Hey guys. 68 with the smog cross over pipe. I have hated the look of this for the 36 years I’ve owned the car. So, I made some .25" thick aluminum caps with through holes and removed the pipe, installed the caps, car wouldn’t start. Nothing. Put the cross over back on and started right up. I thought there was just exhaust going thru this to warm the intake? other members have done this without messing with the secondary butterflies. Any thoughts?
It’s the intake gasses that cross over to the exhaust manifold and come back. If you want to delete the crossover the best solution is to obtain one of the Series 2 factory caps that allow the intake gasses to cross over at the now capped intake side of the crossover. Take out the secondary throttle butterflies too.
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You have misunderstood how this works. The crossover on the 68 carries fuel/air mixture over to a heat exchanger on the rear exhaust manifold and then back into the intake manifold. If you simply block the intake with a flat plate, you cutoff the intake supply. Take a look at the later intakes and you will see the crossover was replaced by a “hump” that links the “to and fro” mixture circuits to avoid the round trip to the exhaust manifold. Time to look up the “Emissions” section of your Workshop Manual to see how it works.
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thanks everyone for clearing this up. I will be on the lookout for that special series 2 caps on ebay.
If you remove the secondary throttle plates, or implement the “Five-minute Strangleberg fix” [[E-Type] Five-minute Strangleberg fix?] you can probably get away with the flat plate you’ve tried, as without the secondary butterflies to impede the flow, all the mixture will bypass the secondary manifold route. That said, the secondary manifold does also serve the function of a balance tube between the mixture from the two carbs, which helps smooth running at low throttle openings - particularly idle.
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Plus 1 on what David said about the air routing being necessary for some balancing between the two carbs. I have messed around with this setup in just about every possible way short of replacing them with another type of induction and carbs and I can assure you that your car will run very well without the crossover you removed but you really need to ensure that the “hump” that has been mentioned is in place.
Another source might be Joe Curto if you strike out with ebay.
Also Dick Maury might have one.