FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: Dieselman966 on July 28, 2019, 12:33:44 AM
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I got my 352 up and running now. And after cam break in I set the timing and was checking for vacuum leaks. I have 12" at idle and 21" at 2400 rpm. When I spray brake clean around the intake bolt holes the idle drops off. Where is it pulling vacuum from by the bolt holes? Is it just leaking around the holes and running up the pcv?
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The bolts don't pass through the ports. It has to be leaking at the intake gaskets.
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Are you referring to the carb bolt holes, or the bolts that hold the intake to the heads? Two different problems. Joe-JDC
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Are you referring to the carb bolt holes, or the bolts that hold the intake to the heads? Two different problems. Joe-JDC
The bolts that hold the intake to the head. I have no leaks around the carb base.
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You can just block off the PCV temporarily and see if it responds differently to rule out that it's getting a whiff through the crankcase.
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You can just block off the PCV temporarily and see if it responds differently to rule out that it's getting a whiff through the crankcase.
I tried that this morning. I had the same result. I'm susprized it's not using any oil if the intake gasket is leaking.
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Are you guys putting any sealant around the intake ports. I did around the coolant passage but not the intake ports. I usually just do it around the coolant passages.
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I've gotten to the point where I always put sealer around the intake ports. Have had small leaks too often there. Use a good sealer, like Ford TA-31, or the Right Stuff (if you never want to take it apart again LOL!).
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I've gotten to the point where I always put sealer around the intake ports. Have had small leaks too often there. Use a good sealer, like Ford TA-31, or the Right Stuff (if you never want to take it apart again LOL!).
The 428 in my car is sucking oil from somewhere and I do use the "Right Stuff" on the intake ports after a previous bad experience. Gaskets are doubled up which didn't cause a problem the last time I used this setup. Oddly, the car runs quicker with no other changes. It comes apart easily if you use the proper persuasion. I suppose the OP's intake could possibly have a vacuum leak at one of the bolt locations but would think other issues would be more obvious first.
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Are you guys putting any sealant around the intake ports. I did around the coolant passage but not the intake ports. I usually just do it around the coolant passages.
Always. I do it on every engine, even non-FE's.
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X3
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I'm fixing to start doping up every port after fighting leaks on the 302 with the tunnel ram and even the go-to air gap. I tried Right Stuff at one time, was not real pleased with the results.
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Sounds like I have a plan then. Remove intake and apply sealant this time. Well see how this works out. How much vacuum do you guys think this is costing me? I took it for a drive yesterday and it wouldn't shift on it from 1st to 2nd until higher rpm. I'm thinking that I dont have enough vacuum for the modulator now.
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Well I'm back to the drawing board now. New intake gaskets with sealant around all ports and it still pulling vacuum around the intake bolt holes. Is there a better gasket on the market than the fel pro blue ones? I dry fit the intake before I put the gaskets and sealant on. The intake looks to be seating nice before hand.
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Stock intake and heads? Let us know if otherwise. Are you using the cork or rubber end seals? When you dry fit the intake, did you use the end gaskets? When you dry fit the intake, did you use the dry intake gaskets? How did you verify the intake to head fit? By sight or feeler gauges? What did the intake imprint look like on the old gaskets? Any apparent alignment concerns, like could you see where the intake was impressing on the gasket and did it look uniform?
A longer shot, but did you carefully inspect the intake for cracks or voids?
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Stock intake and heads? Let us know if otherwise. Are you using the cork or rubber end seals? When you dry fit the intake, did you use the end gaskets? When you dry fit the intake, did you use the dry intake gaskets? How did you verify the intake to head fit? By sight or feeler gauges? What did the intake imprint look like on the old gaskets? Any apparent alignment concerns, like could you see where the intake was impressing on the gasket and did it look uniform?
A longer shot, but did you carefully inspect the intake for cracks or voids?
The heads were machined down .020 and the engine deck was machined down .070. Total was .090. Then had him machine the intake side of the heads .080. The head to intake transition is real close. I checked the fit up of the intake while it was out visually. Everything looked pretty even. Feeler gauges would have been more accurate though. I am not using gaskets on the ends of the intake. Just a thick bead of silicone to seal it up there. The intake gasket kit I am using is MS 90145.
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The intake is an edelbrock ingot from a guy on Facebook. Visual it does not appear to have any cracks.
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Is it possible the bolt are bottoming out? Try 2 flat washers on the bolts and retest.
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Earlier you didn't see any oil usage. If that is still the case and the runners are sealed I would block off the PCV valve and see if the vacuum leak is still there.
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I took it for a drive yesterday and it wouldn't shift on it from 1st to 2nd until higher rpm. I'm thinking that I dont have enough vacuum for the modulator now.
Is the modulator or line to it leaking?
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Is it possible the bolt are bottoming out? Try 2 flat washers on the bolts and retest.
That's a possibility. They seem like they are turning easy still while I'm torquing them down. I'll give it a try though.
