Ok Here we go………..

4 Years ago or so I built a 383 9.3:1 to put in my camaro. I put a CraneCam Energizer cam and lifters 228/228 @.050 .480 lift. I was using my stock 882 heads with z28 springs with CraneCams Roller Tip Rockers. It always had a vibration at about 2500 and then about 3500 up. I changed intake gaskets thinking it was a vacuum leak (Did that 3 times!) Changed carbs 2 times and checked my distributor and cap (Changed cap 3 times) Changed wires 2 times and still had that vibration so I was thinking maybe the harmonic balancer was bad. Well I am thinking if it was the harmonic balancer that was bad the main bearings should be about dead by now 15,000 miles on it now. I also put 2 new poly tranny mounts in. So I was thinking maybe it was the Flywheel because I had a t-5 up till last year. I put a 700r4 in late last year and put a new flexplate in and it was still there. I’ve put in 2 new converters (Midwest 3000stall L/U). Well this year I finally got rid of the stock heads and got me some sportsman II heads (I’m at 10.3:1 now). When I pulled the drivers head I found that I had a blown head gasket between 3 + 5 cylinders thinking well there is the problem right there!! I was happy….lol so I put the new heads on with new gaskets new pushrods and all. I turned the engine over till I had #1 at top dead and lined the balancer up with 0 on the timing mark. After I got the valve lash set I put it back at #1 TDC and set it at 4deg before TDC to get it in the ball park for a good startup with the new heads. I put the distributor in and lined it up with the #1 plug dead on. Put a MSD 6AL box in with new MSD wires. Got everything ready to go went to start is and it did not want to go….. it puffed out the carb?!......I’m thinking well what in the @#$#. So I gave the distributor a turn and it fired right up sluggish but it fired. Put the timing light on it and got the base set at 8deg BTDC.



Now for the questions…..lol…….

I feel that is should have fired right up with it set at 4deg BTDC But it did not. Do you think maybe my roller timing chain jumped or maybe I put it in wrong when I built the engine? And the cam is off timing? I really want to get some ideas here before I tear back into this engine.

Also when I was using the stock 882 heads I was also using the CraneCams Roller Tip Rockers with out guide plates!! I did not even think of that when I put that engine together 4 years ago…….. So the rockers were not lined up right for 4 years…..Could I have flattened a cam lobe??

I am using an edelbrock 750 carb with stock out of the box jetting and my gas mileage is terrible! I get 150 miles out of a tank of gas!!!! No matter how I drive it.( I rebuilt the carb this spring also to rule that out.) And at $2.07 that’s not good! I think the gas mileage has to do with the missing/Vibration because I should be getting better then that! The plugs look golden brown so that’s a go............


Sorry for the long post but I need to get this worked out so I can be happy again!........

 

Any help here would be great

 

What balancer are you using?

it takes quite a bit to flatten a cam lobe. I dont think that just the rockers being off would do it. Besides, if its hydraulic, i think you would collapse a lifter before grinding a cam lobe. And by the engine running, you would hear/feel a distinct noise. Doesnt sound like thats the issue. Sounds more like a timing issue.

 

Using a stock 400 balancer. I was thinking timing more then lobe but just trying to cover all bases. You think it might be cam timing maybe jumped a cog? Because it should have fired right up set at 4deg BTDC........And it just would not run!

 

Also it don't matter if it in in gear or not still have the vibration Just not as noticable when it is not under a load. Maybe the dist. is bad Coil,Pick up???????????.............

 

Come to think of it when I put this engine in I changed the cam 2 times and I used the front crank pulley to jack up the engine till I could put some wood blocks in between the motor mounts both times........If the crank pulley was bent a bit could that make allot of rapid vibration????

 

Something to think about.......

With an externally balanced 383 doesn't the harmonic balancer AND the flywheel have to be counterweighted to balance the engine?

IE; 400 balancer and 400 flywheel?

 

Yes, I am using a stock 400 balancer and a 305 flexplate with a counterweight that bolts between the flexplate and the crank…..

I just went out to look around and see if I could see anything different with the crank pulley or anything else and I think I may have found something…….The motor mounts! The right side (Pass.) Is lower then the left side (drivers) now if I am thinking right when the motor torques the left side goes up and the right side would go down right? If so then I think my right side motor mount is bottomed out.

Here are some picks I took…..

Right side (Pass.)


What do you guys think?? Motor mounts bad?

 

Left side (Drivers side)

 

 

sounds like an engine balancing issue to me I had the same problem after rebuilding an engine cause I didnt have it balanced before assembly