351C Rebuild ADvice

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digithead

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So I bought my 1973 Mustang convertible with 315C about 2 years ago. End started and ran fine but the guy I bought it from never had motor out or knew much about it internally. Its run really strong for the 1500-2000 miles I've put on it. A week ago a bad sound low end knock slowly developed. Quiet at startup, then it comes on worse as engine warms up. Knock is more pronounced at 1800-2200 RPM range. Oil was changed 100 miles ago. Oil pressure is always strong, runs 50-75PSI on new sensor and gauge. So I've had two auto pros stop by and listen, neither liked the sound. Both think its low end bearing sound and not valve related. 

  So my question. If it comes down to pulling motor what are best affordable options? I thought crate motor, but I dont need stupid HP or want to have stupid money in the car. I am about 18K in it now and its mint but this issue. I could pull motor and find local shop and let them rebuild. I could order crate and swap this? I could order crate and store this one for next owner?  My preference would be to keep cost at a minimum as I dont see a $6000 engine a good investment in these cars. Would be awesome to have 450-500 HP but thats too much money. THink I'd be happy with a solid 300HP motor. I've heard the 351C is known for oil not reaching back bearing due to poor design? Is this the time to fix it and rebuild motor? Motor was PERFECTLY strong before this, 0 complaints. Could smoke tires easily.

 
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mjlan

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Oooo, I'm going to be the first one to respond!

You are at the top of a very slippery slope.

Why not pull the engine and check out the bearings and crank/ rods? If you put it on a stand, you could see every thing easy enough and then you would know the condition of the engine.

If the bearings are shot, maybe you could get away with simply replacing the bearings and getting the crank turned. I would guess-timate that you could probably do this for around $2k, but would require you (or a shop) to pretty much completely disassemble the motor to get the crank out. You would then know what the bores look like and whether or not you would need to get it bored/ pistons/ rings etc.

It all depends on where you want to end up with the car. I would say that when it was all said and done, $6k would get you a stock rebuild and cover all of the misc. BS stuff that you replace "while you are in there": like trans seals, oil and filters, hoses, belts, etc.

Good luck!

 

Hemikiller

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Going with mjlan on this one. Unless you are able/willing to do the majority of the work yourself, a crate motor is going to cost you dearly.

You most economical way would be to pull the engine, replace the bearings, have the crank turned, new oil pump, timing chain, gaskets and put it back in. You could probably accomplish this for $500. I give that about an 60/40 chance of going as planned.

Worst case, you have to do a complete rebuild and are spending more.

 

digithead

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Oooo, I'm going to be the first one to respond!

You are at the top of a very slippery slope.

Why not pull the engine and check out the bearings and crank/ rods? If you put it on a stand, you could see every thing easy enough and then you would know the condition of the engine.

If the bearings are shot, maybe you could get away with simply replacing the bearings and getting the crank turned. I would guess-timate that you could probably do this for around $2k, but would require you (or a shop) to pretty much completely disassemble the motor to get the crank out. You would then know what the bores look like and whether or not you would need to get it bored/ pistons/ rings etc.

It all depends on where you want to end up with the car. I would say that when it was all said and done, $6k would get you a stock rebuild and cover all of the misc. BS stuff that you replace "while you are in there": like trans seals, oil and filters, hoses, belts, etc.

Good luck!

----------------------------------------------

Thank you! YEa, thats the direction I am leaning. I mean no matter what it has to come out for something to happen so thats a given. SO the fork in the road is rebuild this one vs. order a turn key Crate. I cant do it myself. I am mechanical and understand motors but have not rebuilt some like this and dont want to learn on my own nickel. I'd rather pay a pro. So tempting to just a order a crate. But then if its numbers matching thats dumb, right?
 

johnwanzel

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$6000 engine not a good investment in these cars????? Those are fightin words in this group hahahaha j/k

 
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You have probably read some of the recent posts on the forum about VIN# on the engine. You need to keep your original engine and not trade for a rebuild. Putting an engine together after the machine work is a pretty simple job just get some good instruction from books and maybe some video. I would pull the valve covers first and see if maybe a rocker has come loose or getting loose. I had one do that once and thought I have blown it up.

I believe the only issue on the oiling would be to get the front cam bearing installed to the proper depth there is a bleeder hole in the casting and if you press the bearing too deep too much oil escapes.

Rod and main bearings usually do not just go boom it is a slow wear process unless you were over reeving and melted a bearing.

I would build it myself if I were you. You can save some money and you will know what you have for sure.

When me and my son kart raced he built his first engine at 9 years of age. I let him do everything even degree the cam, no issues. A car engine is a pretty simple machine hell try working on a player piano with over 8,000 pieces if you want a challenge.

When you do build also spring for a balance job from the front pulley to the driveshaft and you will have a better engine.

I was at the Charlotte swap meet at the race track and they had one of the engine building contests going on. We went in the tent and they were putting Ford 351 C NASCAR engines together. They did torque everything and had to put crank in, rods and pistons, check clearance on one bearing, install cam, push rods and heads, oil pan and valve covers, headers. Put intake on and install distributor. They were doing it in less than 20 min. and they had to fire it up. I think there were three or four on each team.

Don't let anyone scare you away from doing it yourself it is a machine not a black box. Find some local racers they usually know who does the best machine work and will not cost a fortune.

 

Don C

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+1 on removing the engine. Before you do pull it run a compression and/or leakdown test, to get an idea of the condition of the cylinders and rings.

Replace all of the bearings, not just the main or rods. Because you haven't run it much since it started making noise you may luck out and not have to have the crank ground, carefully check it for scoring, roundness, and taper.

Now will be a good time to have hardened valve seats installed, so you don't have to worry about valve recession. Also check the valve guide wear.

Check the cylinders for roundness, taper, and how big the ridge is at the top of the cylinders. Check the ring lands in the pistons for wear.

Pay yourself for the labor involved, not an engine builder.

If you need any machine work done find a good machinist, check out their shop. It doesn't have to look like a NASCAR garage, but the condition and organization of the tools, as well as the shop owner/personnel will tell you a lot.

 
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