I overlooked checking the carb # on my 1970 455 motor. I've been wondering for a long time why I can't get the expected power out of the 455. Appearently the carb is off a 350. The motor only had 23k miles on it when I bought it so I ASSUMED, it was the original carb. I was wrong. I've seen posts before on someone who sell Q jets to the specs of the motor. Does anyone know who that is? Thanks for your help.
I might be able to help. Do you specifically want a 70 455 carb or would you consider an 800 as suggested. Do you use ethanol gas? What is the part number you currently have?
Just because the carb is off a 350 doesn't mean you can't make power with it. It does need to be set up right, but the 350 carbs are 750 cfm as are the 455 carbs(for '70 and earlier). Also it appears that you have a 70 motor in a 71 car so I assume it is not stock. Therefore I would not worry too much about having the correct "part number" carb for your engine. You can find a few folks who do a great job rebuilding/selling BBB 750 or 800 cfm carbs. https://www.v8buick.com/index.php?threads/what-are-the-didferences-between-350-and-455-qjet.338033/ But first you should review Larry's tune up post: https://www.v8buick.com/index.php?threads/power-timing-your-buick-v8.63475/ That will really help you get the power you expect.
The carb # is 7041544 I rebuilt it but I am no carb expert. I use non ethenol gas because I see what it does to mowers, weedeaters, etc with carburetors.
The only thing I have upgraded when I rebuilt the motor was a ta 212 cam and headers. All else is standard equipment.
Some will modify a 350 carb for a 455 but my preference is to start with a 455 carb because it helps to make the whole package appear correct. The air valve on 350 carbs typically doesn’t open fully, those are rated at 675 cfm or so. It’s a simple snip to allow them to fully open. You could probably benefit from idle circuit mods with the changes you made…not all rebuilders do this. I fix a lot of them. Do your research and decide how you want to proceed with your project. I’ll help regardless if I sell you anything. PM me if you like.
I would look for a 71-74 455 qjet. They are 800cfm and have idle air bypass so you get cleaner idle with no nozzle drip. Also the 350 carb will be too lean at idle even with the screws all the way out.
By ‘expected power’ what do you mean? As advised, read (and do) Larry’s thread’s recommendations. You may not have a carb problem. You may have a timing problem, a gearing/cam/converter mismatch problem, or some other issue. Patrick
Not sure where it stems from. It acts like a newer car that has traction control. It still kind of feels like the 350 that was in it. The rear end I also changed after putting in the 455. Was the original 2:83 I believe and now has a posi from a 1970 olds 442. Which is 3:23 I believe. Can't remeber. I guess what I'm saying is it doesn't feel like a large difference from the 350 as far as take off. I had the original th400 rebuilt that came original with the motor. I just did a stock torque converter. I did Larry's post a while back, but maybe I should re visit and go thru it again.
Has someone gone through the 455, any mods? If not, what are your compression numbers (using a screw-in gage, no spark plugs, spinning on the starter, dry).
I bought it out of a riviera that he said he thought had 123k miles on it because the odometer said 23k parked in 93. I rebuilt the entire motor and when I took it apart there was no ridge from the rings in the cylinder walls and it was the original bore. So I'm guessing it was only 23k miles on it. I rebuilt everything anyway. The only mods I did to it was a TA212 cam, headers, and HEI distributor. All else is stock/standard build. One buick guy I talked to around the time I finished it said that I should be able to light up the tires whenever I wanted to. But that's not really the kind of power I'm getting out of it. Not that I would do that all the time anyway, just when I hit it it doesn't seem to feel like what a motor that size would produce.
Send the carb to Ken at Everyday Performance. Dumb question, are you sure the secondaries are opening and the vacuum advance is working properly on disti. Either would dilute your power band.
^^What he said… If you went from a 350 to a 455, verify that when the pedal is floored the linkage is all the way open. Whose HEI did you buy? If you bought a basic parts store unit, it may have a really lazy curve that has very little mechanical advance and/or late advance. Patrick
I vote for throttle not opening all the way. Seen it many times when going from 350 to 455. Also when people change intakes.
I will look into that, thanks. Never really thought of the throttle linkage doing what it's supposed to.
Also, make sure the choke is coming completely off when the car is hot, assuming it's equipped that way. If the choke isn't fully disengaged the secondaries are locked out.
So it seems with the pedal to the floor I can push the throttle on the carb further, but only maybe a quarter of an inch or so. Not a whole lot. Or is it?
