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 Post subject: opinions please.....
 Post Posted: Tue Mar 20, 2012 10:14 am 
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Location: Hardin ky
I had borrowed my buddies alky carb last year that was prepped by Rupert for a bigger motor but on my car it went 1.43 60ft and 6.77. I decided I liked the alky, so traded my gas carb for a fairly new alky carb. I immediately sent it to Rupert for a check over and for him to do some of his tricks, since he has done my buddies carbs. Before I sent it tho, I bolted it on and just wanted to see for comparisons sake how it felt. Well, after removing my borrowed 950 which idled great and throttle response was excellent, I cranked it with the new(er) 750 I traded for. It needed some adjustments of couse, so I did. It seemed to idle about the same, but seemed to miss a little, but i assumed it was just the characteristic of that particular carb. If you reved it up, it seemed ok, but the idle was funny. Just to be sure, I pulled it off and sent it to Rupert. well, he done some things and fixed a warped base plate, put new floats in, and wa la....good as new. got it back about Feb. I just freshened trans and bolted carb back on, seemed to sound the same basically. Drove it down the road, seemed like all is well. Loaded up, went to Holly springs this weekend. Now mind you, the best last year was 6.779 the last race of the year. I did add a cage, so figure roughly 100 lbs over what it was. Off the trailer the car went 7.01 w/ mph of 96. Last years mph was 98-99. 60 ft last year was 1.43 I had a 1.48 on this pass. Car sounded like a tractor staging up. Missing bad till you reached about 3000 rpm's. Came back, looked it over and thought i would try it again, since i had run gas in the system, figured it may have had some left in it. Went back out, 1.47 60ft @7.002. Missing. look it over in pits, remove plugs, look ok, but hard to say with alky. was gonna swap on gas carb, but no time. They call us up for 1st round. I dial it 7.01 and hope for the best. I get a .530 light to her .570, look over my shoulder and romp on it 3 times......6.93 comes on board WTF??????????? lost 5 mph. So, I come back for 2nd entry, dial it 6.93 get a .510 light to Murphy's .503, I nose over on the end and run 6.96 on a 93....all this time its sounding like a tractor. You can pretty much remove all the corner plug wires and it runs the same. Missing on 1,4,5 and 8. I come home and as advised by Rupert I install new plugs, cause he says alky doesnt like running after gas and wont clean the plugs off, makes sense and he knows more than I do, I swap plugs. Plugs were gapped as used for Gas(mistake maybe) .040. Now i have talked to Rbr and he says .027 gap, maybe its putting the spark out with the ammount of fuel its putting in???? I put a gas carb on and it runs great!!!!! I am not knocking Rupert at all, I commend a guy that can build you a carb to run good and never see your car. And maybe some of you can tell me something I have overlooked. It ran fine with my buddies 950, and fine with a gas carb. I havent been able to try the 950 at this moment tho to see if it runs the same as mine back to back, I only did it before I sent mine off. I know they say alky will find a weak link in your ignition system, but theonly way i could see the difference in the 950 and my carb is if mine is way richer at idle and putting the spark out, possibly due to the gap???? I am at a loss here and dont want to waste another trip to the track only to make a couple of passes to come home. Holly springs is a long haul from My house for 4 runs. LOL Any ideas, I am open. Hey Randy, I know you and others will have some info


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 Post subject: Re: opinions please.....
 Post Posted: Tue Mar 20, 2012 11:25 am 
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Location: Elizabethtown, KY
The only real difference between last run and first run this year was the weather. The air really sucked this weekend. We went from 6.79 to 6.98 in 1 week. As far as a tractor sound I'm clueless. But the air was a big change.

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 Post subject: Re: opinions please.....
 Post Posted: Tue Mar 20, 2012 2:03 pm 
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So the way I understand it is this. You had a gas carb on this car and it ran fine last year. You borrowed a 950 methanol carb and it ran fine on that also. You bought a 750 methanol carb, had it worked and it won't run for squat? You put the 950 methanol carb back on this year and it runs fine?

