1971 351C 4V question

Today we imbark on trying to find a replacement engine for my '71 M-code Grande. We discovered a cracked block not long ago and have spent too much time and energy doing a restoration to scrap the car. There is another thread about "how many are left" and this car is not going to be left behind.

What is the difference between a "short" block, "long" block and "block"? I would like to use the existing parts as the engine was rebuilt some years before I owned the car and, except for the crack, all other components are in excellent shape. As I understand, a "short" block is an engine with all components except the heads. Many readers suggested a crate engine but I want to keep this as original as possible. They only made, according to Marti, 100 '71 M-code Grandes with a toploader. If I go the route of a short block or "bare" block, does it matter what year?

On a different note, there are no less than 8 people involved in getting this car back on the road and I only know 3 of them Everyone else wants to help because the car is a Classic Mustang! They are all offering their time, expertise and tools for free. They want to see the car running again.

mike

I think you are making the right decision and it is great that you have you very own pit crew. A block is just that the block itself and usually the main caps, short block is the block, rotating assembly, cam, lifters, and timing set. The last few years I've seen short blocks advertised with no cam and timing set. Long block is short block plus heads and rocker arms. As to the block, it would be nice to find one with an appropriate date code but, it really doesn't matter. It is too bad the original block can not be sleeved. I have a great machinist who used to race Clevelands. If you have a photo I could have him look at it and at least get you a second opinion before you scrap the block. Chuck

Mike,

Chuck is "right on the money" (as usual) with his response.

I agree that it is nice that you have a lot of "help."

Did you get an opportunity to check the mains on the block? I am curious as to whether the mains are 2-bolt or 4-bolt. As previously stated, a "M-Code" could be either. I would think that could influence your quest for originality as you try to obtain a new block.

BT

What are your final plans for the car? Are you going to show it? Get it judged? Drive it? Depending on what your plans are you have several options. Here are two extremes (not including swapping something other than a Cleveland)

1. Show quality concours judge. Find a block with a date code that is accurate for the build date of the car. Obviously a 73 block would not have come in a 1971 mustang

2. Daily Driver 'stock looking'. You could actually swap in any block and rotating assembly whether a 2 bolt or 4 bolt.

The most difficult problem you will have if you want to keep your rotating assembly, including pistons, is finding a block that has not been bored out. In the very least, you will want to get a new set of pistions.

One thing you might consider, depending on your budget and goal, is consider a brand new block. There is a gentleman who is getting very close to finishing his quest to reproduce Cleveland blocks.

I think you are making the right decision and it is great that you have you very own pit crew. A block is just that the block itself and usually the main caps, short block is the block, rotating assembly, cam, lifters, and timing set. The last few years I've seen short blocks advertised with no cam and timing set. Long block is short block plus heads and rocker arms. As to the block, it would be nice to find one with an appropriate date code but, it really doesn't matter. It is too bad the original block can not be sleeved. I have a great machinist who used to race Clevelands. If you have a photo I could have him look at it and at least get you a second opinion before you scrap the block. Chuck

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At one point I played with the idea of dropping a 427 in it :dodgy: but not for long. The car has the toploader, 9" posi and comp suspension package, sooo... Someone posted a picture of some Aussie blocks. Don has a rebuilt block. There is always the junk yard but you don't know what you are getting. I will get a photo when I can but two other machinists said the crack was in a bad spot for a sleeve.

mike

Mike,

Chuck is "right on the money" (as usual) with his response.

I agree that it is nice that you have a lot of "help."

Did you get an opportunity to check the mains on the block? I am curious as to whether the mains are 2-bolt or 4-bolt. As previously stated, a "M-Code" could be either. I would think that could influence your quest for originality as you try to obtain a new block.

BT

Click to expand...

