WEBER 48 IDA'S Help needed

Steve Rivett

Supporter
Hi All
I have a 351w engine bored and stroked to 390 cu in with ported Allen Root heads (1.95 inlet/1.65 exhaust).
Camshaft is a 290 deg Competition Cam, pistons TRW Forged with a 11.5 to 1 compression ratio.
It is currently running 480hp on a 4 barrel Holley.
I am planning a Weber 48 IDA conversion.
Is there anyone with a similar setup that can give me an idea of a base choke/jetting setting.
Also an idea of ignition timing.
The engine will be setup on a rolling road but a starting point would be good.
Planning on about 520hp.
Thanks
Steve
 
Hi Steve,

I would suggest you contact Kenny Coleman at Engine Data Analysis Castleford, I am sure he can advise you. He has always been more than willing to give me advice when required, expert on IDA's as well.


Engine Data Analysis
 

Cliff Beer

Supporter
Steve,

I might start with the following for your 390:

Venturis: 42
Idle jet: 65
Idle jet holder: 120
Emulsion tubes: f7
Mains: 145
Air correction: 160
Pump jet: 59

You could try a 60 idle jet and see if that works better in the alternative.

Highly recommend using 4 calibrated flow meters (one for each IDA) to facilitate sync'ing the carbs.

If you want to do this yourself then mandatory reading is Pat Braden's
"Weber Carburetors" book. If you don't have a detailed inside understanding of how the IDA works then it'll still be a bunch of black magic...and you'll be dependent upon others to get it right for you.

Just my $.02 from my own first hand experience.
 
Steve, there are a lot of other things to consider before just bolting on a manifold and IDAs to a GTD40, give me a call if helpful. Frank
 
Steve ....... I may be wrong and welcome Frank Catt's input, but I think you'll find it very difficult to get through an MOT emissions test with IDA's fitted.

Anyone with solid knowledge in this respect is welcome to comment because I would love to fit IDA's on my car but have decided it may be folly to do so.
 
Steve ....... I may be wrong and welcome Frank Catt's input, but I think you'll find it very difficult to get through an MOT emissions test with IDA's fitted.

Anyone with solid knowledge in this respect is welcome to comment because I would love to fit IDA's on my car but have decided it may be folly to do so.
Hi,

Good point Steve, mine got through IVA 351 with IDA weber's in 2017 due to it having a 1971 block (visual smoke test). There has recently been some recent government proposals to change the emissions to the date of the test not the age of the block, possibly making it retrospective as well, if so you are right mine will not pass an MOT, even though it passed IVA.
 
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Steve Rivett

Supporter
Hi
Thanks for your help with this.
The GTD40 was registered in 1997 so not sure what the emissions test would be.
Although there is an engine number in the log book, I have not been able to get a build date. I will have to remove the starter and get the block casting number for this.
I have sent a private PM to Frank and await a reply.
I have been torn between the Webers and an 8 stack EFI system (both about the same price) with the Webers an easier install but the EFI more control.
Steve
 
Nick ....... you are correct in what you say. The recent consultation has now ended and I, like many others, are awaiting the outcome. The proposal to remove the concession of an 'Engine Dating Certificate' is deeply worrying.
I was involved on several forums with regard to writing letters to the Department of Transport and your local MP regarding aspects of the consultation.
At the risk of offending some people, I contacted various officers of the GT40 Enthusiasts Club (some of whom have now stood down) and recommended they get the members to write and also alert members via the web site. Nothing was done and now it's too late.
If the worst situation comes about, there are many people who will have a car that fails the MOT and addressing the problem will be time consuming and expensive. It is noticeable that there are many cars at the moment that are not selling. So I suspect people are aware and therefore holding off making a purchase.
 

Steve Rivett

Supporter
Hi
I had an in depth conversation with Frank Catt today about the installing of the Webers and the fuel system to support them. What a helpful and knowledgeable person.
It seems the ideal fuel system is a Swirl pot and full return system the same as an EFI system but at low pressure. I was hoping for a simpler system which swayed me towards the Webers along with the looks and sound.
I am now reconsidering an EFI system with Jenvey throttle bodies and a possibly a full ECU controlled ignition.
Having worked on Mazda RX7 EFI engines for the last 10 years I am familiar with fuel injection and ECU controlled ignition and have a very experienced guy to install and map the ECU for me.
 

Cliff Beer

Supporter
Hi
I had an in depth conversation with Frank Catt today about the installing of the Webers and the fuel system to support them. What a helpful and knowledgeable person.
It seems the ideal fuel system is a Swirl pot and full return system the same as an EFI system but at low pressure. I was hoping for a simpler system which swayed me towards the Webers along with the looks and sound.
I am now reconsidering an EFI system with Jenvey throttle bodies and a possibly a full ECU controlled ignition.
Having worked on Mazda RX7 EFI engines for the last 10 years I am familiar with fuel injection and ECU controlled ignition and have a very experienced guy to install and map the ECU for me.
Steve, given your gov't testing requirements, I suspect you'll have an easier time getting the car past the testing with EFI. "Easier" being a relative word there to say the least.

That said, I'm impressed with the multi-port EFI systems now available out there. I've looked at several, and installed one particular system myself to good success. If you know the basics of EFI and you have some skills and facilities then you can handle it. The four-barrel EFI version is a heck of a lot easier to install than the multi-port/8-stack type....I'll say that.

One obvious advantage - you can work the fuel mapping to best effect for clearing the testing....then do what you like after that (tune for power)...to whatever degree you're comfortable with....
 
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