Carb and Header ?
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Senior User
Joined: Apr 2007
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Carb and Header ?
I am getting a late 70's f150 2wd that me and my dad are going to strip of parts down to the bare frame. Right now i have a 78 f250 4wd and my f250 has a 351m and the f150 has a 400. the f150 has a 750 cfm carb and intake and i was going to put them onto my f250 for right now so that i can rebuild the 400. I was wondering if the 750 is going to be big of a carb since the 351 is stock, because i have heard a 600 cfm is a good size. Also if i put the 4 barrel onto it will i need to do any ignition upgrades so that i just don't dump for gas into the engine and waste it. And my other question is the f150 has long tube headers and i was wondering if they would fit my f250 since the frames are little bit different and one is 2wd and the other is 4wd.
Postmaster
Joined: Aug 2001
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From: Delaware
Yes, a 750 CFM carb is too much for a 351M, but it can be made to run OK.
If the 351M is running OK now, and you expect to rebuild the 400 soon, just wait and keep the 750 carb for the 400 rebuild.
You don't need to add a project of trying to tune the 351M, while rebuilding the 400.
The headers may not fit without some modifications.
If the 351M is running OK now, and you expect to rebuild the 400 soon, just wait and keep the 750 carb for the 400 rebuild.
You don't need to add a project of trying to tune the 351M, while rebuilding the 400.
The headers may not fit without some modifications.
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What if i put smaller jets into the carb. Then would it work. If not then i have a friend with a 460 and he has a 600 cfm and his truck doesnt run to good with it, so i will probably trade him carbs.
Postmaster
Joined: Aug 2001
Posts: 4,270
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From: Delaware
Originally Posted by 79f100six
What if i put smaller jets into the carb. Then would it work. If not then i have a friend with a 460 and he has a 600 cfm and his truck doesnt run to good with it, so i will probably trade him carbs.
Smaller jets will just make it too lean. The problem is lack of sufficent air flow at low RPM through the big Venturis prevents the proper metering of the fuel. The result is poor off-idle response and poor driveability.
Swapping for a 600 CFM carb is a better idea, if his carb is in good condition.
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on the rebuild i probably will only make everything stock put the cam staright up, then put flat top pistons on it.
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Junior User
Joined: Jun 2006
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I just finished my rebuild (I am installing in the pickup tonight) using Tim Meyers pistons, stock heads with new springs to go along with a Comp 255 cam and I am installing an edelbrock performer intake and 600 cfm carb. Tim helped a lot with determining what I should use together with my budget. Good luck!
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