Hey guys,

I have a 305 in my '87 SS, and lately, she's been dieseling whenever I push her a bit on the throttle. The only thing is, it's a relatively low compression engine (I think the 305s are 9.3:1?), so 87 octane should run fine on it. I've replaced the EGR valve on her already, thinking that it was jammed or clogged and the cylinder chambers got a littler hotter than they should, but she still does it. Anyone got some ideas? Thanks. -Luke

one thing is the timing is too far advanced.u can just retard the timing or start using 93 octane.mine does that when i use 87 octane.car runs better with the timing advanced and on 93 octane.also the 305 compression is i believe only 8.1.

These engines are pushing twenty years old now and carbon build up can push the compression right on up plus the "hot spots" is creates can cause dieseling---the small bore long stroke doesn't help either--- but there is a product called Seafoam that can disolve the carbon and get her back to normal just use it per the directions on the bottle costs about 7-8 bucks and is more than worth it should be available in any parts store..................Dan

i agree with dan (if i can use your name), run a compression test on all cyl. that should give you an idea about the condition of your cyls. and deffinatly up the octane rating on your gas. and if gas prices in ny are like they are down here, to pump 93 cause at 20c more a gal its only 3 bucks more to FILL your 85's 15 gal tank

if you don't want to go buy some seafoam here's a little trick you can do that should bust up the carbon. take a vacum line from the base of the carb and with the engine idleing use the vacum to suck up small amounts of cold water at a time from like a little bottle or something. its kinda like a crude set up of a water injection system. if you don't use a vacuum line from the base of the carb then you'll prob end up sending all the water to one side.