Rebuilding a 351M
Thread Starter
|
Senior User
Joined: Apr 2002
Posts: 115
Likes: 0
From: Morgantown US
Rebuilding a 351M
Hi guys, I'm gonna try and ask all my questions at once !! I am rebuilding a 351M that I need to get about 20k miles out of till I build my Shazaam Smasher 
..anyway I have got it torn down and I have a few questions before I order parts and reassemble...
1) I'm not boring it out just re-ringing (see note below)..the original main and rod bearings are very worn...should I order .001 (1/1000) oversize bearings for them or just go with standard..on this motor I dont want to go with machining anything.
2) I am breaking the glaze on the cylinders (and cutting out the "ridge") and the old rings were very soft and breakable...should I order .001 (1/1000) oversize rings to make up for some of the wear?
3) The cam shaft was very worn and pitted and the timing chain was way out of spec for deflection..but the cam kit includes a new timing set and new lifters.
4) Should I try to do any "porting" while I have it apart? Would it be worth the effort? I especially notice a "ridge" in the intake side that could be taken out. How polished should I try and make the combustion chamber on the heads?
5) The INTAKE valves had a HUGE amount of a softer brown material built up on them and under that was some very hard black buildup. What is this from? On a few of the valves I dont see how fuel/air could of got in !!
6) Is there any other quick and dirty things you can suggest to help keep it alive for a short time?
Note: Remember this is a temp motor..I realize I cant run it 5,000 rpm and/or expect it to last forever...but I need this stop gap motor cause I don't quite have the money to build my new one but I will in the next 2 years for sure...I am looking now at about $250 in parts. My labor is a labor of love !! Beside I get to use all these shiny tools !
Well thanks in advance for your feedback..you guys (as always) are tops in my book !!
btw Since I have very limited mechanic knowledge to trade to you please note that I am a computer expert
(no really, I am !!) so if any of you have any questions that I might be able to help you with please dont hesitate to ask me!! Dont post here...send to roycline(No Email Addresses In Posts!) !! I also became a member and I am ordering some stuff from "The Store" to try and help out!
..anyway I have got it torn down and I have a few questions before I order parts and reassemble...1) I'm not boring it out just re-ringing (see note below)..the original main and rod bearings are very worn...should I order .001 (1/1000) oversize bearings for them or just go with standard..on this motor I dont want to go with machining anything.
2) I am breaking the glaze on the cylinders (and cutting out the "ridge") and the old rings were very soft and breakable...should I order .001 (1/1000) oversize rings to make up for some of the wear?
3) The cam shaft was very worn and pitted and the timing chain was way out of spec for deflection..but the cam kit includes a new timing set and new lifters.
4) Should I try to do any "porting" while I have it apart? Would it be worth the effort? I especially notice a "ridge" in the intake side that could be taken out. How polished should I try and make the combustion chamber on the heads?
5) The INTAKE valves had a HUGE amount of a softer brown material built up on them and under that was some very hard black buildup. What is this from? On a few of the valves I dont see how fuel/air could of got in !!
6) Is there any other quick and dirty things you can suggest to help keep it alive for a short time?
Note: Remember this is a temp motor..I realize I cant run it 5,000 rpm and/or expect it to last forever...but I need this stop gap motor cause I don't quite have the money to build my new one but I will in the next 2 years for sure...I am looking now at about $250 in parts. My labor is a labor of love !! Beside I get to use all these shiny tools !
Well thanks in advance for your feedback..you guys (as always) are tops in my book !!
btw Since I have very limited mechanic knowledge to trade to you please note that I am a computer expert
(no really, I am !!) so if any of you have any questions that I might be able to help you with please dont hesitate to ask me!! Dont post here...send to roycline(No Email Addresses In Posts!) !! I also became a member and I am ordering some stuff from "The Store" to try and help out! 
Senior User
Joined: Dec 2001
Posts: 356
Likes: 0
From: space city
Rebuilding a 351M
1 & 2 - if you're going to build a "good" motor, then you'll need some precision measuring tools - might as well get them now and get some practice using them on this motor. measure the crank & cylinders, and look up the max/min clearances. maybe consider file-fit rings.
3 - doesn't look like a question
4 - yes! again, it's practice for the "good" motor. you are getting the seats re-done, right?
5 - a combo of pcv & egr gasses, plus maybe leaky valve stem seals. the people whe market pour-in engine cleaners call it "deposits".
6 - work slow, check & re-check everyhing several times, gasket surfaces, all internal parts, inside of block, and anything that will be exposed to oil when the engine is running all need to be clean, clean, clean! give it 5k to 10K miles then go to synth oil. if your bearing clearances are loose, run thicker oil and/or a HV pump. don't forget to check the cam bearings.
3 - doesn't look like a question
4 - yes! again, it's practice for the "good" motor. you are getting the seats re-done, right?
5 - a combo of pcv & egr gasses, plus maybe leaky valve stem seals. the people whe market pour-in engine cleaners call it "deposits".
6 - work slow, check & re-check everyhing several times, gasket surfaces, all internal parts, inside of block, and anything that will be exposed to oil when the engine is running all need to be clean, clean, clean! give it 5k to 10K miles then go to synth oil. if your bearing clearances are loose, run thicker oil and/or a HV pump. don't forget to check the cam bearings.
