Hello,
Just bought my dream car a couple months back...little fingers have been at work on the engine...it packs dual Edelbrock 1404's, and....according to papers that came with it, it's got a performance cam in it, but no info what it is. It is a dog off the line..with that much fuel going down it's throat (500cfm X2), I'd expect to be buying new rear tires soon...nope. I suspected timing...put the light on it @ 700 rpm (auto, in gear) and the mark is way above the timing marks, like maybe 30 btdc! Sticker sez should be 8 deg. BTDC @ 800 rpm. I made sure the wires weren't mixed up, it's an HEI ignition..ahem..not stock...
The car is in excellent shape, but would like to have at least a little PUNCH off the line..now it's just a "go to breakfast car", with a healthy fuel appetite (10 MPG).
Anyone have any ideas??
Thanks..Bill

 

disconnect your vacuum advance to check timing. HEI is stock in 76, I know it "says" to use 8btdc, mine runs the best at 16btdc. using the stock 8btdc will be very good for exhaust emissions, but will suck for power. disconnect the vacuum advance and then post those numbers.

 

Well...I guess I was a bit TOO vague...that was with the vacuum off and plugged....as I said the car runs fairly well to just "slow ride" around, but nothing off the line. Let me explain where this timing mark is when I put the light on it...you know where the timing marks are over the harm. balancer....this mark is barely visible near the top of the wheel, as I said closer to 30 deg....I brought it down to around 16, and the next morning it wouldn't start, so put it back where it was and it fired right over....me thinks I bought a problem....I've worked on Chevy's back in those days (70's) when I was much younger...and this one has me wondering...I've thought maybe I should bring #1 to tdc and place a mark on the wheel, but not really sure what I should do next...any help is appreciated....

 

Oh yes, additionally, this engine is running The D.U.I. (Davis Unified Ignition) HEI distributor....just in case it is helping to make my problem (advance-wise, I mean)....
Thanks..

 

i had a similar problem on my 75. i found out that the balancer had slipped so i couldn't use the timming light. me and my dad just set it were it ran good, took it for a test drive and then adjusted it more if it needed.

 

yeah, I think the harmonic balancer has slipped, there isn't a SBC out there that won't start at 16* BTDC initial timing - (I know, I don't want to hear about your cam'd up, blown stroked etc engine that won't )

 

Sorry to jump in your thread, but where should the timing be set at on a mostly stock 350 SB (76 vette)? I have an Edelbrock Performer carb with an aluminum intake, big valves on stock heads, and a comp cam, 262 int./268 exh, 0.446 int./0.459 exh. Thanks.

 

my mostly stock 350 gained MUCHO power feel by going from 8*BTDC to 16*BTDC, + my 20* mech advance all in by 3000 rpm for a total of the magic number = 36* BTDC at 3000 rpm.

THese were only "retarded" in their timing to increase temperatures to burn off exhaust emissions as part of the mid-70's polution equipment. Remember, a stock L82 vette in 76 was supposed to have timing at 12*.

 

OK...I appreciate all that have replied....but, I must admit, Ruby76, that the timing "appears" to be at the "magic" number, or very near, but how does a person verify that it is on the mark...after all, the timing mark is way up there using the light...almost under the water pump...but as I said, the engine runs fair where it is. Is there a measuring procedure to gauge how far away from TDC the mark actually is (in degrees) or in this case, should be? I guess I am a newbie with this stuff...I just remember after high school working at the Mobil..if ya put a light on an engine, and the book said 8 deg,, ya set the timing at 8 deg....this "magic" number definately has my head spining
Maybe ya can get down to newbie level for me...thanks
Bill

 

okay, I think I see what might be happening. I think what you are describing is what I saw on my 68 chevy truck when I pieced together a 350 smallblock into it. What it ended up being was he wrong harmonic balancer. chevy had two, 1 with the timing line straight up and down (at noon) and the other with the timing line at about 1 or 2 o-clock. If you have the harmonic balancer with the line straight up and down, you'll never be able to correcly time it using a light. Dad and I always would rev her up to about 2 grand, then adjust the timing to the left till it started to stumble, then to the right till it stumbled, then place it right in the middle of the two. A good shade-tree "ballpark" setting. - probably somewhere between 16* and 8*.

