Looking for opinions on what carb size to use on a 66 410.

Just found credible evidence that the stock carb (Autolite 4100-A stamped 1.08) was a 480cfm. I have that carb but after going through it three times with my uncle who's made his living as a mechanic for more than 50yrs we just can't get it running right.

I've got a Holley 4160 (600 cfm) I tried on it and wasn't altogether impressed.

Now I've got a Demon Jr 725cfm that I'm trying out. I was long under the impression that the original carb was a 650cfm, but my recent discovery that it's likely 480cfm has me questioning things. Many people, knowledgable folk said 650 was on the restrictive side for a 410cid.

Wonderin' what y'all think.

BTW--This build is for highway driving and some grocery running, NOT racing. Thanks.

 

Run your Autolite! Or run what you have. You pretty much answered your own Q LOL....

 

Ever heard of Hermiston, OR?

And I can't run the Autolite...or rather, IT won't run. Hence the need for something else, but WHAT something? Is 725 too big? I'm sure it wouldn't be if everything else were tuned for the drag strip, but I'm building this for highway cruising.

 

I know Hermiston Oregon! The Q is......Have you heard of Klamath Falls Oregon??? LOL

That 725 is not to big! Run it and you will find that it will be just fine. Even on mileage! You'll have the get up and go too. Thats only if you need it LOL. Just tune it in and "GO" LOL.

 

Thanks. I'm fighting the 725 right now. Having trouble getting it dialed in. Yesterday it ran fine. Today it wants a real high idle or it will die when I put it in gear, and it's pulsing cruising around town. It was running too rich. Doesn't seem to be now, but might be too lean? Anyway...when I heard the original carb is 480 cfm I thought I might have WAY overshot with my carb and be drowning my intake.


Off topic: I grew up in Hermiston. Know exactly where Klamath is, though Grants Pass and Bend & Redmond are the closest I've been. Love that country.

 

Vacuum issues ?

Went to Wilamina for the Sedan(Glasspar) nice country side but the sun dont peek it's head out till 10am or so in Nov.. WTF???? I've had coffee, mowed the yard, took a crap and gone for groceries by that time of the day!!!

 

Thought of that. Trick I've been told is to spray carb cleaner around the suspected area and see if the engine revs. If it revs, then there's your leak. One problem...I can spray carb cleaner in the carb and the engine won't rev! Ideas?

 

I would agree, if you are having issues with all the carbs and varying idle with the 725 it must be a vacuum leak. If you aren't getting any idle change from the carb cleaner try starter fluid. It is more flammable.

 

Royal--
Vacuum leak wouldn't be a surprise, but starter fluid takes even less to bog the engine down. It just flat won't rev...carb cleaner or starter fluid (ether based btw). Spray too much and the engine bogs, spray any less and no effect. It has me stumped that's for sure.

I may try plugging every vacuum port in it (save for the tranny, brake booster, and advance) and see if that doesn't change things. Though I know that a vac line may not be the source of the leak it's going to be hard to locate if it won't rev. Any ideas on locating a leak are very appreciated though!

 

I have run both a 750 and a 600 on a built 400(414 actually) and both worked fine. I used the 600 most of the time and threw the 750 on when I was towing on the hwy. The 600 will give you better bottom end, the 750 pulled like a freightrain on the hwy.
A varying idle, etc could also be a symtom of a worn distributor bushing, and will dramatically vary points gap and dwell. Since you seem to be having issues with multiple carbs, maybe its not the carbs.

 

The 428CJ only ran a 735 Holley and turned 6,000 with it in stock form. So IMO a 752 is to big for a stock 410. Look here for Holley's remomendation on carb size. The first question answers your question.

http://www.holley.com/TechService/FA...ory=Carburetor

 

My 410 runs great with a 3 duece setup which comes out to around 1180 cfm! But of course it's a progressive linkage, so you get the best of both worlds-2bbl economy and 6bbl performance!! It took a lot of tuning, but there is no bog or anything when dropping the hammer.

 

Why would it take a lot of tuning? Every Ford 3X2 set up I ever put on andengine ran great with minor mixture and idle speed adjustment. With 3 accelerator pumps there was never a hint of bog on everything from a 390 to a 428.

 

I had to tweak the accel pumps (was getting too much, actually), main jets (I lived a mile high at the time), and linkage to get everything working right. Actually, Holleys aren't able to be adjusted for the thin air of high altitude very well, at least compared to the Carters and such that have the metering rods. My biggest problem was under heavy braking (like when the stop light turns yellow), the engine would flood and die. I discovered that since the carbs mount backwards (float bowl to rear) the fuel would slosh out of the float bowl through the vent right into the venturis. The fix was a "whistle" that in effect extended the vent opening to the rear of the float bowl. It was actually made for drag racers to put on the front float bowls for the same flooding problem on hard leaves.

 

The whistle is made for offroaders first. But I never once had a problem adjusting a Holley for living in Denver (3 year while in the military). You maybe better get a Holley How To book because the Carters are a nightmare to adjust compared to the KISS principle Holleys. During the 3 years I raced a 428CJ with a 3X2 set up I never once experienced your problem and I'll bet my sub 12.50 second car at 120+mph was braked harder than you ever have. Sounds like your float levels were to high.