Hello all-Scuzzy here n I spent some $ n wondering if I Messed up? Bought a New Offenhauser Dule-Port n had n a 66 C6AF L 1.12 n plannin on Running it on my 300, I have found out I would B better off with a 1.08, Can I use the 1.12? can I Jet it to Work? Needs a Kit but Jumped on it when it was Avalible becouse it is what I wanted. Any Addvice on what to do will B apresiated! If I can Jet it to work what is the Proper Jets? I got a Srod to Run n a 3.50 Rear Gear! Thanks, Scuzzy
Intake!
- Thread starter Scuzzy
- Start date
Are your carbs 4-barrels? A DP intake manifold requires a 4-V carb.
Ya I got the 4100 1.12 but think I need the 1.8, the 1.12 is a 600 CFM Carb n the 1.08 is a 400 CFM n Offenhauser Recomends a 400 CFM so just thinking the 1.12 4100 is too Big but I wanted a D.P. instead of n Opin Plenim that didnt have any Power till over 2000 RPM, Got it now so just gona try what I got! I allso got the Fulley Exsaust Manifolds n thinkin of the Chevy Rockers-79 300, Thanks, Scuzzy
:hmmm: Hi Scuzzy.Just a thought here,and if I am wrong,FTF can fire up the flamethrower and roast me like a turkey.Why can`t you do a"NASCAR" on the manifold.Use a restrictor plate.
Should`nt be too hard to do.
Good luck.Have fun.Be safe.
Leo
Should`nt be too hard to do.
Good luck.Have fun.Be safe.
Leo
Baron Von Ottomatic
Well-known member
It isn't the ideal size but should work fine. Try it and see. If a carb is jetted right on for one engine it shouldn't be far off on any other engine, within reason.
Don't confuse jet size with cfm ratings. Try it as is as was previously mentioned.
"...1.12 4100 is too Big..." Not necessarily.
"...But dont think I will B the First to run a 600 CFM Carb on a 300!" That is correct. A number of folks run 600s. AbandonedBronco is running/testing a Holley 650 cfm spread bore having run a 600 cfm Holley and a 390 cfm Holley on one of his Broncos. i think he is still running a 600 cfm Holley on his other Bronco. F-250 restorer is quite knowledgeable on Autolites and Qjets and is running/testing a Summit branded 600 cfm carb at this time.
It is somewhat of a misconception to view the maximum flow capacity of the carb as too big or too small. Your engine will run on only the primaries a big part of the time. Generally, one won't see the secondaries begin to open until around 2500 rpm to 3000 rpm (on vacuum secondary or air-flap operated carbs) and not attain full opening even at the highest rpm under WOT.
"...But dont think I will B the First to run a 600 CFM Carb on a 300!" That is correct. A number of folks run 600s. AbandonedBronco is running/testing a Holley 650 cfm spread bore having run a 600 cfm Holley and a 390 cfm Holley on one of his Broncos. i think he is still running a 600 cfm Holley on his other Bronco. F-250 restorer is quite knowledgeable on Autolites and Qjets and is running/testing a Summit branded 600 cfm carb at this time.
It is somewhat of a misconception to view the maximum flow capacity of the carb as too big or too small. Your engine will run on only the primaries a big part of the time. Generally, one won't see the secondaries begin to open until around 2500 rpm to 3000 rpm (on vacuum secondary or air-flap operated carbs) and not attain full opening even at the highest rpm under WOT.
BIG 6 farmer
Well-known member
I agree with all here, both carbs. should work fine. But obvious the smaller one would be more responsive at lower speeds. I worry more if you don't heat the bottom of Intake Manifold, you will play hell getting it to run right if you don't. 
If you live in a cold climate, pull heated air off Exhaust Manifolds for Carb. to suck. 
That is a must for winter driving.
If you live in a cold climate, pull heated air off Exhaust Manifolds for Carb. to suck. That is a must for winter driving.Offy DPs and Cs both have provision for heat to the manifold...it's the area under the carb where a stock exhaust manifold was intended bolt up. Pretty easy DIY project and have been cussed and discussed here and on the FTE site many times. AbandonedBronco and F-250 restorer have both posted pictures of the ones they have made.
You can also tap heat from the exhaust manifolds with a simple "stove" (like dryer duct).
F-250 Restorer
Famous Member
The autolite C6af L originally came on a 352. The 4100 is a great carb. The only problem with them is they are 50+ years old, and have been rebuilt untold number of times, and parts have been changed and there is no master set of serial numbers--that I know of--a person can check to see if you have the correct parts. I assume those books/guides died with Jon from Pony Carbs.
It should have .048 jets. Mine ran best with .046 jets primary. I'll be very surprised if you can even get the secondaries to open. I'd run .050--.052's in the secondaries if you can even get them to open. I say that b/c they are operated by vacuum which flows through the air horn, and it is a persnickety system. Yes, persnickety!
If you have one of those heating plates between the carb and manifold use it. Check Allcarb for jets. Mike's carbs sells them too, but his are hand drilled with a machine burr around the orifice.
**Note: If you can hold the throttle shaft and move it slightly up and down with the carb absolutely stationary, then it needs to have bushings installed and if you don't have it done it will drive you batty trying to get it to run right.
**Note #2: The smaller 1.08 venturi 4100 is 480 cfm, not 400 cfm, as you mentioned. Also, just because you want need a 1.08, be aware there are two vastly dissimilar designs of the 1.08: small block and big block designs. You want the small block design that came on a 289. Run the numbers on website mustang tek to check and know.
**Note #3: The kits usually don't come with the accelerator pump diaphram. It costs extra.
It should have .048 jets. Mine ran best with .046 jets primary. I'll be very surprised if you can even get the secondaries to open. I'd run .050--.052's in the secondaries if you can even get them to open. I say that b/c they are operated by vacuum which flows through the air horn, and it is a persnickety system. Yes, persnickety!
If you have one of those heating plates between the carb and manifold use it. Check Allcarb for jets. Mike's carbs sells them too, but his are hand drilled with a machine burr around the orifice.
**Note: If you can hold the throttle shaft and move it slightly up and down with the carb absolutely stationary, then it needs to have bushings installed and if you don't have it done it will drive you batty trying to get it to run right.
**Note #2: The smaller 1.08 venturi 4100 is 480 cfm, not 400 cfm, as you mentioned. Also, just because you want need a 1.08, be aware there are two vastly dissimilar designs of the 1.08: small block and big block designs. You want the small block design that came on a 289. Run the numbers on website mustang tek to check and know.
**Note #3: The kits usually don't come with the accelerator pump diaphram. It costs extra.
Thanks 250 Restorer n All Outhers, Tought my alot about the 4100, I knew I wanted to run a 4100 n bought a 1.12 when it was avalible, I bought it on E-Bay n Probly got in too big a Hurry, but its a Good Clean Carb n looks to be Runnable as it is-Know I probly gota Kit It But will try it n see how n what I got, Probly gona Buy a Kit off E-Bay but there is so many on there n so many difrent prices n just want to Buy as Compleat a Kit as I can. Just gathering Parts right now for a Spring TearDown n back up but would like to have everything here n ready. Thanks agin! Best ting I ever did was Join this Sight! U All R Great! Scuzz