All this tells me that your 750 carb is horked up some how. Maybe something got over looked? You could "map" your carb and the 950 and most of the measurements should be "close" except for the main circuit and or the main air bleeds.

The IJ (idle jet) and IAB (idle air bleeds) should be close to the same on both 4150 style carbs.

What is your down track fuel pressure and is this a belt drive pump setup? :-k

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 Post subject: Re: opinions please.....
 Post Posted: Tue Mar 20, 2012 2:38 pm 
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I thought I posted this, but guess not. I have a electric pump, holley Hp150 running 8 psi down track. I havent bolted the 950 back on YET. I gotta get my hands on it. I am going to try it though.


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 Post subject: Re: opinions please.....
 Post Posted: Wed Mar 21, 2012 1:16 pm 
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OK so you did put your gas carb back on and the engine sounded "normal" then? You didn't run it at the track on gas though, did you?

FYI, it's damn near impossible to foul a plug on methanol to a point where it won't fire unless you got a bunch of oil going through it. I've been running methanol for a long time and never done that. I do change plug type between gas and methanol though. I run an NGK -10 on gas and an AR3932 on methanol and I DO NOT run plugs on methanol that have been run with gas. Both are gapped at .020 but I'm up at 15.2 to 1 compression. In fact, the metal deposits in the combustion chamber are not real good with either ethanol or methanol. I've always run a few gallons of methanol through the engine here in the shop if it's been run on gas to try to wash out those deposits.

One of the first things that came to mind was that the Ignition was damaged from welding but if it runs OK on gas, then that can't be it.

Dunno Bill, I'd try that other methanol carb to see if it's just a problem with your carb.

ALSO: Map both of those methanol carbs when you get the 950 back. The idle/low speed stuff should be close to the same between the two but the 950 should have larger jets and perhaps a different MAB.

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 Post subject: Re: opinions please.....
 Post Posted: Wed Mar 21, 2012 1:53 pm 
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Joined: Mon Mar 19, 2012 10:48 am
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Location: Hardin ky
Havent ran it at the track yet, but I may.....not sure. But it does seem STRONG with the gas carb on it. It "feels" like it will equal the times on the alky carb, but I know I cant go by that till I get a slip. I will have the 950 tonight, dont know if i will get to try it out or not. I will let you know what I find out.


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 Post subject: Re: opinions please.....
 Post Posted: Fri Mar 23, 2012 9:30 pm 
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Well, havent ran it at track, but bolted 950 on and my wife noticed the difference, so it must be lots better. Will tray it at the track tomm and see. I will keep you posted.


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 Post subject: Re: opinions please.....
 Post Posted: Sun Mar 25, 2012 10:11 pm 
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Just back from the track. After going out 6th round with borrowed carb, it went a 6.82 bolted my carb on and went 6.90. I would be willing to bet it wouldnt do that consistently either.


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 Post subject: Re: opinions please.....
 Post Posted: Sun Mar 25, 2012 10:21 pm 
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fast92stang wrote:
Just back from the track. After going out 6th round with borrowed carb, it went a 6.82 bolted my carb on and went 6.90. I would be willing to bet it wouldnt do that consistently either.


So the 750 was .08 slower than the 950 then. That is 200 cfm less. Can't be a whole lot wrong with it IMHO. Maybe just needs some tweaking.

Map that 950 before you give it back to the owner then do yours to see what the difference is. :-k

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 Post subject: Re: opinions please.....
 Post Posted: Mon Mar 26, 2012 8:59 am 
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Actually the 950 is only 70-80 CFM different, same venturi as the 750, bigger throttle blade. And you need to make at least jet changes to find what your engine wants.


