GreatWhiteZ28

iTrader: (15)

This is for anyone who is running a Comp XFI 230/236, I just installed mine, along with new Valve springs, well heres my question where you guys able to drive your cars to have it tuned or even at all? cause when I put mine in and had everything backtogether, It wouldn't go any faster than about 5-10mph or so, thought it was a timing issue cause these damn maunels are confusing me to **** and back, another thing im confused on is that as far as the manuels go, the dots on the timing chain you need to line up (crank at 12 o' clock and the cam sprocket at 6 o'clock) which I did, and that puts the cam pin at apprx. 3 o'clock, which is set, but the Opti intallation instructions show the cam pin being a whole 180* from 3 'clock to 9 o'clock so the pin and rotor slot line up on the 1 TDC marking on the back of the opti, even though it says the pin is supposed to be at 3 o'clock, but that lines it up with the 6 TDC mark on the opti, which is funny cause I have the motor at #1 cyl TDC. yeah..i'm a lil flippin confused on this and would like some clear info as to how the opti is supposed to be installed, is it at the 6TDC mark or 1TDC mark? 1TDC mark would require me to turn the crank another rotation to put the pin there, oh yeah, It sounds like it has a straight up dead miss sound when it idled a few weeks ago, had a staright up pause in the exhuast note for a moment, about ready to just grab a hammer and start beating things

aboatguy

I bought my tune before the install and it drove great. I have a 95 just like you however, you have me confused on your opti install.
The opti should only fit on the cam one way.

I just ensured that the dowel pin went into the proper slot on the back of the opti (I didn't worry about where the engine was in relation to TDC since the opti indexes to the cam and crank rotation won't change the relationship of the dowel pin to index slot one IOTA .)

GreatWhiteZ28

iTrader: (15)

well I had a bad opti, and now have a nice new MSD unit sitting on the floor....The opti question comes from frustration of being told numerous things that were all different...example, the Crank hub with cast arrow pointing Up (12 o'clock) indicates Cyl. 1 @TDC, ok, good, now put the new timing chain on with the dots lined up, Cranck -12 o'clock cam sprocket - 6 o 'clock. car ran great before, now won't run at all, im thinking I have the cam a whole 180* off cause when the stocker was pulled out the pin was at 9 o 'clock, and now it went back on at the 3 o'clock spot..if that even matters really, some poeple say i have it right but other have told me the cam should have went back in in the same spot as the stocker when it came out

aboatguy

Dot to Dot should be correct.

With aftermarket double rollers its easy to end up a tooth off. If I remember correctly on a double roller 1 tooth is about 12 degrees and will jack things up with a big cam like the 280XFI.

Imnotfast

iTrader: (1)

Cam dot at 12o'clok and crank dot at 12 o'clock is number 1 firing
cam dot at 6o'clock and crank dot at 12 o'clock is number 6 firing
The hub can be installed in any place due to no keyway in it.

92LT1RS

iTrader: (3)

you have that backwards. dots should be close together.

GreatWhiteZ28

iTrader: (15)

ok, Right now as the car sits, the #1 cyl is at TDC, timing gears need to be set where? Dot to dot or both dots at 12?

92LT1RS

iTrader: (3)

dot to dot.

From Hot Rod:

SincalT/A

iTrader: (16)

+1 dot 2 dot

GreatWhiteZ28

iTrader: (15)

ok that's where I have them set at to begin with, was a lil confused cause the maunel im using states that dot to dot puts #6 at TDC and that had me confused as hell

ws6t3rror

iTrader: (3)

dot to dot does put #6 at tdc on the firing stroke however, it doesnt make any difference, theres alot less chance of you fudging it up if you just line it up dot to dot like everyone else has said because both #1 and #6 are at tdc at that point just on different strokes. the rub is that the cam only turns over once for every two times you turn the crank over so both positions are correct.

GreatWhiteZ28

iTrader: (15)

Ok.im pretty sure my cam is around the neighborhood of being 180* off...how to I check to make sure before I go tearing into it, I have thought of just popping the valve cover off and checking by the valves, but wasn't sure if there was a mistake free way of checking...yeah yeah yeah, flame on me for putting the cam in that far off.it was a few days between the removal and install

aboatguy

I agree, spin the crank one more time and you should be DOT TO DOT .
Hopefully you're not a tooth or two off.

GreatWhiteZ28

iTrader: (15)

Well it was 180* off, with #1 at TDC the intake valve was about halfy way open or so.

aboatguy

OUCH! With the 280XFI's lift and duration if you're that far of you probably bent some valves!


If you had the crank timing mark in the 12 o clock position it can't be 180* out read post eleven.

Puck

iTrader: (17)

Courtesy of Shoebox

GreatWhiteZ28

iTrader: (15)

[QUOTE=aboatguy]OUCH! With the 280XFI's lift and duration if you're that far of you probably bent some valves!


If you had the crank timing mark in the 12 o clock position it can't be 180* out read post eleven. QUOTE]

yes it can be 180* off, cause the stocker was pulled up at Cycl 1 TDC, the new cam went in set for Cyl 6 to be at TDC,...I say it can be 180* off cause it was.Im not trying to be rude, but I know that Cyl 1 is at TDC now, it's no big deal just time consuming.

and thanks Puck, I saw that on the shbox site and it cleared alo up

aboatguy

[QUOTE=GreatWhiteZ28]Watch the gif in Pucks post.
Crank turns twice for cam turning once. If the engine makes one revolution its 12 o'clock crank 12 o'clock cam
one more rev time 12 o'clock crank 6 o'clock cam.

Since the opt is indexed off of the cam TDC 6 or TDC 1 means nothing on an LTX (the opti will be correctly indexed) now a regular small block chevy where one stabs the distributor in, #1TDC or #6 makes a big difference.

GreatWhiteZ28

iTrader: (15)

Yes I know that, let me make this a lil easier to understand, Stock cam was pulled out at #1TDC cam pin at 9 o'clock.....NEW cam went in and everything was put back together DOT to DOT...Keep in mind the crank was not turned agian, the timing was set wrong to begin with (not my doing) I mean you can't just throw the cam back in in any spot you want or the valves would open and close at the wrong times, nw as far as I know, if you pull the cam out with the pin a 9 o'clock then it needs to go back in with the pin at 9 o'clock which in my case was not done( also not my doing)

aboatguy

Honestly it didn't matter as long as the crank mark was straight up in the 12 o'clock position!