Not Enough Carb?

Matthew68

Well-known member
Hey Folks,

Getting ready to pull my block for machining and rebuild with my aluminum cylinder head coming next month. Prior to this head, I have the OZ250 pre crossflow head on my 68 200.

I’m curious on thoughts of my carb choice, and if I should go bigger. I’m aiming for 10:1 compression. Schneider Cams wants more info on my build before giving me details on a custom cam and one is my carb choice. I have an Autolite 2100 1.23 Venturi with 356 CFM. Should I be going more? 4100?

I haven’t given it much thought until now. I don’t want to “under carb”. I’ll have 1.84 intake valves and YT 1.65 rockers as well. As much as I’d love to go EFI, that’s not in the budget anytime soon.

Appreciate your thoughts...

Cheers,
Matthew
 
Howdy Back Matt:

WOW!!! Cool build. I'd also want to know your engine rpm range for most of your driving. While the 1.23 would be ideal for most street driving situations the option of a 4100 would give you that with the primary barrels and then more for a stronger top end when the secondaries kick in. Personally, I love the Autolite but, it may be time to consider a Holley for more detailed tuneability. That's my two cents, for what it's worth. Enjoy.

Adios, David
 
CZLN6":p9v5qpuj said:
Howdy Back Matt:

WOW!!! Cool build. I'd also want to know your engine rpm range for most of your driving. While the 1.23 would be ideal for most street driving situations the option of a 4100 would give you that with the primary barrels and then more for a stronger top end when the secondaries kick in. Personally, I love the Autolite but, it may be time to consider a Holley for more detailed tuneability. That's my two cents, for what it's worth. Enjoy.

Adios, David


Hi David,

This will be a cruiser, street driven car (no track racing). I’ll be on pump gas, 93. RPM range between 1500-4500 likely, with the occasional stomping of the pedal to the floor. Since I already have the 2100 I may stick with it for the time being, and then evaluate my options after if it’s not giving me enough top end.

Of the 4100s, what would be my ideal size? I’ll keep an eye out.

Cheers,
Matthew
 
good on ya mate!
ck the link I gave ya - has some Holley v Autolite info...
 
Howdy Back Matt:

Well the 1.08 4100 would be ideal, but the 1.12 is more easily available. The 1.08 is rated at 480 cfm. The 1.12s are more readily available and are rated a 600 cfm. Either would be a good starting place. Tuning main jets, accelerator pump stroke and air screw will be where you will start tuning. Idle and transition are built in internally as well as the booster valve channel restriction. For those reasons I'd recommend the 1.08 Autolite 4100 for your application- a street cruiser.

That's my two cents, for what it's worth. Good luck.

Adios, David
 
X2 the Autolite / Motorcraft 4100 would be a great combo for your street car! (y) :nod:
 
CZLN6":4y29z4rd said:
I love the Autolite but, it may be time to consider a Holley for more detailed tuneability. That's my two cents, for what it's worth. Enjoy.

Adios, David

I am not as knowledgeable as David. But, having built an engine with the VI/CI head. I would opt for the Holley for easier tuning. Just dropping on a carb will give you problems. The Holley will be easier to tune. Swapping jets, power valves, etc...

Just browse the older threads and you will see what I mean.
 
65coupei6":17jvza2g said:
CZLN6":17jvza2g said:
I love the Autolite but, it may be time to consider a Holley for more detailed tuneability. That's my two cents, for what it's worth. Enjoy.

Adios, David

I am not as knowledgeable as David. But, having built an engine with the VI/CI head. I would opt for the Holley for easier tuning. Just dropping on a carb will give you problems. The Holley will be easier to tune. Swapping jets, power valves, etc...

Just browse the older threads and you will see what I mean.
Marco, if you want more carburation i have a custom made cherry for sale. It has annular nozzles for better fuel antimazation.
 
Thanks guys. I grabbed a 4100 1.08 for a great price last night. Wasn’t slighting your advice, Marco - if it becomes a pain I’ll flip it for what I paid but it was too good to pass up in the condition it was in.

That said - any clearance issues with the choke hitting the firewall on the CI/VI intake?
 
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