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WOT falling flat

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Linear Six
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Joined: Fri Dec 27, 2002 11:41 am
Location: Thunder Bay

WOT falling flat

Post #1 by Linear Six » Thu Aug 15, 2019 4:23 pm

I kindly ask for your advice/help in either setting up my Weber 38 or find a new carburetor that will better suit my application.
As everyone else, I'm trying to get the most out of my car.

This is my current setup....
- 67 mustang with a 200 .030 over and block height is .010
- Clifford 272 cam advanced 6*.
- Vintage inline Aluminum Head, no porting performed, Freshly installed this past month
- Weber 38 DGES carb - 50 Idle jet, 160 Main Jet, 210 Air correction jet. Idle speed 3/4 turns in (verified visually that the transition holes are not exposed and no vacuum at 830 RPM idle) idle air mixture screws out 1.65 turns each
- Tremec 5 speed manual transmission 9" organic clutch
- DSII Distributor recurved locally- Initial timing 22*, Mechanical advance 20* with total approximately 41-42* without vacuum advance. All in at 2550 RPM. I plan on purchasing a new distributor from Bill in the near future that will have a better curve.
- MSD 6AL2 Ignition Module
- 1.65 Yellar Terra roller rockers,
- clifford dual header and exhaust
- Rear end is 3.20
The car runs great at idle and above 2000 RPM pulls hard.
The issue is the car fall on its face at WOT from 0 MPH or anytime i go WOT below 1500 RPM. Not sure if its a cam issue, timing or jetting.

any help is greatly appreciated.

DoctorC
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Re: WOT falling flat

Post #2 by DoctorC » Thu Aug 15, 2019 4:31 pm

(edit: nice setup, looks like fun, I'm jealous of ur VI head =)
That is a lot of advance! I've done some of that, but not the Cam. If you're sure it can handle it, go for it.

From what I ve learned here, the best bet for setting up new stuff is choosing 1 thing to dial in at a time. General workflow:

1) Be conservative on everything and get it running smoothly from top to bottom
2) pick something to improve and work on that (e.g. advance)
3) correct cascading effect (advance affects carb, etc)
4) Drive, debug, get running smoothly again
5) Repeat

My ongoing DS2 thread may be of some help viewtopic.php?p=622482
1967 Cherry Red Mustang
Weber 32/36,
MSD 6AL+MSD Coil,
Duraspark 2 dizzy

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B RON CO
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Re: WOT falling flat

Post #3 by B RON CO » Thu Aug 15, 2019 8:54 pm

Hi, I don't have a lot of experience with that kind of setup but it seems like a lot of ignition timing and not enough accelerator pump. Just my guess. Good luck
B RON CO. Still workin' on it!

1933 Ford Pickup - 59A Flathead V8
1966 Ford Bronco - U14 - 170/200 Straight 6
1966 Ford Mustang - 289 V8

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65coupei6
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Re: WOT falling flat

Post #4 by 65coupei6 » Fri Aug 16, 2019 8:45 pm

I am not familiar with Weber carbs. But, I am running 18 for timing. 22 does seem a little high.

Ported or Manifold vacuum? Can you change the accel shot on Weber's?

Here is some good info : https://www.racetep.com/manufacturer/ca ... carbs.html

I have always liked the Holley 07448. They seem easier to tune. (Bill, has a Holley for sale.) Or just dump the carb and get a Sniper or FiTech fuel injection.
...Marco

'65 Mustang Inline 200. VI (CI) Aluminum Head, Holley 350, Schneider 264/274 cam,
Headers, DSII, MSD 6A, and a whole lotta other stuff!

Build That Six With Parts From VintageInlines.com

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wsa111
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Re: WOT falling flat

Post #5 by wsa111 » Fri Aug 16, 2019 10:11 pm

65coupei6 wrote:I am not familiar with Weber carbs. But, I am running 18 for timing. 22 does seem a little high.

Ported or Manifold vacuum? Can you change the accel shot on Weber's?

Here is some good info : https://www.racetep.com/manufacturer/ca ... carbs.html

I have always liked the Holley 07448. They seem easier to tune. (Bill, has a Holley for sale.) Or just dump the carb and get a Sniper or FiTech fuel injection.

Carb is sold.
Yes your total centrifugal advance is too high.
You need to get it recurved for your combination, or purchase one of my DS11's
67 mustang,C-4, with mod. 80 hd, custom 500 cfm carb with annular boosters, hooker headers, dual exh.-X pipe, flowmaster mufflers, DSII dist. MSD-6al & MSD-Blaster 8252 Coil. Engine 205" .030" over with offset ground crank & 1.65 roller rockers. 9.5 comp., Isky 262 cam.
2003 Ford Lightning daily driver. Recurving Distributors. billythedistributorman@live.com
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Linear Six
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Location: Thunder Bay

Re: WOT falling flat

Post #6 by Linear Six » Sat Aug 17, 2019 7:28 am

Thank you for the responses so far.
The vacuum is ported off the carb. The accelerator pump to my knowledge is fixed and the the jet is at it's max at 70.
i agree that the 22* is high when i set the timing down to 18* the idle goes very low and the Webers are very particular on how the idle speed is set. When i test drive it at 18*, it idles low and from mild to heavy acceleration the car pops and stumbles bad.
Bill what a good initial and total timing that i could perhaps try, that will allow me to set up carb?

