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 Post subject: Level 2 carburators?
PostPosted: Thu Aug 06, 2020 6:47 am 
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Joined: Tue Mar 23, 2010 9:56 am
Posts: 116
As i recall... it was once in the rules that a level 2 carb (limited prep) could essentially not be modified as is done for instance with SUs in level 1, (bored out, etc...). I can't seem to find that rule anymore... just stock # of carbs and a size on the spec line (which is not always present). Has something changed? Can modified carbs be run in Level 2 prep? I know the head (non-ported) is still the bottle neck on my MGB... just curious since it raises some options

For instance on a triumph spitfire HP level 1/2... seems I can run on a 1296cc engine a pair of original HS2 (stock or modified) or a pair of HS4 (stock or modified), while on a LP 1500... rune a single downdraft or ?

Neil
# 83 LP HP MGB


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 Post subject: Re: Level 2 carburators?
PostPosted: Thu Aug 06, 2020 9:21 am 
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Joined: Mon Aug 19, 2002 2:52 pm
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Location: Just south of Indianapolis
Neil I agree. It used to be very clear and say stock unmodified carbs for l2 prep. That clearly isn’t there and it seems to be the exact wording for l1

Aaron

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 Post subject: Re: Level 2 carburators?
PostPosted: Thu Aug 06, 2020 9:28 am 
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Not sure if it answers your question, but refer to 9.1.5.E.2.b. (Drive train level 2, Induction System).. starts at the bottom of pg 467 of the most current GCR.
There's some verbiage about what can be done to the carbs, type, alternates, etc.

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 Post subject: Re: Level 2 carburators?
PostPosted: Thu Aug 06, 2020 10:08 am 
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Hi Matt, Arron... Thanks....

yeah... the verbage restricts to same # of carbs and possible alternatives of similar design.... has a few restrictions, but nothing saying you can't use your imagination to modify LP2 carbs within the written restrictions. In the case of my MGB...It used to say specifically "stock, unmodified, 1.5 inch SUs" carbs" on the spec line..when my LP GP MGB was moved to HP LP + 200 lbs (some years now). now its silent.... is it a case of ..if it dosn't say you can... then you can't or is it possibly a mute point since the lack of porting, head work is really the bottle neck anyways so dosn't matter what carbs you put on a LP motor (although there is probably some tuning here to optimize if carbs open to modification)?

Neil


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 Post subject: Re: Level 2 carburators?
PostPosted: Thu Aug 06, 2020 11:05 am 
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It's my firm belief that the rulebook is there to tell you what you can do, not to tell you what you can't do. So whatever you do, you better be able to point to something that says you can do it, when a competitor or a tech inspector comes asking.

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 Post subject: Re: Level 2 carburators?
PostPosted: Thu Aug 06, 2020 11:19 am 
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There was a fair amount of talk on this forum several months ago in regard to the same thing. however due to the auto-pruning functions of the forum, anything older than 6 or 12 months is filed away in an archive and inaccessible.

however, the point is that I remember a similar discussion. I think the premise is that the Prod rules were going through an update/alignment/housecleaning/pruning to clear up many of the ambiguities in the past. Part of that was the "100% stock carb" statements and replies of "everybody was modifying them, and the runoffs tech shed is in for a world of hurt if you take it this way"

obviously that's innuendo and exaggeration, but you get the premise. I believe the rules were never intended to say "no carb mods allowed at all", but somehow that verbiage landed in there OR the L2 guys had all already let the cats out of the barn (speculation and innuendo.)

This was certainly a somewhat recent change though... I dug back through all of my downloaded GCRs, and this section is all red in the Sept 2019 version.

Maybe some of the guys on the Prod committee could weigh in?

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 Post subject: Re: Level 2 carburators?
PostPosted: Thu Aug 06, 2020 1:02 pm 
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Joined: Mon Aug 19, 2002 2:52 pm
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Location: Just south of Indianapolis
I think the question now comes from this:
Level 1 Carbs are governed by 9.1.5.E.b
All inducted air must pass through the venturi(s) of the car’s carburetor(s). Carburetor jets, jet
needles, metering rods and needle valves are unrestricted. Choke mechanisms, plates, rods,
and actuating cables, wires, or hoses can be removed. The number of carburetors must not be
changed from stock, unless otherwise specified by the vehicles spec line. All single carbureted
cars may fit a permitted optional carburetor. Where the use of one (1) 40 DCN, DCNF, IDF
carburetor is specified, a permitted optional carburetor may be substituted. Permitted optional
carburetors are:

which is now identical to Level 2 wording in 9.1.5.E.2.b (through to intake manifolds)
All inducted air must pass through the venturi(s) of the cars carburetor(s). Carburetor jets, jet
needles, metering rods and needle valves are unrestricted. Choke mechanisms, plates, rods, and actuating cables, wires, or hoses can be removed. The number of carburetors must not be changed
from stock, unless otherwise specified by the vehicles spec line. All single carbureted cars may
fit a permitted optional carburetor. Where the use of one (1) 40 DCN, DCNF, IDF carburetor is
specified, a permitted optional carburetor may be substituted. Permitted optional carburetors are:\

and both are governed by a.1 of their section which states:
Stock and permitted alternate components of the drive train can be modified by any mechanical
or chemical means. Modification of a drive train component does not permit relocation of
that component.

fuel injection for both L1 and L2 are very specific that nothing can be done to the throttle body

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 Post subject: Re: Level 2 carburators?
PostPosted: Thu Aug 06, 2020 2:09 pm 
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Hi Arron,

so as you say.....this is the interesting line (in quotes below).....as governed by a.1 of their section which states:

"Stock and permitted alternate components of the drive train can be modified by any mechanical
or chemical means"

....meaning to me (as far as carbs go) as long as the part is stock..... it can be modified (chemical or mechanical) in L1 or L2 prep...as long as carbs are considered part of the drive train (which seems a bit of a stretch... but may be how the rules are written)

Neil


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 Post subject: Re: Level 2 carburators?
PostPosted: Thu Aug 06, 2020 2:33 pm 
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Whaaaaaaatttt? When did level 2 carbs get to be modified.....at all? Level 1 carbs were always allowed to be heavily modified with the only restriction being that they started out as a stock part and met the size restriction at the butterfly. Level 2 carbs had to be bone stock, period. I remember discussions about whether the dashpot parts had to be run even though they had no effect without running the oil in the chamber.

I agree with Kevin - if it doesn't say you can do it you can't in level 2.

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 Post subject: Re: Level 2 carburators?
PostPosted: Thu Aug 06, 2020 2:42 pm 
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Location: Atlanta, Ga
Drivetrain – Those rotating components in a car that convey the driving power from the engine flywheel to the ground and the housings containing these parts. This is inclusive of the clutch, transmission,driveshaft, differential, halfshafts/axles or any systems providing such functionality. Wheel bearings, driveshaft carrier bearings, wheels, and tires are specifically excluded.

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