Thread: SBC350 - Timing - Am I going mad?!?!

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Dear All

Just finished rebuilding a SBC350, thought I had set valves etc. correctly during build and had also determined TDC (metal plate accross short block method), matched timing marks on damper and timing cover.

Anyway, just about to 1st fire.... I primed the engine with oil and rotated the crank to TDC #1 to set the dizzy. OK fine, then I checked to make sure that valves on #6 were rocking (this is how you check your timing is not 180 degrees out?). They were not.

Really confused. I was sure that the timing was OK but #6 definately not rocking at #TDC. Pull the timing cover off etc. Checked the timing gear. Harmonic damper at TDC (as noted checked) so the crank is at the right position. The cam timing gear has the (only) timing mark directly at the bottom (i.e. at TDC) opposite the crank timing gear so everything should be OK?!

The cam timing gear is the type with a single location hole that accepts the cam shaft pin so this can only go on in one position. The crank gear has three possible grooves for the crank key but I am sure the crank it at TDC as it was checked during the build.

Other info:-
- 1992 BTI engine (converted to performer induction)
- Performar cam (street)
- New hydraulic lifters
- Original timing cover and damper

Also, the valves were rocking fine but when I primed the engine with oil they stopped rocking (any idea why?).

The engine rotates fine (always has) so the valves have not hit the pistons so this would indicate the timing is OK and I have got compression.

I have now taken the rocker arms off and I am looking at pushrod movement but #6 valves are moving but still not at TDC#1.

I have been puzzling over this for 3 days now and I am sure I am missing something obvious so any help you guys can give me would be really appreciated!!!! I am really staring to lose my mind over this!

Thanks


John

I will attempt to explain the installation for you as simply as I can with words.

The three position crank sprocket should have the markings of a triangle, a circle, and a rectangle all next to a separate keyway. The standard position would be to install the sprocket on the crank with the "Circle" in the 12 o'clock position when looking from the front of the engine. The crank key will be located at about the 2 o'clock position. The cam sprocket is then installed with the "dot" located in the 6 o'clock position. The locating pin on the cam will be at about 3 o'clock. Now rotate the asssembly (timing chain installed on the sprockets) until the cam sprocket "dot" is at the 12 o'clock position and the crank sprocket "Circle" is also at the 12 o'clock position. The #1 piston is now at TDC on the firing stroke and this is where the distributor can now be installed. Both rockers for the #1 cylinder will be slightly loose and both valves will be closed.

If you install the distributor with the crank "Circle" in the 12 o'clock position and the cam "dot" in the 6 o'clock position this would be for the #6 cylinder to be at TDC on the firing stroke.

Be sure that the three position crank sprocket is installed with the crank in the correct location. Crank key at 2 o'clock (#1 piston at TDC) or the cam will be 120 degrees out and you will bend pushrods and will not get the engine to fire. I've seen this happen before when the three position crank sprocket was installed incorrectly.