Thank you again everyone

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wsa111
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Re: WOT falling flat

Post #7 by wsa111 » Sat Aug 17, 2019 12:05 pm

I would get rid of the Weber & install a small Holley 4 barrel or an Autolite 4100.
If you go that route you will need 6-7# fuel pressure.
You need to run manifold vacuum to the vacuum advance. Email me so i can more info & talk with you.
billythedistributorman@live.com
67 mustang,C-4, with mod. 80 hd, custom 500 cfm carb with annular boosters, hooker headers, dual exh.-X pipe, flowmaster mufflers, DSII dist. MSD-6al & MSD-Blaster 8252 Coil. Engine 205" .030" over with offset ground crank & 1.65 roller rockers. 9.5 comp., Isky 262 cam.
2003 Ford Lightning daily driver. Recurving Distributors. billythedistributorman@live.com
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Linear Six
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Location: Thunder Bay

Re: WOT falling flat

Post #8 by Linear Six » Tue Sep 10, 2019 6:58 pm

Hi All,
Just thought I would post an update. After reviewing everyone's suggestions I moved to digging in deeper on the timing setup. I talked to Bill (excellent knowledge about timing and the performance of our 200's) to confirm my set up and discuss the timing requirements of the VI Head. In short, I purchased a recurved DSII from Bill with timing requirements based on my engine. I installed the distributor yesterday and took it out for a test drive. The car ran amazing! Bill provided the initial timing setup and it seams to be spot on. I highly recommend Bill's services for anyone who's stumbling on their timing or needs some advice on tuning their engine.
I reviewed the carburation requirements with Bill and we both agreed that using the Weber 38 was not maximizing the potential of the engine and that it was leaving horses on the table. The Weber is approximately 360 - 380 CFM (up to 145 ish Hp) and the engine could use between 450 - 480 cfm. I purchased a Holley Sniper as a replacement for the Weber. Hope it's worth the coin!

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xctasy
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Re: WOT falling flat

Post #9 by xctasy » Wed Sep 11, 2019 6:35 am

Linear Six

Yep, I'm with Bill.

The Weber 38 has a lot going for it, but its an air bleed emulsification carb with a very specific method for air fuel ratio triming. David Vizard was re-employed as a consultant back to Tickford, Aston Martins tuner many years back. The old guy who did the Vantage AM V8 up till 1978 had gone, and the team were re-taught how to tune the 48 IDF's 8bbl system for the 580x carbs with oversize venturis and throttles in 2004. Its not just Port on Port independent runner, Isolated throttle body systems that benefit from this kind of stuff, so do conventional Autolites, Motorcraft and Holley carbs, but like DV says, only one hole plugged on the well tube, or one hole added. The common Holley Well tube hole number is 4 or 5 holes, and adding holes leans out, plugging holes richens up. The base jetting on Webers is controlled by restrictions in the float needle and seat, a very bad system compared to the ture beauty of the Holley 2-bbl seat. Weber used the carbs well in 3000GT Capris, and many 2.8 Capris and 2.8 Granadas before the downgrade to Solex carbs in about 1980-1984, but they never really made gobs of power like a good Holley 2 bbl can.

https://www.youtube.com/watch?v=1pkFSA_rRFI

https://www.youtube.com/watch?time_cont ... pkFSA_rRFI
https://www.youtube.com/watch?v=1pkFSA_rRFI

Like ignition, Air fuel requires proper reading equipment. Wide bands, and good distributor discipline always beats bending and gouging out zinc oxide. Bill has always had that side well and truely fleshed out. Bills first displayed Mustang incarnation was the early Weber 38....his advice is real world.

Air cleaners, main venturi size (which can be increased from 27 mm stock with about 300 cfm at 2 " Hg to 34 mm with a potential to make 336 cfm with other modes and without punching into the outer casting)...all of it requires effort. It can flow as much as a 350 cfm Holley 2bbl stock without mods. With mods, its still flows less than the best Autolite 1.33, which is about 424 cfm, and way less than the 500 4412 part number Holley 2-bbl I really like. Venturi sizes for carbs verses throttle sizes, and how to get the best out of them, DV defined long ago. Yes, you can go backwards, but only if the ratio of throttle size to venturi is less than 1.125.


The world is moving on. Three companies in the USA, quite appart from static adjstable carbs from SMI, make kits for 100% adjustable, feedback Holley carb air fuel adjustment on the fly. You have to decide if a Throttle Body Injection system is going to be any better than an adjustable feedback carb with the choke and air horn removed.

Anyway, glad ypour moving forward, and not stuck into the its sucks small carb route many strangle themselves with. Any time a small carb works better than a bigger one, you can bet you haven't tuned it properly.

Linear Six, its really sad when people don't decide to say "Gee, this just isn't working like I wanted it too...its TIME TO FIX IT!"
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FAZER 6Bi (M112 & EEC5) or FAZER 6Ti (GT3582 & EEC5) 425 HP 4.1L/250 I-6
FAZER 6V0 3x2-BBL Holley 188 HP 3.3L/200 I-6 or 235 HP 4.1L/250 I-6
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