Thread: whoa 950 huh

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so as i said before i just purchased this s10 blazer with a 406 in it and it has a 950 proform carb isnt this a little big i havent tuned on it yet it is a lil gassy smelling but will this work or should i try something diff.

A couple sizes to big!!!! I only ran an 800 on my 501 stroker motor, and it was plenty fat....

i really dont want to buy a whole new carb, this one is almost new. i guess i would like to know what gives the carb its cfm rating the main body, the base plate, is the circuits the same or do i have to buy new carb anyway. need to save money here. i would like to know the unknown to me (pipe dreams) 950 down to 650 right

You've already got it, just run it and see what happens. Hot rodding isn't always about engineering, sometimes it's about what you've got and whether or not you paid the right price.

CFM= CID x max RPM divided by 4567.

So if your running a 406, with a valve float rating @ 7200 rpm, then you need 640.07 .
A 650 is what I'd start with, unless you have a massive lift cam, and then jet up if need be.

Start with a fresh set of plugs- run them under YOUR normal running conditions- pull one from each bank and get a reading, they should be a light brown to tan. White is too lean- jet up, Black is too rich - jet down.

You could use the present carb if the camshaft and converter are of the big and small type. The jetting on any size carb is matched to climate relative of any cfm. The big carb may help torque at the drags. On a stock head 400 it is too big. Carb cfm ratios have many variables. Put a 650 on a street stocker. Sorry, yes ,that is the bigger baseplate and body on that 950. The 650 is a series smaller. The 850s have the bigger body within the 4150 format. The 4500s are diff bolt pattern.

ok it is a 3500 stahl lunati solid roller cam 290 duration heads are canfield that have been ported, intake ported, runners are 215cc valves are 2.05, cc chamber is unknown at this time said i was told running 12.5:1 compression runs rich at idle which jets will not help this problem since the idle circuit is all on its own right? i do have lame braim idea my temp never runs consistant like it has a sticky thermostat i know that it has to be at operating temp to adjust idle screws. ima go get stat tomorrow. i still would like to get smaller carb. this may not seem logical but a new smaller main body will not fit my base plate, and smaller base plate will not fit my main body is this what ur saying? so if i got new base plate and main body would my other components such as float bowls and metering plates fit new stuff.(make sense)

Yes I believe the 4150s have a different baseplate. Never tried to mix them, so dont know about smaller. Think 800 is smallest/big. The 950 you have may have adjustable idle air bleeds also. You have enough cam and excellent heads. The idle air bleeds are the holes in the primary choketower base. If they are totally smooth they are probably fixed. Anyhow , you can use all of that carb. The pump shot and or secondary diaphram springs will wake up the launch . You will have to experiment with volume and time of pump to match how your engine gulps air when stabbed wot. I have tried to find a happy medium on the idle screws w/ eng temp. Also there is a screw on the bottom of the baseplate to adjust secondary advance which can majorly affect the idle screws and bleeds. Lastly cam intake/ ex overlap on a roller is fatter on lift ,so some raw some fuel escapes with the exhaust around bdcenter.. Hope that is all relevant .....

Oh yeah , idle and mains are diff circuit. You dont want it lean at wot. May have a bad powervalve?, or one that does not fall a couple of inches below intake vacuum in ratimg. Those will also get your eyes burning and your clothes smelly.