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Discussion Starter · #1 ·
I just finish building up my first big block gsxr. Its got cam motion cams in it i g21 e g28 and I've degree them to a 110 center line. After lots of research and reading I'm not sure thats the best setting to start with and if I need to change it I'd like to do it while its on the bench. Motors 13.5 to 1 compression, 30/26 valves, ported and 40mm mikuni flatslides.
 

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Get it on a dyno and start movin em till your happy with the outcome. Check ptv clearance as well so u don't tap a piston.
 

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Is this a street bike or a drag bike? Big difference where you would set them if it's a street bike. Also, the exhaust cam #s need to be two bigger. Like if it's a drag race motor you would go 110/112. on a street motor I would go 107/109 as long as you have piston to valve clearance.
Ray.
 

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Don't start moving things till you measure P to V where the cams are at.
Closest is 8 degrees BTDC for the exh and 8 degrees ATDC for the intake (IIRC...been a while guys)
IIRC, 2 degrees of cam timing gained/lost .010" P to V..
I made a chart tracing P to V with both intake and exhaust cams and then started moving the cams.
I sold the motor and it was resold, The new owner thought 110-112 was NG and set the cams at 106-108.
Couldn't figure out why the motor slowed down....till he found bent intakes.
.050" P to V on the intakes and .075" P to V on the exhausts minimum...
 

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108/108 to start. Move them to flatten out the torque curve on the dyno if necessary. I like a nice smooth curve. I would keep the numbers somewhere between 106 and 112.
 

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Discussion Starter · #6 ·
Its going to be used for street and strip. I'd really like a high 8 second time slip. P/V is .175 on both sides when checked at the 8° marks on 110° lobe centers.
 

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Just to be clear...you checked intake V to P at 8 degrees ATDC and exhaust V to P at 8 degrees BTDC? Reason I asked is that sounds like an awful lot of clearance.
I usually start to check maybe 20 degrees before and go to 20 degrees after, plotting every 5 degrees or so on both cams.
 

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Just to be clear...you checked intake V to P at 8 degrees ATDC and exhaust V to P at 8 degrees BTDC? Reason I asked is that sounds like an awful lot of clearance.
I usually start to check maybe 20 degrees before and go to 20 degrees after, plotting every 5 degrees or so on both cams.

Naturally Aspirated? I set to the tightest limit = but you have to have good valve springs and an expert operator - no constant over revving and proper deck height allowing for sling out tolerance for 10K rpm. = P-V int 0.080" exh 0.050" and V-V 0.060" - my tight spots are closer to 11 not 8 degrees. let the LC numbers be whatever your combo allows (static deck height main factor). there is no secret combo. you'll get the most overlap and the best mid to high range power -- Idle will suffer and lope under 1500rpm - cam mfg advertise 108 or 110 equal I&X because nothing will hit each other - and idle is good -- but will create a midrange dip in power. it is a give and take - nothing is gained.
I have been running 103 and 115 in a 9.0 second GS,, my 98 1200 bandit #'s have a little have less spread.

just be careful if you decide to have a tight tolerance engine.
 

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Naturally Aspirated? I set to the tightest limit = but you have to have good valve springs and an expert operator - no constant over revving and proper deck height allowing for sling out tolerance for 10K rpm. = P-V int 0.080" exh 0.050" and V-V 0.060" - my tight spots are closer to 11 not 8 degrees. let the LC numbers be whatever your combo allows (static deck height main factor). there is no secret combo. you'll get the most overlap and the best mid to high range power -- Idle will suffer and lope under 1500rpm - cam mfg advertise 108 or 110 equal I&X because nothing will hit each other - and idle is good -- but will create a midrange dip in power. it is a give and take - nothing is gained.
I have been running 103 and 115 in a 9.0 second GS,, my 98 1200 bandit #'s have a little have less spread.

just be careful if you decide to have a tight tolerance engine.
My NA motor had .050" intake v to p with the intake LC at 110 degrees
The exhaust was .080",iirc at 112 LC.
That was with a set of Yosh Stg 2 cams for the 1100, not the 750.
Piston to head was .040". Head was milled but I can't remember how much and all my notes went with the motor when sold. Motor had new Crowers and new valve springs from Bob Carpenter. He did all the machine work as well as the head. The eyebrows had to be cleaned up on the JE pistons.
New owner (200 lbs) in Texas went [email protected] in 12 runs installed in a Bandit...there was more there.
Oh yeah, it was streetable and ran on pump as well as Powermist 137...
I rode it around Daytona during Bikeweek 1 year.
Every motor is different and it pays to measure everything before just moving cams around.
 

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110 and 112 and you were that tight? dang 80 and 50 atta boy make 'er fast-- one thing Milled heads ? yeah remember to change the valve pockets due to change in ggggeometry . lol
 

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110 and 112 and you were that tight? dang 80 and 50 atta boy make 'er fast-- one thing Milled heads ? yeah remember to change the valve pockets due to change in ggggeometry . lol
Redoing the eyebrows gives you a hint about how much the head was milled. Lotta work on the domes too...
All in all a great motor. Made 195 HP and 108 lbs tq on Powermist, a little less on pump.
My whole point is for guys reading this stuff to accurately measure first before changing things around...
 
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