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This is a problem, but not for your potential vacuum leak. The valley doesn't have manifold vacuum. Only the part under the carb and the runners. It is possible to have a leak to the lifter valley but this is between the cylinder heads and the intake manifold. Not intake manifold to block.
Did your engine see some heat cycles? If yes, re torque the intake manifold to spec. But most likely it will still leak. Sorry to hear. Pulling the intake manifold is work, especially the cleaning part. But this happens. Sounds like you did everything right. Did you see the gasket maker getting pressed out at bit? Was the surface clean?
I hear a lot of good stuff about the Right Stuff. However I use Ultra Grey as recommended by my engine designer.
 

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Discussion Starter #42
This is a problem, but not for your potential vacuum leak. The valley doesn't have manifold vacuum. Only the part under the carb and the runners. It is possible to have a leak to the lifter valley but this is between the cylinder heads and the intake manifold. Not intake manifold to block.
Did your engine see some heat cycles? If yes, re torque the intake manifold to spec. But most likely it will still leak. Sorry to hear. Pulling the intake manifold is work, especially the cleaning part. But this happens. Sounds like you did everything right. Did you see the gasket maker getting pressed out at bit? Was the surface clean?
I hear a lot of good stuff about the Right Stuff. However I use Ultra Grey as recommended by my engine designer.
Well damn, now I've got two problems!

Yeah, my engine has seen some heat cycles. Between break-in and the dozen or so runs to adjust timing and fuel, it's been up to operating temperature before. I re-torqued all the bolts after break-in, and after six or so runs up to hot. I did see some gasket being squished out, and cleaned both surfaces thoroughly with lacquer thinner before applying.

Maybe I'll try Ultra Grey next time. This is going to be the third time I've had to install the intake manifold (once during rebuild, once for a leaking water passage) and I'd REALLY like to get it right this time. I guess this now takes priority over the vacuum leak, but that will need to be taken care of at some point too.

One step forward, two steps backwards... some days are like that, I guess (n)(n)

Thanks again for all the help
Alex
 

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How did you lower the intake manifold? Good practice is to use some four old bolts, cut the head and make a small slot so you can apply a flat head screw driver. Bolt them in at all four corners and use them as a guide to lower the intake manifold. Remove them and use the intake manifold bolts. This way you avoid any kind of adjustment.

Heads up, we all know how you feel.
 

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Discussion Starter #44
How did you lower the intake manifold? Good practice is to use some four old bolts, cut the head and make a small slot so you can apply a flat head screw driver. Bolt them in at all four corners and use them as a guide to lower the intake manifold. Remove them and use the intake manifold bolts. This way you avoid any kind of adjustment.

Heads up, we all know how you feel.
Exactly how I did it! I had new hardware, so I cut the heads off the old bolts and used them as guides to lower the new one in. I was able to just twist them out after that. Maybe I didn't tighten the manifold enough? I've read recently that you should lubricate your manifold bolts to get the best torque readings. We didn't do that, but I'm not wild about lubricating bolts that aren't supposed to loosen themselves somehow... something about it just seems wrong.

I might take a day off and go fishing or something, and come back to the job when my new gaskets arrive on Wednesday. I'll pick up some Ultra Grey in the meanwhile.

Thanks for the help and encouraging words!
Alex
 

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Timing is currently ~12° BTDC. Cam is not stock— would the cam card have the vacuum number on it?

I plumbed the vacuum gauge to the rear PCV valve hose going to the carb spacer port.

Thanks for pitching in!
Alex


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I run a custom cam and the grinder provided the specs with the cam. Not all off-the-shelf suppliers do this. I, for one, think it's a much needed spec. A "hot" cam doesn't have to have a low Vac # associated with it. Go back to your grinder and ask the question.
 
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Vacuum advanced removed (I usually use the vacuum advance port for the gauge).
Is the 4100 different then lets say the Edelbrock carb? Because at idle the ported/timed port has no vacuum at idle or shouldn't. If it does that means the throttle plates are not all the way closed.
 

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Is the 4100 different then lets say the Edelbrock carb? Because at idle the ported/timed port has no vacuum at idle or shouldn't. If it does that means the throttle plates are not all the way closed.
Ported vacuum port should not have vacuum at idle. If you see vacuum the blades are slightly open (which can be necessary with a big cam). The vacuum advanced is connected to manifold vacuum.
 

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I think some pictures of the intake, carb and valve covers would help. I couldn’t tell in the video, but it looked like nothing was hooked up to the PCV valve on the passenger valve cover.
 

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Discussion Starter #49
I think some pictures of the intake, carb and valve covers would help. I couldn’t tell in the video, but it looked like nothing was hooked up to the PCV valve on the passenger valve cover.
I’m in the process of redoing the intake manifold, but I’ll get some of those pictures when it’s done. The PCV valve wasn’t being used, you are correct, but it was because I plumbed the vacuum gauge into the rear PCV system hose (the one that goes to the carb spacer). The hose would normally be on the PCV valve.

Cheers
Alex


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Dumb question, have you checked the valve itself? I believe they can fail in such a way that could create a vacuum leak. I am sure someone that knows more than me will chime in.
 

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Discussion Starter #51
Dumb question, have you checked the valve itself? I believe they can fail in such a way that could create a vacuum leak. I am sure someone that knows more than me will chime in.
The valve is brand new and I hear something jiggling around when I shake it— a sign that it’s in good shape and not frozen shut. It did, however, break when I was adjusting it after taking the valve cover off, so a new one is going to be installed.

That’s a good idea though! Thanks for pitching in.

Cheers
Alex


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I think some pictures of the intake, carb and valve covers would help. I couldn’t tell in the video, but it looked like nothing was hooked up to the PCV valve on the passenger valve cover.
Also, no breather cap on drivers side valve cover? Not sure that would make any difference tho if pcv is not in use atm..?

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Also, no breather cap on drivers side valve cover? Not sure that would make any difference tho if pcv is not in use atm..?

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Thanks for the idea. I took the air cleaner and valve cover breather off for testing. Do I need to plug that hole for vacuum purposes? I hadn’t thought of that.

Cheers, Alex


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