Replacing intake manifold gaskets

[Faulkner]

En route to Carlise 2009, I sprayed those behind me with antifreeze leaking from my recently repaired intake manifold. I had it repaired, because it was leaking… (sigh) I’m resigned to the fact that sometimes, if you want something done right, you have to do it yourself. So after consulting with Ed Eckerson, I bought a set of NOS Offenhauser intake manifold gaskets from Gary Pavlovich:

Ed since learned that they are available new from Phethean Racing Products, P/N 5433 for $11.50:

http://www.offyparts.com/
[This link appears to now be busted; and a Google search does not yield a result… (sigh.) Best to check with Gary Pavlovich. -Dan]

These are “composite” gaskets, not metal (as are the FelPro kits available from NAPA) – and are more forgiving of minor fluctuations in the intake mating surface. The important difference, however, is that they must be retorqued – not only after installation, but after burn-in.

Here’s the 318 before I started:

Stripped of parts and manifold bolts, the manifold is ready to remove:

I work a thin-blade screwdriver through the sealer at the front end, and the manifold pops loose. Yow! That sucker is heavy! I end up lifting it off at an angle, and setting it on the floor. Then I peer at the block…

Oh no! There’s antifreeze sitting in pools, next to the lifters! How did this happen? I check the dipstick…

There’s no water in the oil. Whew! A quick phone call to Ed; this happened when I removed the intake manifold, likely from a pool of antifreeze within the manifold. Sure enough, where I set the manifold on the floor, there’s a little pool of antifreeze. I mop it all up, and per Ed’s advice, I “chase” it with oil poured liberally over the cam and ports; I’ll drain the pan and refill before I crank it up, and there should be no harm done.

Next, I clean the block and head surfaces, blocking all bolt holes and ports, scraping off all sealer and other deposits, and cleaning with alcohol…

The FelPro kit I had also bought – and ended up not using – has front and rear “spongy” gaskets, that dovetail into the left and right gaskets:

Ed has a great suggestion: Lock down the left/right gaskets to the head with short cap bolts, and glue down the spongy gaskets in position, knowing their exact placement with the left/right gaskets – let them set up, so that they don’t squiggle around when the manifold is reset:

\

Enough for tonight – tomorrow, I’ll reset the manifold, do the first round of torqueing, and let it sit again. Ed discovered that, within a couple hours, the bolt torque with the composite gaskets dropped – even without firing up! Whatever it takes, to get this finally right.

Here’s a pic of the intake manifold, all cleaned up:

To be continued…

Dan

[rogerh]

a perfect time to take some visegrips and “unscrew” the two “nuts” holding that cover plate on the intake…under that cover is the “Crossover”…a chamber that aids in pre-heating the carb esp. on those cold days. After 50 years. the carbon builds up in here, inhibiting its purpose. (don’t take my word on it, anybody esle think my idea is timely?)

[Faulkner]

I wondered what that plate was for! I’ll give that a try, Roger.

Dan

[Faulkner]

Well, it’s hard to get a pair of vise grips on them… Roger’s since sent me this tech note. Hmmm… I sure don’t want to break one of those suckers. What to do, what to do…

[Faulkner]

“It’s relatively easy to break a rivet.” OK, that’s probably not what I wanted to read; the thought of drilling cast iron and tapping it (with a tap set I don’t have) is not a place I want to go. So, in the “what not to do” department, I’m going to leave well enough alone. I hope this doesn’t come back to bite me! C’este LaVie.

Dan

[Faulkner]

Against my better (?) judgement, I tried to work a thin blade under each rivet, tapping all the around each perimeter…

Nada. These guys ain’t budging.

Perhaps this is sour grapes; but, I bought this as a rebuilt engine (from an eBay seller whose client for the rebuild never showed). Is it possible that he cleaned this when he rebuilt it? I don’t feel any crud when I stick a little finger in the openings… Definitely, I’m going to leave well enough alone. My advice to you when you replace your gaskets, is to pry out the rivets!

Dan

[rogerh]

Completely understandable, Dan. Your intake looks very clean, so maybe it’s been thoroughly cleaned. The crossover feature would probably only be noticed if you were a cold-weather driver..the exhaust heat helps warm up the choke spring more quickly, so your car doesnt run on half-choke for longer than necessary. One of the features of Plymouth Economy (before they switched to electric choke pull-offs).

