View Full Version : 78 mm throttle body
04-22-2012, 09:14 AM
I purchased a throttle body on E-bay than was machined to 78mm instead of 72mm. When I went to install it I noticed that the breather passages were blocked on the one I just received. I contacted the seller and he said the crank case breather doesn't run through the throttle body. It sure looks like it does to me. The breather comes from the valve cover and through the intake and through the throttle body. He said he has sold 1000s of these and never had a problem. My question is what will happen if I block the breather he says isn't there? Thanks for any help
04-22-2012, 09:52 AM
It isn't worth it to try to engineer something for a mod where you *might* see marginal gains from at best. I would send it back. It is not the right part for your engine.
04-22-2012, 12:54 PM
That's what I was thinking. The person I purchased it from swears the crank case vent has nothing to do with the throttle body. It looks like it runs right through it to me.
04-22-2012, 01:36 PM
this for a vortec engine? On my 96 5.7 vortec the crankcase ventilation comes through a hole in the bottom of the intake. I don't remember any other vent. do you have any pics?
04-22-2012, 03:14 PM
Are you trying to say there is a fitting that plugs directly into he throttle body, or does it go to the intake tube BEFORE it gets to the throttle body, as it seems from how you describe in your first post... " The breather comes from the valve cover and through the intake and through the throttle body" tells me it goes to the intake tube, in which case it isn't a big deal to block the tube off and put an open breather on the valve cover where the tube was. If it's the one going directly to the intake MANIFOLD from the valve cover it's likely yhe PCV which I would leave in place since it isn't directly throttle body-related anyway.
04-22-2012, 04:41 PM
The PCV valve is on the other valve cover. My concern is if I put an aftermarket breather on it, I think I will get some oil seepage. I have some good pics but not sure how to post.
04-22-2012, 05:09 PM
The seller wasn't saying the breather wasn't there, just that it doesn't connect directly to the throttle body. If you change your intake tube you'll either need to run a push-in breather or find a push-in fitting that will fit and run a hose to your new intake tube if you don't use the stocker.
Is this the throttle body you're talking about?
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