I am a new owner of a 66 ss 396. The car is beautiful but having some engine troubles. Previous owner claims recent mild rebuild but I'm not sure - no paperwork. Valve train is noisy (uniformly). Old owner claims a solid lifter cam was installed during rebuild. It sounds more to me like it's hydraulic and needs adjust - no noticeable overlap/smooth idle. I have info on adjusting both types of BB valves but my question is how can I tell up front which type of cam & lifters are installed w/o tearing the engine apart?. If I assume hydraulic and tighten down to eliminate play plus 1/4 turn, wont I be damaging engine if it does in fact have solids? In fact my thinking is it probably would barely run due to the valves being so tight. Sorry to bother you guys with such an elementary question but I need some help. BTW engine pings pretty badly with 91 octane and even adding 3-4 gallons of 100 octane did't help much. Timing is 36 deg total and stock at idle. Seems strange for a "stock" 325 HP engine! Ideas appreciated!
Thanks
DWR

A stock 396/325hp had 10:25;1 comp and if there is a mld cam with sort duration causing higher cyl pressures that could easily cause ping/detonation esp with junk low octain 93 fuel.

Those motors were designed to run on 98 oct fuel and not todays low octane 91 fuel thats also been oxygenated,lead removed,and ethenol added unless you build the motors with running todays fuels in mind. I have seena pump gas 540 in a 67 street vette with a 5 spd tremec running 9.90's on crap 93 fuel,now thats an accomplishment for sure.

Running 3-4 gals of 100 oct fuel in 20 gals of 91 wont increase the octain much(maybe 92.5-93) which is why it didnt help reduce or stop the ping.

Buy some Kemco Lead Supreeme Booster thats real lead which increases the octain in full points to well over 100 depending on the mix.

If your running a vac adv check to ensure you dont have any more then 50-52 deg max at part throttle cruise so try holding the throttle at 3k rpm. If you get more then 52 deg at 3k with vac adv hooked up you need to either replace the vac adv with one with less full adv or you need to limit it to approx 50-52 deg for part throttle cruise.

Hook the vac adv to full vacuum all the time for better idle with perf cam.

This is assuming you still have the 36 total your stated the motor was running.

As for your base/initial timing at idle, since you stated the prior owner installed some kind of perf cam the stock approx 4-6 deg initial the 396/325hp motors used is way too retarded,you neeed approx 18 deg initial so your current initial is approx 12-14 der retartded which results in lost power,wasted fuel,por idle,and poor thottle responce. But running the 18 initial the perf cam needs may push the total into the lower 40's which is too high. In that case you need have the mech ahdv in dist recurved for 18 deg max in by 2800-3k rpms to go with 18 initial,then 18 initial & 18 mech in dist = 36 total in by 2800-3k rpm along with bac adv that gives you an additioanl 14 deg or so adv for when at part throttle cruise.

Search " Ignition 101" here in t/chevelle and read it for a more in depth explination of what i am talking about.

As for the lifters,you can easily tell if they are hyd lifters whe adj them with motor running. Back off a rocker untill it clatters.

Then tighten it down just untill the clatter stops which is zero lash.

Now turn the nut down a 1/8 to almost 1/4 turn max and the motor should run rough for approx 30 seconds + - unitll the lifter resets if its an hyd lifter thus smoothing out the motor again.

But if its a solid lifter the lifter will never reset it self after adj it down 1/8-1/4 turn past zero lash thus the motor will not smooth out untill you back off the rocker nut again to zero lash or back out past zero lash untill it just starts to tick/clatter again.

Try this on a couple different lifters to ensure you getting the right responce.

If you end up thinking its a solid cam and dont know which one it is try approx .024/.028 when hot,that should work ok,little noisey but non the less ok.

And no you wont hurt anything trying this adj proceedue to test for hyd or solid cam/lifters just as long as you dont overtighten the rocker adj nut past 1/4 turn down from zero lash.

Scott

Thanks Scott,
Seems like I have some detective work to do. I don't think the lead additive is available here in California but I'll check and look at the other points you mentioned as well. BTW, you own two of my favorite bikes. Is your engine built?. How do you keep it from pinging?
Doug