1968 Camaro "Badmotorfinger" v2.2

[skatinjay27]

Originally Posted by coolwelder62

I think I saw them using the very style motor in the new Fast
5 movie.

naw that thing was used in american graffiti

[sixnina]

Good info Dave, keep it coming. That motor will be done in no time and then you'll be joining richie for some late nights on bmf!

Shane

[Chad-1stGen]

Originally Posted by Flash68

Had a great hour with Mike B the shop today. Man I learn a ton there.

We talked cams in detail and he is a big believe in these oversized base circle cams, either 50 or 55mm for SBC. He showed me a shelf Comp Cams Mopar cam with standard base circle next to one he designed and had cut with a monster base circle (don't know Mopar sizes) but the difference was staggering. And what he said that was really staggering was the larger one made 60 more hp on the dyno. No other changes. Same cam specs.

I don't get this? How does changing the base but not changing the cam specs gain 60 hp? Was he saying that just having the large roller bearing surface frees up that much HP? Any engine experts able to explain this?

[Flash68]

Originally Posted by Chad-1stGen

I don't get this? How does changing the base but not changing the cam specs gain 60 hp? Was he saying that just having the large roller bearing surface frees up that much HP? Any engine experts able to explain this?

There was greater detail in the convo, but remember it's hard for me to keep up with Mike all day.

Something about there's more to it than that (because I asked the same question as you). Something about the lobe shapes and the events happening at an extra 6 or 8 degrees of duration? Something like that? I probably regurgitated it all wrong.

Any smarty pants engine guys care to join in?

The motor in question was a super stocker he built. He does a lot of those.

[intocarss]

Originally Posted by Chad-1stGen

I don't get this? How does changing the base but not changing the cam specs gain 60 hp? Was he saying that just having the large roller bearing surface frees up that much HP? Any engine experts able to explain this?

WIth the 50-55mm cams, the bigger base circle and bigger rollers on the bigger lifters make a wider radius and smoother contact on the lifter, it is also supported better with the nasty pressure angles that are going on.. Simply it's a smoother transition,, So YES it frees up power so to say....plus the 50-55mm cam has a much stiffer core so cam timing stays better front to rear due to less twist on the cam. I'm no cam expert so I hope this makes sense cuz I suck at explanations




I remembered Dave wasn't able to get a pic
So here is a eather a 50 or 55mm SBC cam (not sure which I just grabbed it off the shelf for a pic)



And here is a I believe a regular SBC cam or could be a BBC (again I just grabbed it real quick for a pic) BUT YOU'LL GET THE IDEA



THE MOUSE THAT ROARED,,,THE RATS THAT CRY

[Flash68]

Thanks Jerry. That does sound much like what Mike was talking about.

[FETorino]

Originally Posted by Chad-1stGen

I don't get this? How does changing the base but not changing the cam specs gain 60 hp? Was he saying that just having the large roller bearing surface frees up that much HP? Any engine experts able to explain this?

For the same reason not all cams with advertised duration of say 290 deg are the same. The ramps are very different and hence the actual timing events. That's why a starting point for cam comparisons is to use the measurements of duration at .050 of lift.

Mopars used to have an advantage in the flat tappet cam world because of their larger base circle cams.

Roller lifters allow for more extreme timing events and a larger base circle allows you to have even more aggressive ramps without the lifter binding. Optimizing the opening events is what cam timing is all about and the larger base circle gives you the ability to do so. Cam lobes get closer to square. Open to full lift quicker and close from full lift quicker.

[Sieg]

Originally Posted by Flash68

Any smarty pants engine guys care to join in?

Originally Posted by FETorino

For the same reason not all cams with advertised duration of say 290 deg are the same. The ramps are very different and hence the actual timing events. That's why a starting point for cam comparisons is to use the measurements of duration at .050 of lift.

Mopars used to have an advantage in the flat tappet cam world because of their larger base circle cams.

Roller lifters allow for more extreme timing events and a larger base circle allows you to have even more aggressive ramps without the lifter binding. Optimizing the opening events is what cam timing is all about and the larger base circle gives you the ability to do so. Cam lobes get closer to square. Open to full lift quicker and close from full lift quicker.

Pretty smarty pants for a Ford guy IMHO.

[Vegas69]

This is real race car stuff. How agressive can you get with that opening ramp. To put it in Laymans terms, how fast can you get the valve near max lift and keep it there during duration? Just like many other things in this hobby, it's a snowball effect.

[DFRESH]

And keep the valve train stable with those aggressive ramp profiles. I think Mr. Moderator is using shaft rockers--correct? This new motor is going to be sick. D, will you leave the exhaust the same? Side output?

D