1967 Dart GT convertible.

I need some advice on cam choice. Do I keep the one I have, or select a new grind? Problem is I’m not sure of exactly manufacture and size of cam is installed, and have some confusion how to measure what I have. Figuring lift is easy, angular measurement and correct method of notation of opening and closing events is puzzling. I graphed the events out five or six years ago using a degree wheel and long sheet of graph paper, and came up with two camel humps the tops of which would be highest point of lift at zero degrees for each hump. I plotted both humps on a 720 degree graph to lift so both are opposite each other.

After looking at a few cam cards posted in Engine under Q&A, all before and after top dead center degrees are less than 90*. My plot shows BTDC and ATDC are all in the 120 degree range, which makes me think I should subtract 90* from my numbers which yields angular measurements in 20* to 30 degree range closer to what I have seen on cam cards. Am I on the right tract here?

Below is what I think would be a close approximation of my mystery cam:
Timing at 0.050” lifter rise open and close.

Rocker is stock 1.5:1 ratio

INTAKE TIMING
Duration 236*
Open 31* BTDC
Close 28* ATDC
Cam lift 0.321”
Valve lift with 0.022” lash = 0.460”

EXHAUST TIMING
Duration 235*
Open 31*
Close 23*
Cam Lift 0.320”
Valve lift with lash of 0.022” = 0.458”
Over lap at 0.050” = 22*
Center line separation = 211*
211/2= 105.5*

Below are engine dimensions when I last had engine open in 2008 for valve job. at 18,000 mi., today there is 40,000 mi showing.

Piston down in hole = 0.180” Revised depth previously listed as: 0.158"
Bore = 3.430” 30 over still had cross hatch showing
Stroke 4.125”
Fel-Pro Head gasket compressed 0.040”

HEAD Peanut, no EGR holes.
Shaved 0.075 calculated 9.5:1 static compression ratio.
As of about 2000 miles ago, with valve problem, all six cylinder pressures were 162 psi.
Over sized SS Valves back-cut stem I= 1.70” E= 1.44”
Valve Spring = Mopar P5249847 single damper or 340 spring
Head combustion chambers all @ 44cc, and back side of exhaust valve relived for better flow
Bowls and runners ported, & gasket matched

Clifford Shorty 4v intake manifold
Holley 390 cfm carb
Clifford headers, 2” duel exhaust to rear bumper.

904 automatic , shift kit, deep pan, 2600 rpm stall converter, 3.55: 1 8 ¾” Suregrip, 24.5” tall tires
Idle is 1000 rpm, any lower and the lope starts, and vacuum drops off to a wagging needle 1Hg to 6Hg when in gear at 800 rpm.
2000 rpm = 40 mph, 3000 rpm = 60mph, & 4000 rpm = 80 mph

Most of my driving takes place 55 mph and lower on two lane roads. Some 100+ mile trips on I – 95 where 70, & 75 mph is speed limit, I try not to run much over 3200 rpm on long runs. Engine oil consumption increases at steady rpm over 3000 rpm.

I have for a long time had one, perhaps two, sticking exhaust valves, and suspects are #5 & #6. Engine is a dog below 2000 rpm, so-so to 3000 rpm, and pulls hard like a small block over 4500 rpm. It will run easily up to 6000 rpm and beyond, I try never to crank her over 6K, even though the fellow that built the car as a drag queen said he shifted at 6300 rpm during four racing seasons at English Town, NJ. during early 90’s. Claimed he blew up five engines before he figured out how to make one stay together. Also, he raced using 4.11 gears, but swapped back to 3.55’s for traveling between Mass and NJ to race weekends.

Once I get this valve problem ironed out, I expect some better low end torque to be developed, and vacuum gauge to settle down to steady readings at idle. A comparison to my 1967 International Harvester with a 241cid six cylinder, 4 speed, 3/4ton PU, will pull stumps in second gear at low rpm, and when WOT is applied (first is stupid low), it comes alive, feels like it jumps, and according to factory manual very closely matches factory rated HP and Torque output a stock 225 ci slant. Truck has 4.11 rear gear, but tall 31” tire so final gearing is close to the much lighter Dart.

