351C Rebuild suggestions - Vintage Mustang Forums
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post #1 of 12 (permalink) Old 01-30-2018, 09:03 PM Thread Starter
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351C Rebuild suggestions

For a while my '73 Mach 1 would lose oil pressure after about 30 minutes of driving. It had 5 p.s.i. at idle in gear at one point. Last night, I pulled it around front and it had 60 p.s.i. I got down to 20 after about 15 minutes of running. This morning, I started it up to drive it to work and the gauge was reading 5 p.s.i. It then, dropped to 0 if I revved it up. The engine in the car, as far as I know, is original. It is a 2v Cleveland with an edelbrock intake and Holley 4 barrel carb.

I picked up a 4v Cleveland engine a few months that back that I was planning on building for my '70 Mustang. The engine is rough and I only have the heads, intake, and crank. I don't think the crank is any good. I'm wondering if I should rebuild the engine that is in the '73 and be done with it, or rebuild the '73 block and put the 4v heads on it, or just build the 4v block and swap the engines out. This also leaves me with what I should do with the '70. I have no problem keeping the 302 in the '70 but it vibrates badly and needs a rebuild as well. I could put the 2v Cleveland in the '70 if I build the 4v for the '73. The '70 also has a T-5 and I don't think it would live behind the Cleveland.

All this being said, once I start building the 4v, what would be the best all around performance build? If goes in the '73, I want it to be comfortable to drive yet be fun at the track. The car has a C6 and 2.75 open. If it goes in the '70 it doesn't have to be as tame, but I would still like it to be streetable. This car has T-5 from an '04 mustang V6 and 3.50 equa-lock.

Sorry for this long winded loaded question and thanks in advance for the advice!

1970 Mustang Coupe, 302, T-5
1973 Mustang Mach 1, 351C 4V, C6
1998 Mustang GT, 4.6, T-45
2001 F-250 lariat, 7.3
2015 Escape 1.6 ecoboost
2019 Mustang GT, 5.0, MT82
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post #2 of 12 (permalink) Old 01-30-2018, 09:17 PM
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Step 1 is to verify that you don't have a bad oil pressure sending unit. Remove it and install an inexpensive mechanical gauge using a short line to test the ACTUAL oil pressure. If it IS that low and DOES decrease as rpm increases then the motor needs some attention.

For a street car I'd rebuild the existing 2V with some decent components, an aftermarket four barrel intake for the 2V heads, and go from there.
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post #3 of 12 (permalink) Old 01-30-2018, 09:27 PM
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4V block if your wanting the 4 bolt mains
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post #4 of 12 (permalink) Old 01-30-2018, 09:28 PM
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Quote:
Originally Posted by Woodchuck View Post
Step 1 is to verify that you don't have a bad oil pressure sending unit. Remove it and install an inexpensive mechanical gauge using a short line to test the ACTUAL oil pressure. If it IS that low and DOES decrease as rpm increases then the motor needs some attention.

For a street car I'd rebuild the existing 2V with some decent components, an aftermarket four barrel intake for the 2V heads, and go from there.
You would keep the 2V heads?

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post #5 of 12 (permalink) Old 01-30-2018, 09:31 PM
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Originally Posted by turbo2256b View Post
4V block if your wanting the 4 bolt mains
Only the BOSS, the HO and the CJ had 4-bolt mains. The "plain ole" 4V shared the same bottom end as the 2V.

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post #6 of 12 (permalink) Old 01-30-2018, 09:35 PM
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Quote:
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You would keep the 2V heads?
Unless I was building a stout "race motor", yeah. I'd prefer either the Aussie 3V or an aftermarket closed chamber head with the 2V-sized ports and valves to retain intake velocity (plus low-rpm throttle response, driveability and fuel mileage) but, with the right piston the open chamber 2V heads will be fine.

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post #7 of 12 (permalink) Old 01-30-2018, 09:57 PM
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Cylinder head options:

- Deck the block and mill the 2V heads to boost compression. People will tell you this will make the engine detonate. That's true for wedge heads. Cleveland heads are not really wedge heads. A lot of Cleveland guys do this with no detonation issues. (10:1 static compression with flattop pistons would be optimal.)

- If the 4V heads are closed chambered, you're good for compression. If they're open chambered, again, deck the block and mill the heads to boost compression. (10:1 static compression with flattop pistons would be optimal.)

- Whichever heads you use, decide if you want to spend the money to have them machined for screw-in, adjustable rocker studs. Talk to some local machine shops and see what kind of deal you can get. A lot of shops are hard up for work these days and may offer you a reasonable price. Installing adjustable rocker studs will give you MANY more options for cams and RPM ranges.

- Some people will tell you the 4V heads are no good for the street. This is a myth created by people who didn't properly build a 4V Cleveland then complained it was a dog at low RPMs. You can't build a Cleveland like a small block Chevy. It doesn't work.

