Regular port Commando head clearances

[340commando]

Hello Mopar folks. I have my 340 in the machine shop having x heads swapped out for Aluminum reg port MP Commando heads p4876785. They called and said the engine ran bad and bent push rods and determined the pushrod holes need opened up. After that they called and said "you have a lifter ticking,did it do that when you brought it in?'' I stated no. I found a engine build on the net where a fellow buttoned up a 318 with a different head casting from some cop car and when he fired it up he bent push rods and colapsed a lifter or more than one and they were damaged,so he opened up the pushrod holes and went back at it. These guys did some porting and intake gasket matching on mine and removed the boss in the port runner that reg. port Commandos have when new.
Im looking for comments on what ive got here and the clearance problems with the pushrod holes. Thanks,,,,,,,Matt

 

[len340]

yes the push rod angle is not the same as a x head or j they should bushing the lifter bores to so for longer life of the engine to

 

[boozersdart]

With the commando heads of a 54cc chamber, was the valve to piston clearance checked?

 

[340commando]

With the commando heads of a 54cc chamber, was the valve to piston clearance checked?

I made notes on paper when i dropped off the heads and my truck and requested they check the piston to valve clearance and the valve to valve center clearance because Ryan from Shady Dell was gracious to call me to answer a question. I havent got the call to pick up my truck yet so i dont have accurate info on how they handled the clearance checks. These heads are listed as direct replacements for pre magnum motors. Mine is a 73- 340 with a good comp cam ,750 street avenger Holley,mopar performance dist. and chrome controller,headers ,edelbrock performer rpm etc.I know this is more than you asked but thats the big picture for me. Thanks for responding,Matt

 

[1968FormulaS340]

I think your real problem is your machine shop.

Any machine shop that uses the "Run it and pray nothing flies apart" method should be avoided.

 

[340commando]

I think your real problem is your machine shop.

Any machine shop that uses the "Run it and pray nothing flies apart" method should be avoided.

Yep,thats clear to me now . I put it in the machine shop local to here knowing the swap needs finessed by a machinest and it looks like they bolted it up and wound it on up ,see what works.Crap. I know i blew it. Now im looking for similar problems and solutions from builders,thanks.

 

[Brian Hafliger]

Hello Mopar folks. I have my 340 in the machine shop having x heads swapped out for Aluminum reg port MP Commando heads p4876785. They called and said the engine ran bad and bent push rods and determined the pushrod holes need opened up. After that they called and said "you have a lifter ticking,did it do that when you brought it in?'' I stated no. I found a engine build on the net where a fellow buttoned up a 318 with a different head casting from some cop car and when he fired it up he bent push rods and colapsed a lifter or more than one and they were damaged,so he opened up the pushrod holes and went back at it. These guys did some porting and intake gasket matching on mine and removed the boss in the port runner that reg. port Commandos have when new.
Im looking for comments on what ive got here and the clearance problems with the pushrod holes. Thanks,,,,,,,Matt

Give us more info...was this hyd. roller or???

 

[340commando]

Give us more info...was this hyd. roller or???

My 340 is 73-340 flat top pistons ,Comp Hydraulic flat tappet,292 duration and 508 lift on intake and exhaust lobes. I had x heads being replaced with the reg port Commandos. It has stock stamped type rockers., Thanks

 

[Brian Hafliger]

The intake rockers probably needed to be spaced away from the intake ports more than stock resulting in the rods rubbing the pushrod side of the intake port.
That sucks. Hope you get it figured out...

 

[BJR Racing]

Did they check retainer to guide clearance?
Is the spring coil binding?
Do the pistons have valve reliefs?
Are the pushrods the right length?
Have the heads been cut any, if so how much?
What head gaskets were used, were they thinner if so how much?

If I recall correctly the heads have cast in rocker stands so the rockers should be in the correct location. Did they by chance use a 3/8's pushrod instead of a 5/16? This would close up the clearance a good bit a full lift, and machining the pushrod hole would be necessary. But all this should have been checked in a mock up. Personally the stock rockers are ment for showroom stock engines, if any performance is in mind the rockers should have been changed to aftermarket adjustable ones, and the correct pushrods to fit them. Being mech. or hyd. lifters. Hope this helps and you get it figured out.