Ok, so we have my freind's 455 up and running. It sounds real mean. I cant remember the cam profile, but the ad. dur. is something like 268 or maybe 286? Any way, big cam, and im not sure what it likes for timing. Can someone give me the "Magic" numbers, so we can have the distributor recurved? I know my SBC likes about 24 initial, 12 degs mech for a total of 36.Then 2* retarded after 5000rpm. Buick is almost the same, except it likes 32-34 total. What about olds? We can figure out the advance required at idle, and the mech advance curve on our own, but i just need to know a "typical" curve for an olds with a big cam, so i have something to work off of. The car is running aluminum heads, and will be running premium fuel, so id like to squeeeze all i can out it. Cheers.
Can only tell you what we've found on the Pure stock Olds cars, don't know about knock back retards (7Al?) 36 to 37 degrees total seems to be what works the best with Olds big and small blocks for max performance. This assumes 10.5 to 1 or close C.R. My car is a small block and the curve puts it all in about 2200, no vacuum advance. Hope that helps. Go to HighperformanceOlds.com for tech on this kind of stuff. Don't waste your time with the clowns on realoldspower.com or oldspower.com. Both used to be good, now a joke.
Hey Dave, was hoping youd chime in. Not going as fancy as the 7Al. There will be a MSD 6AL basic rev limiter on there, and MAYBE a MSD 8981. Its a programmable timing curve box from MSD. Otherwise, were just gonna stick a recurved dist. in there. The car probably has close to 10.5 CR. He was telling me you have to be pretty quick between the shifts, because the revs want to come down really quick. Also the brand new starter is already struggling, so the compression is there. My freind's old (olds) 350 was a stout little monster, but we didnt build it. It was timed just perfect, so we never bothered it. It also had no vacuum advance, and seemed to like timing right across the board, but i never knew what the timing actually was. The new motor (for now) is just timed to it starts and idles nice (now retarded from where it was when broken in), and my freind said it made a VERY NOTICEABLE drop in torque. We'ill figure out what kind of advance it wants to idle in a couple weeks, and then build the curve from there. Ill be sure to check out that other site. Were dying to open this thing up, and see what it can do, but we have to be gentle. The engine and trans are brand spankin new, barely broken in, and my freind has to behave for about 600 miles to break in the fancy mcleod clutch. :spank:
I'll second that. We're just finishing up my 400 for my L69 car (again). Plan to start around there. Wish I could afford a dyno run to see what it does and optimize it.
Why 16 initial? That seems a little low.... My freind said that when he took it to the shop to have his floor patched after the 4 spd swap, they put a timing light to it. It was advanced around 30 degrees (definately too high, didnt like to start and idle), and it was backed off to around 20. Starts fine now, idles about the same, but seems down on power.
Hi Dave; Read through the PM. I was just under the impression that big cams like just over 20* initial timing (ofcourse ive only really worked ALOT with chevs before). Ive always loved buick and olds, but really starting to get into the building part now. This is the reason i was suggesting recurving the dist. because i know theres another 20 or so degrees of centrifugal advance to go. But no worries, ill take your word for it. In response to the measurements being off, i beleive the distributor is a new (stock type) replacement. The timing mark was checked to be correct by positioning #1 with valve position, and then cranking with the timing light. Its correct. The harmonic balancer (im pretty sure) is also new. The entire engine was rebuilt, and we'll be the first to put some miles on it. Dont have a dial back light yet $$$.... Going to invest in one soon. For now, just working with timing tape. Ill try the recommended numbers you guys posted, and by the looks of it, i guess that means no recurving either.
You can run 20 or more degrees of initial, but it is the total amount of timing that really matters. The vacuum advance comes into play as it adds timing at part throttle. So if you have 20 at the balancer, the vacuum advance could add another 10- 30 degrees at cruise. Now you have at least 40 at cruise - a guarantee of detonation. Here is what I suggest as my Olds 455 spent a lot of time on the engine dyno. 1. Olds motors do not like any more than 36 degrees of total mechanical advance (initial plus in distributor) 2. You don't want any more than 10 degrees of vacuum advance at cruise. My 455 liked 16 initial, 10 vacuum, and 20 in the distributor. Any changes to those timing numbers lost power.
Thanks Paul. Thats 3 for 3 with 16initial, and 36 total. Will dial it in at that. No vacuum advance for this car. Maybe way down the road if he gets worried about gas mileage.... But with an 850 Mighty Demon, and a high flow fuel pump, i doubt it.
Got it close to that number as possible without having the luxury of a lasermarked harmonic balancer. The shop used tape and measured around, dialed it in at 34* total, which sits right around 14* initial. When we start playing with springs to bring it all in as quick as the engine likes, ill adjust it to 16* and 36* total. The engine is quite torquey, my freind is trying to get used to it. Even though his old hopped up 350 could roast the tires at 2000 rpm, this engine is just something else. On the way home from the car show for example, i was listening to him shift from a start. Slow start, 1-2, 2-3, 3-4, then he got on it a little, and the car accelerated to about 50 instantly, all the while spinning the tires and kicking up a bit of smoke. I talked to him later, and said it sounded real good when he got on it in 4th. He told me he didnt get on it, he wasnt using the gas for the 1st 3 shifts, and just touched the gas for 4th. :shock: Im guessing that will change a bit when the clutch is broken in, but im thoroughly impressed. Thanks for the help. Onto the NEXT issue..... random backfire?
