1972 351C runs crap

[Stanglover]

Hmmm! I'm not qualified to answer this, but from what little I know, you may have a big problem on #5 cylinder as it looks to be oil fouled as you know. #'s 6 & 7 look to be right on, 8 looks rich. I'm sure more experienced members will have a better idea and can offer help. Have you done a cylinder compression check? Again, from what I understand, I'm afraid you might have a ring issue on 5. BUT, it could also be those Champion plugs. I won't even run them in my lawn mower!!

For me with my engine troubles, I was afraid that as the engine was broken in on a stand by the builder who didn't realize it was only firing on 7 ( dead plug) and from subsequent running, that the #4 cylinder had suffered a 'wash down' and screwed up the new rings. I too will need to do a comp test to find out, but so far, I think I dodged that bullet.

I really hope I'm wrong on this one in your case. Very worrying and getting expensive no doubt.

Good luck,

Geoff.

Thank you for the answer Geoff, yes it seems 5 is a bit oily, it reeks of gasoline though so most of it is probably fuel.

I was hoping compression issues was out of the question but seems like i have to check now anyway.

I too only have had troubles with champion plugs in the past, but they were the only ones in stock when i bought the rest of the parts so i got them...

Really hope there is an easy fix to this, cant afford to throw any more money at this thing right now...

Yes, let's hope it IS fuel, but even that isn't good either. Like I said, I feel your pain, mentally and monetarily. This, from the length of this post, has been going on far too long and all you want to do, like me, is drive the s**t out of it and have some fun.

 

[basstrix]

A compression test is definitely in order. Let's hope it's just a bad plug.

 

[Odmark]

Yeah i really hope so too.. Would totally suck to have compression loss with all new engine internals...

Hope i can get the tester down there, so little room especially on the drivers side of the engine.

Wierd it runs so good when driving it on the road, i remember when i lost a cylinder on my olds and had to highway drive it 20km home, it really ran like sh*t!

Same with my old saab, started vibrating at certain speeds and ran like crap.

This though, soon as you up the rpm just a little bit it is unnoticeable.

 

[Stanglover]

Yeah i really hope so too.. Would totally suck to have compression loss with all new engine internals...

Hope i can get the tester down there, so little room especially on the drivers side of the engine.

Wierd it runs so good when driving it on the road, i remember when i lost a cylinder on my olds and had to highway drive it 20km home, it really ran like sh*t!

Same with my old saab, started vibrating at certain speeds and ran like crap.

This though, soon as you up the rpm just a little bit it is unnoticeable.

Hmmm! My engine running on 7 also seemed fine on the road. Ran rough at idle which is when I figured out I had a dead cyl. I know my issue is the distributor. Talking of, did you physically check the internals of your distributor?

 

[Odmark]

No i have not actually checked the internals of the distributor, i just assume it is working because its new :angel:

But i do have spark on all cables (checked with a new plug i had laying around for another one of my saabs) even though i thought it seemed weak.

Still as i said it is hard to see when you are in broad daylight and have to set up the plug and then turn the engine and check for spark from the drivers door.

 

[Stanglover]

No i have not actually checked the internals of the distributor, i just assume it is working because its new :angel:

But i do have spark on all cables (checked with a new plug i had laying around for another one of my saabs) even though i thought it seemed weak.

Still as i said it is hard to see when you are in broad daylight and have to set up the plug and then turn the engine and check for spark from the drivers door.

Distributor: I too have a new one, but the mechanical advance is still way too much for MY engine. The advance stop slots are not even numbered like originals are, they are equivalent to an L15 slot or 30* of crankshaft rotation (15X2) For me I think I need an L10 to start with or 20* crank rotation. If timing ends up as your main issue, you may have to do what I am going to do and CAREFULLY add some weld to the slot and resize it to suit. Trial and error!!

Someone posted a link to Crane Cams website for "adjustable Vacuum advance kit" for Ford V8 1960 to 1974 with single points. I'm sure you can find it on their website. Also, I found "Timing tips for Ford distributors" on a Google search. Useful stuff there too and has helped me understand my situation.

