just picked up a 70 nova last week with a 327, someone put a lot of time and money into but the kid i bought it off of tweeked something and im at loss right now, im "assuming" i have a timing issue, it was straight piped and backfiring all over the place when i bought, i thru flow masters on it and that helped a bit, but once i hit about 3500 rpms it gets bad on acceleration and deceleration. theres a new edelbrock carb on it and a HEI distributor as well. last night i timed it AGAIN, warmed it up, plugged the dist vacuum line and set it 3 degrees past BTDC, a mile down the road it got bad again, so i checked the timing on the roadside and it was about 4 to 5 inches past TDC, so far that no adjustment to the distributor would bring it back down to the timing marker. what would cause this? possibly the distributor not aligned right? major vacuum leak once its fully warmed up? even if the TDC mark on the balancer isnt right how would it get so far gone once driven? any help would be amazing!
The balancer is shot. Not uncommon. You need a new balancer, not necessarily a real high dollar one but not an el cheapo either unless you want this problem again.
Sounds like the distributor is moving. Make sure you have the clamp on right that holds the dizzy down.
Set it at 12*. Test it. If it does the same thing first grab the dizzy and see if it moves. The timing will retard if it's loose causing the backfiring.
take it off and look at it. of its loose at all then its shot. you can also line your number one cylinder at tdc and your timing mark should show zero on the balancer, if it doesn't its shot.
sounds good, ill give it shot this evening, hopefully the ill be able to get it back to 12*, sounds like i could even just mark the dist and the intake or something else with one line and that would tell me if its moved at during driving.
If it turns out your distributor isn't moving and you suspect your balancer is moving or has slipped then get it changed out real soon. If the balancer blows apart you could have a big wreck on your hands.
good point on the suspect balancer, if the balancer is loose will it be noticable still on the engine? like grabbing a hub on a loose wheel bearing? or will it need to come off to see if its bad? but wether i can get it to 12 or even 3 for that matter and tightened it up and found movement on it that would be most likely be the answer wouldnt it? or am i wrong?
Also verify that you have the right timing pointer. Older vehicles used a tab (or tube) on the timing cover that pointed straight up, but newer vehicles (early 70's and up) used a tab at the 2 o'clock position. The balancer and pointer need to match. You can also get an adjustable tab that bolts on to the timing cover bolts if the old one is way off.
i went old school, pulled plug #1 rolled a paper towel like a cigar and put in the cylinder, then bumped it till it launched out on the compresssion stroke which should be TDC, after crawling under the car i found the mark on the balancer at a dead 6 o'clock when then timing plate is at 2'oclock. looks like balancer is shot.
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