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Brake servo/booster question - UPDATE

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thadman Avatar
thadman Silver Member Thad H
Spokane, WA, USA   USA
Will a brake servo unit function with the vacuum hose positioned at the top of the servo instead of out the bottom as was the original location?

Here's the problem: I retrofitted my '80 B with dual HIF4 carbs, and installed conical K&N filters to clear the brake servo. My brake servo began to fail so I purchased a new one and installed it, however the casings on the new servos are slightly different than the originals, and now my air filter will not fit on the carb because it bangs into the servo. The new servo casings have two "ears" in the top half of the servo, and one of the ears just happens to be directly in line with my carb filter (see attached pic). The original servo casing did not have these ears, and thus everything fit. So, one solution I came up with would be to rotate the servo unit 180° so that the "ears" were on the bottom, which would then put the vacuum hose connection at the top. Which brings me back to the question posed at the beginning of this post: will the servo unit work with the vacuum hose coming out to the top of the servo?

Another solution offered was to shave down the plastic spacer block for the carburetor to achieve the spacing needed between the filter top and servo. The question about doing this is, would shaving the plastic spacer block affect the tuning of the carb and engine since it would be closer to the intake manifold than the other carb?

TIA for any help or suggestions!



'80 MGB, de-smogged, Factory OD, Schlemmerized 25D distributor, HIF4's, Bell Stainless exhaust, VTO wheels from Hap, Bits4Brits relay kit, Classic Auto LED's



Edited 1 time(s). Last edit at 2014-04-03 05:31 PM by thadman.

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lewisrn Avatar
lewisrn Gold Member Bob L
Danville, IN, USA   USA
1980 MG MGB "The "B"
It should work with the vacuum outlet in any position. I would just try it and see.

The aftermarket booster I bought for my 80B was actually smaller, back to front than the OE booster so I'm a little surprised to see the problem with your new one.

EDIT - I see you have the HIF4's and I have the HS4's. I don't know if that will make a difference.



In any debate, the side which strays from civil discussion is usually the side that lacks confidence in its debate position or in its ability to win the debate on the merit of their arguments. Making personal attacks on the opponents instead of staying on the subject is also a sign of weakness.

Anyone who always feels compelled to respond in kind to any perceived slight is often suffering from narcissism.



Edited 1 time(s). Last edit at 2014-04-03 10:08 AM by lewisrn.


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reb121055 Avatar
reb121055 Rod Belmore
Danville, P.A., USA   USA
I have never done it, but shaving only one carb spacer would pose linkage problems between the carbs, I would think.

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BumbleB74 Avatar
BumbleB74 William Milholen
Tidewater, Tidewater VA, USA   USA
How much brake line re-routing did you have to do? On my '76, this booster left the brake lines almost an inch ahead of the MC.

The one answer nobody added was you could switch to a Weber down draft….LoL...



1974-1/2 Roadster, "Bumble Bee", Corvette Yellow - in shambles, wire wheels
1976 Roadster, "Virus", Sandglow - "driver" condition (stock + 32/36 Weber DGEV, cast iron header, 25D distributor), bolt on wheels, ON the road!

thadman Avatar
thadman Silver Member Thad H
Spokane, WA, USA   USA
In reply to # 2651125 by BumbleB74 How much brake line re-routing did you have to do? On my '76, this booster left the brake lines almost an inch ahead of the MC.

The one answer nobody added was you could switch to a Weber down draft….LoL...

No rerouting of the brake lines were necessary - they lined up without much adjustment at all.



'80 MGB, de-smogged, Factory OD, Schlemmerized 25D distributor, HIF4's, Bell Stainless exhaust, VTO wheels from Hap, Bits4Brits relay kit, Classic Auto LED's

thadman Avatar
thadman Silver Member Thad H
Spokane, WA, USA   USA
In reply to # 2651036 by lewisrn It should work with the vacuum outlet in any position. I would just try it and see.

The aftermarket booster I bought for my 80B was actually smaller, back to front than the OE booster so I'm a little surprised to see the problem with your new one.

EDIT - I see you have the HIF4's and I have the HS4's. I don't know if that will make a difference.

Thanks Bob, I'm going to go ahead and give it a try. Not looking forward to unbolting everything again and reassembling it - it was a major PITA doing it the first time!