Remote start button: Years ago, I purchased a remote start button thingy. You just need to plug the red to the battery + post and the other to the first solenoid connection ( remove the wire first, closest to the battery and put the car in NUETRAL, brake on). You can then stand in front of the car and turn the motor over and can see exactly if your plug is firing. Useful and cheap tool.

Compression Tester: Buy one that has a braided cover on the hose. It will screw in easier with a better seal as it is far more robust than others on the market. A bit more expensive, but worth it. I have two, one is junk, so I found out the expensive way.

Hope this helps some,

Geoff.

 

[Don C]

Just because you have spark at the cables doesn't mean the plugs are firing. The only way to make sure that a spark plug is firing is to put it in a pressurized tester and crank the air pressure up. A plug may fire fine in the open air, but not fire under compression pressure. You can try swapping plugs around and see if the problem follows the plug, or it's just in that one cylinder.

A leaking intake gasket on the left bank could cause your problems. #5 intake runner likely gets more oil splash than the rest, due to oiling the distributor gear.

 

[Stanglover]

A leaking intake gasket on the left bank could cause your problems. #5 intake runner likely gets more oil splash than the rest, due to oiling the distributor gear.

Good point. To redo an intake gasket set would be far better and cheaper to fix than a bad ring situation. Something for me to remember as well.

 

[rcadd1ct]

When you are setting the timing you are removing and plugging the vacuum port, right?

 

[Odmark]

Okay all, thank you for all the inputs. I really appreciate it.

Seems i was not thourough enough when checking for vacuum leaks.

I found one now... Guess where? You will never ever believe me :whistling: Riiiiight between the inlet runners for cylinder 5 and 6, closer to number 5...:shootself: not even internal (if not both)

So i guess i have to re-do the intake manifold. Well ill rather do that than yank the engine out again

Hope my local part shop has gasket and rtv black in stock, i booked "veichle inspection" on tuesday, and car show at work on wednesday, wich i had intended to take part in.

And rcadd1ct: yes i do

 

[Bill73Ragtop]

I found one now... Guess where? You will never ever believe me :whistling: Riiiiight between the inlet runners for cylinder 5 and 6, closer to number 5...:shootself: not even internal (if not both)

So i guess i have to re-do the intake manifold. Well ill rather do that than yank the engine out again

And rcadd1ct: yes i do

I developed a manifold vacuum leak similar to that a number of years ago. Took me a looong time to find it so I've been there with the frustration. You'll find a re-installed manifold will work wonders...

 

[Stanglover]

Okay all, thank you for all the inputs. I really appreciate it.

Seems i was not thourough enough when checking for vacuum leaks.

I found one now... Guess where? You will never ever believe me :whistling: Riiiiight between the inlet runners for cylinder 5 and 6, closer to number 5...:shootself: not even internal (if not both)

So i guess i have to re-do the intake manifold. Well ill rather do that than yank the engine out again

Hope my local part shop has gasket and rtv black in stock, i booked "veichle inspection" on tuesday, and car show at work on wednesday, wich i had intended to take part in.

And rcadd1ct: yes i do

Sooo glad you found that leak. Once again, I can offer something from my own recent troubles. This is just what I did, not saying it's the only way. After I got my engine back in and running, the clown that built the engine used the rubber end seals and I got a big oil leak at the back of the motor. I had to pull the intake and do it my myself. No big issue really.

Have you done an intake before? If not, perhaps the method I found will help. I have no doubt removing the intake is no problem for you. I found that by using a couple of 5/16" eye bolts in the carb bolt holes and a piece of pipe, made lifting out and back in much easier, but you may need help lifting it.

1: make sure everything is cleaned up and spotless. Wipe surfaces with a degreaser (not lacquer thinner) or alcohol, (not Scotch) Also, make sure nothing gets into the engine and ports.

To save some money and ONLY if your valley pan is undamaged and reusable, you can cut your own paper gaskets from .015" gas proof material. Most will just go buy new, but I'm cheap!! Any doubt, buy a new Fel-Pro set.

2: RTV is NOT gas proof. I had good results using Permatex Form-A-Gasket 2 around the ports. This product does not come with an application tube , but one from an RTV tube will fit. I applied it under the paper to hold it in place and on both sides of the valley pan. The instructions call for a thin bead of sealant on the top side only. You don't need much, but a continuous bead is important.

