Revised engine combo

Skankin · 01-30-2001, 06:47 PM

You'd be better off getting a blower cam.

They typically have more lsa, which is also good for emmissions. (you wanna keep the lobes apart). Here's a handy, generalized rule:

(intake duration@0.05"/2)+(Exh Dur@0.05"/2)-2*LSA = ?

If the number is positive, there's no overlap. The more positive it is, emissions are typically better. A negative number indicates overlap, which is bad (for blowers & emissions).

If the lobes aren't very aggressive (Long advertised durations), the emmissions are gonna be worse than what the general number indicates. Also, if the lobes are asymetrical... forget the formula.

A split duration favouring the exhaust might be a consideration. Are you gonna run 14#?

To make more top end power, and utilize the added displacement, you'll wanna go with a longer duration. Problem is, if you go too long, you either loose cylinder pressure (and power), or you have to shorten the lsa.

Maybe look into a comp cams extreme grind, they've got really agressive lobes... you could really push the "Magic number" down to zero, and be alright.

------------------
'89.5 5L LX, hatch, Medium Canyon Red, 155K Km (No winters), 5sp, 3.08, GT interior, a/c, Alpine CD, K/N, Crane PS91, Walbro 190 LPH, March Pulleys, Mr. Gasket 180 therm (HP balanced), 3 core rad, MarkVIII fan, Variflow controller, Polygraphite front bushings, FMS-5300B springs, 6 KYB's, 73mm Calipers, Maximum Motorsport 4pt chassis brace, Western Motorsport Racing's Sub-frame connectors. Re-ringed bottom end, conv. motor mounts, melling oil pump, FMS-C50 waterpump, GT40P heads (blended, polli

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01-30-2001, 06:47 PM	#3
Skankin Registered Member Join Date: Dec 1998 Location: London, Ontario, Canada Posts: 1,349	You'd be better off getting a blower cam. They typically have more lsa, which is also good for emmissions. (you wanna keep the lobes apart). Here's a handy, generalized rule: (intake duration@0.05"/2)+(Exh Dur@0.05"/2)-2*LSA = ? If the number is positive, there's no overlap. The more positive it is, emissions are typically better. A negative number indicates overlap, which is bad (for blowers & emissions). If the lobes aren't very aggressive (Long advertised durations), the emmissions are gonna be worse than what the general number indicates. Also, if the lobes are asymetrical... forget the formula. A split duration favouring the exhaust might be a consideration. Are you gonna run 14#? To make more top end power, and utilize the added displacement, you'll wanna go with a longer duration. Problem is, if you go too long, you either loose cylinder pressure (and power), or you have to shorten the lsa. Maybe look into a comp cams extreme grind, they've got really agressive lobes... you could really push the "Magic number" down to zero, and be alright. ------------------ '89.5 5L LX, hatch, Medium Canyon Red, 155K Km (No winters), 5sp, 3.08, GT interior, a/c, Alpine CD, K/N, Crane PS91, Walbro 190 LPH, March Pulleys, Mr. Gasket 180 therm (HP balanced), 3 core rad, MarkVIII fan, Variflow controller, Polygraphite front bushings, FMS-5300B springs, 6 KYB's, 73mm Calipers, Maximum Motorsport 4pt chassis brace, Western Motorsport Racing's Sub-frame connectors. Re-ringed bottom end, conv. motor mounts, melling oil pump, FMS-C50 waterpump, GT40P heads (blended, polli