Topic: 2.5 Block Differences

[Wrench]

Clay Smith Cams still lists the AMC 2.5 on their drop-down menu.  You select the cam grind, then pull down the options.

[RNandKT]

OK that explains why when Hesco used to make a performance CAM for the 2.5 they went to 110 centerline.

On Hesco's CAM they also went to 470 lift, but the guy who is doing the regrind was saying that the fuel injected motors can only handle so much before they start throwing codes. Even with the 450 lift you're supposed to richen the mix. Switching to the 4 nozzle injectors will help with that, and other people have done the 450 lift so I thin I am safe with that without causing problems. Hesitant to go to the 470.

As for the centerline. can that be changed on a regrind? Since the Hesco CAM was 470 lift and 110 centerline, would 450 lift and 110 centerline still be a good combo? Would be nice to favor torque. On the Hesco CAM it said it was requisite to change to taller springs, would the mopar conical springs be sufficient?

[RNandKT]

That explains the specs on the Hesco Cam

Advertised duration: 264        214@ .050

Lobe centers: 110 degrees

Lift: 470

They claim that is the best setup, and it is designed for the fuel injected motor, so maybe thats the best way to go. They also say:

This camshaft will require a spring and retainer change because of the increased lift. The valve spring seat will need to be machined in order to set up a taller installed height. Failing to do so will cause severe damage to the camshaft and related components. If the valve stems of your valves have triple grooves for the keepers they will need to be changed to the early single groove valves.


I wonder if the mopar conical springs will work? The most aggressive Purple CAM had 480 lift so I would assume the Conical springs since they work with that would be fine for the 470 on the hesco.

[Wrench]

Yes, the spring pockets should probably be machined deeper.  If I recall, the factory installed spring height is 1.6", which really limits your spring choice.  (I believe the most common Chevy size is 1.8") If you dont have the capability or knowledge to conquer getting the springs correct, take it to a really competent race engine builder/machinist and have them do it.  Getting springs or other hardware that cannot handle the lift you choose is a potential for complete disaster to your engine.  Lightening the valve train will allow for less spring tension required for the lift (ie: lighter valves, retainers, etc).  Just for reference, I had severe valve float issues on the stock cam/lift over 4500 rpm until I went to better springs.  I nearly dropped a valve because of it.

Incorporating lighter valves, beehive springs, and Ti retainers can go a long way in keeping your valves stable at RPM.  I havent looked into it, but I'll bet the LS stuff will fit our heads with a little work.

[sharpxmen]

you can also get longer valves or high length retainers and cup (although I'm not sure if they are available for the stock valve stem diameter), not necessarily need to machine the spring seat but would have to be tested to confirm the max valve travel. You can adjust the preload with spring shims afterwards. As far as I know the Hesco cam is good.