216 carbs on a 261

need an opinion from the folks on this board. am building a 261, 848 head, possible overbore, maybe a cam, definitely a dual intake and a set of headers. what is the opinion of running a matched set of 216 carbs on this motor. i was told that he rule of thumb should be 216 carbs x 3, 235 carbs x 2. but you always here of builds that work w/ a million different combos. just want to hear the opinions out there and mybe what some of you have run or are running. thanks

big ed

 

Your engine sounds pretty mild, so I think that two 216 sized carbs would be fine.

 

Werent they pretty much all rochester model b carbs anyhow? I think the only difference might be the size of the mounting base to the intake. So maybe more important is just matching the carbs to the intake you choose. My two bits.

 

Depends on the rpm you want to make.
If you stay on the streets mostly under 3000 rpm, 2x 216 carbs is all you need.

My 261 bored 0.060 with 254 adv. duration cam has 2x 216 strombergs and there is plenty power left when I go on the highway between 2500-3000 rpm.

 

A pair of 216 carbs will be fine. What type of carb?

Note that the 216 carb is going to have a smaller bolt spacing than your 261 has. You may need to slot the holes on the carbs depending on the intake you use.
If you use an intake that takes the smaller base carbs, it will likely need intake port adapter rings or have the runners punched out to the larger size.

 

The only intake manufacturers that I know of that made 235 intakes with 216 carb spacing were McGurk and Nicson.

 

Correct me if I'm wrong, but early 216 had the Carter W1 and the later ones had the Rochester Model B same carb as the 235 and 261. I think there is a Zenith they put on a few as well, but I hear you should stay away from those.
I agree with Snarl. The bolt spacing is the issue.
Also, some old Fenton intakes had the narrower spacing as well.

 

Before I switched to Mcgurk intakes, I had Offenhauser and Fenton 2x1 intakes for the 216 and bored out the head ports for 235 alignment rings.
You can also get 216/235 adapter rings from Larrowe's & Sons.

 

http://www.thecarburetorshop.com/Dual1barrelcarbs.htm

I picked this out of an earlier carb thread

here is the thread:

http://www.jalopyjournal.com/forum/showthread.php?t=325220

 

Great Read. Thanks.

 

Yeah, I had to ping heathen a bit in there. He is a nice guy and has nice stuff.

 

i have an offy 2x1 for the 235/261. if necessary i would make an adaptor to change the intake from the 235 spacing to the 216 spacing. not a race engine but will run at highway speeds a lot of the time. mine is a 60 261, supposedly it has the same cam as the 53-55 vette 235 motor. may go to a patricks 264 cam for a little more rump in the motor. hope this helps the discussion.

 

Those 216 carbs,Mcgurk intake, and exhaust work together[/quote]


I'd hate to tell that to Bigedpa because I would like to own it.....

 

Patrick's sells Delta cams.
I sent my original 261 cam directly to Delta and had it reground to a 254 grind, which works great with my 3.55 rear without overdrive for the highways.
That grind holds torque all the way up to 3000 rpm and has peak HP around 4000 rpm.
The 264 symmetrical grind gives a little less bottom end torque in favor of more HP at high rpm.
The 'Bulldog' 254/264 in/ex grind is very popular for the 261 and still has good torque for the street.
Patrick's sells that cam.
He is a great guy and very knowledgeable and likes to share what he knows over the phone.

If you go a lot on the highways with a modern transmission and overdrive around 2000 rpm, the stock 261 cam will give you best power/mileage.

I have heard from guys with 235 intakes who filled the mounting screw holes and redrilled for the smaller 216 carb screw spacing.

 

I have heard from guys with 235 intakes who filled the mounting screw holes and redrilled for the smaller 216 carb screw spacing.[/quote]


I had that done at a rod shop on my polished Fenton intake and it was costly. if you do it yourself you will save some bucks but it is tedious to do I think.

 

If you just slot the holes on the carb to match the larger pattern, then you aren't causing anything to be unuseable, and you're not spending any money.
If the intake has the narrow bolt pattern, you can't use the wide pattern carbs (at least with the "B" carbs) because the nuts will be too close to the body.

Chevy used Carter W-1's through '49, then started using Rochester B's in 1950. The B has 2 different bolt patterns and 3 different throttle bore sizes depending on year and application.

 

I thought about slotting them, but I think they look stupid that way. After I did it to a pair, I realized I was right.

 

Use an acorn nut and a flat washer and nobody would ever know...

 

Get aluminum thread stock or a bolt (probably 1/4-20 or 5/16-24 NF).
Cut to length.
Saw the top to make a screw slot.
Run it down the stud holes until just above flush, with LocTite.
File the end down to match the flange.
Drill and tap the new hole - it can cut into the top of the stud without a problem.

 

Is there enough room for an acorn nut? I thought they are too tall and you cant turn it.