camshaft changes with increased cylinder head flow

Have made a change in cylinder heads on our engine combo to a better flowing cylinder head, on the dyno without changing anything but the heads we did not increase power much, we did show a drop in manifold pressure though. I have a feeling with the increase flow we may be loosing it out the exhaust valve before we have taken advantage of the increased flow. I was thinking of possibly increasing lobe separation, taking some duration away from the exhaust lobe or just delaying the opening point of the exhaust valve, any thoughts or suggestions would be greatly appreciated.

 

We did start out fat to be safe and then leaned the motor by plug readings, i do understand that a loss in intake pressure is do to the increased flow of the cylinder heads, i just felt that we might be leaving something on the table and that perhaps a cam profile change could take more advantage of the better flowing heads

 

No Cam expert but what is your lobe sep deg right now?

 

117 lobe sep.

 

We once destroyed a cam and put a new one in with bigger lobe separation. Didn't really notice major changes in power, but we burnt 3 pistons before we had the fuel setup on the safe side again. On our setup we needed LOTS more fuel and lobe separation was changed by maybe 5 deg which didn't seem like a lot. EGT's went down by 90F in the end, but plugs still showed enough heat.
I'm no expert, but I'm guessing the smaller lobe separation with higher overlap on the old cam allowed for more fresh mixture to flow through. You can consider it a loss, but the fresh charge does cool components, which in our case was a more forgiving setup.
So in case you try, make sure you start with more than enough fuel.

 

thanks for your input, i will keep it in mind when we get back on the dyno

 

You have a 117 LS and you are going to go more? Apparantly I don't know my hemi camshafts, are these normal LS #'s for a hemi?

 

Thank You I didn't want to be the first person to ask that. I have a cam on a 116LSA (chevy) and thats huge. When I saw 117deg, I just figured I'd keep my mouth shut!

Corey

 

no worries, if it gets that secret can always private message lol, i have seen lobe seps all the way up to 119, 120

 

i think as with any engine its a combination of parts that makes the engine preform to its potential , we have a cylinder head that flows more air now and i have a feeling were losing some of that flow out the exhaust port before we get a chance to use it to make a little more power, im no engine guru just trying to make our combination the best it can be

 

Asymetrical lobes have changed the lobe seperations somewhat.

 

What would be the benefit of something like this? Later valve events and decreased overlap? Bet they idle real nice.