Weber problems on new 160 hp engine in Cincinnati

[lunglord]

I have a 1966 Elan S3 dynoed to 160hp. It has a long throw crank, 400 degree cams. The engine has 10 to one compression pistons, is thoroughly ported with new Weber 45 DCOEs. It has a Holley electric fuel pump set at 2.5 PSI pushing Shell 93 gas. This engine is new, less than 100 miles. The engine idles fine, but under acceleration it lags, sounds like it is flooding for lack of a better word, with a flat acceleration, sometimes feeling like it has to clear its throat when the accelerator is pushed too much. Above around 5000 rpm it pulls hard but from 2500 to 4000 lousy. Floats have been replaced. It has been rejetted. We are in a quandry. I think maybe the fuel pressure is set too high.

Does anyone know a great carb guy in Cincinnati?
Frank

[pharriso]

It has a Holley electric fuel pump set at 2.5 PSI pushing Shell 93 gas..... I think maybe the fuel pressure is set too high.

Frank

Fuel pressure should be good. Would accelerator pumps do you have? Too big?

[khamai]

Suggest joining the Sidedraft group -
https://vintagetechnologygarage.groups. ... t/messages

Also, please share the following:
Main Jets:
Emulsion Tubes:
Air Correction Jets:
Idle Jet:
Idle Fuel Jet:
Choke size:

Valve size & lift:

Are you still using the same tune as when dyno'd? If so, was the dyno tuning for maximizing power at WOT or for driveability?

Kiyoshi

[gjz30075]

45s are probably way too big. If you can, choke them down to 33 or 32mm chokes. Anxious to
see what specs you give for khamai' s request

[mbell]

Floats have been replaced.

Have you correctly set the fuel height? If so what to? Have you measured the fuel height down the jet?

(Fuel height has significant impact on the carbs.)

[elans3]

Fuel pressure at 2-5 psi is not too high. Anywhere between 2.5 and 3psi should be perfect. I'd agree with the above, that 45's are more than likely too big, particularly with chokes bigger than 33mm.
I had a big bore TC in a hillclimb car that was dynoed at 165 bhp, using 40DCOE's and 33mm chokes. It pulled like a train to 6500rpm and was super reliable, with immense torque.
I'll try and find the sheet that I made up showing the jetting, but don't hold your breath, as it was more than ten years ago.
As above, it would be good to know your choke and jet sizes, to see whether it's been jetted & choked for a street engine, or an out & out track car.

[h20hamelan]

Is the fuel float measured from the bottom of the top plate (under cap) to height of fuel while engine is running?
15mm?

[rgh0]

What cams (maker / lift / duration seat to seat) and what carb chokes and jetting is the starting point. You say "400 degree cams" do you mean 300 ? The new Weber 45's progression holes may also need some work according to Keith at the sidedraft group . If you have a dyno curve with air fuel ratio this also helps.

cheers
Rohan

[2cams70]

If you’ve “thoroughly ported” an engine it can be a bit of an unrealistic expectation for it to be as driveable as a more standard engine regardless of what cams, carbs, etc. you have on it. If you’ve both “throughly ported” it and fitted 45’s well……..

[holywood3645]

I’ve chased similar problems on a Twin Cam - 150 BHP and a 180 BHP. BDA. In fact I’ve gone in circles for a long time. Without going through the same issues I’ll skip the war stories, I’ve used both 40DCOE152 and 45DCOE151. On both engines.
To start you really need an O2 sensor to see where you are. Also My TC is built to the QED420S super sprint spec.
A really good starting point for me is exactly what QED jetting recommendions

However my main issue was idle jet selection, idle, idle mixture, and mechanical balance. When that was all good I got really good advice on idle jet selection.

I think idle jet selection and setup is your main issue
I’ll follow the thread and share/help if I can.
However in the mean time please share your jetting with us
James

[fotsyr]

I would be speaking to the person who dynoed the engine.

chris

[rgh0]

Many dyno runs start at 4000 or 4500 rpm so easy to tune with a torque hole below this. Without seeing the dyno curve and A/F ratio its hard to comment.

In general a 160hp 1600cc twin cam can suffer a torque hole around 4000 rpm. It depends on the cams primarily but also on the porting and valves and the carb choke and jetting. Lots of variables and little data so far.

The poster has 1 post so unlikely he has an Elan. More likely a Cortina, the added weight makes a torque hole even more noticeable. For 160 Hp its possible also has a long stroke 1700cc engine if it does not have a 8000 rpm bottom end.

10:1 compression pistons are stated but no details on actual compression ratio which is dependent on more than just pistons such as combustion chamber size, head gasket thicknest, piston deck versus block deck height,

Until we get more data its all speculation as to what is the real issue.

Happy to help but impossible with data supplied

cheers
Rohan

[elans3]

He does say it's a '66 Elan S3 though Rohan.

[fotsyr]

Rohan, my dyno guy, RIP, dynoed a 1690cc T/C with Dave bean 150hp cams. Fitted to a Caterham 7. It pulled from 2-7000rpm with absolutly no issues. Head work was minimal.

chris

[rgh0]

He does say it's a '66 Elan S3 though Rohan.

Sorry I missed that

cheers
Rohan