I understand that the 93-94 gen 1 optis were not designed to have engine vacuum plumbed through them like the 95-97. My question is, why can't you just drill another hole in a 94 cap and plug an inlet hoes into the intake and then plug the existing drip hole into engine vacuum? What makes the 95-97 caps so much different aside from 2 vent holes vs 1 "drip" hole? I replaced my opti cap recently on my 94 LT1 and noticed that aside from the lack of another vent hole it's identical to a 95 cap...just going off internet pictures for the 95 cap pictures but still, hard to tell them appart. Any thoughts on this?

Thanks!

 

There have been some "conversion to vented" ideas out there for quite a while. Here is one of them.

 

Thanks, wierd it looks like my cap already has the hose fitting for the vacuum harness. Heres a picture of my old cap before I went ahead and just purchased a complete optispark assembly. I always thought that this fitting was just the drip hole.

http://www.deal-hunt.com/ebay/car/opti/2.jpg
http://www.deal-hunt.com/ebay/car/opti/3.jpg

I'm a bit confused from the writeup it looks like his old opti never had this fitting on it. My engine is a 1994 LT1 from a firebird formula, I am possitive it's a 94, the timing cover is a 94 and the 94 optispark plugged right in. The TB Elbow also didn't have a tapped hole for the inlet vent hose... Would it be possible that late model 94s did get the vented opti? or is this fitting just the drip hole?

Thanks!

 

That's interesting. You sould probably double check and make sure that is not a cap and rotor kit for a 95-97. That distributor cap DOES have the vent on it for the vacuum harness for the 95-97 distributor. I am not sure that the cap will fit totally right on the old 93-94 distributor, but I know that some people buy that kit and modify it somehow to get it to work with the 93-94 distributor.

I actually did a 93-94 to 95-97 vacuum optispark conversion of my own. However, I didn't do it using the 95-97 distributor cap. I just drilled a hole on the bottom of the distributor cap and installed a vacuum hose fitting in it. I also drilled out one of the weep holes on the bottom of the distributor body and installed a vacuum fitting on it as well. Then I epoxied the other weep holes shut. Put some sealing compound on the distributor seals and put it back together. Got the 95-97 GM vacuum system harness, drilled a hole in my intake elbow and installed a vacuum hose fitting in it for the intake of the distributor vacuum system, then installed a vacuum T at an existing vacuum line and hooked the vacuum line into the T.

I had done this after my second optispark crapped out on me about 10000 miles after I had just done a cap and rotor kit on it. So far, have had the vacuum system on for almost 10,000 miles and no problems. <knock on wood>

I think that I might have some pictures of what I did, so if you wanted to see them I might be able to put them up and post links to them.

 

Your right, I just ran out into the garage to check my new optispark and sure enough it doesn't have the vent barb, just the 3 holes on the bottom. I'm kinda supprised i didn't notice this earlier , I didn't even think about putting the old/new unit side by side when I installed it. Haha...well glad I learned something new atleast

I will definatly do the vent mod when this one dies, from the previous write ups I read it looked like a redicilus ammount of work but mabey it's not so bad after all. I saw the dynaspark which comes pre-vented among some other improvements but priced a bit steep for me.

Thanks for all the info guys