For getting "degrees" marked on your flywheel there are two ways to do it. either get a degree tape from the local auto parts store, or you can measure he circumference of he HB, then divide it by 10, make a mark every 10th around he balancer and you've got i marked a every 36*, half of that is 18*, half of that is 9* etc. Will get you a good estimate.

 

Hmmmm....you're gonna wish ya never answered me....
?straight up and down?.....?1 or 2?
The line is on the side of the HB, like most engines, horizontally...ahhhh, are you meaning where the mark should be at TDC? At top of wheel as opposed to 1 or 2 o'clock at TDC?
Help.....

 

I mean, I think it was pre-69 or something, that small block HB's had the TDC timing mark straight up and down, at 12o'clock so to speak. Later HB's for chevy's had the line further down on the driver's side, about 1 or 2o'clock so to speak. My 68 chevy truck had a 76 engine in it, but for some reason we put a 68 HB from a small block. The timing line NEVEr lined up right so that is why we did the timing process I mentioned above.

I guess you could remove plug # 1, then find true TDC and see where the timing mark lines up and whether or not the HB has slipped or is the one like I described above.

 

Thanks for all your help....I just advanced the timing until it started to stumble then came back a bit and it seems to have more spunk then it used to...or maybe it's hopeful thinking...
My son will be coming in tomorrow for some hometown vacation (he works in Vegas) and we will mess with it some more...it's definately had little fingers messin' with it, one way or another, but I'll get it figured out..Thanks again, Ruby76!!!

 

I sent an email to Lars and this is what he said:

"If working with a non-adjustable timing light, you have to place a 36-degree line on your harmonic balancer, since the stock timing plate does not go beyond 12 degrees-or-so.

To do this, you can either procure and install a timing tape (available from any of the speed equipment retailers) of the right size for your balancer, or you can determine your own 36-degree mark.

To determine the 36-degree point, measure the circumference of your balancer using a flexible tape measure, such as a sewing tape. Take the circumference number measured and divide by 10. The result of this arithmetic is the dstance from your stock timing line on your balancer to the 36-degree point. Measure this distance clockwise from the stock balancer timing line as viewed from the front of the engine and place a mark on the balancer. In most cases, this new line will be between 2" and 3" clockwise from your stock line.

To correctly time the engine, pull the hose off your vacuum advance control unit. Using your timing light and observing the new timing mark, rev the engine until the centrifugal advance does not advance any further. This will be above 3500 rpm in most cases. Once the advance pegs out and does not go any further, you have hit total advance. At this point, the new line on your balancer should be aligned with the "0" point on your timing tab. Rotate the distributor until you achieve this spec. Once done, snug down the distributor and hook up your vacuum hose.

You know the centrifugal advance has stopped when you don't see any further movement of the timing mark using the timing light. When the advance is still advancing, the line will smoothly move counter clockwise as seen from the front of the engine as you rev the engine.

Lars"

I followed these simple directions and my vette is running a lot better. For my 8" HB, the distance was 2.51".

Thanks Lars.

 

Hey Buzzardz,
Don't know who Lars is, but if ya talk to him, tell him.."THANK YOU!" from me!!!
My son and I worked the timing according to his directions and it's a different car..COMPLETELY! More punch off the line and runs much better mid and top range...she purrrrrrrrs!!
But I also want to give many thanks to all you guys that helped with advise...you guys are great!!!
I'll be hangin' on this forum for sure...THANKS!!

 

The previous owner put one of those advance kits in it. I wouldn't be suprised if it liked atleast 20deg int. advance.

 

Glad to hear it worked for you. My vette is running great as well.

Lars is probably the most knowledgable person on the Forum when it comes to tuning a vette. Do a search on "tuning for beers" and you'll get lots of info about Lars.