving. Many people will change their jets as the weather changes during the course of a series..I used to most definitely down jet when I had to go do emission tests..

p.s you might want to considering purchasing the clear float bowl plugs. They permit you to adjust the float without removing the plug... Also the constant trial & error of trying different jets & power valve is the reason I suggested soaking gaskets in tranny fluid..
 

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Discussion Starter · #8 ·
Well, here are the verdict from the danish referee regarding tripower setups.!

Allthough this tripower setup are a cool item, i have decided that it´s too much hassle, so i am going to find a 4bb intake for it in stead and purchase a new edelbrock to put on the top.

I am sure that it will have plenty of power anyway.

The tripowerthing can stand in my livingroom beside the 2x4 offenhauser setup already there.

Thanks for the help, I´ll be back.
 

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If you switch to a 4 barrel on that setup, I think you want to have at least a 750 carb on it. I had a 360 FE in my old 68 F100 and even on a stock engine, the 650 Edelbrock I put on almost wasn't enough for some reason. I had to jet it pretty fat to get it to run correctly.
 

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Holly's are easy to fix & extremely reliable.. But if you want a balls out carb. Go with a chokechester(rochester). They're a very touchy carb.. Have to be tuned perfectly... But when they're running correctly. They out perform any holly or edelbrock of the same cfm...

http://www.carcraft.com/howto/57178/index.html
 

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Did anyone ever try to balance the carbs with a manometer.And how is the linkage hooked up,progresive or balls to the wall?I snapped my crank in half on my Porsche with one big backfire because the carbs wern't balanced correctly.
 

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Nice intake. I have a freshly rebuilt 750 Holley I'm selling with quick spring change kit the dual feed line. It's ready to bolt right on and go. I just replaced it with a 625 Demon. 750 was to large for me. It has #60 jets in it now which got be great full throttle performance but no good for daily driving. I'd use #70-75 jets for your 390. I'm asking $200 obo for a $350 setup.
 

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I have that same intake on my 390. It looks good and the idle is nice. I did the math on my 390 build and came up with a max air flow at 5500 RPM of 549CFM so I put a 600 on it. Runs nice and the plugs are a good colour. It's not going to hit the drag strip so 5500 won't be seen all that often either. I thought about a tri power set up for it but it was way over carbed. Too much fuel and air is as bad as too little.
 

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Discussion Starter · #16 ·
Tripower!

It turns out that one of the carbs on my tripower setup is an ordinary 2 barrel carb that has been cut off to fit the air cleaner, and i suspect that the jets are a different size then the other two carbs, wich makes the adjustment almost impossible, it´s the one carb that backfires, so it could very well be the problem.

But i have now put the edelbrock manifold on the engine with a holley 650, wich gave me the chanse to check lifters and camshaft/valvetrain wich vere fine, allways nice to exclude problems.

And it fired right up and ran with good throttle response, so i´ll stick with that for this summer.

The plan is to pull the engine from my 66 galaxie cab, wich is a bit low on oil pressure put a rebuild stock 390 in it and then build a 428 on the cab´s engine, if i can find the pistons and a crank. (C6ME block) and then see is the tripower will work with new jets and some more tinkering, i have a comp cams 280S camshaft on the shelf,along with aluminium edelbrock heads with roller rockers, so that should stirr things up.

The damn thing is that i`ll then need one more car to put the tripower engine in, this hobby never seem to have an end, more parts, more cars, "LOL"
 
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