Chasing down a tapping noise

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MOPAROFFICIAL said:
That will be in the same condition as this one? My point made. Cam and kifter kit is under 300 bucks and you don't need new push rods. Do what you like, It's just advice.
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what's the valve to piston clearance like in a commando engine? Will the comp cam 20-246-4 fit?
 
I noticed that the original cams have lifts around .425" or .430" in the later years. What is don't know is the answer to what you asked: the stock piston to valve clearance. I can only guess that is is over .100" as the standard was bigger back at that time, plus this was for production, where things are even more conservative.

But, the ramps are likely faster, even on that Magnum grind, than the older stock grinds, and so that points to an upgrade in valve springs and that cost.

I personally would not pay a lick of attention to what Summit or Jegs says... they are sellers, warehousers, and shippers.

The one consistent warning for the 273 is on the cam size.... don't go too big. If you drop the cubes, then any loss of torque with too big a cam is gonna be a lot worse.

What year of 273 do you have? And trans? And have you looked at the head casting numbers? I am curious of you have the closed chamber ones; sometimes they get swapped due to age and you dunno what you really have. I ask because if the open chambers got in there, then the CR is down and you gotta be even more careful with too much duration.

It may pay you to look at other threads and cams discussed for the 273, you are making several steps up in duration and that is gonna move the RPM band up maybe 1200-1500 RPM. I also depends on how you plan to use the car.....cruiser, driver, or racer....
 
nm9stheham said:
I noticed that the original cams have lifts around .425" or .430" in the later years. What is don't know is the answer to what you asked: the stock piston to valve clearance. I can only guess that is is over .100" as the standard was bigger back at that time, plus this was for production, where things are even more conservative.

But, the ramps are likely faster, even on that Magnum grind, than the older stock grinds, and so that points to an upgrade in valve springs and that cost.

I personally would not pay a lick of attention to what Summit or Jegs says... they are sellers, warehousers, and shippers.

The one consistent warning for the 273 is on the cam size.... don't go too big. If you drop the cubes, then any loss of torque with too big a cam is gonna be a lot worse.

What year of 273 do you have? And trans? And have you looked at the head casting numbers? I am curious of you have the closed chamber ones; sometimes they get swapped due to age and you dunno what you really have. I ask because if the open chambers got in there, then the CR is down and you gotta be even more careful with too much duration.

It may pay you to look at other threads and cams discussed for the 273, you are making several steps up in duration and that is gonna move the RPM band up maybe 1200-1500 RPM. I also depends on how you plan to use the car.....cruiser, driver, or racer....
Click to expand...

I have the 64-65 heads 2465315 heads, automatic trans, street demon carb, performer intake, and those fenderwell headers, not sure who made them. So you think the springs will be too weak?
 
Yes, unless you baby it... but you won't be able to resist LOL. And if you go with that duration, the RPM range will be moved up and that will put more strain on the springs to keep things under control. A step up in springs seems like a no-brainer to me. The 901-16 spring set that Comp lists are a bunch stiffer than the stock ones. I hope the exhaust valve don't recess into the heads too fast with the non-hardened seats..... ooops... .maybe a milder cam is in order?

OK on the heads; tnx.
 
nm9stheham said:
Yes, unless you baby it... but you won't be able to resist LOL. And if you go with that duration, the RPM range will be moved up and that will put more strain on the springs to keep things under control. A step up in springs seems like a no-brainer to me. The 901-16 spring set that Comp lists are a bunch stiffer than the stock ones. I hope the exhaust valve don't recess into the heads too fast with the non-hardened seats..... ooops... .maybe a milder cam is in order?

OK on the heads; tnx.
Click to expand...
Thanks. The melling springs are very close to the 901's and about half the cost. I may give them a shot.
 
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