Back on my Mini V-8

[dsage]

It looks like he has a separate intake runner for each cylinder so each carb will be fully independent and won't be trying to share vacuum. I'm glad I'm not the one trying to tune/synchronise them all though...

Thanks. I missed that detail. It should be very interesting to get that tuned up.

 

[bluejets]

It looks like he has a separate intake runner for each cylinder so each carb will be fully independent and won't be trying to share vacuum. I'm glad I'm not the one trying to tune/synchronise them all though...

I had a similar crazy notion a few years ago and it almost ended in tears.
Trying to tune ( 4 carbies) would result in lean running before one had a chance to realise it.
Lean run can end up locking up.
Engine runs fine on one thankyou.
Perhaps do as suggested and make one active and the rest "dummies".

 

[retailer]

Did you do your own thing with the firing order or go with the common 1-8-4-3-6-5-7-2

 

[Mr.McKinney]

Thanks for the interest and comments. I completely agree that this a crazy concept. Running 8 carbs is definitely very complex. But having them independent is the only way I could think that this concept would work. I'll give it a go. I had thoughts of setting up the carbs off-line, initially, using a flow meter and some means to quantify the mixture adjustment. It's a challenge, which is why I thought of giving it a try.

As for firing order, I'd have to go back and check the crank. I designed and machined the crank many years ago and don't recall. I do remember designing it, modeled from other standard cranks. but can't remember how I did it. I need to do a quick
refresher.

 

[stevehuckss396]

I have worked on two V12 engines. The owner had 6 vacuum indicators made from tubing attached to a piece of wood. Not sure if it was made by him or purchased. A red liquid would be sucked up the tube to indicate the amount of vacuum. The tool was used to get the throttle position matched on the 6 webber carbs. Once the carbs were opening and closing together the tuning begins. Adjust, check vacuum, adjust, check vacuum. After a few hours the engines were both running well.

He owned 13 cars when I met him and needed a ride to the store. 7 years later on the day he passed away on his 75th birthday we had 8 of them running.

 

[Mr.McKinney]

Interesting story. So I definitely have my work cut out for myself

 

[bluejets]

One here you can DIY. ....mod to suit your smaller app.

 

[Cogsy]

I might be wrong (it happens a lot) but I suspect there might be more to synchronising model engine carbs than full size carbs due to the build variations and tolerance differences in the carbs themselves and each cylinder. We all know how 'touchy' model carbs are when setting them up compared to full size (some of mine just refuse to run if they're a 1/4 turn off on the needle and a click here or there changes the running characteristics a lot) so trying to get 8 of them set just seems to daunting of a task for me. I wish you luck though!

 

[Mr.McKinney]

That's an interesting approach. Thanks for sharing that.

I was actually thinking about using a similar technique with a U manometer to precisely measure the pressure differential on each carb's venture (probably at the fuel feed bar). Using water, or a material with a lower specific gravity will make the unit very sensitive. This coupled with a flow meter, to calibrate the amount of air flow, would make it very simple and straight forward to quickly balance the airflow.

Next would be calibrating the mixture. Since each carb is likely to be built a little different, I'll have to be able to measure the amount of fuel flow through each one. For this, I was thinking about measuring the amount of consumed fuel, from a small volume custom graduated tube (filled with fuel). This would be an iterative process, but again would be easy to measure very small differences in fuel flow over a defined test period. Getting the carbs synch'd hasn't been keeping me up at night. I'm confident that I can solve this fairly easily. My thoughts are more around getting the other components machined and actually finishing the engine.

Interestingly, I also do/have done a lot of laser work and read an interesting article on Laser Spark plugs in Laser Focus magazine. The industry has used laser explosive ignitors for some time. Getting the right power to be able to ignite a pressurized air/fuel mixture is not trivial, especially from a single diode package. But the process is very intriguing. It could also be possible to use fiber optic spark plug wires with a single larger DPSS laser for ignition. I'm just looking for ways to overcomplicate this and maybe learn something in the process.