351 Cleveland swapped MII

78 Mach1

Active Member
Feb 17, 2022
German Valley, Illinois
So I’m finally getting back to working on this car. A few other projects sidelined this one until now. My next step is to put the fresh built 351 Cleveland in. I originally thought his would be pretty straight forward since I remember seeing a couple cars years ago with this swap. Well, during my attempt today, things didn’t slip in as nicely as I hoped. The passenger side exhaust manifold makes contact with the passenger side frame rail before the passenger side motor mount lines up. I’m pretty sure I read somewhere that the factory 302 motor mounts and the factory Cleveland manifolds would work. But I’m not seeing that to be the case. The manifolds I have are from a Torino. Or at least that’s what I was told the motor came out of. I have two Cleveland’s. One from a Torino that I freshly built and another I purchased from a gentleman who was going to put it in his 1964 F100. Both motors have the same manifolds. So my question is, what manifolds will work in the Mustang II? Has anyone on here successfully done this swap. If so, any advice is greatly appreciated. I have a set of headers for a 351 Cleveland in a 71 mustang. I’m going to see how close those come to fitting. Maybe I can modify those to work. But if anyone knows what factory manifolds work, I’d love to hear from you.
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I don't have much to offer, but I'm not sure any factory Cleveland style exhaust manifold will fit. I say that mainly because of the angle of the mounting area of heads. Windsor style heads are more vertical than Clevelands whereas Cleveland port surface area align with the block moreso than Windsors. That would make Cleveland ports point almost directly at the frame rail iirc, and I'm not sure that there would be a lot of room for much of anything there. The only possible saving grace would be the taller deck height compared to a 302.

I thought heavily about building a Clevor engine for my car years ago, that aspect is what discouraged me from doing it. The only solution I could think of at that time was custom headers. I wasn't aware of anything factory that would've worked for my scenario. :shrug:
My first attempt with the current factory manifolds failed. The passenger side manifold hits the frame rail right at the donut joint before the drivers side motor mount lines up. I could notch the frame but just not willing to do that yet. Still looking for header options. I heard header companies used to make them for this swap. But I can tell, there isn’t much room for anything. So I’d really like to see a Mustang II with those headers in it. lilcbra is exactly right. The exhaust ports face directly at the frame rail. Angled down much better than a Windsor motor. But still way to close for much of anything for exhaust. I do have a motor plate for it, so when I eliminate the motor mounts, I can shift the motor to the drivers side about 1.25”. This will help but still cutting it close. The early mustang headers I have didn’t even come close to fitting in.
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I decided to remove the exhaust manifolds and keep moving forward and come back to the exhaust dilemma later. Ran into my second issue. The oil pan hits the steering rack before the motor mounts line up. So now it looks like I’ll be sectioning the oil pan to fit. That’s where I’m at now. Luckily, the power brake booster actually looks like it’s going to clear. I thought that was going to be a problem.

Oh, and in case your wandering why I care about the motor mounts lining up since I have an engine plate. My plan is to get everything to fit (hopefully) in the stock location with the motor mounts. Then build the motor plate based off of those dimensions to ensure I don’t throw something else out of whack. Like tranny cross member or whatever else I’m not thinking of. With the motor mounts gone and the motor plate shifting everything over, I’m hoping my header options will be better.
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The mustang ii used the more petite 141 tooth flex plate/ bell housing to make more room for the exhaust.

The pan has a round shape for the cross member part.

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Here’s the Cleveland oil pan. You can see where the transition from deep sump area and more shallow area isn’t quite as steep as the pan you showed. I hit right there on the steering rack. I need about 2” of clearance. I’m pulling the pan today and seeing if I’ll have enough clearance from crank if I cut the shallow section down 2”. If not, I may cut the pan as much as possible leaving safe clearance to the crank and then raising the engine up slightly with the engine plate. I’ll let you know how the pan dissection goes.
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I do have the factory C4, bell housing, and torque converter for the car. I will need to come up with a flex plate. I assume the Cleveland and 302 have the same crank bolt pattern so I can use a 302 flex plate. Don’t know for sure, but I’ve got a flex plate out of a 67 mustang I can test for with.
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Good question. I actually forgot about that. I assume Cleveland’s were 28 oz flex plates like the Windsor was? If my memory is correct the early 302 engines were 28 oz and then went to the 50 oz later on. I can’t remember the date that change happened though.

Thank you for reminding me of this. I ran into this issue with 1969 Mach 1 we just finished. I purchased a 28 oz flywheel for that car but the one I received was not properly balanced. Car shook really bad. Returned that flywheel for a better brand and solved the problem. I still have the out of balance flywheel if someone wants it Lol.
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Test that brake booster. I have put 3 II's back on the road, well 2 mostly back together and 1 actually back on the road in the last few years. All 3 have/had bad boosters. I was able to find one new one off ebay but it wound up causing me a lot of headaches as it was defective. I have not done it but the local NAPA says they can ship it to Dorman or Cardone, can't remember which, and have them rebuilt. NAPA said plan on 6 to 8 weeks turn around time. Hate to see you that far along and have to wait a few months to get it back.

That oil pan in monstrous compared to a II pan. Even the sump looks very deep. Check your ground clearance before you mount the engine. These cars sit low and almost every v8 II I have messed with have the oil pan damaged from bottoming out at some point in their lives. If you plan on lowering it you may need to shorten the sump as well.
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“Is this a budget build?
An aftermarket Moroso or Canton oil pan could resolve this concern.” I wouldn’t necessarily call it a budget build considering everything I’ve already put into it. But I certainly want to save money anywhere I can. I look at fabrication work as a challenge. If you pull up some of my other threads. You’ll see I do pretty much everything myself. Including making my own seat upholstery.

