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Author
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Topic: Bogging off the line??
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steve'66
Gearhead Posts: 9533
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 02-09-2002 08:49 PM
   
Well we got six T&T runs on the '66 today. All were 12.40-12.46 w/1.83-1.87 60'ers. Great traction, but the car would hook, bogg then go again. It's a 750 vac Holley w/ext rear jets, lightest yellow spring launching off the two step and t-brake at 2500, 3000, and 3600 rpm. The convertor stalls at 4100 with this 351w. The trap speeds were 108.0 to 108.9 all day. The 1/8 mile times ranged from 7.82 to 7.88. The front and rear bowls are both adjusted high and there wasn't a puff of smoke during the bogg. What do you think? The timing is all in by 3600, I'm going to lock out the timing next to see if it has any effect. Could it be the vacumm secondaries? Could they be shuting down then opening again? Thanks for your thoughts,SteveW p.s. Those were all record times for the car compared to the manual trannys, I just know it has .3 seconds left in her if we can get the bogg out and pull some decent 60'ers. 
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kid vishus
Gearhead Posts: 6590
From: middle of NC
Registered: Oct 2000
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posted 02-09-2002 09:06 PM
Did the bog get worse the harder you launched or did it stay pretty much the same? I'm wondering if maybe with the floats set on the high side if gas wasnt spilling out of the front vent tube down into the body of the carb. I always used to have a piece of hose from the front vent to the rear with a hole in the top of it to allow them to "breathe" properly.  I had a vac secondary 850 that acted the same way when used with my brake. I never did figure it out. I ended up selling it and buying a mechanical secondary carb. [This message has been edited by kid vishus (edited 02-09-2002).]
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Rustang
Gearhead Posts: 821
From: Clarion PA
Registered: Nov 2000
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posted 02-09-2002 09:29 PM
I ran a 750 vacuum secondary on my windsor and it ran deep 11's. It was even the type that had the secondary metering block with no jets! I ran the lightest secondary spring, and I think i ran either a 35 or 37 pump shooter with the stock cam. One thing I did do was stack washers under the pump lever so it forced the fuel thru the accel pump quicker. Messing with the accel pump and shooters was instrumental in getting my car to leave!------------------
'68 mustang 351 clevor- 10.92@124
'67 Stang, 351W -11.18@118
'69 351C Torino-14.90@100
'78 Pickup 351W-15.56@88
'79 Pickup 460 ET=??
http://www.rustang-racing.cityslide.com/contents/contents.cfm/712231
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kid vishus
Gearhead Posts: 6590
From: middle of NC
Registered: Oct 2000
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posted 02-09-2002 09:46 PM
It wasnt that mine wouldnt leave with the vacuum carb, it would leave, move about 15 feet, then nose over real hard. Then it would come out of it and pull hard the rest of the way down the track. I tried everything I could think of at that time, (which wasnt much since I was pretty new to the whole racing/tuning game). I never did get it to act right. So I sold it.
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Butch Jennings
Gearhead Posts: 633
From: No. California
Registered: Apr 2000
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posted 02-09-2002 09:48 PM
I think I would suspect the vacuum secondaries are the trouble, I personally would ditch it for an 830 annular since you'll be going to a 408 soon. I've built many 355 Chebbies and run the 830 on them with spectacular results, the 408 will be very happy with it.------------------
Butch
460 powered 1967 Comet Cyclone
10.271 @ 130.069
Butcher's Home Page
"Friends don't let friends drive Chevys"
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steve'66
Gearhead Posts: 9533
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 02-09-2002 10:43 PM
Thanks for the tips!I doesn't have anything to do with the squirters 'cause it's leaving flat footed the whole way. I even questioned Melissa if she was lifting after launching off the t-brake, but I don't think so.
Butch, you got a carb for us? Let me know, I'll pick it up with the wheels.
This bog has been with us even with the manual trannys unless the traction was worse. It's best 60'er was a 1.70 at SearsPoint a year ago with smaller et streets. Thanks again and keep the suggestions/thoughts coming. SteveW p.s. I know a little shot of juice would pull it right through this bog.  LOL [This message has been edited by steve'66 (edited 02-09-2002).]
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steve'66
Gearhead Posts: 9533
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 02-09-2002 10:50 PM
KV,The bog was the same no matter how hard it launched. I kept adding launch rpm to the box and it kept bogging with about the same results.  I'm really thinking the vac cab's gotta go. I used to think that the convertor would keep it from nosing over, but that isn't the case.
