My 6.1 retrofit thread

PARTS

1. SRT MAX PLUS - 218/227 @ .50, .565/.555 lift, 110LSA, 114 ICL
2. 2 x Hyd Lifters converted to solid through removal of internal valve and washer spacing the plunger
3. Modelling Clay
4. 10 x M12 Head bolts - P# 6506694AA
5. 1 x Head Gasket - P# 05037592AC

One thing about old school hot rodders…they usually want to do things 110%...and when it came time to ask my buddy to help me with the cam install…he asked the obvious questions…

- Did I plan on degreeing it?
- Did I plan on checking Piston to Valve clearance?


Now on both these counts, I started out happy to accept the cam suppliers word..….but mine WAS ground on a tighter LSA (110) which reduces P-V……….so I figured “what the heck?”


Then the hassle started……I’d have to swap out the Hyd lifter for a solid to do this right.

1. - I needed a solid lifter to accurately measure the valve travel to check P-V,
2. - I’d need new head bolts
3. - I’d need a new gasket if I planned on swapping the lifter…because I had to lift the head to swap the lifters.

I couldn’t get accurate data on the expected P-V other than it would be “closer than most old school builds”..so I agreed and got ahold of two used lifters from a company in the US called “Sharadon Performance”…Jerry and Denny were very helpful and only charged me $15 postage – no charge on two almost new hyd lifters.


I got a new set of Torque to Yield head bolts and gasket from East Coast Moparts..arrived within 10 days…..and we set to it.



My buddy modified the lifter and after a couple of trials we worked out the exact plunger height that allowed the valve to seat.





Applied modelling clay to the piston and replaced #1 Intake and Exhaust lifters for our converted pieces.







RESULT


The cam installed exactly where it was supposed to – at 114 ICL.

But……..Intake came in at .068th and the exhaust came in at 115th.



Now any gear head will tell you that according to the engine builders bible - .068th is too close for comfort for a street car…..but…

….since I first became aware that the intake clearance with most aftermarket cams in Gen3s is close…I’ve been researching the matter and trying to figure out how plenty of owners get away with it.


There seems to be three parts to the answer –

• - Rev limiters (so the incidence of over rev is almost nil),
• - Superior valve train technology (better lifters and springs, less slop in the geometry – all so the instance of valve float is generally less), and
• - Decent valve springs – meaning its crucial to run fresh good quality valve springs that won’t “sack” and cause premature valve float which can result in valve strike.

To be truthful, I don’t think anyone should be happy running such tight clearances on cams in any motor, especially with cast pistons –

HOWEVER………… there seems to be very few recorded incidents of valve strike on start up due to these close tolerances.


The troubles seem to start when relying on weakened factory springs to control cams with lifts exceeding .540 lift.

Valve float occurs, shortly followed by spring breakage and catastrophic failure!!

PART ALERT


So my first resolution is to buy some decent valve springs – I’m told the PSI LS1511ML spring is a straight drop in and ideally rated for the cam I am running.