DRLA 36s and how to stop my bus backfiring?

Quick google says 36/40 - same manifolds. It would be pointless if I can't check the mix screws work and set them up and balance the throttle stops and you need them on a running engine to do that. All systems go!

 

Have you got velocity stacks Sarah?

 

Haven't read through all of this, but have you checked the air bypass screws. There is one for each throat. Make sure that they are not closed and working fine with the tick over.
Sorry if I'm stating the obvious.

 

I won't be tuning for mains, you need to do that with them fitted to your engine and the only real concern there is the AFR under maximum load i.e. foot to the floor through the revs.

I would view them as an essential part of the carb. Velocity stacks do the job of "straightening" the air flow into the carb throat. On the vehicle they came from, the ducting from the air filter to the carbs would have served that purpose but we don't have that.

 

Bless you you've zero need to apologise. You've ignored nothing, simply doubted your ability. All of us that know you understand you've got way more ability with Clem than you give yourself credit for.

 

Hopefully one should not have to adjust these, they were set in the factory and plugged to avoid tampering. Often they are seized solid because they've never been messed with. If I find one barrel obviously out of whack enough to show up on the snail I'd definitely see what could be done though.

 

Like most things, if Sarah saw what I did she'd probably say... I didn't think it would be so straightforward, I could have done that! Sad really that she won't get that opportunity, it's good to know your carbs.

 

I'll post a picture tomorrow from the dells guide showing you where they are.
They are sneaky and if screwed in, can affect the mixture into a cylinder causing it to burn lean and drop valve or seat.
They are monkeys I know from experience.

 

Looking at your linkage/filter base it's made for 40's - they all are which is why there's a big hole in it, bigger than the carb throat. So velocity stacks will be the same size (internal diameter) as your filter bases rather than carb throat and your manifolds same again - made for 40's. So, this causes a step down into the carb and a step back up into the manifolds. I don't think there's any easy way around this and people run with them like this just fine. It would annoy ME enough to get the manifolds welded up and machined, fit some reducers inside the filter bases and make my own 36 sized velocity stacks but who's to say you'd notice any difference? I'd do it anyway so the air path was the same right through with no steps - after all people (including me) match port the manifolds to the heads for that smooth flow.
But it is what it is, you're not going to the drag strip eeking out every HP with the highest smoothest flow you can so it'll rev it's nuts off.

 

They are supposed to be screwed in, you unscrew them to adjust if you have to make an adjustment for one throttle plate not closing exactly the same as it's pair. They could not cause the problem you describe, they are only for smooth idle at no load. I believe you've been misinformed, they are a bypass around the throttle plate when it's closed. As soon as you crack the throttle open they do nothing.

Edit - maybe you are thinking of the manometer ports? If they aren't screwed right in they bleed quite a lot of air in. Some idiot actually cut the inner sealing ends off mine to I have to plug them with pieces of blanked off hose.

 

Thanks.
So it must have been something else that blew no. 2 twice then. Twin 36 dells Type 4..
I don't want to high jack this thread with jet sizes etc.but obviously something was lean.

 

Indeed! The usual suspect would be the vacuum for the brake servo split somewhere or the servo itself diaphram split - mostly the brakes keep performing in those scenarios because they don't need anything like the vacuum they get without a split. Funnily enough I take my servo vacuum from No.2, it plumbed in most easily from that one. 3/4 is too close to the firewall, No.2 provides the most space/right angle to fit the take-off on my manifolds.