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PostPosted: Wed Dec 27, 2017 3:16 pm 
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Joined: Mon Jan 16, 2012 11:02 am
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Car Model: v4 c900 9000aero 9000griffin
So I am not going to pretend I have any knowledge on this matter. I own a 96 V4 rally car. It has a V4 engine in pretty much as modified state as it can be. It has a race cam, circa 1800cc, and a moose horn inlet manifold with two weber 45's.

I have asked someone to set the carbs up for me, and he has given me a buzz asking me about the timing on the car. The car has the extended distributor to match the moose horn carb - so no vacuum advance - and I have no idea what sort of weights are in the carb to give it an advance curve (no markings)

He is asking the question what is the maximum advance. The haynes manual for a standard car gives set up at 6 degrees before top dead centre, but gives no idea of what the maximum permissibe advance. He has set it up saying 22 degrees seems good, but is worried that this seems very extreme.

Anyone have any knoweldge/ experience on this?


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PostPosted: Thu Dec 28, 2017 5:53 pm 
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Saab Nut

Joined: Thu Nov 11, 2010 12:26 pm
Posts: 1619
Max advance when the dizzy is maxed out is about 37-38deg. If it uses the std later dizzy as per sport and rally it will have 8-12deg static timing and max out about 4200 rpm, if it has the earlier dizzy it will max out at approx. 3400 rpm.
Who's car was it? As I may know about it if its a uk car.


Last edited by rallyv4 on Thu Dec 28, 2017 6:06 pm, edited 1 time in total.

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PostPosted: Thu Dec 28, 2017 5:58 pm 
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If he is asking those questions he shouldn't be messing with it. Max advance is usually based as a thumb in the air on combustion efficiency and chamber shape. Someone like Bogg Brothers up at Malton are worth a visit. They will change the weights in the dizzy if they see fit.


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PostPosted: Sat Dec 30, 2017 2:57 pm 
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Car Model: v4 c900 9000aero 9000griffin
Thanks for the reply. Car is OOY 18F without looking at paperwork think originally owned by kieron Patterson? The distributor is providing instant max advance at about 1200 revs, so will check springs and weights. Thanks also for who will be able to set distributor up. Have a more worrying problem, wear in distributor mesh drive, cam looks fine, spin on distributor shafts looks true, anyone had such a problem?


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PostPosted: Wed Jan 03, 2018 3:54 pm 
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Joined: Thu Nov 11, 2010 12:26 pm
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You can get new gears, try Aldon Automotive. Basically try to get a proper Saab workshop manual. In there it gives you the different dizzy timings. Basically double these up as they are at half speed. Are you sure that's what your guy is telling you is what he is seeing with the strobe? 1400rpm on a dizzy in the book will be 2800rpm on the strobe. I was also wondering if your 22 deg was ment to be 32deg, which is plausible.
Does the car still have a CT manifold or a proper Saab one as you can run a std length dizzy on a CT? It should be a good base as its a cat 1 car like mine. Its built to grp 6 rules as per 1967 Gulf rally and 67 RAC. What is good is that Rally 2WD are going to be running all the historic's together again. They have a Face book group under Rally2WD, so please join that! It could also be used for historic day time events if you keep the head lining, door cards and strap a back seat in there.


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PostPosted: Thu Jan 04, 2018 10:26 pm 
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Joined: Mon Mar 06, 2006 7:46 pm
Posts: 665
Location: Sherwood Forest, England
Car Model: 96 V4 - Grp 2 Rally Car
Check the nos stamped into the body of the tall distributor. Mine came from SSR back in 1973.
Markings are Bosh icon followed by B 231 040 517 V in a circle.
Below this BOSCH Inch gap then 72HF 12100 NA ( these have a score through.
Below this Bosch icon 0 231 170 805 or 005 also scored over then JFU 4 <----

The nos don't exactly compare to the centrifugal and vacuum advance graphs in the w/s manual. The rally distributor has centrifugal advance only as the breaker plate is locked. Still using original Bosch points and the rally rotor arm.
Timing not one of my strengths as I need to put a decent timing gun on the Trolls engine.


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PostPosted: Fri Jan 05, 2018 10:47 pm 
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Joined: Fri Aug 05, 2005 6:51 pm
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Location: Cheshire
Car Model: Saab 900 and 99
From what I can remember from when I had twin sidedraughts, the vacuum unit should be removed and the breaker plate should be locked and static timing set to 6 degrees BTDC.

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PostPosted: Sat Jan 06, 2018 3:42 pm 
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Its had that done to it Dave. There are basically two std dizzy curves, I run an early dizzy which hits full advance earlier than the later one. The green car had a later dizzy and static advance was about 8-9 deg. Both where locked off no vac.
I spent ages with a lambda probe setting the carbs up and dizzy, to be honest I would just go to an good old school rolling road, Bogg brothers are good and the other that has done v4s before is I think Mikeanic's at Congelton. Static timing is pretty irrelevant on a competition car, they will start with stupid amounts of advance, you want the right advance mid-full power.
I think its Mikeanics that Steve uses and we have seen up to 15bhp gain on a full house v4. Every car he has touched gained min 7 bhp. The 15 bhp gain was on one Paul Darlingtons cast off, he had been missing 15bhp for years!


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PostPosted: Sat Jan 06, 2018 8:47 pm 
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Location: Cheshire
Car Model: Saab 900 and 99
He has the information to set up the disi, 6 degrees BTDC is the static timing, I can't see what problems he could have, as long as the disi is in working order. You have no control over the disi, it is what it is. The advance can be checked using a strobe light with advance and retard facilities such as the old hand held Snap-on computerised tach guns.

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PostPosted: Sun Jan 07, 2018 8:23 pm 
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Car Model: Sunbeam tiger
If it is running best with 22deg advance at idle or advance all in it would be wise to check that TDC marking on balance shaft pulley is correctly indicating when no 1 is at TDC

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PostPosted: Sun Jan 07, 2018 9:17 pm 
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Joined: Fri Jun 16, 2006 9:26 pm
Posts: 497
Probably will need quite a lot of advance to get a reasonable idle if you are using a competition cam with quite a bit of overlap. More important is the all out timing at max throttle and revs. Probably around 30 odd degrees depending on compression ratio etc.
With old clockwork type distributors used on a competition engine the timing is often just set to give best power at wide open throttle at higher revs as small throttle opening and low revs don't really matter. You could spend a lot of time tweaking the springs and weights on the centrifugal advance to give the best performance at all throttle openings and revs. If the rules allow you could get some thing like an Aldon Amethyst system which will allow you to program a bespoke ignition curve without messing about with springs and weights. Not a proper 3D system but very simple and does not need a crank position sensor.
http://www.aldonamethyst.co.uk/


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PostPosted: Mon Jan 08, 2018 2:36 pm 
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Joined: Thu Nov 11, 2010 12:26 pm
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My max advance is 37 deg. I mark this on the pulley then set it up on the strobe. I never use static timing at all, just rev it so the advance hits the stops and set at full advance.
Make sure the vac is locked off, you seem to be getting issues that you sometimes see on a std dizzy on a std car with the vac pipe removed, they start to pick up advance not that much after idle.
The only difference with the two curves is that the older one hits max advance before the other more common later one.
Obviously a good rolling road will go in steps finding out what is best for your engine and try to mod the mech advance by altering springs, changing weights, or limiting the max advance. It will help if you have a lambda fitted.


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