Holley 850

[Guest h8tcivics]

I have this setting on my freshly built 355. has new power valve from last car. I can nevr get it set right. is there anyone that knows how to make the carb work for the engine?? I cant figure it out. trying to get my project up in running so I can drive it around while fixing my primary car. anyone who can help please drop me a line.

[desperado]

Actually I do. Find some one that has a smaller carb and trade em. Not knowing anything about the motor you have, or the intake, I can still say honestly that an 850 Holley is a bit big.

 

That is unless you are making 600 HP with it or you expect to spin it at say 9000 RPM or so.

 

I figure that neither is the case. Here is what will happen. In the small end, lower RPM's the motor will be very rich, to the point that I figure that you will be washing down the cylinder walls with fuel, there will be gas in the oil is short order (which I bet was happening before too), so in order to get it leaned out you would need to put small jets in it, to the point that on the big end (upper RPM's) you would lean out and at best loose power, or maybe even damage the motor.

I am going to make a couple asumptions, one is that you are running a dual plane intake. The other is that this carb is a double pumper, finally that this is a hot street engine, in front of an automatic tranny.

 

Now any of these three things with an oversized carb makes things bad. Add two of these things and you are replacing the rings on the motor.

 

If you are interested in getting a carb that is better suited, and getting it properly tuned for your car. Let me know. I have several 650's both double pumper and vacuum secondary, and will help you out. I also have one of those eldibrock carbs that is a set and forget type of thing but I do personally prefer Holleys, biggest thing is being able to tune then correctly.

 

If you are really pressed to get it going on that carb. Disable the secondary's, either remove the linkage rod that connects the secondary butterfly, on a doublepumper or if it's a vac secondary carb. Ziptie the secondary shut.

 

PM me if you want my number and you can give me a call and we can get together and fix this if you want some help.

[nurkvinny]

What he said. An 850 is way too big for a stock or medium-built 350. Post some details about your engine set-up, and we can post some size suggestions.

Also, if you want "make it run NOW", the Edelbrock carb mentioned above would be best - very little tuning and they work fairly well (even though I prefer Holly's also).

[Guest chochmo]

I got a 750 Holley double pumper for sale with 11000 miles on it. Just put a new power valve in it. I guarantee it not to leak or anything. Pm me if you are interested

[nurkvinny]

A 750 double pumper is still too big unless his 355 is very healthy. I guess we still need his specs.

Here is a formula to help choose a carb:

 

**Engine size (cid) x max. rpm/3456 = cfm** This formula is for full race-prepped engines. You should take some off for street applications.

 

In this case: (355 x 6000)/3456 = 616cfm. This formula recommends a 600-650cfm carb.

 

I think this formula works well, in my cases:

383 x 7500 / 3456 = 831cfm. I am running a 750cfm carb(street engine), and it is not too rich.

 

355 x 7500 / 3456 = 769cfm. I am running a 700, and again, it's right on.