Originally Posted by charcoal03silvy

I have the knock sensors desensitized according to the "Tuning the right way" pdf. Its a 4.8 with bolt ons, converter, 4.56's anda 226/229 cam and some BR6EF plugs. It pulls past 6800 rpm easy but its on a stock timing chain and owner is afraid to push past it. Don't have easy access to a dyno unfortunately. I do have the virtualdyno software and know it can be pretty useful for seeing gains/losses but not necessarily accurate at a real HP number. Haven't tried it out though.

Just trying to get some different opinions.

Originally Posted by smokeshow

Stock compression on 4.8s is relatively low...so that's likely where you're getting your '4.8s like a lot of timing' information. As for there being a particular number that all combos like, I would forget about it... Every cam/heads/intake/power adder combo is going to change the MBT values. When someone tells you that LS 'combos' make the best power at 28 degrees of timing...you can just assume they haven't done their homework.

Originally Posted by Rhino79

Whats the intake valve closing point ABDC on the cam card?

Originally Posted by Rhino79

Taking a wild guess that your intake valve closes at roughly 67*abdc and assuming stock compression ratio, your dynamic compression ratio is roughly 7.2. A good target would be around 8-8.5. Even if the heads are milled .025" it still would only be about 7.5 dcr. That setup will definetly have to spin high, and should respond well to very aggressive timing as it will not be very efficient at low-mid engine speeds.

Originally Posted by charcoal03silvy

I know that every setup is different and even two cars with an identical combo are still going to want things a little different. What they mean really is stock/bolton and cam only type setups that generally want about 28* degrees. I knows better heads tend to no need as much timing, as well as more compression needs less timing, etc etc

Wish I had easy access to a dyno where I could make a good number of pulls starting around 27* up to around 35* but I don't.

Originally Posted by smokeshow

A cam generally wanting 28 degrees...thats the thing. Rhino already mentioned it...DCR. A cam is going to change the DCR which changes the MBT. You just gotta figure out whats best for what combination of parts.

Originally Posted by 1dirtybird

**** yo I brought that up way back on post 5. You's a slackin.


Spin that 4.8 with out worrys. If it blows they are cheap as hell on c/l as no one really wants one. The short rod to stroke ratio helps keep the stress down on the pins and rod caps. I'd be more worried about running out of engine managment on the stock pooter.