BBC timing gear alignment?

[mobythevan]

when I tore down my BBC last year it has a copper or brass thrust bushing behind the cam gear, about .030" thick. The machine shop said it must have come with the last timing set that was installed. So I put on my new timing set today and was curious to pay attention in this area. I notice that if I spin the engine over a few times and let the cam float to where it naturally wants to be (no lifters installed) the cam gear and cam moves forward a tiny bit. I can just push it back in until it bottoms on the front of the block, you can see that this mis-aligns the timing chain a tiny bit. I would have never even looked at this if the thrust washer/bushing wasn't there when I tore it apart. Is that anything to be worried about? The machine shop measured the surface that the cam gear touches and says it is factory.

[dr_hunt]

when I tore down my BBC last year it has a copper or brass thrust bushing behind the cam gear, about .030" thick. The machine shop said it must have come with the last timing set that was installed. So I put on my new timing set today and was curious to pay attention in this area. I notice that if I spin the engine over a few times and let the cam float to where it naturally wants to be (no lifters installed) the cam gear and cam moves forward a tiny bit. I can just push it back in until it bottoms on the front of the block, you can see that this mis-aligns the timing chain a tiny bit. I would have never even looked at this if the thrust washer/bushing wasn't there when I tore it apart. Is that anything to be worried about? The machine shop measured the surface that the cam gear touches and says it is factory.

 

Is it on an engine stand? If so that's leaning forward so the cam will walk out when you rotate it.

 

Under running conditions when the engine is steady state or accelerating the distributor and oil pump drag pulls the cam to the back of the engine. When decelerating the cam will move forward, changing timing slightly. No biggie, run a thrust button if your really worried about it. The rear thrust is necessary to keep it from wiping out the front of the block.

[mobythevan]

I went ahead and buttoned it up. I ordered the last parts I need to test fire the engine on a stand. If they all make it in by this weekend it should be running. Can't wait to see how the supercharger works.

[Pyro]

If you are using flat tappet lifters (hyd or solid), then the lifters will be pushing the cam towards the rear of the engine. There is a slight taper on the lifter faces that force the cam back.

 

If you plan on using a roller cam then you will need to use a thick walled timing chain cover along with a thrust button and a roller bearing at the block timing chain interface. And the proper cam back lash must be set with the timing chain cover and the thrust button.

 

Please use diesel engine oil in your engine. BBC are very sensitive to cam lobe damage. I have built many BBC's and have learned the hard way.

[dr_hunt]

The supercharger won't work, take it off and give it to me. I'll use it for a paperweight.

[mobythevan]

Please use diesel engine oil in your engine.

 

will do, I have heard that so figured it is easy for the break in.

 

The supercharger won't work, take it off and give it to me. I'll use it for a paperweight.

 

I was afraid of that, but it looks really good on there.

 

After working with turbos for the last three years I wanted to try a SC. It just seemed like the best of all worlds for a street rod/fun car. It does pain me sometimes to know how much more efficient a turbo could be, but I'll get over it. And since my friend is doing turbos on his SBC will we have a neat comparison between the two rods, one with twin turbo SBC and the other with supercharged BBC.