db's 66 Belvedere ***FOR SALE***

db · Post by db » Sat May 05, 12 7:44 am

Is there any point fitting a permanent vac gauge? My carb only has a vac port under the butterflies so would tha show me anything useful?

Pete · Post by **Pete** » Sat May 05, 12 9:07 am

Some people do but I would not bother, its best used on initial set up..........a lambda sensor would be more use through the range - see Ade's posts on this...........

db · Post by db » Sat May 05, 12 10:21 am

Ta, there's an old Sunpro vac gauge up for a fiver no bids that caught my eye, no point if it's no use tho.

I'd like an AF gauge but funds won't allow just now...

Dave-R · Post by **Dave-R** » Sat May 05, 12 11:51 am

Vacuum gauges are fine for tuning your primary jet size. Cheapest way to do it.

Idle mixture you can do measuring vacuum or rpm. I usually use both.

db · Post by db » Sat May 05, 12 12:07 pm

Dave wrote:Vacuum gauges are fine for tuning your primary jet size. Cheapest way to do it.

Idle mixture you can do measuring vacuum or rpm. I usually use both.

Measuring vac below butterflies?

Pete · Post by **Pete** » Sat May 05, 12 12:59 pm

And spark port so that you know the butterflies are nearly shut...........

db · Post by db » Sat May 05, 12 1:03 pm

Spark port?

Guy · Post by **Guy** » Sat May 05, 12 2:33 pm

Spark port is the vacuum port in the metering block just above the mixture screws, it should only show a vacuum once the throttle blade move into the open position. This would normally be the take off point for the vacuum advance unit on the distributor.

Dave-R · Post by **Dave-R** » Sat May 05, 12 2:34 pm

db wrote: Measuring vac below butterflies?

Yes. Called "Manifold Vacuum".

Dave-R · Post by **Dave-R** » Sat May 05, 12 2:38 pm

Guy wrote:Spark port is the vacuum port in the metering block just above the mixture screws, it should only show a vacuum once the throttle blade move into the open position. This would normally be the take off point for the vacuum advance unit on the distributor.

Yes.
At idle there should be zero vacuum on this port. If there is you have to open the secondaries a bit more so you can close the primaries. The slot that is exposed by the edge of the primary throttle blades should only have a tiny bit exposed at idle. Enough to make the slot look like a tiny square.
The slot is called a "Transfer Slot". It assists with the transfer from idle circuits to main jets.

db · Post by db » Sat May 05, 12 6:51 pm

I take it this is my vac port? It appears blanked off...

Dave-R · Post by **Dave-R** » Sat May 05, 12 9:28 pm

db wrote:I take it this is my vac port? It appears blanked off...

Yep it has been blanked off. Shame that.

db · Post by db » Tue May 08, 12 5:03 pm

LADIES AND GENTLEMEN, WE HAVE TICKOVER!!!

Mick - I found an air leak on the nitrous plate. Bolts are too long to delete the plate so I've bunged the hole.

I gave the plugs a soak in carb cleaner and a whizz with a brass brush to get them sparkly clean and checked the gaps- all bang on 41 thou!

I've programmed the fan controller to come on at 185*f and go off at 175*f.

Dave - spot on as usual. It just needed lots of tiny carb tweaks!
I turned the idle screws richer 1/2 turn, then another (to 2.5 turns).
Then I opened the secondaries 1/2 turn at a time until it suddenly stayed running all by itself! This was at 2000rpm, I took this opportunity to wind it up to 3000 and set the timing to 34*.
I backed off the primary idle adjuster but it wouldn't drop below 2000.
I backed off the secondary until the revs dropped below 1000 and i could change it with the primary. Some very fine balancing (like a 12th of a turn at a time!) between the secondary and primary stops and i had a lovely lumpy 750-850 idle

I checked the timing at this, I make it 17* initial.
I ran out of time at this point

Next job is to check the float heights again at idle, then fine tune the mixture screws for maximum vacuum at idle, this will give me the figure to work out the correct power valve. (see, I was paying attention

)

I'm still buzzing at the sound of my car just idling all by itself!!

Thanks again for all your help folks, i've learned a lot the last couple of weeks and actually have a bit of confidence around my carb now

Pete · Post by **Pete** » Tue May 08, 12 5:08 pm

Well done Paul, it's been a long time coming; I bet it sounds sweet

All the best.

Pete

Guy · Post by **Guy** » Tue May 08, 12 5:35 pm

Very happy for you Paul, it is a great feeling when thing start to go your way isn't it. Hopefully I will be hearing mine in a couple of weeks too

Anyhow this post of yours now needs a video

Mopar Muscle Association UK

db's 66 Belvedere FOR SALE