351C questions
Freshman User
Joined: May 2008
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Let's end the debate, shall we....
It has already been said before . If it FOR SURE came out of a 1971 LTD and is the original engine, it's NOT a 351C. The ONLY options in '71 were a 400 or 429. So if what you have DID come from a '71, consider youself one lucky *******. The '71 400 was the only year that it had stock 9.0:1 compression. From '72 on it dropped to either 7.5:1 or 8:1 .
I bought a '67 f100 that someone had already dumped a '73 400 in. I'm trying to find a '71, but there are none to be had around here.
The only downside to this higher compression is that you might struggle with detonation if you ever want to throw on a set of Aussie 302/351c heads and plan on running even 91 octane from the corner gas station.
I bought a '67 f100 that someone had already dumped a '73 400 in. I'm trying to find a '71, but there are none to be had around here.
The only downside to this higher compression is that you might struggle with detonation if you ever want to throw on a set of Aussie 302/351c heads and plan on running even 91 octane from the corner gas station.
Last edited by relient3074; May 16, 2008 at 06:46 PM. Reason: wrong info provided
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Mountain Pass
Joined: Jul 2007
Posts: 131
Likes: 3
From: MA
hi,
well i truly dont know what to say... ive dug thru a bunch of my old junk this evening dying to find the bill of sale for the LTD...just hoping i had written the VIN down...its killing me cause this is all so wild.. i think if i dig deep enough i even have pictures of the car..i hated the idea of scrapping it..it was beautiful inside..just rotted beyond believe underneath. hopefully in another mnth or so ill have the motor back out of teh truck its in now..i cant wait to try to get some block numbers...this has now become such a wild thing...fun to imagine or try to figure out why i have this motor out of this car...all i saved was the motor/trans/d-shaft and steering column...
what if i threw away some rare bird? haha.... oh well.. like u guys said.. it is what it is...im happy as hell w/ what i have...just wish i understood the mystery a bit more....
well i truly dont know what to say... ive dug thru a bunch of my old junk this evening dying to find the bill of sale for the LTD...just hoping i had written the VIN down...its killing me cause this is all so wild.. i think if i dig deep enough i even have pictures of the car..i hated the idea of scrapping it..it was beautiful inside..just rotted beyond believe underneath. hopefully in another mnth or so ill have the motor back out of teh truck its in now..i cant wait to try to get some block numbers...this has now become such a wild thing...fun to imagine or try to figure out why i have this motor out of this car...all i saved was the motor/trans/d-shaft and steering column...
what if i threw away some rare bird? haha.... oh well.. like u guys said.. it is what it is...im happy as hell w/ what i have...just wish i understood the mystery a bit more....
Freshman User
Joined: May 2008
Posts: 29
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No worries guy...
Don't worry about it. The "rare bird", as you call it, is what was under the hood, not the car itself. Like stated before, the '71 400 with the 9.0:1 compression was a one year only production in the LTD. Finding 70's LTD's may not be tough, but finding a '71 with that engine in good condition can be a chore. I've been searching for one for a while now. 
Freshman User
Joined: May 2008
Posts: 29
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another option...
I mentioned a little about it already, but if you find another year 400 other than '71, you can still solve the compression issue. Get a set of heads from an Australian 302/351. With stock internals and the switch in heads, it should give you 10+:1 compression. Then, if you have a '73-79 400, advance the timing from the stock timing and you open it up pretty nicely. On top of that, from the research I've done, the Aussie heads are made to work very efficiently with a 2V (2bbl) carb. I had a buddy in school that ran 400 hp on a 400 with the same set-up.
The downside to the '71 is that, if you add the Aussie heads, the compression could increase to the point where you can't run off 91 octane because of detonation
without adding an octane booster or seriously retarding the timing.
The downside to the '71 is that, if you add the Aussie heads, the compression could increase to the point where you can't run off 91 octane because of detonation
without adding an octane booster or seriously retarding the timing.
New User
Joined: May 2008
Posts: 24
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i always heard that a 400m was a better boat anchor then the cleveland considering the cleveland is pretty much a boss 302 as far as head design goes and it has freakin huge valves im pretty sure the cleveland can put more power to the ground well maybe not to the ground but it im pretty sure it has a ton more potential then a 400m
Freshman User
Joined: May 2008
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understood, however...
The 400 is basically just a 351C block, but has a 1 inch taller deck height to allow for a longer stroke. Two differences that the 400 did have is that it ran with larger main-bearing journals and square dimensions, with a 4.0 in bore and stroke; thus a 1/2" longer stroke than the cleveland. Being "square" makes things pretty balanced.
So when it comes down to it, comparing a 351C and 400M is like comparing one apple to a slightly bigger apple.
So when it comes down to it, comparing a 351C and 400M is like comparing one apple to a slightly bigger apple.
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Freshman User
Joined: May 2008
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Big Block killer... Hmmmmm, could be...
Essentially, yes. Alot of the parts are interchangable from the 351C to the 400M. If you look at alot of the descriptions for 351C aftermarket, they usually list all of the 335 series engines as compatible with the same parts. I.E. Aussie heads will even fit on any US Cleveland block: 351C, 351C Boss, 351C HO, 351M, 400M, and 302/351. Also, the 400 came with a bellhousing pattern that makes it able to be paired up with a C6 tranny.
I would check with Edelbrock if you don't feel comfortable going with my opinions.
As a reminder though, the 400 block IS BASED on the cleveland, not the SAME as. The main difference is that the block deck height is 1" taller. So, though cleveland parts may be interchanged with the 400, one would need to verify they are safe using 400M parts with a 351C. I heard of someone with a 351C try to use a crank, rods, and pistons from a 400M in his engine because he got bad info. The person that told him that he would be ok heard 351 and didn't verify C or M. Luckily, we got things cleared up before he wasted the time trying to put it all together.
I would check with Edelbrock if you don't feel comfortable going with my opinions.
As a reminder though, the 400 block IS BASED on the cleveland, not the SAME as. The main difference is that the block deck height is 1" taller. So, though cleveland parts may be interchanged with the 400, one would need to verify they are safe using 400M parts with a 351C. I heard of someone with a 351C try to use a crank, rods, and pistons from a 400M in his engine because he got bad info. The person that told him that he would be ok heard 351 and didn't verify C or M. Luckily, we got things cleared up before he wasted the time trying to put it all together.
Posting Guru
Joined: Jan 2005
Posts: 1,299
Likes: 2
From: The Vieux Ford, Kansas
Check with TMI he sells the CHI heads that are better than the edelbrock, he is the sponsor for the 335 engine series forum you should check out his site and see some of the 400 builds he even has a 434 stroker kit for 400s now.
-Johnboy
-Johnboy
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The CF symbol you describe is the iron foundry mark. The casting #'s on the small flat area behind the starter are what you need for a positive id. If you pull the intake off you can look on the backside of the heads for that casting #. They will give you valuable info to start from.
I have seen several "sleeper" vehicles that were factory original with Cleveland motors even though they weren't "supposed" to be there. I was told by an old timer that back in the day, car dealerships would special order vehicles for family or special customers with muscle car motors. Apparently it was easier to get what you wanted in a vehicle back then.
I have seen several "sleeper" vehicles that were factory original with Cleveland motors even though they weren't "supposed" to be there. I was told by an old timer that back in the day, car dealerships would special order vehicles for family or special customers with muscle car motors. Apparently it was easier to get what you wanted in a vehicle back then.
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