People hate seeing the Mustang just sitting there. Can you believe it. Two of them own 60's Mustangs that my mechanic works on for a song. I have not seen the car since it was towed and it is safely tucked away in the Santa Cruz mountains. We ( I am using the word as a synecdoche) did find a second cylinder on the other bank that had a piston stamped 040 so that explains how they dealt with the imbalance issue, sort of :s I will get pictures and numbers soon and post them.

mike

What are your final plans for the car? Are you going to show it? Get it judged? Drive it? Depending on what your plans are you have several options. Here are two extremes (not including swapping something other than a Cleveland)

1. Show quality concours judge. Find a block with a date code that is accurate for the build date of the car. Obviously a 73 block would not have come in a 1971 mustang

2. Daily Driver 'stock looking'. You could actually swap in any block and rotating assembly whether a 2 bolt or 4 bolt.

The most difficult problem you will have if you want to keep your rotating assembly, including pistons, is finding a block that has not been bored out. In the very least, you will want to get a new set of pistions.

One thing you might consider, depending on your budget and goal, is consider a brand new block. There is a gentleman who is getting very close to finishing his quest to reproduce Cleveland blocks.

Click to expand...

Have not decided on what to do as there are many options. I would like the VIN to match the engine and that is about all. We do plan on showing the car but not as a Concours correct restoration. The fact they only made 100 of these means we need to keep it as original as possible.

mike

If you are not going for concours correct then focus on finding a good block of any year.

What are your final plans for the car? Are you going to show it? Get it judged? Drive it? Depending on what your plans are you have several options. Here are two extremes (not including swapping something other than a Cleveland)

1. Show quality concours judge. Find a block with a date code that is accurate for the build date of the car. Obviously a 73 block would not have come in a 1971 mustang

2. Daily Driver 'stock looking'. You could actually swap in any block and rotating assembly whether a 2 bolt or 4 bolt.

The most difficult problem you will have if you want to keep your rotating assembly, including pistons, is finding a block that has not been bored out. In the very least, you will want to get a new set of pistions.

One thing you might consider, depending on your budget and goal, is consider a brand new block. There is a gentleman who is getting very close to finishing his quest to reproduce Cleveland blocks.

Click to expand...

Have not decided on what to do as there are many options. I would like the VIN to match the engine and that is about all. We do plan on showing the car but not as a Concours correct restoration. The fact they only made 100 of these means we need to keep it as original as possible.

mike

Click to expand...

Mike,

I reviewed your "Marti Report" again and I am 99.99% sure that based on your engine build date of march 1971 that your Mustang came from the factory with the 4V 2-bolt main block as supposedly all 4V built through 1971 had the 2-bolt mains.

That having been said, and keeping in mind that your 1 of 100 distinction has to do with the engine and transmission (1971 351C 4V with toploader transmission), I do not believe you should have a problem finding a 2-bolt main block. There were actually 419 Coupes built in 1971, so your 100 number is probably the number of Grande Mustang built - - a rare Mustang to be sure.

I actually have a 2-bolt main block with a date code of 2E23 (1972-May-23) which tells me that the 2-bolt main 351C blocks were built at least through May of 1972.

Hope this helps.

BT

Have not decided on what to do as there are many options. I would like the VIN to match the engine and that is about all. We do plan on showing the car but not as a Concours correct restoration. The fact they only made 100 of these means we need to keep it as original as possible.

mike

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If you get a different block, the VIN won't match. You may match the casting and date, but not the VIN. I have seen blocks welded and sleeved, but the machinist needs to really know what he's doing, and it depends on where the break is. At .040 overbore, you would have been looking at a new block or total resleeve in the future anyway. I'd just buy another block and save the old one in a corner until you find someone that can fix it correctly and you feel like putting the money in to it that it will need.

Steve

I think you are making the right decision and it is great that you have you very own pit crew. A block is just that the block itself and usually the main caps, short block is the block, rotating assembly, cam, lifters, and timing set. The last few years I've seen short blocks advertised with no cam and timing set. Long block is short block plus heads and rocker arms. As to the block, it would be nice to find one with an appropriate date code but, it really doesn't matter. It is too bad the original block can not be sleeved. I have a great machinist who used to race Clevelands. If you have a photo I could have him look at it and at least get you a second opinion before you scrap the block. Chuck

Click to expand...

At one point I played with the idea of dropping a 427 in it :dodgy: but not for long. The car has the toploader, 9" posi and comp suspension package, sooo... Someone posted a picture of some Aussie blocks. Don has a rebuilt block. There is always the junk yard but you don't know what you are getting. I will get a photo when I can but two other machinists said the crack was in a bad spot for a sleeve.

mike

Click to expand...