Because of Dart’s lackluster off the line performance, I suspect a cam change may be helpful, perhaps a little more compression added would help. Something with low rpm grunt, but able to run to 6000 rpm to preserve its high rpm performance.

I would prefer to have my cam reground as it plays nice with oil pump. I recall Oregon Cams mentioned for such work, is the right?

Any suggestions welcome.

Bill

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Erson 270/270 or the 280/270 would have had nice manners and good power...

OCG791 is a good cam, but would be better for closer to 10:1...

I would be curious if a 1416 with a 108-109 LSA with some advance dialed in would do the job you are looking for...

low idle vacuum goes hand in hand with a cam that has a lot of overlap, due to lots of duration or a tight LSA or both.

that also means a lot of reversion with exhaust gases pulled back into the combustion chamber at low engine RPM's.

This is just an idea and will not substitute for a more street friendly cam, but you should try dialing in more initial advance and see if that helps the idle and low rpm performance. A combustion chamber laden with exhaust gases that are mixed with the clean air/fuel charge will be slow to ignite and slow to burn, more advance at idle and low RPM may help,, and I am talking about a lot more initial, maybe going up 15 to 20.

You will need to watch that adding initial does not overrun your total when the centrifical advance goes full,
Have you ever put a vacuum gauge on the car to see at what road speed the vacuum advance kicks in?

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

That is not a terribly big cam. I would not go drastically smaller on 9.5:1 myself, but others would. Yes, you need at least 12-15 deg of ign advance at idle to have that cam have "manners". Also, I would degree it at 100 installed centerline. As John said, too little ign advance at idle and low RPM cruise will make it a bear down low.

For me, I would find another stock cam core and have Oregon grind what you want. No reason to wipe out a perf cam when used stock cam cores are pretty easy to come by. I am away and with limited time, but will look again at your specs and desires and recommend a cam within several days...

Lou

_________________
Home of Slant6-powered fun machines since 1988

Thanks guys,

DadTruck, initial or base timing set at 15*
Governor advance kicks in @ 1400 rpm, all in by 2800 rpm. Using small black spring & long heavy black spring with long loop.

I often get some spin-back when shutting down engine. Sometimes its a little whimper, and other times a full blown embarrassing multi revolution backspin ending in a long asthmatic wheez, or it just stops. Killing engine in gear below 850 rpm greatly limits backspin events.

Where would one get a stock cam core?

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

I would go up on the initial advance another 10 or so, that will raise the idle speed which can then be brought down by adjusting the idle set screw, that has the effect of closing down the throttle plate. Getting the throttle plate to cover more of the throttle bore fuel inlets will have a big effect on preventing run on.
See if that also increases the engine vacuum at idle, if you can get the idle vacuum up to 8 or so, you can get off ported vacuum and go to manifold vacuum at idle and that really helps as you can then dial in a ton of advance at idle I am talking 30 + degrees,, 15 initial and 15 from the vacuum can. Which really helps idle and off idle performance. Remember manifold vacuum goes away as the throttle is opened, total advance at WOT is not affected as manifold vacuum at WOT is near zero. Vacuum advance at part throttle can be controlled with the right adjustable vacuum can

keep in mind your motor is no longer stock, so stock tune up setting no longer apply.

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

This whole thing is a bit confusing. Hard to see how you would have such low idle vacuum AND spin back. Usually the latter would mean too much compression for the cam. I have not seen those go together unless comp is quite high. 9.5 is not high. I assume you are running premium gas?

Lou

_________________
Home of Slant6-powered fun machines since 1988

Do I remember some sort of anti-dieseling device attached to the carb butterfly back in the dark ages of smog system development... where the device served to shut the throttle blades fully so that the engine would shut off cleanly.. ?

Throttle Blades Open, exactly why the motor is running on after shutdown,
Lots of egr at low engine speed results in a no idle condition, so the idle control screw gets turned in till the motor idles, remember he said the motor is idling at 1000 rpm.
There is a rough / no idle because the fuel mixture is not igniting soon enough for a proper burn due to the EGR in the mix. Shoot a lot of ignition advance to it at idle and I am thinking it will idle fine. Then the throttle set screw can be backed out and the throttle blades will close. Off idle and low rpm performance will also improve.

