just fired off my new 489 stroker tonight. started and runs like a champ. after the break in period we try to set the time and discover the timing is still coming in after 4000 rpms (vacum disconnected). then the timing is going up and down during idling and it won't stay still long enough to get a good reading. we are using a dial back timing light with a tach. the timing gun is reading about 300 to 400 rpm higher than my mechanicail tach. the cap and rotor and points are new. dwell set on 30. think the mechanicail springs are too weak and causing the timing to bounce? but the timing should be in way before 4000 rpm's? thinking of going petronix or ebay mechanical tach drive hei unless i can fix it. also, when i move the distrubitor a small amount it makes a hughed difference in the timing, way more than it should.
thanks,
gerald

 

it depends on if you are a gotta have a numbers matching car person or a as long as its running person.

 

Numbers matching keep it. If you don't care put it aside and get a new one. You will spend more rebuilding and setting this one up than if you bought a new one. I ditched the tach drive years ago and converted mine to and electronic tach. Much smoother tach action and your choice if distributers is much better.

 

I've got a dumb question. Where are you pointing the gun to get a reading? And where is your timing tab located. On my dads 71 454 w/ AC there is nowhere to fit a gun unless you're under the car. Any pics of your timing tab and line of sight?

 

Keep it, fix it & run it. Yes I know about the cheap TDHEI. Take a good look at your EndPlay ... bet it's way too much ... shaft moving up & down too much ... as it does, the helical gears cause twist ... & timing variation. Shim the endplay & ensure the mech advance is moving freely, No rust /binding. Check your SidePlay too, worn bushings. Sounds as though your tachdrive works OK so it won't cost much to freshen yours. There's papers available from Lars & BarryK that'll walk you thru whatever you need to do.

-add- another Very common cause of a bouncing timing mark is a failed harmonic damper/balancer. The rubber gets old / oiled & the outer inertia ring (has the timing mark) slipps in relation to the hub that's keyed to crank. Check that FIRST.

 

Yes, the above, but if you want it rebuilt....PM me for the email of a friend who can do that for you, fairly and cheep....

 

I got about 50/50 mix on opinions about the cheap ebay tach drive. Some said it was junk and some said no problems. I could not resist a 69 buck solution to all my points dist problems and aggravations so I took the chance. The engine is not in the car but set up on a stand to run complete with pumps, pulleys, belts, hoses, radiator, trans. I visually checked the new dist for all the defect and poor quality issues mentioned in here from other users and I could not find the same conditions on it at all. I put it in and after having it back out a couple times trying to get my cable gear pointing the right direction, it started right up and run better than it ever has in a year. I have had many ignition and carb problems since I got it running, now with a new holley and a new HEI all the problems seem to be gone. I dont know about ALL the cheapies out there but this brand seems to be fine so far and I'm glad I went this way. I only have about a dozen starts and maybe 45 minutes run time so who knows, but so far so good..

http://cgi.ebay.com/ebaymotors/SBC-C...Q5fAccessories

ps. only downside, I see no way yet to make the chrome cover and brackets work with the bigger cap at all but I only took a glance at it to see it wont work the way it is.

 

thanks for the replies. it will still be a number's matching car if i put it on the shelf and keep it, so i had rather have a nice running usable car. like i said i just broke the motor in last night. this thing idles perfect. even down to 650 rpm's it has a very strong idle. it is so responsive, feels quicker than my 327 tune port camaro. i haven't driven it yet but ii believe that sean micheals carb is right on the mark. thanks smi !! anyway, it is a new balancer that came with the balanced stroker kit so it is unlikely to be bad already but not impossible for sure. i have a very small window to view the timing tab.(actuall sit it on the radiator hose in front of the altinator) my timing gun has the roll back option so i can keep it on zero even when it;s at 34 degrees. i don;t think i could set the timing without out it, just not a large enough window to view the timing tabs. if you don;t have one like this you need to invest in one, plus it shows the rpm's so you can tell when all your advance is in. like mine, 4000 rpms before it all came in. i have open headers on it now so it is hard to listen to the motor when setting the time, but it is running so strong, never tries to die or anything, just weird on the timing all over the place. my friend has a hei that i might try today just to double check everything else.