Mike, You might look into finding a local shop that knows how to do Flame Spray Welding. I know OEMs including Ford use it so it does work if you find the right person with the right equipment and experience. I have no idea about the cost. It might be out of sight, I don't know but it may be a way to save the VIN numbered block. Just a possibility. Chuck

after going through the ordeal to keep my engine just because it turned out to be a matching numbers block, I would not do it again.

I would seriously have grabbed a 351W crate engine and dropped it in and saved myself like 3000$.

if you get a 72 or 73 or later block as a replacement, don't worry too much if the block is a 2 bolt or 4 bolt main, first if you want to make a 2 bolt into a 4 bolt it can be done and any machine shop should be able to do it, just be aware that the change over will require the crank bearing supports re-aligned and honed, and cost will be higher. the Cleveland is meaty enough on the bottom end and should have no problems sticking with a 2 bolt main.

i would go with a closed head higher compression ratio that runs on 93 to 97 octane. I went with a open chamber 4V head setup and its been nothing but problems its very finicky when cold and requires a crazy amount of fuel when accelerating due to the lower compression and super large intake paths. Closed chamber is the way to go with any 71,72,73 block. the 2V is more punchy on low speed and has throttle response, the V4 is lazy before 2500rpms and then opens up all the way to 5400+ the V4 likes shorter rear gears below 3.25 the V2 is more highway and traffic freindly.

Does the car own you or do you own the car?? It really only matters to a buyer of your car (or (maybe) concourse judge.

You can get carried away with this "numbers" stuff but buyers only care if it's rare AND desireable. Like an investment grade Mach1 429 or Boss 351, you definatly should keep those origional. A stick is always more desireable than auto, but other than that, it's a coupe with a fairly common 351c. IMHO you're over thinking the "desireable" part. I went thru the same "keep it origional" delema with the Mach1 because I wanted a stick, I finally decided that the car does not own me.

BTW, I thought only the mfg date code was stamped on the block, and only the Boss351 had the VIN stamp.

Does the car own you or do you own the car?? It really only matters to a buyer of your car (or (maybe) concourse judge.

You can get carried away with this "numbers" stuff but buyers only care if it's rare AND desireable. Like an investment grade Mach1 429 or Boss 351, you definatly should keep those origional. A stick is always more desireable than auto, but other than that, it's a coupe with a fairly common 351c. IMHO you're over thinking the "desireable" part. I went thru the same "keep it origional" delema with the Mach1 because I wanted a stick, I finally decided that the car does not own me.

BTW, I thought only the mfg date code was stamped on the block, and only the Boss351 had the VIN stamp.

Click to expand...

Don't really care if the numbers match but need to keep the car an M-code. True, it is a common coupe, Grande in this instance, but it has a toploader and according to Marti they only made 100 of these. As far as I know, this could be the only one left after 40 years. Does not matter what the car may be worth, I would never sell it. Maybe the car does own me, the whole restoration project has taken on a life of its own. I have not seen any of the numbers yet but I am not looking for matching numbers, just a car that matches the VIN.

mike

after going through the ordeal to keep my engine just because it turned out to be a matching numbers block, I would not do it again.

I would seriously have grabbed a 351W crate engine and dropped it in and saved myself like 3000$.

if you get a 72 or 73 or later block as a replacement, don't worry too much if the block is a 2 bolt or 4 bolt main, first if you want to make a 2 bolt into a 4 bolt it can be done and any machine shop should be able to do it, just be aware that the change over will require the crank bearing supports re-aligned and honed, and cost will be higher. the Cleveland is meaty enough on the bottom end and should have no problems sticking with a 2 bolt main.

i would go with a closed head higher compression ratio that runs on 93 to 97 octane. I went with a open chamber 4V head setup and its been nothing but problems its very finicky when cold and requires a crazy amount of fuel when accelerating due to the lower compression and super large intake paths. Closed chamber is the way to go with any 71,72,73 block. the 2V is more punchy on low speed and has throttle response, the V4 is lazy before 2500rpms and then opens up all the way to 5400+ the V4 likes shorter rear gears below 3.25 the V2 is more highway and traffic freindly.

Click to expand...

