Lumpy idle when cold...

That cam has a naturally lumpy idle.

If the valve adjustment was fine a year ago. They are fine now.

Unless you modified the heads to use the screw in rocker arm studs, then that is a bolt down and go adjustment.

You only adjust them by shimming the rocker arm pedestals and that would only be if there was an indication that they were too tight.

The entire point of hydraulic lifters is that they need no adjustment.



Diagnosing from afar is difficult.

Since this seems to be only on one side of the engine I say it is likely the carb and likely that you have debris in the idle air bleed on the side of the car that is effected.

This would probably be corrected using a numbered drill bit of the correct size mounted in a pin vise.

The carb should be removed, disassembled on the bench for one reason. You need to blow the debris out of the carb and not into the idle air/fuel well.

You could jamb it up more if you don't and if you do it on the car, it will just blow the debris into the intake manifold. You do not want that.

Just using something like Gumout on the jets will just wash the debris into the idle well. Don't do that.

Adrian,
It sounds like you might have actually adjusted the rockers down too much and you are now pressing the valves open, too tight, it is easy to compress a hydraulic lifter. There are quite a few different ways to adjust the rockers but try this method. Instead of twisting the pushrod to start the adjustment, try this up and down method.
https://www.youtube.com/watch?v=LpkrNouFauA

The valve lash really should not have changed from a year ago with hydraulic lifters unless there has been abnormal wear on a cam lobe.

But even a appallingly large amount of wear will be compensated by the hydraulic lifters and thus keep the valve lash correct.

I had a cam with 0.150" worn off a inlet lobe and the engine still ran and idled fine. Fuel economy was crap.


Do a compression test. If the valves are adjusted down too far and are hanging open your compression will be low.

Otherwise start the engine from cold, let it idle (rough as it may be), shut it down just before it starts to smooth out as it warms up and then take the plugs out and see what colors they are eg: black, brown, tan, white ect.

This will give you some idea if your idle mixtures are rich/lean, the same in all cylinders, rich in some cylinders lean in others, or whatever.

Then you can check out your carb for possible causes and a means of rectifying the issue.

Remember it will only concern the idle circuits of the carburettor.

Have a look at your plug wires and distributor cap as well for any damage, burning, arcing, anything that may prevent a good spark to one or more cylinders.

Sometimes a less than perfect plug wire or distributor cap post can make a engine rough when it is cold but when it warms up better vaporization of the fuel allows the compromised cylinder to fire normally even with a bad spark.



Also every 351C i've had ran rough when it was cold and smoothed out when it warmed up until i changed to fuel injection. It could just be the nature of the beast ?

Better fuel distribution and cold temperature fuel control of the EFI cured a heap of rough idle troubles.



.

if it's running worse after you worked on the valve lash / preload settings than it did before, go back & check your work, probably plan on doing the job over completely

FWIW the first time I ran the lash I messed it up, and lumpy cams can be tricky to find the base circle too. I've found that less preload on the lifter plunger makes for a happier running engine, you may have the plungers down farther than they were resulting in the lower idle rpm. what type of adjuster nuts do you have & how much preload did you dial in?

hydraulic cams & mechanical solids for that matter IMO can be set better cold

Thanks Guys,

So to answer a couple of questions, I followed the 'hot procedure' mentioned above and set the preload to zero plus 1/8th initially... made the idle low and almost felt mechanically 'rough'.

Today, I did it the method in the video (same as comp cams site) but with 1/4 preload. It was interesting to note that most of the lifters initially 'relaxed' and the roller rocker moved up slightly (a good thing I feel as it showed the lifter had not bled down). Also when adding the 1/4 turn they gave some resistance as the preload was added. The others seemed to have no resistance (lifters may have bled down - an issue?).

On starting up this time, they were all a bit noisy, but most settled down as it warmed up. I also noted at last it went to high idle straight away. Again though the engine was lumpy (more than before I started all these adjustments!) but when warmed up, went to the original 850 RPM idle (so I improved some aspects at least back to where they were). However, it is still noisy (possibly should have gone to 1/2 turn preload?).

I have manually exercised the valves and they are smooth and you can also feel the lifter spring working if you move the pushrod up / own in all cases (some firmer than others though).

As for compression tests, all read 168 psi.

As for the carb, it is new out of the box and seemed fine, but I noted at idle some cylinders are indeed black and others the right colour, I think the dual plane manifold may have and effect on this....if you revved it before or drove at speed, come back and kill it, the plugs were all fine.

