:::RHMT::: Real Home Made Turbo
General Category => Hybrid/Tech => Topic started by: HiProfile on September 21, 2010, 11:46:45 PM
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Any of you OG's try the old skool method of offset cam keys for changing cam timing? I know the older v8 crowd will know of this, and maybe some stock-class import racers. I'm looking at a cunthair more topend for the DD-ish b18b1 I'm putting in my new beater. I'm curious if I should even bother with this, and if I do, which cam to advance or retard.
BTW I can never remember this - is cam timing based on crank degrees or cam degrees? I presume saying "+1* cam advance" is 2* at the crank.
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retards like top end.
Mill the head .060" to retard the cams approx 2 degrees.....free compression bump!
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I'd rather stuff in modded p72 pistons and new rings for the price of milling. This motor doesn't look beat, just old. Bearings and crank look mint.
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Offset cam (or crank) keys are used for circle track cheating, sir.
If it were a SOHC I'd say go for it as they are a really simple. Retard to pitch power upward, advance to pitch power downward. DOHC cam gear settings, uh, not so much. Advancing and retarding both cams with relation to the crank doesn't have a wholly predictable effect. Dialing in more overlap pitches the powerband upward, dialing it out does the opposite. Getting a balance of overlap vs absolute position with regard to the crank is something you determine by walking the engine through 5-9 settings on the dyno before going back a couple positions to the one that worked best - that's a fuck in the ass w/ a DOHC motor.
It's kind of a fuck in the ass, anyway, since dyno time = $, and is basically the only way to measure the subtle changes in power band that accompany cam gear adjustments. I'm a big fan of buying used china gears for $5, and not trusting them longer than the dyno experience. Replace with offset keys when done, sell gears for $10 and make $5 off the experience.