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

Well, today I got a chance to pull lifters, and look at cam lobes. They looked not bad, no discoloration or galled surface, all lifters looked like new nice and shiny. Then I got out the dial indicator and magnetic base to measure lift on each lobe until the one of the clamps on crane's arm that holds indicator striped and wouldn't hold by the time I got to #5 E... So I'm missing values for 5E, 6 I&E.

1 I= 0.317" E= 0.318"
2 I= 0.316" E= 0.269"
3 I= 0.318" E= 0.318"
4 I= 0.320" E= 0.317"
5 I= 0.320" E=?
6 I= ? E=?

That 0.269" on exhaust tells me a new or reground cam is needed.

When I plotted the cam events back in 2011, only Cylinder #1 got measured yielding: I= 0.321" And E= 0.320" with head in place; vs. today's readings I=0.317" & E= 0.318" with head off using same push rod each time.

The good news is Trick Flow is sending me a complete replacement magnetic base & crane with all the arms & clamps for nothing, zip, zero, with just a short phone call and no groveling. The kit I have is TFS-90000. Can't beat that service for a seven year old tool... which I only used once before in Jan of 2011.

Now that I have the head off, and it's away at the machine shop, what method or chain attachment points should one use to pull the engine?

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Those specs look very close to the Clifford 276 cam I have in a short block still on the stand. When it was running in a low compression 225 it was very lack luster. I am hoping a boost to 10:1 compression and a looser converter will help, a lot.

_________________
“Buy the ticket, take the ride.”
― Hunter S. Thompson

drgonzo:
When I got the car in 2008, I found name of one previous owner that built & made all the engine mods to drag race, and gave him a call. He said; "I called up Clifford and got the biggest cam they had at the time" (c. 1990).

Last night I spent some time looking up specs of several cams listed as suggestions for my engine, and most were close to what I measured for lift just under 0.5", and duration 230ish.

Can the cam I have now with one lobe worn down about 0.040" be reground to a new profile, or is it junk?

I have a lead on good used stock cam with matching oil pump, and NOS purple cam with one, described as, slight pit on one lobe for regrind.

I examined the lifters, and they look brand new, nice and shinny. Would I need to purchase new, or can they be reused?

All cams DI and others suggested I suspect take a 340 spring or like, is this correct? Currently 340 spring or like are what my engine is equipped with. Head is a machine shop, and probably all springs will need replacing.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

to reuse lifters with the existing cam in its existing condition you need to have kept the lifters organized so that each lifter is returned to the exact lobe that it originally ran on.

if you install a re ground cam you need to use either new or re ground lifters,
Oregon can regrind lifters, pricing is close to new lifters,

to help in the decision on using new or reground lifters, check the weight of the lifters you have now against the weight of the new lifters that may be bought. Lighter is better.

also with a reground cam / new or re ground lifters, be sure to use a cam break in lube on the cam and follow an established cam-lifter break in routien

and on your existing cam, look closly on the ends, about all cam manufacturers will stamp a serial numer and grind ID code.

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

Most likely Oregon or another place can regrind the worn cam you have. If your oil pump works well with that cam, I'd do that. Somehow, I have never worn out a cam lobe...

Let us know if you want a cam recommendation. Remind us of your desired driving parameters and converter stall.

Thanks,

Lou

_________________
Home of Slant6-powered fun machines since 1988

If a lobe got wiped during the initial run in process, I would suspect insufficient splash lube, too high spring pressures, something along those lines. But for only one cam lobe to have excessive wear after a couple of years use,, I would be looking at that specific lobe to make sure it was hardened properly.
If that one cam lobe is soft, putting a reground shape on top of it will just get you back where you are now.
Talk with some good local engine shops, there should be someone in the area that has a Brinel machine. If the hardness is good, also check with the regrind shop to verify they can work within the remaining stock.

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8