It is important we keep this M-code. How we achieve that is yet to be determined. I thought only the '71 Boss had four bolt mains. We changed the oil pan a while back and the current broken block has four bolt caps but only uses two bolts.

mike

Does the car own you or do you own the car?? It really only matters to a buyer of your car (or (maybe) concourse judge.

You can get carried away with this "numbers" stuff but buyers only care if it's rare AND desireable. Like an investment grade Mach1 429 or Boss 351, you definatly should keep those origional. A stick is always more desireable than auto, but other than that, it's a coupe with a fairly common 351c. IMHO you're over thinking the "desireable" part. I went thru the same "keep it origional" delema with the Mach1 because I wanted a stick, I finally decided that the car does not own me.

BTW, I thought only the mfg date code was stamped on the block, and only the Boss351 had the VIN stamp.

Click to expand...

Don't really care if the numbers match but need to keep the car an M-code. True, it is a common coupe, Grande in this instance, but it has a toploader and according to Marti they only made 100 of these. As far as I know, this could be the only one left after 40 years. Does not matter what the car may be worth, I would never sell it. Maybe the car does own me, the whole restoration project has taken on a life of its own. I have not seen any of the numbers yet but I am not looking for matching numbers, just a car that matches the VIN.

mike

after going through the ordeal to keep my engine just because it turned out to be a matching numbers block, I would not do it again.

I would seriously have grabbed a 351W crate engine and dropped it in and saved myself like 3000$.

if you get a 72 or 73 or later block as a replacement, don't worry too much if the block is a 2 bolt or 4 bolt main, first if you want to make a 2 bolt into a 4 bolt it can be done and any machine shop should be able to do it, just be aware that the change over will require the crank bearing supports re-aligned and honed, and cost will be higher. the Cleveland is meaty enough on the bottom end and should have no problems sticking with a 2 bolt main.

i would go with a closed head higher compression ratio that runs on 93 to 97 octane. I went with a open chamber 4V head setup and its been nothing but problems its very finicky when cold and requires a crazy amount of fuel when accelerating due to the lower compression and super large intake paths. Closed chamber is the way to go with any 71,72,73 block. the 2V is more punchy on low speed and has throttle response, the V4 is lazy before 2500rpms and then opens up all the way to 5400+ the V4 likes shorter rear gears below 3.25 the V2 is more highway and traffic freindly.

Click to expand...

It is important we keep this M-code. How we achieve that is yet to be determined. I thought only the '71 Boss had four bolt mains. We changed the oil pan a while back and the current broken block has four bolt caps but only uses two bolts.

mike

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Mike, save the caps, that's a bonus.

If you get a 2 bolt block and caps, those 4 bolt caps would sell on ebay for good money

Don

I agree with H on closed chamber heads. You have a advanage as your car is a 4 speed so you can keep RPM's up for drive-ability. You would have to run premium fuel.

The 2 bolt VS 4 bolt has been debated for years. Years ago [ I think it was ]Jack Roush that said there was no difference as what you gained with 4 bolts you lost by drilling the block.

I now see why you have had the " odd " problems with your motor over the last couple of years.

Let me know if I can help.

Don

4-speeds were really rare in the 71-73 models. I heard from somewhere that only 1% of all 1971 Mustangs had a 4-speed. Not sure if that includes the Boss 351 (as those were all 4-speed).

A 351W-4v is still an M code, at least it was in 1969 (1970s had the 351C also) and if you're not selling, only you would know (or care ).

Personally, I would put in a 351W stroked to 427ci, it would be cheeper, much more power and may even get better MPGs than the Cleveland (which as mentioned, really suck gas).

4-speeds were really rare in the 71-73 models. I heard from somewhere that only 1% of all 1971 Mustangs had a 4-speed. Not sure if that includes the Boss 351 (as those were all 4-speed).

A 351W-4v is still an M code, at least it was in 1969 (1970s had the 351C also) and if you're not selling, only you would know (or care ).

Personally, I would put in a 351W stroked to 427ci, it would be cheeper, much more power and may even get better MPGs than the Cleveland (which as mentioned, really suck gas).

Click to expand...

