Elevation drama with my twin webers or,,,

[CrisinColorado]

"how I've spent my last two summers"

I know that a man has got to know his limitations....., so I've sought help from a local Elan racer
who's done all his own dirty work for decades. He's been so patient with both myself, and the car.
I know just barely enough to be considered dangerous. We've been fighting this ever since the engine went into the car. Numerous weekend afternoons always followed by great Mexican food.

My tall deck twin cam in my Hillman Husky has always had a 'hunting idle' and run wicked rich, so
much that it fouls the plugs. Plugs are good for about fifty miles *sigh*. Idle will go from about nine, and then after the carbs are released back to idle it might be at 15-1600.

At throttle tip in from off idle it chugs-barks up to about 2700rpm unless you slip the hell out of the clutch with a high rpm start. The slip the hell out of the clutch thing is getting 'old' to say the least. When it does decide to 'run as designed' it's like a light switch has been flipped, and it's glorious in both sound and forward motion. Just awesome. But chugging around parking lots is not how I envisioned this. Semi un-docile sure, but not this on/off crap. It also misses slightly when the good noise is being made. Carbies have been gone thru twice now, always seem to check out fine. By two different local twin-cam Weber guys. But yet this persists.

We've thrown so many jets-airs-tubes at this thing that the folks @ Pierce Manifolds in Gilroy CA know
me by name now :-0)_ and I've got a nice collection of little metal bits that I had to buy a bigger plastic box for them all.

Can anyone provide a baseline for about a 3/4 race cam set up.? I've been running 110* octane race
gas mixed with leaded 92 (50-50) in this 11.3 to 1 dual 40engine that's running a modified Elan header.
I can provide motor build specs, current carb settings, air filtration set up and how it did on the dyno. Don't know why this doesn't show up on the engine dyno, perhaps because it's always under a partial load while connected to the dyno.?

Perhaps the engine's just pissed it has to power the Husky and has had quite enough.

Cheers & thanks in advance.

[mbell]

It's recommend you buy your self an air fuel ratio gauge, then you have some clue to what is happening to the mixture and therefore possible adjustments or faults.

You get a get a decent AEM for $150 these days which is probably a lot less than you've spent on on jets etc.

Also check your fuel pressure, could be carbs flooding.

[el-saturn]

i could tell you what my jetting looks like , but i'd take a look at your distributor and those settings. i also have about 11mm lift, 41,3mm intake valves, steel and forged everything etc. etc.., but my car runs like a pussy cat! sandy

[CrisinColorado]

It's recommend you buy your self an air fuel ratio gauge, then you have some clue to what is happening to the mixture and therefore possible adjustments or faults.

You get a get a decent AEM for $150 these days which is probably a lot less than you've spent on on jets etc.

Also check your fuel pressure, could be carbs flooding.

.
Yeah, we've thought about that (the a.f.r.g.). He ran one in his Elan wehen he was getting it set up. I'm not trying to get it 'dead-nuts' but in the ballpark sure would be great. Suppose we could mount one temporarily. Under hood f.pressure gauge is reading 2-2.5 #'s of pressure which is pretty close from what we've used before on other weber-ed setups.
To the other poster it (the engine in the car) was the backup bullet to my buddy's Lotus 23 sports racer. Not all the bells/whistles, no stroker crank for example but nice rods, pistons etc. The distributor is a new Pertronix Mechanical advance that was checked for 'shaft slop' before install. Timing was checked for accuracy while it was on the dyno. Ignition spark is handled by an MSD box, configured for 4 bangers and my distributor.

Thanks for the input, would love to hear more (hint hint).
Cheers,
Cris

[rgh0]

Some details on the cams lift and timing and duration. The carb current jets and cokes and the ignition timing static and and advance curve timing would all help. I should then be able to have a go at a basic setup to start from. Also what model 40DCOE do you have as the progression holes drilled in the bodies vary

Have you checked the position of the throttle plates versus the progression holes as that return to a fast idle and stumble off idle is typically a symptom the throttle plate not covering the first progression hole fully.

cheers
Rohan

[Chancer]

Were you running the same exhaust on the engine dyno?

I should ask the question also of the Dizzy, carbs, air filters etc but my initial thoughts are an inlet stand-off caused by the exhaust primary lengths and valve overlap.

Never seen it manifesting over such a large rev range though, I recall a highly tuned Hillman Pimp belching around the track like that for nearly 3/4 of a lap before it cleared its throat and got on cam and then it really flew.

[bill308]

To me, this issue seems like it could be a carb synch problem. How did you balance the air flows?

Bill

[CrisinColorado]

Hi guys, I'm currently out of state up in the Pacific N.West (looking at a car, like I need another money pit!).
I'll post what I have when I get back home Monday night.
What size chokes are you folks running.? Could it be over choked.?

Sorry I can't update much now but all my notes are at the shanty.
Cheers & have a great weekend.

Cris

[rgh0]

33 or 34 mm chokes is probably biggest you would want for a road use twin cam with DCOE 40's

cheers
Rohan