Intake manifold question

[Baba Ganoush]

So if I bolted up an intake to my brand new crate engine (306, e303, gt40 heads), torqued it down to spec, didn't run the engine yet, and then decided to use a different intake, should I replace the gaskets with the new intake?

I did re-apply the blue rtv to the front and back, but left my felpros in place. I'm wondering if it is a possible source of a vaccum leak, and if it's worth it ripping it off again to put fresh gaskets on.

Also, does anyone know if a carb spacer is needed on an air gap intake when using a Holley 80457 (600 cfm 4bbl) It seems the consensus is no, but I'm trying to solve what seems to be a pretty serious vaccum leak.

Car starts but won't idle without the throttle jumping way up, then dropping and almost dies, then surges way up again.

[turbos66coupe]

I would of replaced the gaskets. Make sure the pcv vacume port at the back base of the carb is plugged

[Baba Ganoush]

I would of replaced the gaskets. Make sure the pcv vacume port at the back base of the carb is plugged

I'm regretting not doing it. Oh well, time to fix it.

I'm using that port for my pcv that is running from my valve cover.

You think I should be running a carb spacer?

[shumpertdavid]

if it will run long enough, spray around the base of the carb and around the intake ports with carb cleaner to see if you get an rpm drop. If so you've found the source of the leak. You can also remove your pcv and plug it, and spray carb cleaner into the valve cover and see if there is rpm drop. You could have vacuum leak at the base of the gasket and it will pull a vacuum on the crankcase.

[Baba Ganoush]

if it will run long enough, spray around the base of the carb and around the intake ports with carb cleaner to see if you get an rpm drop. If so you've found the source of the leak. You can also remove your pcv and plug it, and spray carb cleaner into the valve cover and see if there is rpm drop. You could have vacuum leak at the base of the gasket and it will pull a vacuum on the crankcase.

I used an air hose and pressurized the crankcase and it seemed to hold pressure really well. The best part is no leaks on my pcv system. I'm still suspect of the intake gaskets, even though I'm not leaking coolant anywhere. My problem has to be there or where the carb bolts up. I'll grab some carb cleaner and try that method. I'm using all new components and it should run like a top, but I'm a newb when it comes to carborated setups.

[shumpertdavid]

I wouldn't recommend pressuring the crankcase, that's a possible way to blow seals and gaskets

[Blackpony]

I would not use blue rtv on the intake. It will break down when exposed to oil. Use either black or grey only. You should be fine reusing the gaskets so long as they never seen a heat cycle. I would double check your torque on them before you go to tearing into it.

[Baba Ganoush]

I didn't use too much air, just a quick test to see if my pcv system was air tight. I've double checked my bolts with my torque wrench, and made sure all unused ports are plugged.

No blue silicone (gasket maker)? I thought that is what everyone used on intakes? I've used it before with zero issues.

I figured the intake gaskets would be fine, since the engine was never started, but I'm trying to rule out anything that would lead to a vacuum leak. I'll do a carb spray test tomorrow and try and track it down.

It's just not running right at all, it almost sounds like it's missing. My timing is right, well as close as I can get it until it will idle, and the ignition system is all new MSD everything, so the hunt for the problem continues.

[shumpertdavid]

are you running the ho firing order or standard firing order. If the firing order is wrong then it will miss on 4 cylinders.

[projectPONY]

If I'm not mistaken the blue and gray gaskets makers are NOT intended for use in oily situations. Says so on packaging. I've always the copper stuff.

[Baba Ganoush]

are you running the ho firing order or standard firing order. If the firing order is wrong then it will miss on 4 cylinders.

Yes I'm using the H.O. firing order. It's a Ford Racing X302 crate engine and I followed their instructions to the letter, per the 13 page document that came with the engine. This isn't my first rodeo, but I've never even touched a carburetor until now.


Damn thing runs like its missing two cylinders. It's probably something to do with the mixture, vacuum leak, or something else small that I overlooked. Time to find an old(er) guy.

If I'm not mistaken the blue and gray gaskets makers are NOT intended for use in oily situations. Says so on packaging. I've always the copper stuff.

Hmm, well I know plenty of people using permetex gasket maker blue on every intake they do, and have had zero issues. It is some really good stuff. All of their silicone is resistant to oil, with copper being the best.

[garycrist]

Did you match the manifold or just "bolt er up"? Peek down the port runners and see if the floor of the manifold is higher than the floor of the intake port. If it is, then the leak is under the manifold.

[Baba Ganoush]

Did you match the manifold or just "bolt er up"? Peek down the port runners and see if the floor of the manifold is higher than the floor of the intake port. If it is, then the leak is under the manifold.

Just bolted her up. If that was the case, my oil should show signs of gas, correct?

[garycrist]

Not necessarily. Fuel should not puddle up under normal conditions.

I milled my intake by 120 thou. to get it to sit deep enough to match the floors and roofs.

[Baba Ganoush]

Well I'll tear into it one night this week. I wish the problem would jump out at me, but it's making me work to find it. I'm ready to drive this thing, dammit.