- The 2V heads still flow quite well, but not as well as the 4V heads. The 2V heads work well for lower RPMs up to around 6,000 RPMs. The 4V heads don't work as well as low RPMs, but come like the proverbial gangbusters up high. ("Charging Rhino" is the Cleveland guys call it.)

- "Aussie" heads are another option. Those have the 2V ports with closed combustion chambers. These are what I put on my Cleveland because I found a good deal on a set which were already machined for screw-in, adjustable rocker studs.

Block Options:

- Use whichever block is in the best shape. There's no need to machine a Cleveland block for 4-bolt mains. Two-bolt mains are more than adequate.

- It's a VERY good idea to install lifter bore bushings into the block. This can be expensive, but it's worth it. The Cleveland block does in fact have some oiling issues. All the "fixes" from the 1970s were mostly bunk. High pressure or high volume oil pumps don't fix it. External oil lines to the rear of the block don't really work. The only mod which actually solves the oiling problems are lifter bore bushings. Oil restrictors in the cam bearing areas also help, but you still need the lifter bore bushings.

- Have the machine shop install ARP studs into the connecting rods. Use ARP nuts for the end caps as well. The actual problem is the nuts, but it's not much more expense to install new studs as well.

- If your 4V heads still have the factory, two-piece valves, don't use them under any circumstances. They are prone to failure; catastrophic failure!

- Use whichever crank is in the best shape. The factory crankshaft is more than adequate.

Camshaft Options

Here's where things get tricky. Cams that work well in most small block V8s don't work well in a Cleveland. What does work well is a Boss 351 grind or a custom grind from a shop that actually knows something about Clevelands. (Bullet Racing Cams is a good source. They can machine a hydraulic Boss 351 cam or anything else you like.)

Do not use a cam grind designed for a small block Chevy. Be careful of this since some "off the shelf" cams use exactly this.

Other Things

- The factory distributor is fine, but have it calibrated to match whatever cam grind you go with. Nothing wrong with an MSD unit, for example, but you don't really need it.

- If you go with the 4V heads, you need a big rear gear allowing the engine spin up fast. A 3.90 or bigger is a good idea. (Using a small rear gear is one of the reasons people complain about 4V Clevelands being dogs.)

- The Edelbrock Air Gap intake would be a good choice.

- Run headers and have a good, free-flowing dual exhaust fabricated for your car. A Cleveland has to breathe! Shorty headers are fine.

Have fun! I'm attaching a picture of my Cleveland for inspiration. (Haven't yet run it. I'm getting close.)
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File Type: jpg 007.jpg (94.8 KB, 21 views)
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Last edited by Klutch; 01-30-2018 at 10:01 PM.
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post #8 of 12 (permalink) Old 01-30-2018, 10:44 PM Thread Starter
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Quote:
Originally Posted by Woodchuck View Post
Step 1 is to verify that you don't have a bad oil pressure sending unit. Remove it and install an inexpensive mechanical gauge using a short line to test the ACTUAL oil pressure. If it IS that low and DOES decrease as rpm increases then the motor needs some attention.

For a street car I'd rebuild the existing 2V with some decent components, an aftermarket four barrel intake for the 2V heads, and go from there.
I do have a mechanical gauge in the car. It was originally equipped with a dummy light. I know the oil sender is the last place oil reaches so I'm getting readings post cam and main bearings.


Quote:
Originally Posted by Klutch View Post
Cylinder head options:

- Deck the block and mill the 2V heads to boost compression. People will tell you this will make the engine detonate. That's true for wedge heads. Cleveland heads are not really wedge heads. A lot of Cleveland guys do this with no detonation issues. (10:1 static compression with flattop pistons would be optimal.)

- If the 4V heads are closed chambered, you're good for compression. If they're open chambered, again, deck the block and mill the heads to boost compression. (10:1 static compression with flattop pistons would be optimal.)

- Whichever heads you use, decide if you want to spend the money to have them machined for screw-in, adjustable rocker studs. Talk to some local machine shops and see what kind of deal you can get. A lot of shops are hard up for work these days and may offer you a reasonable price. Installing adjustable rocker studs will give you MANY more options for cams and RPM ranges.

- Some people will tell you the 4V heads are no good for the street. This is a myth created by people who didn't properly build a 4V Cleveland then complained it was a dog at low RPMs. You can't build a Cleveland like a small block Chevy. It doesn't work.

- The 2V heads still flow quite well, but not as well as the 4V heads. The 2V heads work well for lower RPMs up to around 6,000 RPMs. The 4V heads don't work as well as low RPMs, but come like the proverbial gangbusters up high. ("Charging Rhino" is the Cleveland guys call it.)

- "Aussie" heads are another option. Those have the 2V ports with closed combustion chambers. These are what I put on my Cleveland because I found a good deal on a set which were already machined for screw-in, adjustable rocker studs.

Block Options:

- Use whichever block is in the best shape. There's no need to machine a Cleveland block for 4-bolt mains. Two-bolt mains are more than adequate.