 

if your standing in front of the car it will be in the 1 or 2 o'clock postion by the altinator. i actually rest the gun on the upper radiator hose. now my car has the eckler's tilt frontend but i would think a stock fender car would have enough room. if you can see the tab then you just need a roll back timing light. if your intial timing is 20 degrees, then you would retard the timing light by 20 degrees and you would be looking at the 0 degree mark. (which would actually 20 degrees). basically you just keep the timing mark and the 0 mark lined up and the timing gun does all the work. that way you can work in a small viewing area without loosing the timing mark. sorry i could not explain it better

 

Check end play. most distributors I worked on had excessive end play.It simple remove roll pin note the direction the gear is in relation to rotor.Dot faces driection of rotor. You should have about .015 end play. Hope this helps

 

PIA! Made worse with bad eyes! My engine is not even in the car and its still hard to see past the pulleys/tensioner ect.. but it can be seen, straight down a little to the driver side, theres one exact spot you can see all 6 points on the timimg tab. Yes I agree that a light with a dial is way better, first time I used one, with that and the Timing Sticky info its been fun to play with instead of a frustration.

 

i'll check it thanks

 

did you have any clearance issues with the firewall with that big ebay dizzy? i have a big block. not to worried about the ignition shield cover. might order one of those dizzies. they look nice, wish the cap was black instead of red.

 

When I was doing my project(identical to yours) I was also researching distributors. I was going to go with the Summit HEI tach drive....well when talking to the builder about it he was dead against me running one....He said to either run an actual GM HEI(non tach drive), rebuild the factory points distributor from my SB(but this was NOT his preference) or go with the whole MSD setup with the tach drive. As much as I hated to, I went with the whole MSD setup(Pro Billet tach drive dist, 6AL box, Blaster II coil, 8.5mm wires)....SO I did all that and I am happy with how it all came out and how simple it was to wire up. Not to mention this is all top quality stuff and should be very reliable and perform top notch all the time. Unfortunately a month into it, my tach quit working due to an issue with the cable and adapter thing the Pro-billet dist. requires. I still haven't figured it out....Luckily I have a shift light with a digital tach built into it.

Point being is....I could have saved a lot of money by running the Summit HEI and probably still have a working tach, not to mention no coil to mount etc.....The downside is it doesn't have a rev limiter, doesn't look as stock and can't run the ignition shielding...if thats not a big deal to you and you are tight on funds, I would probably roll the dice on the chinese HEI.

Pay attention to what type of distributor drive gear the cam has and make sure its compatible with the dist. I know the MSD comes with the correct gear for a billet roller.

 

i went with a solid flat tappet cam so the regular old gear will work for me. i hate to here you had all those problems especially after doing everything highend like that. if my little 70 dollar ebay hei goes out i will be expecting it, but if i had spent what you did i would be pissed. that sounds like my luck. the motor sounds so strong and is more responsive than my 327 tune port camaro. cain't wait to get the 3" exhaust and new hei in it. my car is an auto so the rev limiter is not that big a deal (i hope the ebay dizzy will work with a msd box for later on).

 

i don't see a vacum adv on the ebay dizzy. is that right? or is it just not in the picture. the one 71coup454 listed above.

 

I wont know if it fits till I get the engine in the car but I found some pics on here of HEI caps and it looks close. All the parts in my new dist are regular GM tune up parts available anywhere. Late 70's, early 80's style I think? Standard Ignition has caps in black, I may replace mine with a black one but I was hoping to cover it with the chrome shield.

 

the one io saw on ebay did not look like it had vac adv. on it

 

HEI fits w/ chrome box-lid & brackets for 75-77.

msd probillet td uses a cable adapter w/ a "tang" on it ... to mate w/ vette's .104" square-end cable. The tang widget is a separate piece & should've come w/ the new msd dist.

double check timing w/ light WITHOUT rollback/dialback ... dialback circuits have been known to drift/wander.

scribe aligned index marks on hub & ring ... to check for slippage.

 

yep its on there, came all complete, hook a wire to batt term and go