new valve covers, now car won't start

[ahirsh]

I have a 331 stroker motor with a GT 40 intake. It's wired with a Painless EFI Harness, and I have a BBK 75MM throttle body. I changed the following:
1. installed taller valve covers,
2. I also went from a half inch to an inch spacer under the upper intake to accommodate the slightly taller valve covers.
3. I replaced the gaskets above and below the spacer.
4. took my trick flow oil filler tube with vacuum attachment and installed in new valve cover. I ran a hose from the oil filler to the throttle body, same as with my previous valve covers, but I used a length of fuel hose.

Now the engine will turn over, starts to fire but then dies. The strange thing is, this is the second time I've been through this. I installed these valve covers once before but I had the shorter spacer under my upper intake so I thought my problem was that the intake was hitting the VC and letting in air. I went back to my original set up and it ran fine again.

Now, my upper intake is not contacting the valve cover, everything is attached that should be attached, but the car won't start, so I am guessing that was not my problem with the last attempt. If air is sneaking in around the space under the upper intake would that cause this?

Any ideas on what I can check? I didn't make any radical changes, and I'm pretty sure if I were to go back to my original setup I'd be back in business. I just want to figure out what is going on.

[videodude]

Sure sounds like a serious vacuum leak to me. Got a vacuum gauge? Maybe a leaky spacer . . .

Video

[frankb]

You might try removing and plugging the hose from the oil filler (to eliminate air from entering the throttle body that direction) and then try to start. If it starts, the extra (and unmeasured) air is leaking in that way.

Frank B

[ahirsh]

thanks guys. the more I think about it, the more it does sound like a vacuum leak, which brings me back to to the new spacer and gaskets on my intake. I did try unplugging the hose at the throttle body and got the same results. After the initial shock of WTF as I think about the basics the most logical culprit is that my intake is not getting a good seal so I don't have vacuum so the engine can't start. When I rule out the things that have nothing to do with it, the intake and spacer is the place to start I think. I'm going to pull it apart again and have closer look.

[davekp]

I had a similar situation. Turned out to be a bad MAF. I'd check all the electrical connectors.

[ahirsh]

It turns out the problem was a vacuum leak, and I am to blame. Truth be told, I hurried through the gasket change portion and did a sub standard job cleaning the old gasket material off, there was enough left behind that it was preventing a good seal. Initially I focused on everything but the thing that made the most sense! This also supports my theory about my last attempt with my original spacer that was too short to clear the valve cover - also a vacuum leak with a different cause. I made damn sure the mating surface was clean, put it all back together and she fired right up.

thanks for the feedback and the sanity check!

[GoDadGo]

It turns out the problem was a vacuum leak, and I am to blame. Truth be told, I hurried through the gasket change portion and did a sub standard job cleaning the old gasket material off, there was enough left behind that it was preventing a good seal. Initially I focused on everything but the thing that made the most sense! This also supports my theory about my last attempt with my original spacer that was too short to clear the valve cover - also a vacuum leak with a different cause. I made damn sure the mating surface was clean, put it all back together and she fired right up.

thanks for the feedback and the sanity check!

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