[Faulkner]

The sponge gaskets have set up nicely, and the composites are in place with just a little dab of sealer at each end. Now I coat the ends and top of the sponge gaskets with sealer, and prepare to put the manifold back. This time, I enlist Marie, and I hang two chains on the carb bolts to assist in managing:

Up and over the fender it goes! Keeping it aloft we lower it down almost exactly in place. A little translation towards the front, and… There. Lined up perfectly, and bolts find purchase in the head. Nothing moved!

Look at how nicely the sponge gaskets align with the manifold! No slippage at all. Great tip, Ed!

And now, I go for a walk: From right side to left side, torqueing a bolt at a time, working from the middle out, first 15 ft. lbs, then 25, then 30. I must have walked 5 miles in the garage!

I’ll let it sit for a good while, then I’ll torque them again at 30. Off to Pep Boys to get some oil!

[Faulkner]

OK, for those who want to do it the right way, here’s a set of pix from Roger, with some commentary:

@Roger

I have an intake here in the driveway and I wanted to demonstrate the cover removal, but you are already back together…
The rivet WAS difficult to loosen..it took repeated taps with hammer and old chisel both at the rivet edge and then at the edge of the cover itself.

Once it loosened, I put vicegrips on it and twisted it out easily.

I was supposed to loosen the other rivet, but got impatient and just lifted/bent the cover enough to reveal what was inside.

My goof was in thinking that exhaust gasses passed thru here. That of course would be ridiculous, but the area somehow permits heat transference or dispersion or both…under the carburetor. The heat helps pull off the choke sooner. Maybe excess crud here causes heat to remain in the area, leading to vapor lock on hot days. I do not know.

I didn’t clean the area out. I put it back together. However I must tell you there is no way to feel with finger if there is crud in there as no ports open into that area.

[Faulkner]

Wow, that sucker really is crudded up, even at the perimeter where you can see. My manifold looked nothing like that – let’s hope I’m OK. Nice shot of the rivet – so that’s what they look like. Thanks, Roger!

Dan

[Faulkner]

Ed was right: Let the manifold sit for a spell and come back, the bolts will need retorqueing! Some were where I left them, others dropped maybe 10 lbs of torque (just from the feel of it). I’ll let it sit some more – mostly, because I’m not allowed to play mechanic any more this weekend! I’ll try to finish it up during the week, and with any luck I’ll drive it to my cousin’s party next weekend, weather permitting.


…and not spray anyone driving behind me

Dan

[Denver_59_Fin_Conver]

Dan, that metal plate/shield actually keeps the oil in the valley area from splashing up hot oil directly to the underside of the intake manifold.

As you can see when you removed the shield it still traps some oil and eventually cooks it to sludge like carbon build up. My 413 and my 440 engine has this same shield and the same sludge. Even boiling the intake does not remove all this stuff.

Without this baffle shield the underside of the maniforld heats up quicker and the non-electric choke comes off earlier then expected.

John Q.

[savvy59]

John Q. and All,

I agree - in fact during my rebuild of my LA 318 from 1976 I used a Windage tray from Milodon that covers the entire valley.
It does reduce the amount of heat that transfers though the intake manifold to the carb. I don’t believe that Milodon sells such a pan for the Poly 318.

Curt

Provides protection from oil splash-back.

Milodon Windage tray - 1976 LA318

Ideal for street and strip applications, these Milodon windage trays are specially contoured for a good fit. They permit rapid oil return and protection from oil splash-back, while providing increased power. They’re available in either a solid design with louvers or a high-tech screen design.

[rogerh]

This is not clear to me.
While reducing “splashback” is good for more efficient lubrication, I don’t see how you get increased power. According to the 1958 Plymouth Service Manual, the baffle is there to help vaporize fuel in the carburetor above. John Q says it is there to reduce heat at the carb.
I have removed intakes before and found foil-wrapped insulation underneath. Were these insulators factory-original?
In any case, excessive carbon build-up should be cleaned out.

[Denver_59_Fin_Conver]

Roger, you are indeed right it does help to vaporize the fuel during tcold start ups for fuel atomization process, but there is a narrow window of time that it helps the fuel issues on cold starts before the overall heat of the oil becomes a more enduring problem and starts overheating the bottom of the intake causing to much atomization of the fuel.

The advent of external air delivery during the 60’s and 70’s (shaker hoods, Fresh Air hoods & Ram Air hoods helped deliver cold or relatively cold air to the carb before the shear heat of the engine would then help atomize the fuel. It is a delicate balance.