Ignition checks - new distributor cap / leads / plugs and I have used my 8 spark testers with the engine running and the spark is massive on each cylinder and at the right time. That said, I put 4 thermometers on the headers of the left bank and number 5 runs 80 degrees C less than 6/7/8 (odd)? Also if I now pull off plug lead 5, the engine drops 200 RPM and labours - taking the others off one by one has a slight dip in RPM (a clue?).

So my thinking is that there was an original issue when i got the car, but attempting to check the lash again (Peter the previous owner hinted that to make the noise reduce, they added a little additional preload when running to reduce the noise on some rockers...). So I appear to have made it worse by slackening it off I guess.

I take the point about diagnosis from afar and am also speaking with Johnny Woods on the issue...and it has puzzled him also!

I think the approach initially will be to take the carb off, clean it thoroughly and also have another go at setting the lash on the valve train. Hopefully, having say 1/2 a turn preload may improve the issue (either that or replace the lifters - 824-16's I believe) and start from scratch! I am obviously concerned that it does not go too far and leave valves hanging open!

Thanks for all your thoughts and Happy New year!

I will let you know how it goes

Regards as ever

Adrian

Carb. New means very little.

Good point Doug,

I also have the Holley overhaul kit for the 770 street avenger, so will take it apart and rebuild it also (I will have 2 carbs to test with).

Will let you know what happens. I also have a friend (Bill) who lives about 60 miles away with a Euro GTS Pantera and a spare Holley 650, so again more to substitute with.

Adrian

Was cylinder 5 one of the black plugs ?

quote:

Originally posted by ABW351:
Good point Doug,

I also have the Holley overhaul kit for the 770 street avenger, so will take it apart and rebuild it also (I will have 2 carbs to test with).

Will let you know what happens. I also have a friend (Bill) who lives about 60 miles away with a Euro GTS Pantera and a spare Holley 650, so again more to substitute with.

Adrian

I'm not sure if this is a good idea. Most likely it will just confuse you more.

Two things to look for in the carb. 1)debris in the idle AIR restriction, jet, or passages 2) ruptured power valve.

Probability is very high on both.

You need a power valve tester. Fuel in the vacuum chamber behind the valve between the metering body and the main body would be an indication BUT because of the way the carb needs to be disassembled, IF there is fuel in there, it wouldn't be scientific.

The quality of assembly on virtually EVERYTHING is suspect now.

It seems that NO ONE semmingly will pay an actual human to check the product before they box it up.

In some cases there is over a 50% rejection or failure rate because of this now.

Take the thing apart. Use compressed air to blow out all of the passages and visually inspect each one to verify that there isn't something in there.

Use the new power valve in the kit.

Make sure there is a power valve check valve in the the throttle body as manufactured. If not, install one.

Also note that just because there is one does not guaranty that the valve is 100% effective.

Whoever the supplier on these power valves is should be shot. If not 007 should be sent out on an op. The lack of quality on these things is nothing less than industrial sabotage.

I recently went through about a dozen power valves that I had in my "Holley" section and only three or four were good.

You are adjusting your lifters wrong.
the job should be done cold, ( adjusting is done hot on SOLID lifters )their should be no lifters that are pumped up.
By the way, no carbureted modified Cleveland will idle smoothly prior to warming up. Lifter noise if adjusted correctly, your engine lifters will sound very quiet, like a well oiled sowing machine. Do you have anyone who has some experience working on engines in the neighborhood? Incorrectly adjusted valve lash can cut choke your engine at best break your valve springs at the worst. The adjustments on your carburetor for idle are the air /fuel screws, have you adjusted them? With 244 on duration and 560 lift, 850 rpm is to low, make sure your advance is at 16 degrees at idle and 1000 rpm. It sounds like your problem was way back at the beginning, your 780 carburetor, everything you have described could have bin a adjustment or overhaul of your original 780.
Adjust your valves one cylinder at a time, with a helper to turn the motor over, when the exhaust valve is totally open ( rocker all the way down ) turn the motor till the rocker just start to go up, then adjust the intake valve, do the same with the exhaust, then do number 2.
When the valve is totally closed, rotate the push-rod with your fingers as you slowly tighten the adjustment screw , when you feel a restriction as the rocker presses down on the push-rod , stop and then turn the screw 1/2 turn and tighten the nut.Their are many great books on the building of engines, to adjusting and rebuilding carburetors. and now also available on DVD, you will learn much faster using these sources. Good luck, don't give up
experience is learned, hopefully without to much pain.

Ok Guys,

So a lot of good points there. In regard to Aus Ford, yes actually number 5 plug was black...what are you thinking...?