According to "Marti", the percentages for 4-speeds in 1971 Mustangs was actually closer to 5% - - 7,067 built out of a total of 149,682. This 7,067 includes the 1,805 Boss 351s which equates to a bit over 1% of the Mustangs built that year.

It is true that the "M" Code was a 351W in 1969 but the 351W 2V (and 351C 2V) carried an "H" Code for 1970. The "M" Code for 1970 was for the 351C 4V, as was the 351C 4V for 1971.

Numbers and Codes aside, I think Mike is doing the "right thing" by getting as much information as possible prior to making his decisions. That is what we are ALL here for - - keep the conversations going.

BT

Mike, save the caps, that's a bonus.

If you get a 2 bolt block and caps, those 4 bolt caps would sell on ebay for good money

Don

I agree with H on closed chamber heads. You have a advanage as your car is a 4 speed so you can keep RPM's up for drive-ability. You would have to run premium fuel.

The 2 bolt VS 4 bolt has been debated for years. Years ago [ I think it was ]Jack Roush that said there was no difference as what you gained with 4 bolts you lost by drilling the block.

I now see why you have had the " odd " problems with your motor over the last couple of years.

Let me know if I can help.

Don

I like that Roush explanation Have always heard Clevelands don't need four bolt caps. The "odd" problems started with trying to put a standard Holley 4150 design 600 CFM on it. The engine did not like it much so we went with a 670 CFM and it wanted a bigger one Then there were the timing and vacuum issues not to mention trying to balance the carb.

Thanks for the offer of help.

mike

4-speeds were really rare in the 71-73 models. I heard from somewhere that only 1% of all 1971 Mustangs had a 4-speed. Not sure if that includes the Boss 351 (as those were all 4-speed).

A 351W-4v is still an M code, at least it was in 1969 (1970s had the 351C also) and if you're not selling, only you would know (or care ).

Personally, I would put in a 351W stroked to 427ci, it would be cheeper, much more power and may even get better MPGs than the Cleveland (which as mentioned, really suck gas).

Click to expand...

According to "Marti", the percentages for 4-speeds in 1971 Mustangs was actually closer to 5% - - 7,067 built out of a total of 149,682. This 7,067 includes the 1,805 Boss 351s which equates to a bit over 1% of the Mustangs built that year.

It is true that the "M" Code was a 351W in 1969 but the 351W 2V (and 351C 2V) carried an "H" Code for 1970. The "M" Code for 1970 was for the 351C 4V, as was the 351C 4V for 1971.

Numbers and Codes aside, I think Mike is doing the "right thing" by getting as much information as possible prior to making his decisions. That is what we are ALL here for - - keep the conversations going.

BT

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Yes, keep the information flowing. This forum has been the biggest help in my decision making. Contacted a local Mustang group of which I am a member ($35 a year) and their basic response was , DUH! "Have not bought Cleveland parts for years" was the answer. Have a feeling they like to wash their cars and show them and don't know much about the nuts and bolts. Thanks for all the advice and keep it comin'.

mike

4-speeds were really rare in the 71-73 models. I heard from somewhere that only 1% of all 1971 Mustangs had a 4-speed. Not sure if that includes the Boss 351 (as those were all 4-speed).

A 351W-4v is still an M code, at least it was in 1969 (1970s had the 351C also) and if you're not selling, only you would know (or care ).

Personally, I would put in a 351W stroked to 427ci, it would be cheeper, much more power and may even get better MPGs than the Cleveland (which as mentioned, really suck gas).

Click to expand...

Another posting mentioned there were 149,682 Mustangs built in 1971 of which 7,067 had four speeds, or ~5%. My Grande M-code with toploader is one of 100. Not good at math but that is less than 1%. That is the main reason for all the research and the car must remain an M-code. This forum is laced with the reasons why. Have to admit I am getting bored with walking to work every day. Albeit only a 5 mile round trip but it is uphill in both directions.

Here is a picture of what the engine once looked like and will look like again.

At least we get a chance to clean and paint the engine bay

mike

Your toploader is 1 of 100 of GRANDEs with a 351.

There were 7067 toploaders in ALL Mustangs (including Grandes, Mach1s, Boss, and plain coupes).

It makes sense, someone who wanted a 4-speed would probably have wanted the sporty Mach1 instead of the luxury Grande version.