I have windage trays on my two RB motors and one on the 340 motor on my Cuda Convert. These windage trays help in keeping the oil from being whipped up to a oily foam by the rotating mass of the crank and the pistons. Windage trays slow down the oil being returned to the crank by directing it to cetain areas to fall to the crank area with out being whipped up. these trays help on bottom end oiling. Valve covers also thru time have different baffles of steel to do the same in keeping oil from being foamed up by the Rocker assemblies.

John Q.

[Denver_59_Fin_Conver]

I forgot to mention the foil packs that Roger talked about. I have mostly seen these on B and RB motors. These packs are being reproduced for the Muscle car era cars by a company back east. Bill Rolik Restoration I believe makes these packs.

I did have these Foil Pack on my 1960 413 motor but was almost disintergrated by oil , dirt and heat.. These pack were foil wrapped inuslation packs that were placed (Two of these packs) undereath the B/RB motor intake manifolds and the Valley pan. My old 70 Challenger Convert had these packs too.

The B and RB intakes are not subjected to direct contact with the lifter galley oil splash. So Cold starts are assisted by the intake Manifold to Cylider Head cross over tubes that help the B/RB motors heat up. My 60 413 Intake was caked shut with carbon deposit, which did not allow good cold start chracteristics. Had to chisel these open before boiliong the intake.

The Insulation Foil packs are easy to make your self for show points. They do provide some degeee of heat mitigation to the bottom of the B/RB intake from the Valley pan gasket. A minor point would be some quieter noise of the liter valley by these foil pads due to the kettle drum effect of the valley pan. I have not notice any sound deadening, but a long forgoton article in one of the Mopar Magazines had mentioned it. But the heat insulation aspect is why they are there on B/RB motors.

John Q

[Faulkner]

Roger points out this page from the shop manual, regarding the utility of the cross-over for preheating the fuel…

@Shop Manual

Layers of carbon act as a heat insulator and retard the heating action of the exhaust gases in the heat chamber of the intake manifold. Thus, fuel will not vaporize as much as it could, causing poor engine performance.

Dan

[RICKYMOPAR]

Hi, I am going to give you the old mechanical tech view of the oil baffle/shield and windage tray and what they are intended for without going to the deep end of the pool;
Oil baffle/shield, The heat crossover in the intake manifold gets so hot that it bakes the oil and impurities to the bottom of the intake, hard and chunky junk as shown by your pictures, the baffle/shield reduces the amount of this carbonized crud as well as captures that which is formed and keeps it out of your oil pump and screen. engines last longer
Some industrial engines didn’t have a exhaust heat crossover, they were coolant heated intakes and didn’t require the shields.

Windage trays help remove oil from the crankshaft recipricating area, using gravity and crank rotation. oil is slung off the crankshaft at pretty high speed, the oil flying up lubes the camshaft lobes and cools the bottom of your pistons. and is also thrown back down into crankshaft rotation. The windows in the tray shear and separate then direct the oil back to the sump of the oil pan. also stopping oil from splashing back into the cranksnaft from the oil pan sump. keeping oil in the sump is good.

[rogerh]

Hi Ricky Mopar:
IF this crossover collects crud, why have it in the first place? Why create a plce where oil, etc can cook and bake into crud? Is there a purpose to pre-heating the intake? Is there a performance improvement? I can understand that keeping oil in the sump is a good thing, as well as having oil distributed evenly and consistently. what about the insulating pad I found in other engines?

[RICKYMOPAR]

Roger, The exhaust gas crossover and early fuel evaporation control valve or heat riser is entirely for driveability in cold weather driving and cold start units with automatic choke units. Again I was trying to stay out of the deep end of the pool where all the bodys are.
The latent heat of the vaporization of fuel is so great that the carburetor is actually a refrigeration unit, without some heat carburetors ice up and become non-functional.
The heat also aids in increasing fuel economy to a great extent. unfortunatly when the weather is warm the performance is seriously hindered by its existence, Oil refiners used to blend fuels for seasons and altitude,‘The reid vapor pressure measurement system’, I am afraid this no longer is a priorty. The drivability here in Colorado on a 90Degree F. day with our old cars can be very trying because of drivability problems like vapor lock and other causes of stalling due to the heat. We also have high solar radiation background heat added to the mix during the afternoon. I am thinking of blocking my heat crossover and using a water heated carb mount. being I seldom drive in below freezing weather any more. I hope this answers your question.