Pesky vacuum leak.

Author	Message
ErnieL	Posted 4 Years Ago
Supercharged Group: Forum Members Last Active: Last Year Posts: 28, Visits: 9.0K	I’ve developed this over the last 3 months and it’s driving me to start drinking. Stock 1957 Merc 312, BT manifold, Summit 600, 1” open spacer. Runs awesome cold and warm, but once it heats up, I get a very audible vacuum leak while driving once the load comes off the engine. Any speed, but it’s more noticeable around town with less road noise. The audible leak goes away as RPM gets close to or reaches idle. Once hot, idle quality goes way downhill and becomes rough. All bolts are tight to spec. A propane search finds nothing. A carb cleaner search finds nothing. Changed out the rubber line to the distributor, no change. Capped it off at the carb, no difference. Swapped carbs, still there but seemed different, less or more depending on the carb. Tried a rubber style insulator above the aluminum spacer, seemed a bit better, torqued down the base nuts a few inch pounds more and broke a mounting ear. FVCK! Checked intake bolt torque, all good. Checked intake carb mounting base. Straight, no nicks. No change. Today I pulled the intake. The gasket surface seems good with no sign of a blown gasket or change in seal pattern. Scraped head surfaces, all look good there as well. I looked VERY carefully at the rear of the intake where the power brake port was plugged. No cracks, no obvious issues. I’m out of ideas. I’m thinking maybe an angle issue between the intake and the heads? I pulled an ECZ-B off the shelf and I think I’m gonna try this next. I’ll need to extract a couple carb studs broken off below the surface, (fun), but it’s better than this crap. I’ll attack the ports with my Drexel just to say I did, but I’m sure for street putzing around it’ll make no difference at all other than making me feel better. Save the BT for the aluminum heads I suppose. For the first time in my life, I’m actually out of ideas. Car is a 56 with Fordo. This irritates the crap outta me because other than the dog whistle, this thing runs like a scalded ass cat. 56 Meteor 4 dr hardtop 56 Meteor 2 dr hardtop 55 Sunliner 53 Lincoln Capri 2 dr hardtop 58 Skyliner Anna, Tx
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Joe-JDC	Posted 4 Years Ago
Supercharged Group: Forum Members Last Active: 41 minutes ago Posts: 754, Visits: 21.9K	Does your BT have the slot in the divider? If so, you will need to use two open gaskets to match the spacer. If the propane did not make a difference, the angle is not enough to cause the leak. Check your PCV valve if you have one. Do you have a vacuum port to any other accessory such as a trans modulator, power brakes, windshield wipers, fuel pump, etc.? Did you remove the tin bead on the exhaust crossover gaskets? If not, you need to get rid of that bead on both sides. Use a high temp RTV after you remove the metal bead, but leave the flat metal there. You can torque an iron intake down and it will crimp the bead, but the aluminum will dent and not crush the bead. Look at that closely if you remove the intake again. Joe-JDC JDC
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ErnieL	Posted 4 Years Ago
Supercharged Group: Forum Members Last Active: Last Year Posts: 28, Visits: 9.0K	Now that makes sense. I used the small hole crossovers of course, so I’ll pull a set out and look. I’ll need to go out and look at my BT again to verify the slot. I should probably run a 4 hole spacer anyway. A bit more bottom end grunt. So are you telling me to use TWO stacked gaskets between the spacer and the manifold? I can do that of course. I can put two under the carb itself as well. I’m running a 1” wood open spacer. I really like wood, the world’s best insulator, and in Texas that means everything. But assuming the metal centers on the crossover gaskets have ridges, I’ll remove them and reinstall the BT. I really hate to lose that manifold. I’ll use the RTV, and hopefully, if lucky, I’ll have enough left to glob all over the internal gaskets in the carb and inside my FM as well. Maybe seal the VB and servos up REAL GOOD. 🤣 56 Meteor 4 dr hardtop 56 Meteor 2 dr hardtop 55 Sunliner 53 Lincoln Capri 2 dr hardtop 58 Skyliner Anna, Tx
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Joe-JDC	Posted 4 Years Ago
Supercharged Group: Forum Members Last Active: 41 minutes ago Posts: 754, Visits: 21.9K	What I suggested is an open gasket under the spacer and an open gasket above the spacer. Some folks put a four hole gasket on the bottom, and it flutters, or whistles with a open spacer. What Ted and I found on dyno testing several combinations of spacers on the BT is the dual oval or four hole spacers work best. Joe-JDC JDC
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ErnieL	Posted 4 Years Ago
Supercharged Group: Forum Members Last Active: Last Year Posts: 28, Visits: 9.0K	Interesting. OK. I’ve had open everything. One above and one below, and the noise I hear is definitely a vacuum leak. It only happens once the engine has reached full operating temp. You may have hit on something regarding the intake gaskets though. There are signs that the ridge around the crossover restrictors was unevenly crushed. Do you recall the part number for the truck intake gaskets with the restricted crossover? Im going to see if the local Summit warehouse has some before I order from a mail order house 56 Meteor 4 dr hardtop 56 Meteor 2 dr hardtop 55 Sunliner 53 Lincoln Capri 2 dr hardtop 58 Skyliner Anna, Tx
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PF Arcand	Posted 4 Years Ago
Supercharged Group: Forum Members Last Active: Last Year Posts: 3.3K, Visits: 238.8K	Ernie: If you can't find the Truck "restricted" intake crossover gaskets elsewhere, try "Gasket City" as advertised in Hemmings, under "G" in Services. "Al" at Ph.# 888-335- 4686 (Eastern time) toll free or alambert@gasketcity.com Ships out of Ontario Can.. I got mine from him some time ago.. Paul
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ErnieL	Posted 4 Years Ago
Supercharged Group: Forum Members Last Active: Last Year Posts: 28, Visits: 9.0K	I can get them from any of the mail order houses, but nobody seems to carry Victor Reinz locally. Fel Pro is what’s around here and they only offer the open style. Irritating 56 Meteor 4 dr hardtop 56 Meteor 2 dr hardtop 55 Sunliner 53 Lincoln Capri 2 dr hardtop 58 Skyliner Anna, Tx
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paul2748	Posted 4 Years Ago
Supercharged Group: Forum Members Last Active: Yesterday Posts: 3.6K, Visits: 497.5K	CASCO sells the restricted gaskets 54 Victoria 312; 48 Ford Conv 302, 56 Bird 312 Forever Ford Midland Park, NJ
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DryLakesRacer	Posted 4 Years Ago
Supercharged Group: Forum Members Last Active: Last Year Posts: 1.7K, Visits: 340.0K	Anyone selling “Best” will hav then also they have the metal restrictors. Forgive me but I don’t understand the vacuum leak in that area. I use an aluminum dual quad manifold with tubes thru it for the chokes and it’s never been a problem. I looked at my BT manifold and assume the clamping washer would hold the same. If it didn’t I think you would hear exhaust ticking or noise. Thanks. 56 Vic, B'Ville 200 MPH Club Member, So Cal.
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ErnieL	Posted 4 Years Ago
Supercharged Group: Forum Members Last Active: Last Year Posts: 28, Visits: 9.0K	Yeah I’ve been chasing the vac leak for months. It’s irritating. Only shows up hot on decel. The intake is the only thing I haven’t redone. 56 Meteor 4 dr hardtop 56 Meteor 2 dr hardtop 55 Sunliner 53 Lincoln Capri 2 dr hardtop 58 Skyliner Anna, Tx
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Pesky vacuum leak.

Pesky vacuum leak.

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