Stock cam questions.

[toppers33]

I have a 1966 Dodge Coronet that has a 383 4 barrel with a 727tf. I cannot set the base ignition timing as the timing mark jumps around way too much and is never steady. I had reason to take the oil pan off recently and sure enough I noticed the cam chain had loads of slop. So this winter's job is to replace the timing chain.

I do not know the cam specs. The engine has been apart at some point in it's life. It is 30 over and has the later low comp pistons. I measure and calcultaed CR at 8.3:1 some time ago. It's just a street cruiser so I can live with the low CR. It has a performer intake, 1 3/4" Doug's headers on a 2 1/2 system to flow master 40s. A 600cfm Holley vac sec carb and that's all I know about the engine.

I require a sanity check before I start the timing chain replacement. I know the correct way is to degree the cam but not knowing the specs makes it a much bigger job than just finding TDC and setting the timing gears so both 0 markers are in line. Would this be a no no? If so I guess I'm going to have to measure the duration, lift and calculate the ICL of the cam before I can try and work out what it is. If I then work out what the cam is I would need to find a copy of the cam card to see what the recommended instal would be?

Am I over thinking the job? Advice appreciated before I start the work.

Regards,

Lee

 

[66 Sat]

If the engine runs fine at present then just install the new timing chain with everything in the same position as before - you don't need to degree the cam in.

 

[69 GeeTeeX]

Also check the oil pump drive gear. If it’s moving up and down (bouncing) it will create the problem your experiencing. Hughes Engines makes a collar that mounts onto the bottom of the distributor shaft to hold the drive gear in place.

I had the same problem with a 440 and that’s what was causing it. Installed the clamp and timing was solid.

 

[toppers33]

Thanks for the advice. It runs absolutely fine. I just have to set initial by ear and response. It's that bad even my dial back timing light won't pick up a reading. I'll fit cam chain as is and check the pump gear at the same time.



Lee

 

[69 GeeTeeX]

http://www.hughesengines.com/Index/...YnV0b3IgU2hhZnQgTG9jayBDb2xsYXI=&partid=25200

 

[Don Frelier]

Maybe you will get lucky and the end of the cam has marking on it. If so degree it.
Get a high quality timing set. I've seen a new set be 5 degrees retarded.

I would also suggest putting a new balancer on it if you still are using the original.

 

[Tim Ziegler]

I degree all cam/timing chain jobs cuz I've seen the keyway off on the sprocket and not accurate so it would need correcting

 

[beanhead]

If you're only replacing the timing set degreeing is not necessary provided neither the crankshaft or cam are allowed to move when the sprockets are off. You can do it!

 

[Tim Ziegler]

Good luck not moving anything when replacing the loose old timing chain with a new tight timing chain. The cam was retarded a few degrees just from the old timing chain slop

 

[Tim Ziegler]

If the motor is in the car, probably not much room for a degree wheel. Understood

 

[66 Sat]

Good luck not moving anything when replacing the loose old timing chain with a new tight timing chain. The cam was retarded a few degrees just from the old timing chain slop

Nothing is going to move if the pushrods/valve springs are all installed (which they will be), the cam won't just rotate on its own. I agree there will be some slack in the chain, but how much are we talking? A couple of degrees either way isn't going to make any difference on a low compression street cruiser.

 

[toppers33]

Cheers for all the further recommendations. Good shout on the balancer as I recall the rubber isolator looking dry and cracked the last time I peered in.

I'm in the UK and will be ordering parts from USA so need to have everything at hand before I start the job or I'm then stood waiting on extra parts.

Now I know I want to keep this task as simple as possible and we've discussed degreeing it v fitting mark to mark...please don't shoot me down but if I was to put 4 degrees crank advance into it (using the mark to mark timing method), given the CR is so low at 8.3:1 and the pistons are approximately 0.083" down the hole ( 0.120" squish makes me wince but its been like this for at least 20 years) would I still gain low end driveability improvement or is the huge squish and potential 4 degrees advance going to cause me running problems? As I say I don't use the engine hard, but if the option to add advance is there and there's no reason to take adavtange I maybe a well do so given it would be low end driveability improvement. I welcome thoughts on this one

The parts im considering ordering unless someone looking at this post says 'under no circumstances use that part' are;

Melling Timing Chain Set 40407 .220" wide double roller with +/- 4 degree crank gear. OR
Melling Timing Chain Set 40203 .250" wide double roller with +/- 4 degree timing gear.

Pioneer Street Performance Balancer 872039

Front end gasket set
FEL-PRO TCS124602

I've already got a new water pump in a box that will get fitted. So the above should be all I need to order?

I've a sneaky feeling my piston stop won't reach the top of the piston due to spark plug angle and the distance the piston is down the bore at TDC. I'll see how it all lines up when it's apart. I did mark true TDC on the damper the last time I had the head off ( broken exhaust bolts in the head when swapping the headers out) so I'll be able to get TDC no problem regardless.

I can machine a spacer for the oil pump drive no problem so will take a look at the play when it is apart. I do have a suspicion that the dizzy is past its best too but until I get it pulled apart I won't know.

The car runs fine but is far from as it should be, things are showing wear. I've put life back into quite a lot of the car and this front end work on the engine is pretty much the last part to have an injection of life again. The fact the car runs fine with all the wear I've found over the last few years is testament to how forgiving these big lumps are. I'm hoping the work I've done so far and do next will keep her going a good many more years ;-)

 

[Cranky]

'Checking' cam timing is ALWAYS a good idea imo and even though it's tougher to do in the chassis, it's not impossible. You can also plot your cam's valve events while you're in there. Pulling all of the sparks plugs will help make it easier to bar the engine over. Years ago a buddy and I (mostly him) changed the cam timing while at the drag strip in his 70 big block Challenger just to see if advancing it would make an improvement and it did....

