Rough idle and I am stuck

[Anonymous]

Ok, I am something of a newbie and trying hard to learn, but I am out of ideas and would appreciate some advise.

'66 200 cyl: Bought a "rebuilt" engine (cheap) from a guy who decided to go V* after rebuilding the 200. Everything in it was completely new (pistons, cam, rods, rings, bearings etc) and unused. I do not know if they used a stock cam.

Problem: Starts but runs very very rough. No smoke. Set timing at 14 degree with dist adv plugged. Vacuum hovers around 8-10 but drops regularly. When accel, vacuum increases but becomes erratic. Note: I am in CO at high altitude so I expect to lose some vacuum but I am not sure how much to expect. This seems excessive.

New Parts: new rotor, cap, duralast wires, autolite plugs, pertronix ingition, pertronix coil, completely rebuilt and bench tested autolit 1100 carb from Pony Carbs, all new hoses and lines (every one), teflon tape at all vacuum joints (careful not to block openings), alternator, PCV, and just about everything else in the engine compartment, except the Distributor. Considering going to Duraspark but just not there yet.

Tried:
- WD40 at all vacuum points (no change)
- converted back to points from electronic (no change)
- checked dist gear does not appear to be worn nor does the shaft
- adj mixture on carb both in and out 2 turns until it starts to stall. returned to position when shipped by Pony Carb
- no vacuum at the dist vacuum port on the carb (normal per Pony)
- vaccuum at the auto choke (normal per Pony)
- compression test: no material variances at all between cyls both wet and dry although compression is low at 90-100 lbs each.
- spring height (compressed and uncompressed) within tolerances
- new tappets and push rods
- pulled head. lots of carbon esp for such little use. pretty evenly spread throughout each cyl but only within the head up by the valves. Cyl's and pistons themselve are still pretty clean.
- new oil seals

My Theories:
- This may be just may inability to properly tune the vehicle.
- The regular drop in vacuum leads me to believe its a valve problem but I swapped out the head with an older one I had. It didnt seem to have any effect.
- Vacuum leak within the integral head that I have not been able to find yet. Suggestions on where else to look?
- Need to replace distributor, cause literally everything else under the bloody hood has already been replaced. ug!
- Valve guides in the head are worn (although a mechanic friend feels that they arent that bad) and I would have expected to see a diff when I swapped heads.
- Wrong cam for this engine. (This is just a SWAG only b/c I am out if ideas)

Any other suggestions?

 

[cfmustang]

If that vacuum drop is at a regular interval, it may be valve related.

Perhaps it is something as simple as needing to adjust the valve lash? I know after my engine was rebuilt, the garage never readjusted tha valves and I had a pretty wicked vacuum leak on one or two valves...

 

[Anonymous]

I thought on the '66 200s you couldnt adjust the lash. The original shop manual says to install shorter or longer push rods. Is there a way to adjust the valve lash?

 

[t-west]

Just a thought, but are you sure that the TDC mark actually is TDC? The harmonic damner/balancer thing is known to slip, and I'm not sure if the rebuild would include a new one.

--tom

 

[80Stang]

Just some simple thoughts I came up with:

double-check, no, triple-check that spark plug wires are the way they should. I know this sounds stupid but I've seen a 200 run with wires in right order but attached to the dizzy cap to wrong direction.

Do the damper position check too as t-west advised. I just adjusted one V-thing that had it some 13* wrong...

Then if nothing seems to work you might be willing to remove the timing chain cover and check that the cam is timed right.

Although new please check the new goodies, plugs & wires etc for proper function.

 

[jahearne]

Sounds like you have a good engine. The only way to adjust valves is to get adjustable rocker arms that came on the earlier engines. The earlier engines had solid lifters, but you can use the adj. rockers on hydraulic lifters. You can find them on Ebay and FSPP. But you're right, normally the 200s are not adjustable. It sounds like valve timing problem because the vacuum readings are so low or a real bad intake leak, but you checked for that. Have you looked for cracks in the intake log? You swapped heads though. Try adjusting the idle mixture using the vacuum gauge for the highest possible reading not until it stalls, but I think you did that, right? It doesn't sound like bad valve guides because the vacuum reading would be steady when you increase RPMs. It might be worn or weak valve springs. Either the ignition timing is way off ( I'd do what t-west & 80stang mentioned ) or you just might have a "hot" cam in there. How's does it run on the road? Does it ping or stall?

 

[Anonymous]

I am 100% sure the wires are aligned properly. I've checked those thing a dozen times and had others do it for me just in case I was blind.

On the harmonic balancer, when i last pulled the head i made sure that t TDC the timing markers lined up and they do.

