ok with vac. advance disconnected i get 28º total and with it connected its reading 48º what should it be at.. i thought that it was supposed to be set at 36º with adv. plugged but that would make the total with it connected around 60! or is this # irrelevant due to no load on the motor?? please help me out.. the motor seems sluggish! also something completely different...anyone know info on the 'myth' of a .060 bore overheating??? thanks
Roger

The 36 total is kind of a baseline setting...your engine may want more or less. The total timing is your mechanical advance plus the initial...how did you get your 28 total number? Vac advance isnt used to figure total timing...all that told you is that you have a 20 degree can in the distributor. That is an awful lot for a performance engine...I normally dont run anything more than a 8 or 10 degree can (or vaccuum pot...whatever you want to call it).

As far as a .060 overbore causing overheating, I have heard of it but never seen it myself...on any engine.

the 28 is with vac plugged. so should i set it to 36 with vac plugged.

where do i get a dif canister and how hard is it to put in.. does dist. have to come out?

You can buy an aftermarket adjustable vacuum advance can that has adjustments for amount and spring tension (speed of return) or just buy a cheap adjustable cam to add to the stock can. I have one in my distributor. It is like an egg shaped piece of sheet metal with steps that limit the travel of the advance can. Slick, cheap, invisible and installs with 1 existing screw. Remember, this advance can does absolutely nothing while you are at wide open throttle.

Realy concentrate on getting the advance curve right first, then worry about the vacuum advance after that. As a general place to start, have the centrifugal advance start at around 1000-1200 rpm and be fully advanced at 3000 rpm. The small block chevy likes about 36 degrees of timing at and above 3000 rpm at wide open throttle. Get your distributor to stop advacing at 3000 rpm by changing out the springs then set the timing for 36 degrees while the engine is running at around 3500 rpm or so. Lock it down and see how it runs. You may need to remove some of the advance from the centrifugal mechanisim for optimal low speed operation (lazy at low speed) but you are now in the ballpark. When you change out the springs it is OK to mix and match tensions. Try to keep those factory weights if they are salvagable as they are better than the crappy ones that come in a distributor recurve kit. You will need a timing tape to do this yourself or have your distributor set up on a distributor machine at a competent speed shop.

As for .060 overbore, it can become more likely to overheat but this does not always happen. You gotta dance with the one you brung.

Good luck,
-Mark.

ok...the advance comes in by 3000. so i'm almost 10º low and will change that tomorrow.. i am using dialback light so its no prob with checking it. i know timing can severely rob a car, and this motor is new and wasn't driving how i figured it would.. i hope this cures what seems to be wrong. it just doesnt' have that beefed up 350 ride to it. as far as the cam for the canister...where would i pick one of those up at?

The guys have you covered with the timing issue..so I will dispell the overbore issue.

What makes wasted heat is the increase in fuel that is being utilized. The increase in bore or cubes is a horsepower issue and of course pulls more fuel charge into the chamber, so their is more fuel being burned and thus more wasted heat to remove. On the other end of the issue, the water jacket has not been altered one ioda with overboring. This means that the heat transfer ability has not been compromised.....no changes there. So, to the extent that the engine is "larger" and using more fuel is the ONLY source of more heat that needs attention. The fact that the cylinder walls are thinner does not play significantly into the mix. MOst of the generated waste heat is withdrawn at the heads anyway.

So, simple precautions and a good sound cooling system design will be adequate for your 350, or your 355 or your 357 or your 360.

For more on cooling go to www.inccn.net/techlinks.htm (http://www.inccn.net/techlinks.htm) ...enjoy.



------------------
STEVE JACK
ConceptOne Pulleys and Brackets

The vacuum can limiter cam is made by Crane Cams and is available from PAW for about $4 bucks. PAW part number is CRA-99619-1. I bet the Crane number is 99619 if you want to buy it from another source. Good luck!

-Mark.

<BLOCKQUOTE>quote:</font><HR>Originally posted by stingr69:
The vacuum can limiter cam is made by Crane Cams and is available from PAW for about $4 bucks. PAW part number is CRA-99619-1. I bet the Crane number is 99619 if you want to buy it from another source. Good luck!<HR></BLOCKQUOTE>

This little "cam" will also increase initial timing by 2* while "retarding" the vacuum can 2* to according to Crane.

So If I were trying to have a combined timing of 22* at idle using full vacuum and the can I have on the distributor, which is pulling in 16*, I would have to set the initial to 6* and set the "cam" back 4* giving me (6+4) + 12 from the can = 22*.

Correct?

-Funk

Adjusting the cam will change the available advance from the can but as a side effect it will advance/retard the distributor initial/total setting but not add or remove advance from the distributor. It's like it rotated the distributor housing. It actualy is rotating the breaker plate as the vacuum advance stop cam is what sets the breaker plate's location. So if you remove 2 degrees from the can (say from 18 to 16), you will need to reset the initial timing with a timing light to the original setting. If your initial was 12 degrees at idle, it would now be 14 degrees at idle and you would need to set it back to 12 with a timing light. Now you have the same advance in the distributor but 2 degrees less available from the vacuum can. I hope this was not too confusing.

-Mark.

Not at all, it makes perfect sense.

Set my inital to where I want it (12*), "dial out" the vacuum I don't want with the "cam" (6*) and reset the initial timing. That should give me 12 initial plus 10 vacuum for a total of 22* using full vacuum.

Any tips on installing the "cam" in the distributor?

-Funk


[This message has been edited by CFunK (edited 04-01-2002).]

The cam installs using one existing screw. It just about installs itself http://www.camaros.net/forum/biggrin.gif

I did mine while the distributor was out of the car. My can had 20 degrees and I figured I need about 16 or so. I will know more after I fire the motor and play with it a bit.

-Mark.

my name is flattop and I am a closet 0.60 overbore, I got tired of trying to explain how thinner walls have nothing to do with it. When they tell me they heat up faster,now I just tell them, they cool off faster too. If the cooling system is sufficiant and you get the timing and carb right you shouldn't have any problems, esspecialy if its an older block.

<BLOCKQUOTE>quote:</font><HR>Originally posted by flattop:
my name is flattop and I am a closet 0.60 overbore, I got tired of trying to explain how thinner walls have nothing to do with it. When they tell me they heat up faster,now I just tell them, they cool off faster too. If the cooling system is sufficiant and you get the timing and carb right you shouldn't have any problems, esspecialy if its an older block. <HR></BLOCKQUOTE>

Yer a closet something or other. What the hell does that have to do with ANYTHING we are discussing?

And who the hell are THEY?

-Funk



[This message has been edited by CFunK (edited 04-01-2002).]

rogleete asked in his first ? about the 0.60 overbore causing an overheating problem, I was making a funny about how everytime someone asks me whats under the hood If I tell them its a 350 bored 0.60 over, I have to listen to their reason why it should overheat. I think it would be easyier to tell them its a 360 but then they would think its a f*rd engine.

Sorry dude, I had forgot where the thread started. I get it now, jolly good show

-Funk

[This message has been edited by CFunK (edited 04-01-2002).]

Thats ok, I can see why you were a little weirded out about what I was talking about. anyway rogleete is your problem fixed yet?