SU Carbs - HIF v's HS?

[Davi]

Looking at fitting a pair of SU's to my beetle engine. I know it'll probably be a bit of a fiddle with setup but have seen it done successfully before!

I'm looking at a few options, seems to me that 1 1/2 inch are the size to go for, but anyone know which are the better carb? HIF and HS seem to be the ones that come up most frequently so they're the most likely options

If anyone here is a pro with SU carbs i could probably do with a chat LOL

[PeterBurgess]

The HIF will be the best option as they are not prone to cornering/braking g surge which the HS ones are. This is because the HIF float chamber is under the carb not alongside. We have been contemplating a single HIF44 on a 1640 mildly tuned Kamper engine. At present we are running a 28/36 downdraught Weber which works well. Beware heat on the float chamber which upsets fuelling with the SU, use a heat resistant spacer to the inlet manifold and a heat shield under the float chamber. It would not be worth fitting twin sus you would be better fitting two twin choke downdraughts, one above each bank.

Hope this helps

Peter

[Davi]

Cheers for the info.

You say it wouldn't be worth fitting twin SU's, any reason why? I was going to put one over each head just like other twin setups to get rid of the awful manifold.

[PeterBurgess]

The standard manifold is better than it looks, hence thinking about 1 SU. Two SUs will not be as good as two single choke downdraught carbs, better still is a pair of twin choke downdraughts with smallish chokes to make things work in a sharp, crisp manner.

Twin SU fitment usually has a balance pipe twixt the carbs, this would have to be rather long on a VeeDub engine

Peter

[DrDeAtH]

Other options are:

A pair of solexes off of a Type3
A twin 34 ICT kit
A single 45 IDF
Dual 40 IDFs
DUAL 48 IDAs

I would probably go for the single 45 as it would gie a good balance between power and economy, and would be easier to keep in tune as opposoed to the twin carb kits

However, the dual 48s would give the best power and not too drastic economy, but could end with some ruinous fuel bills....

final option is fuel injection..... like Haltec or megasquirt

[PeterBurgess]

It never ceases to amaze me how VeeDub owners have a tendency to overcarb. We often have engines running large carbs with large chokes, the throttle response is appalling as is the economy. Max bhp is less than with correctly sized carbs and chokes as the atomisation is so poor. For example, a 2.2 litre engine running a pair of 48s and 120 bhp at 4000 rpm at the engine when that will supply a 2.4 Pinto engine running 200 at the wheels at 7000 rpm!

Peter

[Davi]

There are other reasons I want twin, if I'm honest - most notably to get rid of the manifold and a lot of other stuff in the middle of the engine, so really do need a twin setup. You're right about the balance tube, on past versions this was part of the manifold rather than the carb as is in other applications.

Also contemplating starting with a much bigger engine LOL

[davepoth]

Davi said:

There are other reasons I want twin, if I'm honest - most notably to get rid of the manifold and a lot of other stuff in the middle of the engine, so really do need a twin setup. You're right about the balance tube, on past versions this was part of the manifold rather than the carb as is in other applications.

Also contemplating starting with a much bigger engine LOL

What sort of capacity and power are you looking at?

[DrDeAtH]

I wouldnt run 94mm pistons and barrels on a camper as the barrel walls are too thin, you will benefit from thick walled (90.5) at most, you could get away with 92s

as for losing stuff from the middle of the engine... 911 fan conversion by chance?

[Davi]

DrDeAtH said:

I wouldnt run 94mm pistons and barrels on a camper as the barrel walls are too thin, you will benefit from thick walled (90.5) at most, you could get away with 92s

as for losing stuff from the middle of the engine... 911 fan conversion by chance?

Apologies for tardy reply, the thread got swallowed up by dross on my desktop

Not 911, no. I researched the power sap from those things - scary! I'm building a test bed for some 'alternative' cooling set ups so basically I want nothing at all across the middle. I'm also planning on testing a few forced induction set ups on it later and it would be very nice to have it all above the centreline rather than swathes of pipework but that's another matter...

Edited by Davi on Saturday 17th November 01:30