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 Post subject: Re: opinions please.....
 Post Posted: Tue Mar 27, 2012 9:50 am 
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Location: Hardin ky
Yes, as Ken said, it was only .o8, but the key here was consistency. The way it seems as my carb is just really rich at idle and was washing the cylinders down and milking oil. When I put it on the other day, the temp was already at about 150, so it was warm and carb seemed to sound way better. It seems like if you use my crab for warm ups, the cylinders get washed down and it just never recovers??? I dont know if that makes sense or not. The main thing is the consistency issue. I did run 1 6.82, but Thats because i hooked really well. My other runs were all in the 6.86-6.87 range, but I was lifting losing around 4mph on the end. Last time to the track, mine ran 7.01, 7.00, 6.93 and 6.96.Cant win any races like that. But I see what youre saying Jmark. We are trying to contact Rupert now and see what he recommends.


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 Post subject: Re: opinions please.....
 Post Posted: Tue Mar 27, 2012 10:43 am 
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If it's rich at part throttle then that can be fixed with some tuning. Did you MAP both carbs yet? You need to post that info so we can see what we're dealing with. I've got a feeling that both carbs will need about the same IFR, IAB so if the 950 works better than the 750, that may be a way to fix it without sending it back to Rupert.

I wasn't aware that the 750 and 950 carbs shared the same venturi size so they "might" need somewhere near the same stuff all around.

And always remember this, YOUR carb will never be any better than your ability to tune it!! A guy 300 miles away talking to you on the phone CANNOT know exactly what YOUR engine wants. Some get lucky and get it right, others not so much!

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 Post subject: Re: opinions please.....
 Post Posted: Tue Mar 27, 2012 11:49 am 
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well, I have to find out what mine has in it, and the other one. My jets "say" 148, but Rupert drills them i think the 950 has around a 168-170, but dont know, only going by what i was told....Thats the bad part, i have no jets. Guess i will have to buy some. It was my understanding that it would come back pretty well right for my engine, but I do understand that is hard to do. I really wish I kept my gas carb I guess. My ability to tune gas carbs is ok, but I been working with them for years. Alky is very new to me, and I never have time for test and tunes, so its time trials for me. The closest track is 2 hours away, so you hate to chance it.


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 Post subject: Re: opinions please.....
 Post Posted: Tue Mar 27, 2012 1:25 pm 
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Bill you remind me of myself, ie, up until a few years ago I was basically a jet changer. Then I met up with Maley on ST and well, the rest is history. Now there's guys here on this board that can help you learn what you need to know. Jmarkaudio, Nomad, Shrinker, Scott Smith and a few others that come to mind are usually willing and able to steer you in the right direction on most any carb problem you might encounter.

Not that I'm the sharpest knife in the drawer mind you, but along the way I did come to realize that carb tuning is a necessary evil if you want to have a solution for problems you may encounter. It's not rocket science but it does require some attention to detail and a willingness to learn and put time into it.

On that 950, pull a metering block off it and check the Idle Jet (IJ), aka, Idle Fuel Restriction (IFR) and also the E hole diameters and locations.

I'm going to assume it has no Power Valve (PV) but if it does, then check the Power Valve Channel Restriction (PVCR) also.

Note what the Idle Air Bleed (IAB) size is too along with the Main Air Bleed (MAB).

I've got the info on my dual 750s here somewhere and I'll see if I can find that to see how it correlates with what you have there on those two carbs.

FYI, my 750s have .156 jets square in'em on a dual setup. I have run as much as .166 MJ in'em.

My favorite track to test at is Piedmont Dragway which is a 260 mile round trip! ;-)

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Necessity is the plea for every infringement of human freedom. It is the argument of tyrants; it is the creed of slaves.

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 Post subject: Re: opinions please.....
 Post Posted: Sat Mar 31, 2012 11:20 am 
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Joined: Mon Mar 19, 2012 10:48 am
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Location: Hardin ky
I cant do much testing due to work schedule, need to unload at track and be consistent. Any one have a idea how much Ken Jones charges to fix a carb?


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