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HS4 Carb Rebuild for Cross Flow Head

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Fieldbuilder Kevin Hart
NC, USA   USA
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1974 MG MGB "RED"
1975 MG MGB "AutoX"
1977 MG MGB "BaLou"
I'm going to send a set of HS4's off for a rebuild.
Running a Cross Flow Head on a modified 1975 Autocross Car.
With SU's they let me run Street Class, Not Street Modified.
AUD135 have Solid Throttle Disks. Use Velocity Stacks. No filters.
Should I look at Needle Change's, or any other changes that should be
requested?
Thank you, in advance. Kevin

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Rick Fawthrop Avatar
Rick Fawthrop Gold Member Richard Fawthrop
Langley, WA, USA   USA
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Run filters.
Go to the Innovate Motorsport website and buy a wide band O2 sensor gauge. Hopefully one with a data logger.
Get a fuel pressure gauge such as an Auto Meter liquid filled.
And buy a good oil pan with trap doors and stuff.

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geezer Silver Member charles durning
Magee, MS, USA   USA
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1967 Morris Minor 1000 Saloon (2-door) "Marvin"
1974 MG MGB GT "Foghorn Leghorn"
If you want to get the tech guys to scratch their heads, put another set of inop carbs on the exhaust side of the head. I saw a pic of a Magnette with a xflow head and 4 carbs. Looked great. Just can't find it right now.



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Know the rules well so you can break them effectively. Dalai Lama

That is why I always say, who cares how the factory did it, they did so many things so wrong, they were never the example to follow. Hap Waldrop

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oleanderjoe Avatar
oleanderjoe Platinum AdvertiserAdvertiser Joseph Baba
Fresno, CA, USA   USA
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Kevin: Want to try a set of my SU Carb spacers.???? Check my Web Site (See my Home Page) The Spacers were used by MG to keep the Twin Cam alive. That motor used to burn up pistons, ran lean on the top end. I have them for the HS and The HS-4 Carbs. (Each is a different style.) Moss used to buy them from me but dropped them for lack of sales. Really helps, up on the top end of the REV band. MG Factory Race Proven. If you want I can send you a set "NO CHARGE" Glad to help a fellow Autocrosser. Cheers



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"Strive for perfection in everything. Take the best that exists and make it better. If it doesn't exist, create it. Accept nothing nearly right or good enough"
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co-founder of Rolls-Royce .

"I take no credit for my own, of another man's fame".
Joe Baba 2021


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oleanderjoe Avatar
oleanderjoe Platinum AdvertiserAdvertiser Joseph Baba
Fresno, CA, USA   USA
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Kevin: click on my "oleanderjoe Avatar above or www.originalduplicates.com PM me your address and I will put a set in the mail for you, Cheers



IN ALL SUBJECTS.: For those who believe, no proof is needed. For those who don’t believe, no proof is possible.

"Strive for perfection in everything. Take the best that exists and make it better. If it doesn't exist, create it. Accept nothing nearly right or good enough"
Sir Henry Royce
co-founder of Rolls-Royce .

"I take no credit for my own, of another man's fame".
Joe Baba 2021


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oleanderjoe Avatar
oleanderjoe Platinum AdvertiserAdvertiser Joseph Baba
Fresno, CA, USA   USA
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Kevin: I said No Charge, send me your address. Thanks



IN ALL SUBJECTS.: For those who believe, no proof is needed. For those who don’t believe, no proof is possible.

"Strive for perfection in everything. Take the best that exists and make it better. If it doesn't exist, create it. Accept nothing nearly right or good enough"
Sir Henry Royce
co-founder of Rolls-Royce .

"I take no credit for my own, of another man's fame".
Joe Baba 2021


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tahoe36c Paul Hruza
Panama City, FL, USA   USA
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1969 MG MGC GT "Little Red Rocket..."
1972 MG MGB GT "Tiny Dancer"
2002 Harley-Davidson Dyna
You can do all of the rebuild yourself except the throttle valve (butterfly) shaft bushings... Strip the carbs, clean them and send off to Joe Curto in NY. $100 to ream and install new bushings. He also has the rebuild kits you need.

P.S. HS6 would be better!!! Just saying...



Those who confuse Burro and Burrow don't know their @ss from a hole in the ground...


Attachments:
HS6 Finished 01.JPG    58.3 KB
HS6 Finished 01.JPG

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Speedracer Platinum AdvertiserAdvertiser Hap Waldrop
Taylors, SC, USA   USA
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1967 MG MGB Racecar "The Biscuit"
It depends on what you have done to the engine/head, if unported, and you already have the twin HS4 intake for the X flow head, then this is probably the best choice, they don't really flow much more than a siamesed intake head, and twin HS6s would probably be problematic, if the head is well ported than maybe HS6s would be a choice, but I would argue, modded HS4s would give one better throttle response. Sounds like you're dedicated to the HS4s, so if the head is unported, start with the stock #5 solid needles, then get a set of #6, (next step richer) then if it were me, I would head off to chassis dyno with a good AFR set up, needles in hand, start out with the number #5 about .050 down, then pay with then as for lower the jet and richening than of the AFR numbers tell you that, if you to point where you are flirting with .100" down, on the jet, now time to play with the #6 needle, start again at about .050" down and chase the AFR number, look for about 12-12.5 at WOT. The chassis dyno sounds to many like a luxury, but it really is a saving of time and money, if you go prepared with a plan you can do this in a 1 hour session, just get the car running as well as you can before you go, so you fine tuning, and thrashing to get the car to run. Be prepared to let the dyno operator run the dyno and you do the tuning, which with SUs is easy enough to do.



Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com


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