3.8 to 4.2 Stroker
- Thread starter monti83
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i kinda figured COME racing doesnt use reworked cranks just the new cast crank and they offered a billet/forged crank option a while ago back when they first released the kits down under.
your still reaching a point of diminished returns past 5500rpm
you took a low/mid rpm tq monster and made it a low rpm tq monster, i see no reason to rev it past 6k except at the track/dyno to determin whther reving it higher actually does anything for you...reving over 6k may be worthwhile if at the shifts you drop down to the tq peak.
hey 10sec, remember that night we were scanning my GTP and that lifter blew?
well i was looking through old logs and found the one from that night. the engine was a tick over 6700RPMs. shift point was set to 6k
heads+cam+IC+3.0 on a stock 130k trans = :squirts:
i shoulda sprayed the 100 shot
lol It tried sooo hard to shift
Double D spun his car past 6800 on track day, but the stock junk holds up instead of those oe-r p.o.s. lifters. I'm sure my car was around 6800 as well, left it in 2nd... seems to happen a lot lately 
my suggestion, dump your wallet out for this
http://i24.photobucket.com/albums/c45/muvro/090902TarkVT_0093jpg.jpg
thats the 3300 (200ci radial entry) lysholm (early swedish made whipple) it's the big brother to this bastard, the 2300ax (140ci axial entry) nothing custom is cheep, unless your a redneck or a rednecks friend
slow o2 responce.... vac leak, cam overlap, pre o2 exhaust leak, bad/contaminated o2 sensor all can cause it. we had to delete the code on the riv due to the IS4 overlap and boost bypass delete.
so what do i do? the car runs fine other than the idle is odd........ when its idling it to me sounds out of time instead of the.............. blut blut blut blut its more of a............ blut blut blut vroom blut blut blut vroom however we tuned the car then i have been driving it so i am assuming that with the breakin it needs retuned.....
That is most likely the Cam... find out the cam measurments; lift, duration, overlap and we can say more definitively, but a cam to go with Stage 4 heads will not have a smooth idle, unless you idle at 2k
Grind# GM38 3314S/3316S HR113.0
Spc Instr 1: REDUCED BASE CIRCLE
INTAKE EXHAUST
Valve adjustment HYD HYD
Gross valve lift .536 .555
Duration @
.006 Tappet Lift 275 287
Valve Timing OPEN CLOSE
@ .050 INT: 2 BTDC 42 ABDC
EXH: 54 BBDC 2 ATDC
these specs are for cam installed
@ 110.0 INTAKE CENTER LINE
INTAKE EXHAUST
Duration @.050 224 236
LOBE LIFT .3350 .3470
LOBE SEPERATION 113.0
of all those numbers what are the ones i need to know when asked
Spc Instr 1: REDUCED BASE CIRCLE
INTAKE EXHAUST
Valve adjustment HYD HYD
Gross valve lift .536 .555
Duration @
.006 Tappet Lift 275 287
Valve Timing OPEN CLOSE
@ .050 INT: 2 BTDC 42 ABDC
EXH: 54 BBDC 2 ATDC
these specs are for cam installed
@ 110.0 INTAKE CENTER LINE
INTAKE EXHAUST
Duration @.050 224 236
LOBE LIFT .3350 .3470
LOBE SEPERATION 113.0
of all those numbers what are the ones i need to know when asked
All of it is good, but the important parts are:
Gross valve lift .536 .555
Duration @
.006 Tappet Lift 275 287
Duration @.050 224 236
LOBE LIFT .3350 .3470
And this tells you the overlap(amount of time both the exhaust and intake valves are open):
Valve Timing OPEN CLOSE
@ .050 INT: 2 BTDC 42 ABDC
EXH: 54 BBDC 2 ATDC
(you have 4* of cam movement that both the ext and int valves are open)
Doesn't look like a smooth idle is in you future
there is no good or bad, just better for certain situations, more overlap is better for high revs, so is lift to a point, then past that point, it becomes more likely to float, but is open better at lower rpm, so low-mid range Torque is created at the cost of being able to rev higher.... there are dozens of trade offs, seems to me like a a decent cam for your setup, I actually expected a little more overlap, and a little less duration, your exhaust valve opens 54* BTDC, and the intake not closing till 42* into the compression stroke, that means you are venting out the exhaust for more than half of your power stroke, and loosing a little air to your intake during the compression stroke although this will help up top, this def will hurt Idle.....
