cams, timing, knocking...help!!!

[Paul]

Last year I rebuilt the engne in my '86 GW. I took a class at a local community college, and I did everything I was supposed to do. It runs well, with one very exasperating exception: If I time the engine to provide good low end power and torque, it knocks and pings like crazy when I go up a hill (especially with a trailer). When I back off on the timing to reduce knock, I lose all my low end power. I have not been able to get both low end power and eliminate knocking at the same time. I have taken it to several mechanics, and no one has been able to solve the problem. One guy told me that the lack of an EGR was causing excess cyclnder temperatures. I recently stopped at a local performance shop and talked to the guys there. They said the lack of an EGR would not have a significant effect on cylinder temperatures. They suggested a different cam--an Isky 256--to replace the Edelbrock cam I have in it now. Does anyone have any suggestions? What about my vacuum advance? Could that be the trouble? Any comments would sure help. Thanks!
Here are the specs:
AMC 360
bored .030 over
Edelbrock Performer Package cam and intake manifold
Carter AFB 625 CFM carb
Thorley headers
Port matched heads
Compression ratio 8.75:1

P.S.--higher octane fuel doesn't help much, neither do octane boosters

[ironroad29]

egr is there for a reason plus there is a updated EGR kit ,others here have the p/n egr affects the cylinder temp in a major way mainly because the 2 brl motorcraft is jetted so lean if you don't want to instal egr ,you would be advised to rejet the carb a little richer that should take cae of the knocking .

[ClarkGriswald]

Those guys just want to sell you parts


Lack of EGR will cause a lean condition in mid/part throttle and cause all kinds of pinging.. Bad for your engine..

I had this same exact thing after removing ALL of my emmisions garbage and simplifying things..

Its all in the tune.. you should be able to rejet to make things richer and eliminate the lean condition.

Dont let some parts counter yahoo's sell ya stuff you dont need.. there is no reason that any motor cant be tuned to what it is..

[JeepFreak]

I had a condition close to yours. Mine is a 360 with the same parts as yours except 600 carb and higher compression. I had to go with the .401 primary jet with a 70-47 metering rod and I left the secondaries at the .395 jet. You have to make these carbs go fat if you want to do away with the pinging. Also you may want to change the vacuum springs depending on where you live. I run the orange (5) springs on mine. It took alot of jet swapping until I got it right but now she can runs with more intial timing and no pinging when the rpm's go up.

[nograin]

sounds like excellent advice.

new cam to solve a problem. no way! buy a new cam if you want to change the performance curveor the old one is worn out.

Just like the guys said. Ping can come from excessively lean conditions justs even though timing is usually first suspected. Too much advance and too lean in the carb creates about the same condition in the actual firing - thats true for the emmissions, even shows about the same in the emmissions.

Since you've tossed the EGR, you can run like a pre 1970 car and hook up the manifold vacuum right to distributor if you haven't done so already. That will help your idle and gas milage by providing more advance when the engine isn't under load.