Which 2bbls. to put onto a 40hp engine w/83mm p/c's?

[Jim H.]

I'm assuming this topic has probably been gone over a few times already, but I can't find it in the topic board. I want to install the 83mm slip-in's on my 40hp motor, put on a header exhaust, and install a weber/solex/delleroto 2-barrel (center-mounted) carburetor. What would be the best size carb to go with (i.e..32/34, 26/26, 40/40,) or is an 'IDF' better to run than the 'progressive' type? All help is greatly appreciated!!

[GTV]

The only single two barrel carbs I know of that have 40hp manifolds are the DCNF and Zenith. All old stuff, can be found used but not produced anymore.

You would be much better off with dual single barrel carbs.
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[earthquake]

I would think a single Zenith of DCNF would work well on a 40hp, I would get a 010 or 019 distributor for it. Get a set of square boss heads and a 1965 case or have the case machined for cam bearings. You can find used headers in the classifieds every now and then, That would add a few hp's.
Don't forget a Holley bugspray carb just make sure its the 200 cfm model.

Casey
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[spencerfvee]

Hi Jim if I were you .i would run a zenith carb there are manifolds out there for the zenith carb that's the easy way .the hard way is to run a weber carb .there are all kinds of parts for the weber carbs.there are lots of intake manifolds you can cut up and make end castings for. to make them work on a 40 hp motor .but when you look at the size of the 40 hp manifold .and look at the size of the weber manifolds is way bigger than the 40 hp manifold . So all the work you would do to put the 40 hp small end casting on the weber manifold . It just would not work well at all .my friend .but go for it if you want a weber carb on your 40 hp motor good luck

[Kjell Roar]

Hi!

You need to know the flow in your heads, and then look at this flow table, to choose matching carburators:

It might be a good choise to find a set of 1300 heads, more intakes for them, and bigger valves.


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[Jim H.]

The 1300 heads would go onto a 1200cc case, without having to modify anything? And their intake-ports are bigger..to accomadate a bigger Weber carb manifold?

[Kjell Roar]

[Syncro Rob]

I don't post often but thought I could chime in with my experience.

I've built a somewhat similar engine with the larger single port heads.
There are many things that needed to be customed in my engine to make it all function and did required certain skill and machinery equipment.
My main goal was the look of a mostly stock looking engine with some punch.

The heads were Flow tested and tuned on the flow bench. The end result was a much better flow than a standard DP port. I also bumped the compression half a point.
I used the larger DP intake manifold and joined with rubber sleeves to the larger single port head manifold tubes.
Carburation was a Solex 34 PICT-3 with choke tube removed. Idle jet was modified as was a custom main jet.
Distributor is 019. Previously, a Mallory dual point which worked great until the rotor broke and i had no replacement.
Exhaust was a vintage Deano extractor 4 into 1.
Empi 4:1 ratio rockers.

The engine has 83mm p/c and 64mm crank
End result was 63hp DIN@4400rpm and 81ftlbs @2750.
The little motor has an impressive power curve and pulls over 60hp from 4000-5000rpm

The ratio rockers did yield up to 7hp in the mid range but only 3hp at the top rpm. I do feel the motor is still choking above 4k and the next mod will be a pair of type3 32PDSIT's to hopefully free up the last bits of upper end power.
I'll let you know how it turns out. Should be fun.

Good luck. Robert

[Jim H.]

Very nice engine!! A question though. How did you compensate for the shorter 64mm stroke with longer cylinders & heads? I was talking with a person a few days ago about putting 1300cc heads onto my 40hp to accommodate the larger intake manifold. But he mentioned that those heads are longer in diameter to work correctly w/ the shorter crank stroke.

[spencerfvee]

hi rob nice motor looks great . it must be fun to drive .how fast will it go on Germanys highway where there is no speed limit. I will bet it does 95 mph spencerfvee

[Syncro Rob]

-The p/c's are cheapo CIP replacements, item vwc-111-198-057-ab. No issue. No modifications.
-4 head studs on both banks needed to be replaced with longer factory studs.
-Originally i ran the stock rockers and they needed to be shimmed further out to correct the geometry . Afterwards I replaced them with ratio rockers and I custom cut the pushrods to suit.
-The pushrod tubes are the plastic expandable/collapsables with pressure spring also from CIP.
-The intake manifold and tubes slide together nearly perfectly and compensate for any length difference.
-I also cut sleeves for the exhaust to automatically compensate and give a perfect fit. One can be seen in the photo.