SteveW
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steve'66
Gearhead Posts: 9533
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 02-09-2002 10:55 PM
Rustang,That might work if she footbraked it. Might try that next time, but we're trying to get Melissa some experience with the t-brake. Which she loves BTW! Most of her lights were in the high .500s, one .485 and one 1.07, LOL. It's all new to her, but I think she'll get it. SteveW
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TomP
Gearhead Posts: 6120
From: Delta BC Canada
Registered: Dec 99
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posted 02-10-2002 01:07 AM
Oh my... first the (to me) beloved manual tranny gets ditched... now the beloved vacuum secondary carb too? Steve... tell us you aren't considering a 350 Chevy for it? please 
I don't think the vacuum carb design has anything to do with it... many much harder launching cars use them... some of us nuts like 'em so much we use several of them 
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steve'66
Gearhead Posts: 9533
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 02-10-2002 01:39 AM
TomP,Nuttin personal! What do you think it is if it isn't the vac secondaries? Huh????? I'm all ears. Tell me what to do.... Besides put a manual tranny back in it, 'cause it bogged then too. SteveW
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n2oMike
Gearhead Posts: 2831
From: Spencer, WV
Registered: Jan 2001
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posted 02-10-2002 07:20 AM
Chances are, the secondaries are opening too fast. Since there is no squirter for the secondaries, if they open too fast... it's bog city. Try a stiffer spring.Having all the timing in earlier is also a good thing. I'd just try one thing at a time though, so you know which modification did what. If you can't get it fixed (which you should) those 950HP Holleys are tough to beat. I haven't been able to find anyone who has used one that didn't like it. Recipe... Smoothed out 750 sized throttle bores with downleg boosters (good) mixed in with a 850 baseplate. Result is a great signal, great flow, and excellent horsepower. Good Luck! ------------------
Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367
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Rustang
Gearhead Posts: 821
From: Clarion PA
Registered: Nov 2000
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posted 02-10-2002 07:28 AM
Sorry bout that Steve I should have read that a little closer!My only experience with a trans brake is driving my buddy's car for a pass where I managed to hit the trans-brake button again right after I launched the car! By the way, sounds like Mike's on the right track with the stiffer secondary spring.
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Just Jim
Gearhead Posts: 381
From: So Cal
Registered: Feb 2000
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posted 02-10-2002 12:18 PM
Hey Steve,
Rustang and Mike are on the right track,the secondary spring is too light causing the secondaries to open too soon.I had the same problem on the Morris and tried all sorts of cures only to find the secondary spring was too light.Sounds like the car runs better with the C4 and is more consistent. ------------------
"Just Falcon Around"
1962 Falcon 351W
1958 Morris Minor 289
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Moneymaker
Administrator Posts: 27499
From: Lyons, IL, USA
Registered: May 99
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posted 02-10-2002 02:06 PM
I will give my thoughts on the subject after Pomona later today. ------------------
Alex Denysenko
Co-Administrator and Moderator
NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
US Class Nationals link
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SteveLaRiviere
Administrator Posts: 45869
From: Saco, Maine
Registered: May 99
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posted 02-10-2002 05:38 PM
quote:
Originally posted by TomP:
Oh my... first the (to me) beloved manual tranny gets ditched... now the beloved vacuum secondary carb too?
Don't mind him, he's just trying to go faster.  ------------------
'70 Mustang Mach 1 M code 351C 4V/FMX/3.25 open
'72 Mustang Sprint Coupe 351C 4V/FMX/4.30 Trac Lok
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
'97 Probe GTS 2.5L DOHC
MCA Member # 47773
Speak softly, but carry a BFH!
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Butch Jennings
Gearhead Posts: 633
From: No. California
Registered: Apr 2000
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posted 02-10-2002 09:22 PM
quote:
Originally posted by steve'66:
Butch, you got a carb for us? Let me know, I'll pick it up with the wheels.
No I don't have a carb anymore, I sold both of the ones I had and bought a down leg booster 850 (got a good deal on it) for the Comet to run on my Victor intake.
I'm not saying that you couldn't get that 750 to work, I agree with these other guys that a stiffer spring would probably clear it up. I'm a mechanical secondaries fan on a race only type combination, I think when Melissa was driving the car alot the vacuum carb made alot of sense. It seems to me that the car is quickly becoming more of a race car and less of a street car, I would go with a mechanical secondary. This is just my opinion/preference, I've seen many race cars with vacuum carbs work fine. ------------------
Butch
460 powered 1967 Comet Cyclone
10.271 @ 130.069
Butcher's Home Page
"Friends don't let friends drive Chevys"
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steve'66
Gearhead Posts: 9533
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 02-10-2002 10:59 PM
What do you think of the old screw in the secondary's bell crank trick? Is it worth a try?SteveW
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Just Jim
Gearhead Posts: 381
From: So Cal
Registered: Feb 2000
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posted 02-10-2002 11:06 PM
The old 'screw in the secondaries'trick would create a bog for sure. That's why they make double pumpers.It would be like a double pumper with no secondary pump.------------------
"Just Falcon Around"
1962 Falcon 351W
1958 Morris Minor 289
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n2oMike
Gearhead Posts: 2831
From: Spencer, WV
Registered: Jan 2001
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posted 02-10-2002 11:10 PM
The point is... The back barrels on a vacuum secondary carb don't have an accelerator pump squirter. That squirter is what keeps the car from bogging when they are yanked open suddenly. You MAY get it to work somewhat by using a 50cc pump up front with a BIG pump cam and HUGE squirters... along with alcohol carb squirter parts. But a stiffer spring would really easy first try. ------------------
Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367
http://www.mustangworks.com/cgi-bin/moi-display.cgi?220
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Fordwiser
Gearhead Posts: 442
From: Metamora, Illinois
Registered: Dec 2000
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posted 02-11-2002 12:28 AM
Like Steve said, she's leaving flat footed with the brake, so there is no pump shot. I think I would try the screw in the secondary slot, then you'll know if it's actally a bog or the secondaries opening and closing.
