quote:

Originally posted by Robbie Welch:
Well I made it to the track Finialy and I'm having trouble getting down the track. What spark plug heat range should I be running with alcohol? My combo SBF 427 Brodix track1 heads 13-1 compression. Thanks for your help

Can you give us a little more information than just "having trouble getting it down the track?"

Is the car spinning, bogging, missing, laying over on top end or what?

I've been to the track twice the first time I didn't have any parts to try (Jets, booster pump Nozzle's etc.)Here's the carb, its a Braswell 850 it had 158pri and 160 sec jets with pri & sec 6.5 power valves and 47booster pump nozzles. The only thing I did was put jet extensions and float with cut out's for them on it(the carb came off a 434ci dirt car)and ran good on the dirt car. The first time down the track the car had a slight hesitation going on the chip but left ok and ran thru low gear ok. After the 2nd gear shift about midway through the RPM range it started missing badly (like it was possibly lean). Not having and jets I was pretty much done. Before I ran again I found a couple problems and corrected them (the jet extensions where not drilled out big enough for alcohol (they where.145 so I drilled them to.180) the other problem was the breather hold down bolt hole was drilled through the base plate and I didn't have it blocked off (vacuum leak).With those problems corrected I also changed the BP nozzle from a 47 a 45 and tried it again. Same problem. So now I started changing jets I put 170 square in it and a 40 BP nozzle (remember I'm fighting 2 different problems) Same thing so the last thing I could try (we got rained out)was I pulled the power valves and left the 170 jets and 40 BP nozzle. Going on the chip was much worst and down the tract was the same. But 1 thing of note the car had it best 60ft on alcohol 1.281? All the problems are in 2nd and high gear mid range RPMs somewhere around 6000 but when its missing if I back of the gas and just ease back in to it run's good? I'm leaning towards wrong plugs or wrong plug gap (I run .032 gap) because every thing I've tried with the carb really hasn't made a difference down track. I do think I need to go the other way on the BP nozzle because less made it worst. Sorry for the long post

You have too many unknowns going on here. I have run electric pump alky systems but I wont ever have another one. Everything has to be just right . Your fuel system is suspect until it proves otherwise. You dont know if the carb is right either. I bought a brand new custom carb from a big name (three letters) and battled that thing for two seasons before I went to Nickerson and he straightened it out. I would suggest try to borrow a known good carb to try with your fuel system or maybe ask someone with a beltdrive setup to try your carb. The thing about alky is it will go down the track somewhat even when its not right. If you want to home brew a fuel system you need to at least know the carb will run if supplied with fuel. Good luck.

your idle circuit is lean
youhave a delivery issue ie pump,hose needle&seat,float level ect

quote:

Originally posted by rusty:
your idle circuit is lean
youhave a delivery issue ie pump,hose needle&seat,float level ect

What Rusty said...

I'll add if you are not running a -9 NGK you should be. I've killed a butt load of -7's after going to methanol.. Like you sounded like it was missing. Also, if car lays over in high, lean or fuel delivery issue..

Dave

I'm running NGK -8s gaped at.032. The plugs I took out showed signs of detonation (I think the last run with the power valves out may of been on the lean side?) I'm going to tighten up the plug gap to .025 on new plugs. On the carb I'm going back with the power valves and up to .180 jets with the 47BP nozzles and adjust the idle screws out a turn from 1 1/2 to 2 1/2. Things I've checked I checked the spark with a spark checker it looked great jumping well over a 1/2. I checked fuel flow through the fuel bowls PRI and SEC both looked good and fuel press never moved from set even with full flow of either bowl. As suggested it may come down to borrowing a known good carb to eliminate the fuel system we'll see. Thanks for the suggestions and help

What do you have your ignition timing set at?

quote:

Originally posted by rusty:
your idle circuit is lean
youhave a delivery issue ie pump,hose needle&seat,float level ect

BINGO.

A few things.
Lean jetting usually doesn't make it pop, just slow down and gain more water temp. I've jetted my personal engine so lean on the dyno that it lost 50hp, no pop, sounded normal, and nothing hurt. Extremely rich can make it miss and pop.

When you plugged the PV's, you may have needed to go up as much as 20 jet sizes, depending on the size of the PV channel.

I have run, and seen -8 NGKs work with methanol in many different combinations without issue. I would suggest closing the gaps to .025" for what you are seeing, trying -9's won't hurt anything.

If fuel delivery were the problem, my experience is that it will just lay over in high gear as Dave Covey said, not miss or pop.

Call Braswell, they are great people and will be able to help you with jetting the carb.

My $.02

Chris I have it set at 35degs. A friend that's run alcohol for ever said 31degs is what he run's. He slowed down with more timing? I don't think that's my problem with the missing. 1stGen and everyone thanks for the info we're running this weekend and I have a known good carb to use. Hopefully I'll get this figured out this weekend. Thanks

I believe you have a fuel supply issue. Runs good until float bowls get low. Plus I would not have removed the powervalve from the front in fact unless your car is running faster than say 6.50 in the 1/8 I would not remove it from the back. The only reason you would remove the rear one is because it uncovers under hard acceleration but the front one never uncovers no matter how hard you launch.
Same with the rear jet extensions. If you put them on make sure you still have full float travel or the float bowl will not fill up fast enough creating a fuel supply issue. Only reason you need jet extensions is if it launches hard enough to uncover rear jets.

If it was me I would put the carb back exactly how you got it and work on the supply issue then start changing things if you need to.
Why do I think it is fuel supply? You said it ran good off line, through first gear and mid way through second. That tells me the motor is using fuel faster than your system can fill it. Fattening up carb then just empties it faster. Fix the fuel supply first.

quote:

Originally posted by bugs2653:
Go to BLP racing Products and read on fuel pumps and Alcohol , What Rusty said your stuff not gonna work. BLP makes a belt drive pump the requires no by pass one line in one line out simple . Been using it for more years than I can remember.

Your pump has the bypass (regulator) built into it.

When you don't have enough pump>

Years ago a fellow had one of those 3 block long cars, an all steel Charger with a decent single 4, gasoline engine. 10 second car.
It would launch wheels up and then fall on it's face. He had already gone through all the usual diagnostic steps.
We got to talking about it and I asked what fuel pump he had. He had 2 Holley blues at the rear. Mathematically it was enough to do the job....but it did not. Actually math wise, 1 pump would have done it.

I had seen the car launch so I convinced him to move one of the pumps half way to the front. Did that in the pits. End of problem.

The next year when he had a even stronger engine he put a small cell up front that was fed from the rear. Same concept many injected racers use.

Moral of story.
You have to let mother nature do as much of the work as possible. Gravity and g forces are not your friends.

quote:

Originally posted by Rawe Power:

quote:

Originally posted by rusty:
your idle circuit is lean
youhave a delivery issue ie pump,hose needle&seat,float level ect

BINGO.

Agreed. Circle track carburetor's typically don't do well on drag car applications. That's been my experience with them, anyway.