Quote:
Originally Posted by Cliff R
"Cliff, I may send you a bump stick to try...."
What application?
HIS, if you move the cam to a tighter LSA it will INCREASE overlap and decrease cranking pressure. You might offset this some by advancing it, but I've tried all that stuff and the 455 engines absolutely LOVE the ICL in the 108-110 range and LSA out in the 112-114 range.
Doesn't mean they woln't run OK with tighter LSA and advanced intake positions. Even with that said my past experience with these things has shown that until you get into pretty "big" cams, moving the LSA tighter than 112 degrees doesn't work as well.
For our full "race" stuff, we usually have them on 110LSA's, and .050" numbers 260 @ .050" or greater. Since we're over here in the street section, most of our street engines use 112 LSA, and on occasion will move them out to 114. Lots of variables in the equation and decision making matrix for that deal, we just do what works well based on the testing we've done.
I think I posted this dyno sheet earlier on another thread, but here's what happens when you let the customer supply their own custom ground cam highly recommended for their 455 engine build from another vendor.
We built a 455 like many others we've done using the 290cfm KRE heads from Dave at SD. In this instance the owner supplied the cam, 244/252 on a 110LSA. We usually see around 550hp/600tq with the exact same engine using the Old Faithful cam from Dave at SD. Look at the dyno run below and see how much power we left on the table and the engine quit much earlier in the rpm range..........Cliff
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Doesn't hurt to experiment a little.....that's how we learn. I've found that the tighter LSA stuff can work well with the right combination.
The 244/252 cam against the Old Faithful cam looks to be just a mismatch of appropriate parts. It wasn't the LSA's fault, but possibly could be running out of valve spring, too aggressive of a lobe, or the duration did not match the cylinder heads/intake.
My drag race stuff is almost always at a 107-108 LSA and I have a '73 250 hp 455 Stock Eliminator camshaft that is certainly not a 112 LSA....
Just thought if you had some time to play, we could float some parts back and forth.