LT1-LT4 Modifications 1993-97 Gen II Small Block V8

how to go vented

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Old 03-28-2009, 03:16 PM
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Default how to go vented

So i think my opti just went out cause my car wouldn't crank only turns over. I need to go out and check the voltage from the opti to the pcm tomorrow when the weather is better. I havn't used the car in a week and tried starting it yesterday durring the rain, but only turns over. I don't feel like puting another non vented POS in my car again thats only gonna last me 2 years. Can anyone fill me in w/ part #'s and everything i need to convert it to the vented kind. thanks
Old 03-28-2009, 04:12 PM
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Originally Posted by sepno77
So i think my opti just went out cause my car wouldn't crank only turns over. I need to go out and check the voltage from the opti to the pcm tomorrow when the weather is better. I havn't used the car in a week and tried starting it yesterday durring the rain, but only turns over. I don't feel like puting another non vented POS in my car again thats only gonna last me 2 years. Can anyone fill me in w/ part #'s and everything i need to convert it to the vented kind. thanks
To do the conversion, you need a new cam for the longer dowel pin and deeper hole for the opti snout. Best to do the conversion when you're doing a cam swap.

On top of that, you need the vented opti (of course), vacuum lines (12555323), electrical harness (12130319), new 95+ timing set (cam gear is different), a '95 timing cover (10214196), and one new intake fitting (14082470).
Old 03-28-2009, 04:17 PM
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If you want to change to a vented from non-vented, you have to do many things. It may not be cost effective unless you are doing a cam swap at the same time.

Besides the optispark itself (GM p/n 1104032), you need:
  • 95 or later timing cover [1995 front cover (includes round seals) GM p/n 12552426]
  • late model cam (or have your cam modified by drilling the hole in the front to the proper size [.500"dia. X 1.0625" deep] and a longer dowel pin added
  • 95 and later optispark electrical harness GM p/n 12130319
  • optispark vacuum harness GM p/n 12555323
  • vacuum fitting [GM p/n 14082470] or "tee" to provide vacuum for the opti
  • 95 or later timing set components (or at least the cam gear) cam gear (GM p/n 10206039), crank gear (GM p/n 10128346), chain (GM p/n 10128485)
  • timing cover gasket GM p/n 10128293
  • water pump gaskets [2] GM p/n 10128343
  • intake manifold gaskets if you are pulling the cam GM p/n 12524653
Old 03-28-2009, 04:24 PM
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k thanks both of you. i am doing a cam swap prity soon. this dose seem like a lot of stuff. do ya think its worth it?
Old 03-28-2009, 04:38 PM
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i bought the msd vented unit for my 94. basically bolts on and nothing else needed to be changed. just had to drill a hole in my elbow for the vent.
Old 03-28-2009, 04:58 PM
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Originally Posted by C_Rules
i bought the msd vented unit for my 94. basically bolts on and nothing else needed to be changed. just had to drill a hole in my elbow for the vent.
did you just buy the cap and rotor or the whole opti distributor?
Old 03-28-2009, 05:00 PM
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Buying the MSD is hit or miss. Personally, I'd do the entire conversion to use the AC Delco opti.
Old 03-28-2009, 05:18 PM
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i bought the whole distributor.
Old 03-28-2009, 05:19 PM
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Originally Posted by RamAir95TA
Buying the MSD is hit or miss. Personally, I'd do the entire conversion to use the AC Delco opti.
what usually goes wrong with the msd units?
Old 03-28-2009, 05:38 PM
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i was recomended to this site http://www.eficonnection.com dose anyone got more info on this?
Old 03-28-2009, 05:43 PM
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The dynaspark will also convert it to a vented style and is a great unit from my research. Just not cheap.
Old 03-28-2009, 05:45 PM
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Originally Posted by sepno77
i was recomended to this site http://www.eficonnection.com dose anyone got more info on this?
There's a huge thread on it.

