Vacuum leaks suck August 28, 2012, 11:45:30 PM I went to the track this past Friday and I was expecting to turn in some great new times. Now the weather was py (93*, 70% humidity, and a 31 baro) but I was expecting it to run better. It was trapping 95 mph. Now even though the car weighs 3710 with me in it I was expecting a trap speed of 98-100 mph. I decided that something must be up so the next day I decided I would double check the adjustment on the valves, thinking that perhaps I had done it wrong and it was costing me some speed. As I went to remove the upper intake manifold I noticed a large crack by the short bolt hole on the passenger side that runs to the #1 and #5 intake runners. It turns out that you can even hear it whistle when you rev the engine, something you can't hear with the windows up. So I now have a new upper I'm cleaning up to replace the one that's on the car. With the new upper and advancing the timing a bit (I had it at 14* base, 30* total so I'm going to go up to 18* base, 34* total as long as it doesn't ping) I'm hoping to get the MPH that vacuum leak caused the car to lose. Plus it should be about 15-20 degrees cooler the next time I go, which should help. Quote Selected
Vacuum leaks suck Reply #1 – August 29, 2012, 12:48:41 AM that litterally sucks but something of an easy fix with spares.good luck on the time / speed goal Quote Selected
Vacuum leaks suck Reply #2 – August 29, 2012, 08:56:37 AM What are your thoughts/observations running the intake spacer? Quote Selected
Vacuum leaks suck Reply #3 – August 29, 2012, 09:09:55 AM Eh, that intake can be repaired. Out of curiosity, what was that bolt torqued to and is that is phenolic spacer I see peeking out between the upper and lower? Quote Selected
Vacuum leaks suck Reply #4 – August 29, 2012, 12:45:30 PM The intake spacer is on the car so there is more clearance between the throttle cable and the valve cover. I don't think it makes the car faster. The upper still gets hot due to the EGR gases and the coolant flowing through the throttle body spacer.I'll probably get the intake repaired at some point. Right now it's easier just to swap a new one on. Besides if I ever get that Mark VII I've wanted for awhile I'll have all the stuff to do a GT40 upgrade on it... Quote Selected
Vacuum leaks suck Reply #5 – August 29, 2012, 08:58:59 PM Thats a THICK spacer. Maybe it sank to much and put stress on the uppers ear. We had issues like this on some HONDA ENGINES. Sometimes those thick spacers can cause uneven clamping. Just a thought!!! Quote Selected
Vacuum leaks suck Reply #6 – August 29, 2012, 10:29:14 PM Quote from: TOM Renzo;396956Thats a THICK spacer. Maybe it sank to much and put stress on the uppers ear. We had issues like this on some HONDA ENGINES. Sometimes those thick spacers can cause uneven clamping. Just a thought!!!You may be right, but IIRC, those bolts are only supposed to be torqued to 25ft. lbs. or so. It isn't very much, which is why I asked. The stress which you discuss would likely only happen if the manifold was already damaged or weakened in that area... or maybe something hit the manifold...like maybe the hood? Quote Selected
Vacuum leaks suck Reply #7 – August 30, 2012, 05:21:51 AM Well just for the record 25 FT/LBS is quite a lot of force!!! Especially on an aluminum part like that upper EAR!!! It does not take much to crack something like that. Clearly it had a clamping issue as it is cracked in a down words direction. That is why we stay clear of parts like that. Over the years we also learned the hard way. Looking at the ear on that upper their is no other explanation i can think of!!! Can you?? Quote Selected
Vacuum leaks suck Reply #8 – August 30, 2012, 02:53:01 PM Quote from: TOM Renzo;396975Well just for the record 25 FT/LBS is quite a lot of force!!! Especially on an aluminum part like that upper EAR!!! It does not take much to crack something like that. Clearly it had a clamping issue as it is cracked in a down words direction. That is why we stay clear of parts like that. Over the years we also learned the hard way. Looking at the ear on that upper their is no other explanation i can think of!!! Can you??I never use specs on the upper, specially with a riser in between. I hand torque them in sequence. And then check with starting fluid or brake clean "1001 uses". To see if it's sealed. That is a weak spot on that intake. Quote Selected
Vacuum leaks suck Reply #9 – August 30, 2012, 03:32:03 PM Quote from: Kitz Kat;396989I never use specs on the upper, specially with a riser in between. I hand torque them in sequence. And then check with starting fluid or brake clean "1001 uses". To see if it's sealed. That is a weak spot on that intake. I don't normally torque the upper to spec using a torque wrench. I usually just do what you do, torque them by hand till they are snug and won't turn anymore. That results in no leaks and a perfect seal. I had the torque wrench out when I swapped the new heads on so I figured since it was out I might as well use it to torque the upper intake bolts to spec. I won't be doing that with the new upper :hick:. I'm going back to the way I did it before. Quote Selected
Vacuum leaks suck Reply #10 – August 30, 2012, 03:33:43 PM Quote from: TOM Renzo;396956Thats a THICK spacer. Maybe it sank to much and put stress on the uppers ear. We had issues like this on some HONDA ENGINES. Sometimes those thick spacers can cause uneven clamping. Just a thought!!! It's only a half inch. They make 1" spacers for the GT40 and most other 5.0 EFI intakes (Trickflow, Edelbrock, Holley). Quote Selected
Vacuum leaks suck Reply #11 – August 30, 2012, 09:21:02 PM Quote from: thunderjet302;396994It's only a half inch. They make 1" spacers for the GT40 and most other 5.0 EFI intakes (Trickflow, Edelbrock, Holley).Clearly it was cracked with a uneven clamping force to crack the EAR!! Like i said those gaskets are a bit to be desired. Aftermarket GIMMICKS are loaded with faults and can and do mess up engines. This is from many years of experience. And why the insulator. Really what does it actually do?? I would think NOTHING!! As far as torque specks i can look it up but is has to be around 20-25 FT/LBS. This is enough to break the ear with uneven gasket compression. I would love to mike that gasket for uniformity. Grab a one inch mike and see if that gasket is uniform. I am willing to bet it is not. Many many years ago i learned about things like this and i learned the hard way. Stay away from GIMMICKS. What is wrong with a stock gasket any way??? Just me and my $.02 Quote Selected
Vacuum leaks suck Reply #12 – August 30, 2012, 09:26:51 PM Not all aftermarket stuff is junk. Just most of it. Here is a set of mounts i bought and beat the OUT OF. Side stepped the clutch at 7K and have dun endless block long BURNOUTS with them. They are one of the exceptions. They are well engineered well built and they work great. Not all aftermarket stuff is junk JUST MOST OF IT!!!THESE MOUNTS ARE GREAT. I will disassemble them. Bead blast them paint them put them back together put them right back in my car. I have dun many a 1320 run with them and they never failed me THEY WORK PERIOD!!! Quote Selected
Vacuum leaks suck Reply #13 – August 30, 2012, 09:35:35 PM Are those Chuck's mounts?I've a set of his on my 5.0, and they are awesome. I'll get some of the other type (Mustang 5.0 style) when I put the other engine in the 'Stanger. Good stuff. Quote Selected
Vacuum leaks suck Reply #14 – August 31, 2012, 06:08:47 AM Spot on 302 they are the best i have ever used. I ABSOLUTELY LOVE THEM. And they are reasonable priced. I wish he had GM mounts as well. I am not so happy with my GM units as with CHUCKS. Chuck makes an aw-sum set of mounts. I latterly beat the OUT OF THEM. Just look at the PHOTO. Those mounts are well used and still 100% usable and not a bit of stress on them. LOVE THEM!!!! Quote Selected
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