1951 Nash Rambler Build Thread

That's pretty cool. Which is the outlet and which is the inlet?? You could easily plumb that with a single SU, suck through, and then do a split outlet to the carb mounts.

 

The middle opening is the inlet, and the outer opening is the outlet. I am planning on running two Carters, and run the plumbing to both of them (if that doesn't work, I will build a pressurized airbox that will mount on both carbs)

 

Very nice car and the engine is great

 

Thank You!!!

 

Probably the best way to go. SUs don't work well in a "blow through" set-up, the slides don't want to lift.

 

An SU type carb would have to be mounted on the super charger similar to the photo in post #89. With only 5-6 psi a blow-though setup should work without an air box, guess D. will find out! As far as I can tell the head is set up for two of the original Carter YFs.

 

I do not believe the carters will work with pressure on them. They will loose gas and the internal vacuum signals will be voided unless you put them in a box. At low boost 4 to 6 lbs, suck through is not a big deal. Does the blower have a magnetic clutch on it?? So you can run without the blower on all the time.

 

Well, the blower has "low Boost" and "High Boost" setting This means when the car is idling and at cruising speed its only getting minimum boost, about 1-2lbs. But when you floor it and the rpms go up, it goes to "high boost" which is about 4-5lbs. From all the info, i've been reading i haven't come across anything that said any specific carbs can't be used.... hmmm

But right now I am starting the vacuum system on the supercharger...

 

The first vacuum is from the nipple on the supercharger this goes to the distributer vacuum advance, and the vacuum gauge.


Now the problem im facing now is the vacuum switch that activates the solenoid to put the supercharger in "high boost" mode. The vacuum line is suppose to go to the inlet manifold, bug I don't have an inlet manifold, since the head and intake are the same....

If you have any ideas.... HELP!

 

Either drill into the "manifold" in the head and tap for a fitting or make some spacers for below the carbs and tap the vacuum there.

 

So, if I was going to make spacers underneath the carbs, would I need to tap into both carbs, then T it into one line? or would I just make one spacer, and one vacuum from it?

 

Frank,

Thanks for the heads-up. Do you know if the '61-'63 Ramblers have any more room? I know the chassis parts are the same. I could probably do without a heater, but would prefer to keep it.

Mike

 

Been doing some reading, and it seems that your SC is built to do blow through carbs, but you carbs are definately not. the floats are designed to work at atmospheric pressure that is equal inside and out side the carb. Also it is recommended that fule pressure be 4 to 6 lbs higher that blower pressure as it needs to overcome that pressure for fuel to flow into the carb.

You are probably going to need to build a box for the carbs to live in so they will be in a pressure neatral evironment. So how you deal with linkage, throttle return springs and choke linkage, is goig to make your project intereting.

There are several sites about carburetors and super charger on the web. Hope you ca get it figured out because it sure looks neat.

http://vs57.y-block.info/road_test.htm

Some good info in the pdf links here.

http://www.raylinrestoration.com/TechnicalPages/McCullochVS57.htm



Here is a shot Of a Kaiser stock installation with the carb hat, notice the spring steel over pressure relief valve at the top of the enclosure.

 

Well I haven't purchased any carbs yet, so what carbs can I use so I can just use a carb bonnet on top?

 

What was the stock carb??

 

The stock carb was a Carter YF

 

Probably just one if the "manifold" is connected in the head.

 

Ok, I think that will be my best bet... I really DONT want to drill into the head... because Edmunds Nash heads, they don't pop up to often...and I hate to mess it up...

 

Do you know the reason why I can't just go off the carbs vacuum? Is it different then the inlet manifold?

 

Another little update. I started the plumbing for the supercharger. I am planning on using an Edmunds Custom filter, I think it will look fitting in there

 

There should be a plug in the side of the block near the top edge just under the head on the carb side. That would be for a power brake vacuum hose. If there are no plugs near the top edge/carbs then drill the side of the block about 1/2" down from the top and tap for a barbed hose fitting. The late 60s models had a 1/2" hole drilled and tapped in the center right under the carb for a PCV hose. A vacuum line in just one of the spacers should do the trick.

You might want to investigate a suck through design if you have to use carb enclosures since you have twin carbs.

 

I would check with some body who is familiar with this Type of SC. They may not tolerate a fuel air mix passing through them. If you decide to build the box, I would go with 2 stock carbs as they are simple and easy to cobble linkage for. Your box would just need to be drilled and grommeted to allow the fuel line, choke cable, and throttle linkage to pass through.

Carb vacuum and intake vacuum are opposite signals. Ported vacuum is usually from the carb, as it reacts to speed and air flow increase through the carb. It is lowest at idle, increases at WOT and decreases at cruise. It is usually the signal used for vacuum advance. Manifold vacuum is highest at idle, and decreases at WOT. Thats why its used for power brakes, as brakes do not usually operated when the throttle is opened.

So you eed to ascertain which signal moves the controller on the SC the right way for the WOT signal. It might be either but I would bet it is manifold as it would work against a spring, and the low vacuum would allow the spring to engage the SC, and high vac at idle would pull against the spring to shut down the SCat idle and cruise.

AS noted the windshield wiper/brkae booster port is probably the best to use, or to tap another near it.

 

I forgot about the windshield wiper port! That model would have vacuum wipers. Just put a T in the line between the intake (port on side of block) and fuel pump vacuum booster.

Good call on checking if the SC will take a suck-through carb!!

If you have to build a box for the carbs, use a cable throttle linkage. Easier to grommet a cable through the box. What I think I'd do is link the two carbs with a hard linkage then run a short cable from the rear carb to just outside the box. Then have a bracket and connection for a second cable. Would be easier to seal the cable if it doesn't move. Just make a single box for both carbs with a removable lid -- sealed of course!

 

Thanks for ALL the great info! I was doing some research last night and on the VS57 website, it said it is not required to have them in a box, bonnets will work, BUT it wont be as efficient. Interesting....

 

The McCulluch can NOT suck an air/fuel mixture. It would damage the insides. It only blows thru.

 

Is there a way I can get a bigger jet, for the stock Carter? And if I can what do you guys think will be the best bet?

 

Some things to consider

Adding a carb essentially halves the air flow through each carb, therfore it also halves the fuel being drawn through each carb

adding the SC at 6 lbs of boost is equal to about 1.5 atmosheric pressure so you have added about 1/4 back to to the flow to each carb when the SC is providing boost. But still less to each dual carb, than the flow at 1 atmoshpere through 1 carb.

If anything you would need smaller jets. However you have added Compression ratio through the after market head, and addtional apparent CR with the pressure from the blower. Stock was 7 to 1 so you might be 9 to 9.5 with the head and the boost. Keep in mind that most boosted engines actually come from the factory with lower CR's than non blown models.

That said it is much better to run a bit rich, than to run too lean, you do not want to have preignition and start melting piston tops and rings, which can come from too lean a mix.

Set up stock and read the plugs and react to actual running conditions.

you will need a bigger plug gap and perhaps a colder plug, and some more initial static timing when you are ready to get it set for start up.

Another item to consider, the thread area for the spark plug is thicker than stock head, so you will probably need to do ome searching for a similar plug with longer reach to get the electrode back down ito the combustion chamber. The stock plug will install with the electrode shielded up in the head casting. not good for ignition and also not goos to have the lower threaded area of the head exposed to the flames and temperatures of igition especially with aluminum.

 

Thanks for the heads up. I will go stock first and go from there, can u still get jets for the stock carters?

 

Started the plumbing from the supercharger. It's looking good!

 

perhaps these folks could be of assistance

http://www.uncommonengineering.com