Someone with more knowledge will chime in with better answers for you (like directly relative 3800 responses)
Then again, I could be way off base, or reading those numbers wrong you never know
you deserve that davey you remembered shit from school even after all them benders and fucking all them cheerleaders 
but ya fergot that would be overlap at .050 tappet
but since you rarely if ever see a lobe chart with cams ya gotta figure shit
(at least cams nowadays reference crank angle)
intake from .006 and .050 is a 51deg diff (you can aprox 25.5* at each end of the ramp -this of course can depend on the slack or cushion ramp design)
exhaust from .006 to .050 is also a 51* diff so 25.5 at each end of the ramp
25.5+25.5+4 soooo 55* overlap
is it installed straight up? (im assuming you have a aftermarket chain?)
on the otherhand the is4 is at 120+* iirc
valvetrain deflection makes things a bit more hairy but we're working on the ideal numbers for now
your still bleeding o2 and fuel into the exhaust thats likely triggering the code if there's nothing else youll want a leaner comanded afr at idle to about the bottom 1/4 or 1/3 of the cam rpm range where induction events make the overlap less noticable
in the is4 lobe map you can see the different lash ramps at the leading and trailing edges, you notice how gentle tyhe closing ramp is to lightly set the valve down on the seat and avoid bounce
dd and his spreadsheets
but ya fergot that would be overlap at .050 tappet
but since you rarely if ever see a lobe chart with cams ya gotta figure shit
(at least cams nowadays reference crank angle)
intake from .006 and .050 is a 51deg diff (you can aprox 25.5* at each end of the ramp -this of course can depend on the slack or cushion ramp design)
exhaust from .006 to .050 is also a 51* diff so 25.5 at each end of the ramp
25.5+25.5+4 soooo 55* overlap
is it installed straight up? (im assuming you have a aftermarket chain?)
on the otherhand the is4 is at 120+* iirc
Ok, so it is 4* of over lap that they are both full open.... yeah, Like I said though, with that cam a smooth Idle isn't going to happen
no its 4* of overlap at .050 tappet and .080 valve lift (1.6 rocker ratio)
even though the overlap area is fairly large the valves arent open all that much...but at lower rpm's a short rod motor breaths very well so a good bit of air can get past the exhaust valve as the induction event begins, the 02 reads this as being lean and can command more fuel to the detriment of the idle mixture
you need to TUNE "evabody must get stuned"
widebands help greatly but it can be done with a narrowband
what you find is that dep on the cam your comanded afr at idle will be closer to 15-16 to1 though in the actualy combustion chamber at time of ignition you will actually be at/near 14.7, your basically stuck doing this trial and error to find the best idle quality,
you may still end up smelling fuel in the exhaust, but without something far less restrictive than the oem pcm (BS3/KAM/FAST etc) you wont have the ability to adjust the injector firing time to begin after the exhaust valve closes.
after you get the idle afr correct so she runs good youll end up using the perpm/time table to ease it back up to the true afr at the rpm where cam overlap esentially disapears.
but as edsel so eloquently put it a smooth idle isnt gonna happen but it will idle, everything is a compromise...you cant have a stock idle with a big bumpstick and you cant make big power with a tiy bumpstick
the riv gets driven with both feet due to the idle surge but it's a compromise he's willing to deal with for the PAH.
:rly:
See link in my signature for my L67 swapped 87 Fiero GT. Be glad to help with any questions you may have, the swap is well worth it!
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