351m heads
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Mountain Pass
Joined: May 2012
Posts: 186
Likes: 1
From: Voorhees NJ
351m heads
Looking to upgrade my heads from a 10 year old build. Was thinking aluminum heads, but too much money, and used ones aren’t readily available. If I get a set of 351c heads, what’s different from them to the 351m heads. Will my intake (performer2171) and headers mount up with any trouble? TIA
Logistics Pro
Joined: May 2015
Posts: 4,474
Likes: 974
From: Tri Cities, TN
If you are talking about the 351C 4V heads they won't work with what you have now. The intake won't seal on those big ports the exhaust might bolt up but it likely won't seal either. No one makes a manifold for those heads on a 351M/400. The 2 bbl. heads are essentially the same as what you have now, some of the early ones might have slightly smaller combustion chambers.
You would probably be better off if you could find the parts to make it a 400. 50 more cubic inches is a big boost in HP and torque.
You would probably be better off if you could find the parts to make it a 400. 50 more cubic inches is a big boost in HP and torque.
Tuned
Joined: Jan 2019
Posts: 308
Likes: 27
From: Fallout Shelter
The 351c 2v open chamber heads will bolt up just like the m heads no issues. Same valve sizes. However, It’s been noted that the m heads have about a 2cc larger combustion chamber, a large air injection hump in the exhaust port, and maybe a somewhat raised restrictive floor in the exhaust area.
The 2v open chamber C heads are technically a better head. Not sure how much you’d actually gain by just the swap though.
It is worth mentioning that the Australian 302 Cleveland 2v heads are a closed chamber design with 58cc chambers and same ports as American 2v’s. Depending on deck clearance these would produce a static compression ratio of about 9.5 - 10 to 1. These work best when block deck is cut for zero clearance to take advantage of quench affect. Deck clearance for Stock 351m engines is usually around .016” or so. These heads can make for a very nice hot higher rpm engine when done right but require a larger duration cam to stave off detonation and probably wouldn’t be the ticket for a large truck. Plus they are getting pricey and very hard to find lately.
Either way you go make sure you have a good quality straight up roller timing set and read up on recurving the distributor especially if mods are done.
The 2v open chamber C heads are technically a better head. Not sure how much you’d actually gain by just the swap though.
It is worth mentioning that the Australian 302 Cleveland 2v heads are a closed chamber design with 58cc chambers and same ports as American 2v’s. Depending on deck clearance these would produce a static compression ratio of about 9.5 - 10 to 1. These work best when block deck is cut for zero clearance to take advantage of quench affect. Deck clearance for Stock 351m engines is usually around .016” or so. These heads can make for a very nice hot higher rpm engine when done right but require a larger duration cam to stave off detonation and probably wouldn’t be the ticket for a large truck. Plus they are getting pricey and very hard to find lately.
Either way you go make sure you have a good quality straight up roller timing set and read up on recurving the distributor especially if mods are done.
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kyle1979ford
335 Series- 5.8/351M, 6.6/400, 351 Cleveland
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Dec 2, 2018 10:13 PM
purecountry
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Jul 11, 2008 09:32 AM