3: on the ends, spend a few more bucks and buy a small tube of Permatex 'The Right Stuff'. You will need a corking gun. The casting surface must be wiped clean and dry. Apply a bead at least 1/4" and up the ends of the heads as well part way so the corners don't leak. Reassemble the intake within 5 minutes. A two man job!!! I didn't do it, but a couple of 5/16" threaded rods long enough that you can take them out again can be use to locate the intake. I just used two of the bolts, one on each side. Bolt it all up and torque to 27-33 ft lbs. on the 3/8th bolts, 20-25 ft lbs on the 5/16". Re- torque again to be sure. I don't have it, but someone may have a diagram of the torque sequence and can post it, but basically start in the middle and work outward from one side to the other if that makes sense.

I know you are very capable and I don't mean to state the obvious or insult your intelligence, but sometimes it is the obvious things we miss. Been-there-done-that!!!

Leave it for 24 hours and hopefully your troubles will be gone.

Good luck,

Geoff.

 

[Odmark]

Hello again. Yes i have been installing intakes before, when i did my 455 olds rebuild i was told to use red rtv around the intake ports and instead of end seals, and supra blue around water ports. Still no leaking there

Now i was told by a friend at work to use rtv black on both intake ports and end seals.

Would form-a-gasket no.3 work around the intake ports? Cant find no.2 in stock anywhere near.

The right stuff was in store at a local shop.

I will buy new fel pro gaskets, valley pan if needed. As well as long bolts for centering.

Thank you for all the tips Geoff

 

[Don C]

The only thing I would add to Stanglover's instructions is to tighten the bolts in three increments, finger tight or no more than 5 ft-lbs, then half the final value, and then all the way. At each stage go over them all, at least once, as the first ones tightened will be loose after getting the rest tightened. This should help keep the manifold from twisting or leaning, which is the biggest problem with intakes on 351Cs.

 

[Odmark]

Absoluteley, thanks Don C.

Could you list some suitable products for use around the intake ports, then ill have to ser what i can get hold of tomorrow.

As i said "The Right Stuff" was in stock at a local shop so that is no problem, just around the ports.

 

[Stanglover]

Hello again. Yes i have been installing intakes before, when i did my 455 olds rebuild i was told to use red rtv around the intake ports and instead of end seals, and supra blue around water ports. Still no leaking there

Now i was told by a friend at work to use rtv black on both intake ports and end seals.

Would form-a-gasket no.3 work around the intake ports? Cant find no.2 in stock anywhere near.

The right stuff was in store at a local shop.

I will buy new fel pro gaskets, valley pan if needed. As well as long bolts for centering.

Thank you for all the tips Geoff

I don't know #3, but you don't want #1 as it is a hardening type. #2 stays soft and pliable. Even these gasket dressings are not really gas proof, but RTV will go gummy if it is in contact with gas. There may be other gasket dressings that are more suitable, but I couldn't find any and was told that Form-a-gasket 2 will be fine. If someone knows of a better material, that would be welcome info for the future.

 

[Stanglover]

The only thing I would add to Stanglover's instructions is to tighten the bolts in three increments, finger tight or no more than 5 ft-lbs, then half the final value, and then all the way. At each stage go over them all, at least once, as the first ones tightened will be loose after getting the rest tightened. This should help keep the manifold from twisting or leaning, which is the biggest problem with intakes on 351Cs.

Thanks for the correction. I totally missed that.

 

[BeerDontCount]

Just wanted to give a shout out of thanks for the intake install instructions. I will be using them soon. Appreciate the info.

Scott

 

[Stanglover]

Here is the torque sequence for the 351C

 

[Odmark]

At least no.3 is also non hardening. Really would need some help with this.

Cant even find no.2 on a swedish website for mail order, lots of no.3 but absoluteley no no.2.

Thank you for the torque sequence Geoff!

Edit: Can edelbrock Gasgacinch work? Part no 9300. Thats what is recommended in the edelbrock intake install instructions.

That is IF my local US-Car parts store has it in stock.