 

[beanhead]

Good luck not moving anything when replacing the loose old timing chain with a new tight timing chain. The cam was retarded a few degrees just from the old timing chain slop

So turn the crank a little bit first to take the slack out. Should be doing that anyway, just like when degreeing a cam. As 66 noted above if the valvetrain is left installed nothing's going to move without some effort...

 

[Tim Ziegler]

If its a winder ie; 318, 340, 383, 400 advance the cam 4 degrees. If its a stroker ie; 360, 426 wedge, 440 install the cam straight up

 

[toppers33]

Update time:

Today I got it back up and running. I only have a few hours a week to mess with it so its taken a while. Its winter here so there was no rush.
Jobs done:
Timing chain replaced for a double roller.
New damper fitted.
New water pump.
New stat. Original was a 160 now has a 180.
Power steering pump cleaned up and a leak repaired.
All removed engine parts for the chain replacement blasted, primed and painted.
K frame cleaned an painted as thorough as I could be with it still in the car.
Radiator (26" 3 core) sent away for a re-core as many of the cores were gummed up and it had a weep from the top tank soldered joint. Though it never overheated.
New rad hoses.
New 'monster' Mercedes fan and PWM controller fitted. The original fan was pretty beat up and I fancied putting something a little more efficient in......though install has been tight. The clearance between the waterpump pulley and the fan motor is tiny. So much so I can't get an alternator belt through the gap :-( Still working on the clearance issue.
New oil pump intermediate bush fitted.
New Mopar performance intermediate shaft fitted.
New distributor fitted.
New distributor collar (to stop intermediate shaft want to ride up) fitted.

No cam specs were stamped on the cam so I chanced it and fitted the timing chain 4deg adv as I'm pretty sure it'll be a stock cam (8.3:1CR with pistons best part of .100" down the bore).

I welded up the mech adv slots in the distributor (Mopar electronic pick up) so that the mech adv was reduced from 26 degrees to a calculated 16 degrees. I took a flyer on the springs and went with a couple of lightweight ones as the dizzy was delivered with x2 heavy springs. My previous dizzy has 1 missing and the other very light!

It fired up perfectly today. Yay, I can now see my timing mark and it is are STABLE! Initial set at 18 deg at 600rpm, vac disconnected and plugged. Engine starts first time, cranks instantly with no laboring and the engine 'sounds happy' at 18.
Adv starts at 1350rpm, 24 deg @ 1730rpm, 28 deg @ 2000rpm, 32 @ 2200rpm and full mech adv 35 deg @ 2390rpm. All tested parked up. I can't drive it yet as the weather here is on the cusp of snowing.

It idles at 16".

Problem - when I connect the vac adv (connected to ported on a Holley 600 VS) it adds 20 deg of timing at 2400rpm and when holding the rpm at 3000 there is a misfire. Disconnect the vac and it runs clear. The vac can is not adjustable on this distributor however my old worn distributor has an adjustable vac can so I will swap that out tomorrow. My question is - would you suggest I limit the total vac adv to a lower number (if so is there an ideal value for total vac adv?) and also should I tighten the can so it comes in later in the rpm range? If someone could give me some pointers I'd appreciate it.

The monster fan is just that, blimey it moves some air. I have it set to come on at 195deg F at 25% speed and it modulates its speed via the controller to 75% speed at 205 deg F. As soon as it kicks in it pulls the temp down very quickly. I'm really hoping I can make a little more clearance between the fan motor and the top pulley otherwise it may have to come off. I didn't need to do this mod as the Mopar fan clutch metal fan worked perfectly before, I just fancied having a play with other technology.

Pics follow to show progress.

 

[toppers33]

Few more..

View attachment 1065409

 

[Don Frelier]

It sounds like a rotor phasing problem to me. Spark is jumping to the previous post in the cap. Is it electronic ignition?
If so Rick Ehrenburg sells a multiple keyed reluctor on eBay.

 

[toppers33]

It sounds like a rotor phasing problem to me. Spark is jumping to the previous post in the cap. Is it electronic ignition?
If so Rick Ehrenburg sells a multiple keyed reluctor on eBay.

Hi Don, Rick supplied the replacement distributor. It is electronic ignition. The distributor is described as having the a correct Mopar reluctor though I never noticed it could be multi phased when I had to remove it to adj the adv slots? Just x2 small roll pins holding it in place. Just to add, I checked out ebay and can see the multiple mounting slots. Pretty sure mine doesn't have these features but I'll check tomorrow. The misfire goes when I pull the and plug vac advance, does this not prove that the vac adv timing is responsible for the misfire?

 

[toppers33]

Hi Don, Rick supplied the replacement distributor. It is electronic ignition. The distributor is described as having the a correct Mopar reluctor though I never noticed it could be multi phased when I had to remove it to adj the adv slots? Just x2 small roll pins holding it in place. Just to add, I checked out ebay and can see the multiple mounting slots. Pretty sure mine doesn't have these features but I'll check tomorrow. The misfire goes when I pull the and plug vac advance, does this not prove that the vac adv timing is responsible for the misfire?

I've been and done some reading and I can see your point about checking the rotor phase. Maybe be it was just poor
phase from the manufacture of the distributor, I may even have put the reluctor back on after modifying the mech adv unaware of which of the x2 positions was optimum. I'll take a look and report back tomorrow. From what I've just read and understood it os only vacuum lever operation that pulls the pickup further away from the reluctor so your suggestion now makes sense if the reluctor to pickup was slightly off from the start.