Holley 4bbl settings?

[Sean Wetgen]

I might be trying a holley 4150 4bbl carb on my 345 some time in the future(friend wants to know if it works), but the bad thing is the jets were changed for a different "tricked" motor, and I think the jets would be too big for my 345. Its a 600cfm Holley, vac. secondaries, single pumper. It is close to the ones used on the 392(looks like ours on our 392), anyway what jets would be a good choice to start with, for a stock 345? The carb is still together and he doesn't want to take it apart right away. But I just need to know what jets to start with. Then I'll go from there.

Also I was trying to find an old webpage I found on carbs mechanical vs. vacuum secondaries. I couldn't find it anymore. But I just wanted to find out which would actually be better for a stock, street motor, with minor towing now and then. I suppose the vacuum secondaries? If that Holley is any good I might leave it on there and sell my Edelbrock. But al depends on that holley if its any good yet, cause it may need a kit again(sat for awhile). Ok, Thanks!

[surfcraft]

Sean---

I put a 4150 600cfm 4bbl on my 345 and drove it for almost 10 years.

I played with jets, accelerator pump cams and nozzles. I eventually got rid of a a bog on take-off, and overall performance was "acceptable", but mileage was so-so.

I have come to believe that the 600 cfm is just too big.

JW

[John Donnelly]

Sean,

Click here I think this thread will help you a lot with this particular question.

-John

[DavidWTravelallfan]

you might want to try the newer 350 cfm 4 bl holley squ bore with vac sec. Its made for smaller v-8 and v-6 engines, will probably work great for the IH engines. Jegs has it for around 250 or so.

A Holley 600 should be about perfect for a stock 345 CID engine. Vacuum secondaries are far superior for street use and offer much better economy.

As for jetting? There's a lot of variables, but maybe start with some 62's in front. As I recall, thats what the 600's come with. Then again, it may be better to start on the fat side and work your way down. Maybe start with 68's.

I think the carb you described will have a jet plate in back instead of actual jets. They do have different size plates available and you can find charts telling you what they are as far as equivilant jetting. I prefer to add a metering block on the back side so I can use jets on all four corners.

[timpage]

The 4150/4160 series carb I just put on (600 CFM) in the past month or two (the truck in John Donnelly's link) has been succesful over all. There is more tuning and testing that I'll be doing in the coming months.... I'd work faster at it but the truck gets used little this time of year (usually dont have the extra $$$ to keep it fueled during the winter months as well). But when I use the truck more this spring I will be able to get some good fuel mileage estimates, as well as some longer road trips to see how well it does beyond the occasional in town/local trip.

I've noticed so far that this particular carb works well, but I certainly wouldnt want anything larger.... the 390 CFM Holley 4 bbl would probably be as good as or better of a choice for the 345's, but I got a good deal on the Holley Reman'ed unit I bought (1850 list).

More will come as I play with the truck in John Donnelly's link.

Tim