my first question - help with timing in a Chevy 327 in MD

[notherone]

Well, I'm a newbie, and thought maybe this would be a good place to post this question.  If it's not the right place, feel free to move it or delete it.

I have a '66 Chevelle with a 327 in it- I built the 327 myself.  It has 10.5:1 pistons in it, and they are running under camel hump/double hump heads with 64cc combustion chambers.  The combo together is putting me at around 11:1.  The cam is a 272/284 duration cam.

I'm running HEI and although friends claim it should be possible, I cannot run 93 octane in this engine without it pinging.  I have to run a minimum of 98 octane.  I've been told by a few people that I should be able to just retard the timing to fix it, but I don't think that is accurate.

What is everyone's take here on the scenario?  I will say too that all that's on the engine is the HEI distributor, no added aftermarket timing add-ons or anything.  And when it comes to timing, I know how to read a chilton manual, find the suggested timing, move the distributor to it, and that's about it.  The car is a plain-old cruiser, so $8.49/gallon really slows up the cruises!

Thanks in advance,

Jim

[Cajun Kid]

Those oll Iron GM heads at a 11 to 1 "should" be Ok   with 93 Octane.. but with todays pump gas you may be on the edge.  What is your total timing ?  Does the HEI have a vacumn advance ?  Is the motor making a bunch of vacumn?  If so the timing could be advancing to much to soon..

When the engine is hot , does it crank/re start easy or does it turn over slow or buck ?

Before you make any major chnages you may want to find the answers to the above questions. 

You could try blocking off the vacumn advance and seeing if that helps (temporary fix)..

Also rather than paying for high octane fuel,, you may try a  $7.00 can of octane boost (Lucas is good) STP is just OK...  You can also mix a gallon of 110 race gas with your 93 pump gas and that works on slight pings.

Many fixes, no good answer till you have more info...

Good luck 

Charles

[Joe Timney]

Did you degree the cam? Did you check that the timing marker is true top dead center ? What timing do you have in it?

joe

[notherone]

Thanks guys so much for the help.  When I installed the cam, I made sure that the timing mark corresponded to the crank gear as it was supposed to according to the instructions from the manufacturer, but did nothing beyond that.

In response to the question about the engine having hard starts when it's hot, it doesn't overheat on the water temp gauge, but it would give me some difficulty starting if it had been hot and I shut it off and wanted to restart it shortly after.  I just attributed the issue to the headers I have on it, and put a protorque starter on it with a ceramic solenoid.  After that I had no further starting issues.

And finally, in regard to what timing I set it to, I'd have to dig out my Chilton manual and see what number I used.  It's been a little while back since I set it up initially but it would have been whatever the Chilton manual said for a 327 with that cam duration (or close to it).

Jim

[Cajun Kid]

A safe start to limit to much advance for that SBC would be 8 to 12 degree before top dead center.  I would try 10 degrees BTDC.. and see if that helps.   Make sure to unplug your vacumn advance when you check/set the timing... also check it at around 2000/2500 rpm's...  I like more advance, but I run much hotter cams and high compression  as well as 110 Race gas...

Hope this helps...

Joe T can give you better advice,, I am a driver and ( and half arse mechanic) LOL

Charles

[notherone]

A safe start to limit to much advance for that SBC would be 8 to 12 degree before top dead center.  I would try 10 degrees BTDC.. and see if that helps.   Make sure to unplug your vacumn advance when you check/set the timing... also check it at around 2000/2500 rpm's...  I like more advance, but I run much hotter cams and high compression  as well as 110 Race gas...

Hope this helps...

Joe T can give you better advice,, I am a driver and ( and half arse mechanic) LOL

Charles

Thanks Charles- I have a feeling that's the timing range I was in already, but I will definitely check again!

[notherone]

Also rather than paying for high octane fuel,, you may try a  $7.00 can of octane boost (Lucas is good) STP is just OK...  You can also mix a gallon of 110 race gas with your 93 pump gas and that works on slight pings.

Charles

I'd always heard octane boost destroys your carb gaskets, so I've avoided using it. 

[lsr6769]

HI Jim, Get yourself an adjustable vaccum advance for you hei, bit of a pain to get set up but well worth it. You really need to make sure your timine marks are correct.

Scott

Well, I'm a newbie, and thought maybe this would be a good place to post this question.  If it's not the right place, feel free to move it or delete it.

I have a '66 Chevelle with a 327 in it- I built the 327 myself.  It has 10.5:1 pistons in it, and they are running under camel hump/double hump heads with 64cc combustion chambers.  The combo together is putting me at around 11:1.  The cam is a 272/284 duration cam.

I'm running HEI and although friends claim it should be possible, I cannot run 93 octane in this engine without it pinging.  I have to run a minimum of 98 octane.  I've been told by a few people that I should be able to just retard the timing to fix it, but I don't think that is accurate.

What is everyone's take here on the scenario?  I will say too that all that's on the engine is the HEI distributor, no added aftermarket timing add-ons or anything.  And when it comes to timing, I know how to read a chilton manual, find the suggested timing, move the distributor to it, and that's about it.  The car is a plain-old cruiser, so $8.49/gallon really slows up the cruises!

Thanks in advance,

Jim

[jimmy six]

IMO you need to give up some of your total advance. This in the balence weights and the vacuum; both need to be limited. As said, 10 will be fine for idle but if you have your vacuum ported under the carb and not in it (above the butterflies) you are sitting with all of it in when signal turn green and you drive away. Every time I had it this way, my 11-1 engines would ping.

You need to know how much total your distributer advances and the RPM it does it. Lets say with the vacuum above the butterflies and you have a total of 23 degrees in the distributer. The vacuum port could let all 23 + the 10 initial in at once  giving you 33 as you move away from the light and I guareentee tis will ping an 11-1 engine with 93 octane.

A good distibuter guy can set the vacuum can to only allow 10 degrees in and as the RPM comes up the 23 will come in later in the RPM range and you will not ping. The engine will be a little sluggish on the bottom but it's the sacrifice for 11-1 ans 93 octane. You can loose a little milage here too. I never minded a little ping but did not want to hear it at every crack of the throttle in normal driving. You did not say anything about engine shut down. I had to turn my engine off in drive too keep from run-on. Wife hated that....Good luck