My 948+ build

How to upgrade your Austin...and further......
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gazza82
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Re: My 948+ build

Post by gazza82 »

Hurtzberg wrote:I did put out a wanted add for a 1098 but no one replied.

Having a battle with myself as I'd like to keep the original engine (But then I am modifying the engine so does it matter?)
Got a 1098 gearbox ... From A40 MkII :-)
"If you're driving on the edge ... you're leaving too much room!"

Club WebEditor.

Cars: "Project 757" '59 A35 2-door bought in 1971 & Subaru BRZ SE LUX Auto plus "family fleet": Alfa MiTo, Peugeot 206, (Ex '98 Alfa Romeo 156 2.0 TS)
Jimbo
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Re: My 948+ build

Post by Jimbo »

Get your head gas flowed & ported with hardened seats new valves & double springs, Duplex timing gears. MG metro cam, 2 or 4 bolt center main strap, have the flywheel lightened, flowed exhaust manifold & system. maybe an 11/2" SU .
Hurtzberg
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Re: My 948+ build

Post by Hurtzberg »

This was built up in the end and is working ok.
997 Cooper S cam
1.218 inlet
1.03 ex
- 80 thou from head ~ 23-24cc combustion chamber
+ 30 flat top pistons.
double valve springs.

Took the plugs out the other day. If I just let it idle for 5 minutes, the end up black like it is way to rich (I did previously increase the richness) if I go for a full throttle drive, the end up the correct colour.

Is that normal ?

I assume it is a sign that the wrong needle is fitted so I have a choice of correct at idle/weak at full throttle or overrich at idle/correct at full throttle.

Thanks.
Andrew

1957 A35
Big Daddy
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Re: My 948+ build

Post by Big Daddy »

Hurtzberg wrote:This was built up in the end and is working ok.
997 Cooper S cam
Think you mean 997 Cooper cam (Cooper S was 970, 1071 or 1275cc). Haven't researched but didn't the 997 engine have the narrow 3/8" cam lobes :?:

Sounds as though your carburation needs setting up... :wave:
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Hurtzberg
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Re: My 948+ build

Post by Hurtzberg »

Hello Big Daddy,
Thanks for the quick reply.
Yes, the 997 Cooper (Sorry about the extra S) with the 3/8" lobes.

I'm here for help with the carb setup, Sir. Obviously a Dyno/Rolling road is ideal but it would be good to get a "Close enough" setup for now.

Additional info, Hs2 carb. A40inlet/exhaust forged manifold with a normal a35 pee shooter exhaust. K&N filter.

Just managed to persuade the carb to let me remove the needle and it is an M needle.

Any advice BD as I might not make it to a rolling road til the new year. I assume richer is safer for the engine than leaning out too much.

Cheers.
Andrew

1957 A35
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gazza82
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Re: My 948+ build

Post by gazza82 »

M is the rich needle for a 998 mini with an HS2. 997 Cooper had twin HS2's as standard.

Standard 998 needle is EB, and weaker is GG, all with red spring.

Got info from here .. http://www.7ent.com/pages/articles-tech ... eedle.html
"If you're driving on the edge ... you're leaving too much room!"

Club WebEditor.

Cars: "Project 757" '59 A35 2-door bought in 1971 & Subaru BRZ SE LUX Auto plus "family fleet": Alfa MiTo, Peugeot 206, (Ex '98 Alfa Romeo 156 2.0 TS)
Hurtzberg
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Re: My 948+ build

Post by Hurtzberg »

Thanks Gazza,

Mike H (on here) previously gave this info about my carb:
Early Mk2 A40s had the 948cc engine and SU carb (AUC980)
Std needle----- M

Weak----------EB

Rich---------- AH2

Red spring

But not sure where he got it from.

When I enriched the mixture, the top end was definitely improved.

Thanks for the needle codes. I looked on the "Minty SU" site and compared the ones mentioned by you and Mike and it appears very little difference in richness between M and EB at idle. It's only on more throttle that it starts to make a difference.