- It's a VERY good idea to install lifter bore bushings into the block. This can be expensive, but it's worth it. The Cleveland block does in fact have some oiling issues. All the "fixes" from the 1970s were mostly bunk. High pressure or high volume oil pumps don't fix it. External oil lines to the rear of the block don't really work. The only mod which actually solves the oiling problems are lifter bore bushings. Oil restrictors in the cam bearing areas also help, but you still need the lifter bore bushings.

- Have the machine shop install ARP studs into the connecting rods. Use ARP nuts for the end caps as well. The actual problem is the nuts, but it's not much more expense to install new studs as well.

- If your 4V heads still have the factory, two-piece valves, don't use them under any circumstances. They are prone to failure; catastrophic failure!

- Use whichever crank is in the best shape. The factory crankshaft is more than adequate.

Camshaft Options

Here's where things get tricky. Cams that work well in most small block V8s don't work well in a Cleveland. What does work well is a Boss 351 grind or a custom grind from a shop that actually knows something about Clevelands. (Bullet Racing Cams is a good source. They can machine a hydraulic Boss 351 cam or anything else you like.)

Do not use a cam grind designed for a small block Chevy. Be careful of this since some "off the shelf" cams use exactly this.

Other Things

- The factory distributor is fine, but have it calibrated to match whatever cam grind you go with. Nothing wrong with an MSD unit, for example, but you don't really need it.

- If you go with the 4V heads, you need a big rear gear allowing the engine spin up fast. A 3.90 or bigger is a good idea. (Using a small rear gear is one of the reasons people complain about 4V Clevelands being dogs.)

- The Edelbrock Air Gap intake would be a good choice.

- Run headers and have a good, free-flowing dual exhaust fabricated for your car. A Cleveland has to breathe! Shorty headers are fine.

Have fun! I'm attaching a picture of my Cleveland for inspiration. (Haven't yet run it. I'm getting close.)
I have closed chamber heads. I knew there were things that should be done to aid the oiling system. I was thinking the gears I wanted to change to would be 3.50 for highway and city mix. The '73 has an aftermarket hei style distributor. Someone I work with suggested I build the 4v engine and install a higher stall converter in my C6. Another option to look at is go ahead and build the engine with 4v heads and find another set of heads when I'm ready to build the '70.

1970 Mustang Coupe, 302, T-5
1973 Mustang Mach 1, 351C 4V, C6
1998 Mustang GT, 4.6, T-45
2001 F-250 lariat, 7.3
2015 Escape 1.6 ecoboost
2019 Mustang GT, 5.0, MT82
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post #9 of 12 (permalink) Old 01-31-2018, 08:52 AM
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I have a 351C 4v with Closed Chamber heads, Hydraulic Roller modeled off the stock 351CJ cam and a T5Z. The car drives very nice and pulls like an animal, I'm not a believer that 4V heads aren't for the street.
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Last edited by cj428mach; 01-31-2018 at 08:55 AM.
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post #10 of 12 (permalink) Old 01-31-2018, 10:01 AM
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I went through this with my 73 Mach. 351 C 2V. My problem with oil pressure was main bearing wear. So I rebuilt it. I punched it .030" over, reconditioned the stock crank and rods (stock rods are very good). Aluminum Hyperutechtic pistons, comp cam .519" lift both intake and exhaust. I went whit this as to not screw up my power brakes. Heads reconditioned, I also polished the chambers. Edlebrock Performer intake and Edlelbrock 750 carb. Rebuilt my FMX trans and put a 3:55 Richmond gear in the rear and added traction loc, was 2.75. It runs perfect on the E way or around town.

So what I am saying is why not rebuild your original motor. Also most everything I have read says the 2V heads are better for street use. Or you can go to aluminum, they're just not cheap.

Good luck.

https://www.facebook.com/john.garron...261685/?type=3

73 Mach 1 351 clev.

Last edited by jsgarron; 01-31-2018 at 02:55 PM.
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post #11 of 12 (permalink) Old 01-31-2018, 10:11 AM
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THE LAST 351c build i did with closed chamber heads around 10 to 1 compression. ported heads, ported torqer, short oval track cam pulled 500 ft lbs @ 4200 rpm and 500 HP @ 6000 rpm on Jomars engine dyno operated by a ford engineer. It could have done much more

2V heads ported will flow as much or a bit better than as cast 4v heads but better air speed

Last edited by turbo2256b; 01-31-2018 at 10:14 AM.
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post #12 of 12 (permalink) Old 01-31-2018, 10:29 AM
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a 351c powered 73 mach I i had installed 2 v heads and 4 v heads, headers and a intake that fit either think it was a torker for 2v heads. results engine would only turn about 6500 rpm. the 4 v heads didnt seem to pull as well in until a bit over 6000 rpm. this was with stock springs and the 73 4 v cam.

pic of the car a few months before a guy did a hit and run on me and took out the passenger side
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