II crew. Thanks for the heads up on the brake booster. At this point, I’m still not sure if I can stick with the factory booster or not. I currently have clearance, but once I delete motor mounts and go the plate route, I’ll be moving the engine towards driver side. The factory booster may not clear anymore. Once that determination is made, I’ll look into my booster options.

I’ll check ground clearance the moment I get the motor sitting all the way down in there. I do have 2” drop spindles on the front. So yes, she does sit pretty low. But those are 15” wheels and tires up front, so that helps some.
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Since you are moving the engine this is probably a moot point but the engines sit about 1" offset to the passenger side from the factory.

I am 95% sure they had different springs left and right from the factory. This is a latent memory from working on them back in the 80's. I think they had about 15 spring options back then. All v8 cars cars had a heavier spring on the passenger side. A/C cars had an even heavier spring setup. I may be confusing things in my cobweb riddled brain but I am fairly certain it was these cars that had the odd front spring setup.

With that in mind... adding in you having a heavier engine, the stock springs are very soft. 340lbs or there abouts. Are you planning on sticking with stock style springs? If it's in your budget look into coil overs. This past winter Speedway put me together a kit for right at $400 for QA coil overs using speedway brand 500lb chrome springs. I have to say it made a world of difference in the ride quality. Best single suspension upgrade I have done. By far! Well worth the money. It rides much smoother using the heavier springs.

I already had tubular upper and lower a arms but you should be able to do the same with just tubular lower arms. I had stock spring style tubular lower arms and just cut the perch off. I had to get the 7/16 lower mounting bolt coil overs. They are usually 1/2". I had to call Speedway to get the 7/16 kit. It is not listed on their website. I would imagine since you can fab you could use the stock lower arms by cutting the spring perch. You may have to add some reinforcement but just cutting enough of the perch to clear the coil over shouldn't compromise the integrity. I would avoid the speedway a arms. I had issues with the ball joint hole being out of round on 2 of the 4 arms and the ball joint would not tighten down. Someone else here, I think it was here. May have been another forum. They had a similar issue and had them welded in place. Just avoid that hassle and get the heidts brand if you getting new arms. That's what I wound up doing and the ball joints screw right into place.

I am rambling about this now so you don't end up with the car sitting lower on one side vs the other. You may be fine using oem springs but moving the engine and what I imagine has to be a heavier engine, on drop spindles you may end up lopsided.
I actually upgraded the springs already. They are stock style but the spring rate options these days are endless. Unfortunately I think I went with too heavy of a spring. With all the Cleveland’s weight sitting on the car, the front still feels very stiff to me. The spring barely compresses and rests at almost full extension. I had to add weight to the front to get the shocks bolted on. This could be because I went with all new poly bushings as well and they just need to break in and settle. But I already plan to have to do something with the springs. I’m waiting until I have all accessories hanging on the engine and the front bumper sorted out to decide my spring rate. Since I apparently already guessed wrong. I went with a recommendation based on the Cleveland. I bought them several years ago before doing the mini tub. I honestly don’t even remember what they are at this point.
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I just realized, I should provide some information about the car. You need to know what’s been done and what the end goal is. That will help you understand what I actually have.

Wheels: Weld 15x4 front Weld 15x12 back
Suspension: stock style leafs in back and custom ordered coils in front
Brakes: Willwood 4 caliper front disc and Ford Explorer rear disc, factory power booster
Frame: back halved and cross braced with fuel cell cage. Full weld in Frame connectors
Interior: all stock with sectioned rear seat to fit between tubs.
Transmission: stock C4
Engine: mild build 351 Cleveland. All fresh
Differential: shortened 8.8, cut to center yoke, with ford racing 410 gears, disc brakes, Strange 35 spline axels, limited slip with extra clutch packs for harder lock up.

I’m sure I’ve forgotten a lot. But this gives you an idea.

The end goal is a really nice street car built with old school styling. That should help explain the leaf spring ladder bar setup and engine choice. All in the name of sticking to the theme. Just the right stance and a mean sound. I’m going more for that wow factor then actually being concerned about speed. The Cleveland is an important part of the theme. That’s what people were doing with these M IIs when I was a kid in school. It’s always been my dream to build one just like you would have seen on the streets back in the mid to late 80s.
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Spring wise don't judge them just yet. My car rode like crap on the stock v6 springs. Everything was new but the springs. Car had 40,000 miles when I rebuilt it a few years ago. I assumed good shocks, new control arms, thickest front sway bar I could find new, ect it would ride nice. Not the case at all. It felt like a 3/4 ton truck suspension up front. Before I installed the engine I had to have my adult sons, plural, on the bumper to get the ball joint started. Stock springs are only about 300lbs on a v6 car without a/c. I thought it would be too soft with the v8 now installed. It bounced over bumps. Rode like a heavy truck. I had to jump on one corner to get any compression of the springs. So I went digging around and ran across the cheap coil overs and went that route. I now have the 500lb springs and it rides so much better. You having the Cleveland I imagine the proper spring is 550 lb, Maybe even 600lb.

Now that the front end feels right the rear end is the same. Feels like air shocks back there. I did some more digging and I actually think it's the kyb shocks. Which were new on all 4 corners. They are just not meant for this light of a car on the street. I think they are geared towards track cars or just heavier cars in general. They do not compress unless hitting a hard bump. What shocks are you using?

Decades ago I had a Monroe rep tell me to use the cheaper shocks as the better monroes used a 9/16's piston and it would ride like :poo:. The cheaper monroes used a 1/2" piston and would ride better. I had forgotten that bit of info until I was back in the thick of it trying to make my car ride better. So pull a shock and see what happens. I think you will find the springs may be correct but the dampening of the shock is just too harsh for a street car.