Earlier you didn't see any oil usage. If that is still the case and the runners are sealed I would block off the PCV valve and see if the vacuum leak is still there.
I still dont see any smoke out of the tailpipe yet and I did pull the pcv valve and plug it. Still have the same issue.
I took it for a drive yesterday and it wouldn't shift on it from 1st to 2nd until higher rpm. I'm thinking that I dont have enough vacuum for the modulator now.
Is the modulator or line to it leaking?
I haven't checked that yet. The line looks good but I'll get a new one and put it on there. Maybe its cracked pr split and I cant see it.
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Check the angles between the heads and intake. I caught this on my new build during mockup. I verified the block and heads were machined perfectly at 45 and 90°. I knew the problem was the intake. You could see it slightly by eye with no gaskets in place. I dry fit the gaskets and could wiggle the gasket in certain places on the bad side and was fine on the other. I pulled the intake and checked the angles and found one side fine at 45° and the other off by 1-1.3°. I had my machinist mill the angle back by that amount. The intake was used and milled in the past. After another dry fit, I snugged the intake down slightly and checked the gaskets for witness marks all around the ports. Everything looked good.
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Brake booster?
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Don’t just throw a couple flat washers on there, measure how deep the hole is with a Phillips screwdriver, The idea of bottoming bolt is good but your likely to pull the threads out of the head if you do it by experimentation. Depending on the intake every hole can be different too so be sure to measure all
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Depending on the intake every hole can be different too so be sure to measure all
This is a good tip for every fastener used in an engine. With aftermarket parts, new bolts, etc., it's always prudent to check every single fastener length to make sure you have adequate thread engagement. The biggest issue I see is with some camshaft bolts, as well as cam thrust plate bolts and oil filter adapter bolts on aftermarket blocks.
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Don’t just throw a couple flat washers on there, measure how deep the hole is with a Phillips screwdriver, The idea of bottoming bolt is good but your likely to pull the threads out of the head if you do it by experimentation. Depending on the intake every hole can be different too so be sure to measure all
I checked all of the bolt holes for length. None of the bolts were bottoming out.
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I cleaned up my intake tonight and I decided to compare it to my stock 4bbl one. The ports are way bigger on the stock one vs. The edelbrock performer 390 one. I wonder how much this is hurting the performance? Does the edelbrock really work better than the stock one?And could this be contributing to my vacuum leak problem?
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These tiny Edelbrock intake ports definitely can’t support very much power. They may be good for a low RPM 360 or 390 motor but not a high RPM performance motor. Without any mods I don’t know how much power they can support but I would guess 400hp is probably not obtainable with any cylinder head. In fact, maybe 300 hp is more realistic. Someone else who has more experience with this manifold would know more about this.
If you decide to port match the intake to your gaskets or head port sizes be aware you need to ensure the intake runner cross section (further up inside the manifold) is similar size to your port opening size. In other words you don’t want a small runner leading to a larger port opening. This would accomplish nothing, the manifold would still be the bottleneck.
But this still doesn’t explain your vacuum leak.
I suggest placing a straight edge on the manifold to look for warpage or low spots possibly caused my aggressive gasket scraping or a power gasket scraper.
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Check the bottom of the ports on the intake manifold to see if they are sitting on the head gasket, or block. Some of the Edelbrock intake manifolds had too much material cast into the ports lower edge, and must be cut off so the intake will sit down properly. Also, you need to make sure the oil drain back area at the front of the manifold is actually cast into the manifold, so you will not have a oil drain back problem. As for the manifold actual flow, it is not as good as the stock -H, -F, or -J aluminum Ford intakes. A couple of the ports only flow around 220 cfm as cast. Joe-JDC
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Check the bottom of the ports on the intake manifold to see if they are sitting on the head gasket, or block. Some of the Edelbrock intake manifolds had too much material cast into the ports lower edge, and must be cut off so the intake will sit down properly. Also, you need to make sure the oil drain back area at the front of the manifold is actually cast into the manifold, so you will not have a oil drain back problem. As for the manifold actual flow, it is not as good as the stock -H, -F, or -J aluminum Ford intakes. A couple of the ports only flow around 220 cfm as cast. Joe-JDC
It ended up being the head gasket in the way. I've never had that problem before. Now I know to check that before putting sealant down on the gaskets. The intake is sitting on the heads nice and even now.
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Has anyone ever checked for manifold vacuum leaks before putting the rocker shafts back on. I was thinking I could use my hand vacuum pump and check for leaks before putting it all back together.
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If you try it, have someone record a video of it and post it up.
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I tested for vacuum leaks by torquing the intake down and putting duct tape over the carb opening with the carb gasket and lifting plate bolted down. I pumped it down to 10" of vacuum. And it took 1 minute 32 seconds to come down to 9" of vacuum. I cant imagine it getting much better than this.
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There's no way that would do any better than that considering. It would sound as if you're good to go!