'80 MGB, de-smogged, Factory OD, Schlemmerized 25D distributor, HIF4's, Bell Stainless exhaust, VTO wheels from Hap, Bits4Brits relay kit, Classic Auto LED's

lewisrn Avatar
lewisrn Gold Member Bob L
Danville, IN, USA   USA
1980 MG MGB "The "B"
In reply to # 2651182 by thadman
In reply to # 2651036 by lewisrn It should work with the vacuum outlet in any position. I would just try it and see.

The aftermarket booster I bought for my 80B was actually smaller, back to front than the OE booster so I'm a little surprised to see the problem with your new one.

EDIT - I see you have the HIF4's and I have the HS4's. I don't know if that will make a difference.

Thanks Bob, I'm going to go ahead and give it a try. Not looking forward to unbolting everything again and reassembling it - it was a major PITA doing it the first time!

I hear you. It was a major PITA when I changed mine and I would surely hate to have to do it twice. Evidently the booster you bought is close to OEM size, because I had the same experience with mine that William did.

I bought my booster at the BHive. Where did you buy yours?



In any debate, the side which strays from civil discussion is usually the side that lacks confidence in its debate position or in its ability to win the debate on the merit of their arguments. Making personal attacks on the opponents instead of staying on the subject is also a sign of weakness.

Anyone who always feels compelled to respond in kind to any perceived slight is often suffering from narcissism.



Edited 1 time(s). Last edit at 2014-04-03 12:47 PM by lewisrn.

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thadman Avatar
thadman Silver Member Thad H
Spokane, WA, USA   USA
In reply to # 2651202 by lewisrn
In reply to # 2651182 by thadman
In reply to # 2651036 by lewisrn It should work with the vacuum outlet in any position. I would just try it and see.

The aftermarket booster I bought for my 80B was actually smaller, back to front than the OE booster so I'm a little surprised to see the problem with your new one.

EDIT - I see you have the HIF4's and I have the HS4's. I don't know if that will make a difference.

Thanks Bob, I'm going to go ahead and give it a try. Not looking forward to unbolting everything again and reassembling it - it was a major PITA doing it the first time!

I hear you. It was a major PITA when I changed mine and I would surely hate to have to do it twice. Evidently the booster you bought is close to OEM size, because I had the same experience with mine that William did.

I bought my booster at the BHive. Where did you buy yours?
I bought mine from Basil Adams.



'80 MGB, de-smogged, Factory OD, Schlemmerized 25D distributor, HIF4's, Bell Stainless exhaust, VTO wheels from Hap, Bits4Brits relay kit, Classic Auto LED's

r dutot Avatar
r dutot rick dutot
Leamington, ON, Canada   CAN
1975 MG MGB
I had a similar problem and to correct it I shaved as much rubber off the AIR FILTERS that I could which gave me enough room to clear the servo.

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thadman Avatar
thadman Silver Member Thad H
Spokane, WA, USA   USA
Success! Rotating the servo resulted in achieving the necessary clearance for the air filter - ended up with about 3/16" clearance.



'80 MGB, de-smogged, Factory OD, Schlemmerized 25D distributor, HIF4's, Bell Stainless exhaust, VTO wheels from Hap, Bits4Brits relay kit, Classic Auto LED's


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NellyH Neil H
St Thomas, Virgin Islands (US)   VIR
Hi Folks, Anyone help with this please?

Whats the little square electrical unit with two small black hoses going to it and two wires also that is bolted on a bracket off the top of the brake servo units lid, it is shown in this picture above top right two fasteners and a v shaped bracket.?? Mine has no pipes going to it.....

Cheers
Neil

Gerald O Avatar
Gerald O Gerald O'Docharty
Wake Forest, North Carolina, USA   USA
1978 MG MGB
In reply to # 3742641 by NellyH Hi Folks, Anyone help with this please?

Whats the little square electrical unit with two small black hoses going to it and two wires also that is bolted on a bracket off the top of the brake servo units lid, it is shown in this picture above top right two fasteners and a v shaped bracket.?? Mine has no pipes going to it.....

Cheers
Neil
That is the 4th gear vacuum ignition advance cutout valve. It is fitted to the smog engines to reduce NOx emissions by reducing the ignition advance, and hence combustion temperatures, except in 4th at cruising speed, if I recall. The wires connect to the 4th gear switch on the gearbox, and the vacuum advance hose would connect to the valve before going on to the distributor. These are often bypassed in the interest of getting better power in all gears.



Edited 3 time(s). Last edit at 2018-05-25 09:54 AM by Gerald O.

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