Roger
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bluestreek
Gearhead Posts: 1724
From: Athens,GA
Registered: Jul 2001
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posted 02-11-2002 01:18 AM
Steve, let me know if you figure it out. I had the same problem at the end of last season when I started getting into the 1.8- 1.7 60 footers. I was thinking that maybe the fuel pickup in the tank was coming uncovered, because my spotter said I was sloshing a little fuel out the rear cap with only 5 gallons in the tank!! BS
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n2oMike
Gearhead Posts: 2831
From: Spencer, WV
Registered: Jan 2001
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posted 02-11-2002 09:25 AM
I'd try it both ways... with and without the screw. If it will leave fine with the screw, it will be fine for track use, but street driving will be a pain. If it still bogs, the engine might not be able to handle that much throttle at that rpm, and the stiffer spring will be needed. I don't remember your stall speed, but cars without super loose converters often leave better on 2bbls than 4.... then as the rpm's come up as the car moves down the track, the secondaries come in and a good, smooth run results. Is the car still street driven? If so, the screw in the throttle linkage will be a pain. Good Luck! ------------------
Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367
http://www.mustangworks.com/cgi-bin/moi-display.cgi?220
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steve'66
Gearhead Posts: 9533
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 02-11-2002 10:13 AM
Mike,It's street driven in fair weather around town only. But it would be easy enough to pull the screw out, along with changing to street tires etc. SteveW
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capri man
Gearhead Posts: 7611
From: doerun, ga.
Registered: Nov 2000
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posted 02-11-2002 10:32 AM
steve, did you ever try yhe plastic tube on the vent tubes like kv suggested. that could very well be your prob. good luck------------------
mike r
racing is real
everything else is just a game.
81 capri-7.56 @88mph 1/8
1.56 60 ft.
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steve'66
Gearhead Posts: 9533
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 02-11-2002 11:00 AM
Mike,No, but I will next time. The car didn't look rich when it nosed over though. No black exhaust smoke. It's just like KV's experience with a vac carb. SteveW
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Moneymaker
Administrator Posts: 27499
From: Lyons, IL, USA
Registered: May 99
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posted 02-11-2002 11:45 AM
Just a reminder that 99% of the NHRA/IHRA Holley equipped superstockers are vaccum secondary. They also leave off of a trans brake. If the car didn't bog before with a stick, I suspect that there may be another problem brewing. A simple driveway test would be to set the trans brake and flat foot the gas while Steve is under the hood looking at the carb to see if the secondaries are indeed opening while on the brake. If they are, then the opening rate may be to fast and a stiffer spring is called for. What happens it you don't use the brake and just whack the throttle? ------------------
Alex Denysenko
Co-Administrator and Moderator
NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
US Class Nationals link
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steve'66
Gearhead Posts: 9533
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 02-11-2002 08:59 PM
Alex,I'll try that. Should the secondaries be closed while on the two step? They would be open with a mechanical secondary carb. If they are closed while it's popping then the secondary springs will have a big effect. I like the idea that they are wide open and ready to rock when the button is released. Tell me more, SteveW
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Moneymaker
Administrator Posts: 27499
From: Lyons, IL, USA
Registered: May 99
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posted 02-11-2002 09:15 PM
In a perfect situation they should be wide open on the limiter Steve. What I suspect is that they are not opening until you release the brake and then you are getting the "bog" during the transition. The converter may be to tight, but that would be hard to diagnose this way. WHat will it stall to without a chip in it? ------------------
Alex Denysenko
Co-Administrator and Moderator
NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
US Class Nationals link
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steve'66
Gearhead Posts: 9533
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 02-11-2002 09:54 PM
4100 AlexThis convertor was custom built to the future 408's specs, but comes pretty close for the 351w w/ 282S cam and rpm heads too. SteveW
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Moneymaker
Administrator Posts: 27499
From: Lyons, IL, USA
Registered: May 99
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posted 02-11-2002 10:52 PM
Rule of thumb is to be 2000 RPM prox below peak RPM Steve. Is 6100 max on the 351? ------------------
Alex Denysenko
Co-Administrator and Moderator
NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
US Class Nationals link
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steve'66
Gearhead Posts: 9533
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 02-11-2002 11:37 PM
Alex,We shift at 6,000 and go through the traps at 5800. So yeah sounds about right to me. SteveW
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