I will pull the timing cover again but I did check that beofre install as well. I dont have experience dialing in a cam (it was already installed) but I did make sure that the dots on the timing gear and the cam gear were aligned. They were.

I am beginning to feel like I am only left with the distributor or the wrong/too aggressive cam, but I dont really want to pull the cam unless i am not left with any other choices.

I am going to try to tune in the carb/timing/mixture a little more and see what I can accomplish. But one other thing, the exhaust sound is also a lot stronger than i expected, sounds more like a V8 exhaust. I have a stock system from Mustangs Unlimited, leads me to believe I might have a non-stock cam in it too.

thanks for all the advise. i will comeback and update on what i find over the next few days.

 

[jahearne]

I appears that the only thing you haven't tore apart yet is the cam. With the exception of a 6 into 1 header and port divider, my engine is pretty much stock and it barely makes a sound. I'm ready to put my money on the fact that you're running a radical cam.

Where are you located? I have a used stock cam you can have.

Best of luck,

 

[addo]

A comparison of wet and dry compression would be interesting. Also removal of the head and measuring chamber volume, dish volume and deck height to calculate static CR is a good pointer.

Cam timing could be plain wrong. That would be next on my checklist.

Cheers, Adam.

 

[Anonymous]

I am pretty much resigned to checking the cam, but as I have said I dont have much experience with cams. If I pull it, how do I know if I have the wrong/radical cam or not - I dont think they are labled .

jahearne - thanks for the offer. i am in Colorado. I probably wont be able to work on the car this w/e but I hope to soon after.

BTW - you guys ROCK! I posted over on Stangnet before finding out about this forum. None of the V8 guys even wanted to offer suggestions.

 

[addo]

Cams are almost all identified on the far end from the timing gear. You will see a stamp or engraving with letters and numbers, like CC13674 or whatever. That will tell you the maker and original grind. Some regrinds may be identified also.

However - I would expect someone to tell you if the cam was aftermarket; that is why I still suspect the CR or rings (low compression being the indicator), or bad valve timing if the CR checks out fine.

Regards, Adam.

 

[80Stang]

Ask the guy who sold you the cam which one it is. If no info is available and you want to find out its characteristics, you can measure it in the engine or you can have it measured at the shop. Need to pull damper, timing cover, valve cover and need to have the set of tools to do it (a degree wheel, a precision gauge and a stand for it). Plus add knowledge. By measuring in the engine you'll avoid need to pull the head, strip off the radiator, pull the lifters and cam out and so on to have access to

I still don't think cam itself is your problem if it is properly installed and the break-in was good. A hot cam can sound and feel rough if you are used to smooth-as-silk modern engines. It will require way more idle speed than stock cam, but you'd still be around 800-1000 in most cases. I will require more initial advance depending how much CR you have there. A brand new 200 can stand a lot of initial at low rpms especially if you don't hook up the vacuum advance at all. Try carefully.

As jahearne asked; is it driveable? We can't right imagine how bad it is, I mean the "roughness".

 

[Anonymous]

Thanks. The problem is I did not buy the long block from the guy who had it rebuilt and that was 3 years ago. i am going to dink around iwth the timing/tuning again before i pull anything.

 

[Lazy JW]

Just a thought, but are you sure that the TDC mark actually is TDC? The harmonic damner/balancer thing is known to slip, and I'm not sure if the rebuild would include a new one.

--tom

Yup. This is critical, but fortunately not too difficult. You will need to establish this data point before you can dial in the cam.

Before pulling the timing cover, dial in the cam. All you really need is a degree wheel and a dial indicator, plus some patience.
Joe

 

[Anonymous]

After a year long battle with my I6 and lots of advice from this forum, I finally found the problem and learned a valuable lesson. Never buy a "cheap engine!"

After ruling out about everything I could think of, I pulled the cam last weekend. It was the wrong cam. I had a stock cam from my old engine which I installed and it is ALIVE! I still need to tune it a bit, its a little rough under load but it RUNS!

I can finally paint and move on to finishing it. Thanks for all of the help and advice.

 

[mugsy]

FSPP sells an adjustable timing gear set. I have one on my car. It will help you dial in the cam timing. The intake valve closing point is crital for a smooth idle.

Also look into an adjustable rocker set. I bought mine off of Evil-Bay, and it was prety cheap if I remember.

Have Fun!

tanx,
Mugsy

 

[Anonymous]

mugsy - and specs or maker i should look for on that adj rocker arm set? i'm not quite sure what to look for under e-bay

thx for the advice

 

[JackFish]

Here's one:
http://cgi.ebay.ca/ws/eBayISAPI.dll?Vie ... %3AIT&rd=1