Posting Guru
Joined: Mar 2002
Posts: 2,070
Likes: 2
From: Boise, Idaho
Rebuilding a 351M
[updated:LAST EDITED ON 10-Oct-02 AT 03:06 AM (EST)]>1) I'm not boring it out just re-ringing (see note
>below)..the original main and rod bearings are very
>worn...should I order .001 (1/1000) oversize bearings for
>them or just go with standard..
Yes, and hope for the best. Did you notice that any of the rod bearings were loose when you disassembled them? That's a bad sign; the big end of the rod is getting beat up.
>2) I am breaking the glaze on the cylinders (and cutting out
>the "ridge") and the old rings were very soft and
>breakable...should I order .001 (1/1000) oversize rings to
>make up for some of the wear?
Are rings available this way? I don't think this will matter much.
>3) The cam shaft was very worn and pitted and the timing
>chain was way out of spec for deflection..but the cam kit
>includes a new timing set and new lifters.
Really? Too bad. The stock 351M cam is supposed to be a good grind. Again, hope for the best.
>4) Should I try to do any "porting" while I have it apart?
Sure. It won't hurt and it might help low end power if you go easy.
>Would it be worth the effort?
No, but it will be some fun and good practice. If you rebuild this engine into a 400 then you can re-use your 'ported' heads.
>How polished should I try and make the combustion chamber
> on the heads?
Don't bother polishing the combustion chambers. It doesn't help anything.
>5) The INTAKE valves had a HUGE amount of a softer brown
>material built up on them and under that was some very hard
>black buildup. What is this from? On a few of the valves I
>dont see how fuel/air could of got in !!
Leaking valve seals and/or leaking or out of tune carburetor that 'coked' the raw fuel on the backs of the intake valves. Let them soak in Simple Green. I use a mayonaise jar or two. Keep the lid on the jar while they soak. The longer they soak, the easier they clean up.
>6) Is there any other quick and dirty things you can suggest
>to help keep it alive for a short time?
Hand lap the valves. Check the tips of the valves for peening. If they're beat-up you may have to scrounge for better valves. I've done this kind of quick and dirty refresh on a motor and it works ok. A lot of effort for a shaky motor but you do what you have to do when you're not rich enough to gold plate a rebuild. Be sure to pre-lube the engine before starting it. Don't use cheap oil or filters (please don't use Fram filters. Use Purolator PureONE or NAPA/Wix or Motorcraft).
I have re-used oil pumps, too. Why not? They live soaked in oil.
Check the exhaust cross-over in the intake manifold to make sure it's not clogged shut. Use drain cleaner/lye to eat the carbon build-up out of that. If it has/had EGR, try to get that working again.
Do you have a vacuum tester? Test the brake booster on the power brakes. If the diaphragm on the brake booster is ruptured, it will screw up the tune on the carburetor and you'll never figure it out. Makes a big difference when you find and fix that!
Best of luck,
>below)..the original main and rod bearings are very
>worn...should I order .001 (1/1000) oversize bearings for
>them or just go with standard..
Yes, and hope for the best. Did you notice that any of the rod bearings were loose when you disassembled them? That's a bad sign; the big end of the rod is getting beat up.
>2) I am breaking the glaze on the cylinders (and cutting out
>the "ridge") and the old rings were very soft and
>breakable...should I order .001 (1/1000) oversize rings to
>make up for some of the wear?
Are rings available this way? I don't think this will matter much.
>3) The cam shaft was very worn and pitted and the timing
>chain was way out of spec for deflection..but the cam kit
>includes a new timing set and new lifters.
Really? Too bad. The stock 351M cam is supposed to be a good grind. Again, hope for the best.
>4) Should I try to do any "porting" while I have it apart?
Sure. It won't hurt and it might help low end power if you go easy.
>Would it be worth the effort?
No, but it will be some fun and good practice. If you rebuild this engine into a 400 then you can re-use your 'ported' heads.
>How polished should I try and make the combustion chamber
> on the heads?
Don't bother polishing the combustion chambers. It doesn't help anything.
>5) The INTAKE valves had a HUGE amount of a softer brown
>material built up on them and under that was some very hard
>black buildup. What is this from? On a few of the valves I
>dont see how fuel/air could of got in !!
Leaking valve seals and/or leaking or out of tune carburetor that 'coked' the raw fuel on the backs of the intake valves. Let them soak in Simple Green. I use a mayonaise jar or two. Keep the lid on the jar while they soak. The longer they soak, the easier they clean up.
>6) Is there any other quick and dirty things you can suggest
>to help keep it alive for a short time?
Hand lap the valves. Check the tips of the valves for peening. If they're beat-up you may have to scrounge for better valves. I've done this kind of quick and dirty refresh on a motor and it works ok. A lot of effort for a shaky motor but you do what you have to do when you're not rich enough to gold plate a rebuild. Be sure to pre-lube the engine before starting it. Don't use cheap oil or filters (please don't use Fram filters. Use Purolator PureONE or NAPA/Wix or Motorcraft).
I have re-used oil pumps, too. Why not? They live soaked in oil.
Check the exhaust cross-over in the intake manifold to make sure it's not clogged shut. Use drain cleaner/lye to eat the carbon build-up out of that. If it has/had EGR, try to get that working again.
Do you have a vacuum tester? Test the brake booster on the power brakes. If the diaphragm on the brake booster is ruptured, it will screw up the tune on the carburetor and you'll never figure it out. Makes a big difference when you find and fix that!
Best of luck,