That means (I think) that going for the richer needle (AH2) should allow me to weaken the mixture a little to not be over-rich at idle and the needle should make the mixture rich enough at full throttle.
Andrew

1957 A35
Big Daddy
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Re: My 948+ build

Post by Big Daddy »

Hurtzberg wrote:Any advice BD as I might not make it to a rolling road til the new year. I assume richer is safer for the engine than leaning out too much.
I haven't played with SU carbs since 1977, even my old A35 racer had a Weber 45 DCOE... :whistle:

There are many on this forum who can offer better advice on SU's such as Gazza and Dave Clark. Rolling roads have limitations so we prefer to set up on road using a wide band HEGO sensor. But from experience, optimum calibration of fuel and spark comes from an expert with his own engine dyno... :thumbs:

Rich fuelling is always safer because the extra fuel vapourises and cools the charge, delaying onset of detonation and dreaded pre-ignition. Play safe by not running leaner than stoich (AFR 14.7:1) and enriching to maximum power (12.6:1) at wide open throttle. AFR of 12.6:1 is our target for the race cars but for engine safety on the track, we avoid AFRs leaner than 13.5:1 at all throttle openings ... :wave:

Figure-15-Effects-of-air-fuel-ratio-variation-on-the-fuel-economy-and-power-generation.png
Figure-15-Effects-of-air-fuel-ratio-variation-on-the-fuel-economy-and-power-generation.png (31.15 KiB) Viewed 686 times
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Edosan
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Re: My 948+ build

Post by Edosan »

Hi Andrew, Think you need to go at least EB, following advice on here I recently changed from standard AN on my 1098 to Weak EB and what an amazing difference, engine running better right through rev range and its the sweetest tickover I've ever had. Reason is basically modern fuels. Needles relatively cheap and so easy to change so suggest you simply experiment and find which one it runs best with. :wave:
Big Daddy
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Re: My 948+ build

Post by Big Daddy »

Edosan wrote:Reason is basically modern fuels.
Good point Ed... :thumbs:

All petrol sold in the EU typically contains up to 5% ethanol (E5 – the “E” stands for ethanol and the “5” stands for the maximum percentage of ethanol content) with E10, E20 and greater ethanol content in future. Wonder what will happen here after Brexit :?:

http://epure.org/about-ethanol/fuel-market/fuel-blends/
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babyofo
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Re: My 948+ build

Post by babyofo »

Hi there,
A friend of ours helped us set up the ignition and su carbs on ofo, his snippit of advice was to increase the plug gap to 30 thou to deal with modern fuels, ofo does run better( especially after swopping out a brand new faulty spark plug for an old one which does spark all the time, not when it feels like it)
Hurtzberg
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Re: My 948+ build

Post by Hurtzberg »

Thanks Chaps. I'll try the spark plug gap idea (Mine is currently whatever the plug manufacturer set)

I'm ordering the AH2 (I remember Mr Clark recommending a richer needle to me previously) and I've got a friend with a spare EB needle that I can try if the AH2 makes things worse.

Today, I lowered the mixture back down. The idle was cleaner but the spark plugs were too pale after a run and it felt gutless in the top end compared to the rich mixture so I really do think the richer needle will help. I'll report back.

I have a new timing gun on the way too to check that the dizzy doesn't have issues that are leading me to false conclusions.

Thanks for everyones help, Andrew.
Andrew

1957 A35
Edosan
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Re: My 948+ build

Post by Edosan »

just for info I tried weakening the mixture with my standard needle and the plug ran too pale and it didn't run properly overall. It was only one flat on the adjuster but clearly too much. Changing the needle had an entirely different effect. I'm running standard gaps on my spark plugs. One other thing though is I'm using super unleaded, not sure how much difference that makes but my impression is that it runs better and I'm getting better mileage so it pays for itself.
Dave Clark
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Re: My 948+ build

Post by Dave Clark »

With my first A35, on an SU (In 1962) I ran it with whatever needle came with the Morris manifolds and carb.

It went fine, as far as I could tell , but I soon discovered that if I was going for an overtake or a fast take off it went a lot better if I pulled the choke out, returning it progressively as the revs came up.
Could be a test to see if the car is running too weak on full throttle ?
Big Daddy
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Re: My 948+ build

Post by Big Daddy »

Dave Clark wrote:It went fine, as far as I could tell , but I soon discovered that if I was going for an overtake or a fast take off it went a lot better if I pulled the choke out, returning it progressively as the revs came up.
Sounds like transient under-fuelling. Could this be improved by changes to damper spring rate and/or oil viscosity :?:
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