And you don't need to switch cams, but you do need to switch the dowel pin to the longer style, which more times then not would be easier to get a cam from someone with a newer vehicle who upgraded (and so they have their stock cam that is of little use to them anymore). The pins can be very hard to remove, as was the case with the B-Body cam we got that we were putting in a TBI motor, for that we had to shorten the dowel, and trying to tap it in or pull it out didn't happen, so we just cut it to length heh

I haven't heard but maybe a handful of horror (not even horror really) stories with MSD cap and rotors, so that'd bet he route I'd go

Just thought of it, but anyone know if you can swap the opti drive shaft out of a newer style to the splined that us older style have?


Originally Posted by gregrob
The dynaspark will also convert it to a vented style and is a great unit from my research. Just not cheap.
They've apparently gone down hill. The Optis are still decent, but apparently not as good as originally, and their customer service has also totally gone to pot according to a few who've had to deal with them. That is if they get customer service heh
Old 03-28-2009, 05:49 PM
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Good thing I have an older unit.

I think the "redesigned" MSD is a really good piece too. I wouldn't hesitate to loctite the rotor screws and run that unit as well.

My buddy has it on his car and it seemed to run the car better than the stock opti and is holding up great!
Old 03-28-2009, 05:53 PM
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Originally Posted by Formula350
There's a huge thread on it.

And you don't need to switch cams, but you do need to switch the dowel pin to the longer style, which more times then not would be easier to get a cam from someone with a newer vehicle who upgraded (and so they have their stock cam that is of little use to them anymore). The pins can be very hard to remove, as was the case with the B-Body cam we got that we were putting in a TBI motor, for that we had to shorten the dowel, and trying to tap it in or pull it out didn't happen, so we just cut it to length heh

I haven't heard but maybe a handful of horror (not even horror really) stories with MSD cap and rotors, so that'd bet he route I'd go

Just thought of it, but anyone know if you can swap the opti drive shaft out of a newer style to the splined that us older style have?




They've apparently gone down hill. The Optis are still decent, but apparently not as good as originally, and their customer service has also totally gone to pot according to a few who've had to deal with them. That is if they get customer service heh
No, you need a NEW CAM. There are two differences that need to be addressed. Most people know about the drive pin (switching from a .300" pin to a .700" pin). But vented optisparks have a longer snout that engages the camshaft deeper than their non-vented counterparts. The 92 to 94 camshaft has a shallow tapered hole. You need a new cam, period. Don't even try to debate it.

The drive mechanism between the two optisparks cannot be interchanged.
Old 03-28-2009, 05:59 PM
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Originally Posted by RamAir95TA
No, you need a NEW CAM. There are two differences that need to be addressed. Most people know about the drive pin (switching from a .300" pin to a .700" pin). But vented optisparks have a longer snout that engages the camshaft deeper than their non-vented counterparts. The 92 to 94 camshaft has a shallow tapered hole. You need a new cam, period. Don't even try to debate it.

The drive mechanism between the two optisparks cannot be interchanged.
You're right, sorry. Forgot all about that! Would a machine shop be able to accommodate the factory cam if the correct dimensions were provided for drilling?



Old 03-28-2009, 06:43 PM
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from doing a lil research that Dynospark has caught my attention prity good. might just take this route.

Last edited by sepno77; 03-28-2009 at 06:53 PM.
Old 03-28-2009, 06:49 PM
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Originally Posted by sepno77
from doing a lil research that Dynospark has caught my attention prity good. might just take this rought.
No complaints then if it takes forever to get, their tech support blows ***, or anything else lol Cuz I warndededed you!

haha It's "route" btw
Old 03-28-2009, 06:56 PM
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Originally Posted by Formula350
No complaints then if it takes forever to get, their tech support blows ***, or anything else lol Cuz I warndededed you!

haha It's "route" btw
lol mybad fixed... ya but i need an opti that will last for 5+ years. if i could get rid of it completly i would spend the money and never worry about it again.
Old 03-28-2009, 07:38 PM
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you can just go to efi connection and get rid of it with their harnes and get a better computer too
Old 03-29-2009, 01:14 AM
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i change my mind. can someone post up a link of where i can buy a Delteq from. thanks in advance.


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