Doug, those are interesting observations and quite a revelation in regard to quality control... I will have to see if I can get a power valve tester to be sure with my set up(s). I have no overhaul kit for the Quickfuel QFT carb, so will contact Larry Stock or Quickfuel directly to obtain a few and go from there.

In the interim, I did remove the carb and ran alcohol through the jets / metering block etc over a white cloth and found one small black bit of 'dirt', but that was it. I then used a compressed air line and blew through the jets. It is now sitting in a polythene bag ready to go back on while waiting for an overhaul kit.

Thanks also to Pantera Chris for the comments/advice. It seems there are too many methods out there which is confusing. I have never had problems with other engines I have set up... but they did have solid lifters.

I will start again today with using a bleed down tool to ensure the lifters are not pumped up when I start adjusting. I will stick to the cylinder at a time method and will do it in engine firing order (so 1-3-7-2-6-5-4-8) and use 1/2 turn instead of the original 1/8th which was suggested... unless people go for 1-2-3-4 etc etc?

It is also interesting about what you say about the noise. Indeed when the engine previously had warmed up, the engine had no rattles and was quiet as you say with no valve train noise.

Since adjusting the lash(remember I did it to remove the potential over adjustment Peter had dialled in on the left bank to remove the rattle he had - later found to be a crane roller rocker hitting the oil baffle in the cover...which was then removed), the valve train noise is quite noticeable now, but having adjusted it to 1/4, the fast idle returned as did the 850 kerb idle, so I think I am getting there...

Sadly there is no one locally with 'good / qualified' knowledge, so am doing it on my own.

In regard to your method Chris, I note you have the exhaust 'fully open' before adjusting the inlet. I used the comp cam method last time where they say exhaust 'just starts to open' and then adjust the inlet...obviously by going to fully open, this is a significant difference and so it would indicate I was not on the heal of the cam lobe and so an issue!

Can I assume that you are also using the same for the inlet in that is is fully open before you adjust the exhaust? There is contradiction on comp cams / CPG site as in one place it states fully open and then just starting to close...in one other place it states fully open and travelling to nearly closed (but do not go beyond half way) - confusing!

As always, thanks very much for your advice guys

Adrian

Forgot Chris, I have not adjusted any of the 4 mixture screws on the carb...wanted to do one thing at a time to see what the effect was on the cold idle issue... so valve lash was chosen after the new ignition was fitted, finally I was going to get to the idle mixture screws (currently set at 2 turns out each side - I was told it was flow tested on a rig before I got it...) after doing the lash. Timing is set at 15 degrees currently but can dial in 16 degrees after the lash is set up!

Hydraulic lifters are a complete waste of time. This is going to be going on for ever.
You will always be wondering if they are working right.
I went to solid lifters years ago for this very reason plus I get the actual valve lift and not a percentage of that depending on the oil pressure in the lifter.
You never get 100% lift in a hydraulic lifter.
It is only theoretical lift based upon the lobe lift x the rocker arm ratio.
Also you loose lift by going to stronger valve springs.

The explanation for where your exhaust valve is in relation to setting the intake is " when the exhaust is fully opened the intake is fully closed, the intake valve is now ready to be adjusted in the valve closed position, this will be obvious as the rocker arm will be free from any downward pressure as the valve spring pulls up the intake valve sealing it to the intake port on the head. You should before you start to adjust the valve at this point loosen the adjustment screw (about a half turn ) until their is no load on the push rod, then start the procedure to set the preload.ALL carburetors have to be adjusted, the manufacture of the corroborator doesn't know what engine it's going on, what cam your running ect. 2 turns out is the safe setting to start to adjust.your air fuel mixture, you will need a vacuum gauge connected to the correct vacuum port on the carb, this is outlined in any holly catalog. Your Quick fuel is a modified Holy.
If you idle mixture screws are not right, your engine will not idle right! Please BEFORE you do anything else get a manual for your engine, then get a manual for holy carbs, really you can wreck your engine if you don't know what your doing.

When you measured the exhaust temps and found number 5 was significantly colder than 6, 7 and 8 that is a indicator that number 5 was very rich or not firing properly.

When you pulled the plug wire on 5 and it slowed down and laboured it showed it was firing so the black plug and low exhaust temp says number 5 is very rich at idle.

Question is why?

Is 2 black ?

What is 3 and 8 like compared to 1, 4, 6, 7 ?



Also get a dial indicator and set it up on each rocker arm and check that the cam is lifting the valves the correct amount.

You may have wear on one or more cam lobes. This could make adjusting your rocker arms a problem, not to mention make the engine act weird.