Surging stalling above 30mph

[Grodr625]

So I just finished up the intake manifold gasket/carb rebuild/tune up. I feel mostly defeated.

The carburetor had rusty sludge in the bottom of the bowls. I cleaned everything up and found that the float hinge pin was missing. A small piece of 2.5mm all thread from my rc parts came handy here.

Engine was hard to start and sounded like it was sucking air. Had to keep the throttle out to keep from stalling. There is an intermittent rattling sound that is not affected by rpm increase. It seems to me that 1. The gasket did not seal properly and is creating a vacuum overcome by high idle and 2. That I dropped something into the intake during the install and is now bouncing around rattling every once in a while.

Anyone have this happen? Could it be a stuck valve?

[Wildergarten]

The issue was a partially clogged fuel filter in the inlet of the carb. Some fuel would get past but not enough to maintain normal operation. Thus the above symptoms.

Useful observation, thank you.

[Grodr625]

So I am planning on redoing the intake manifold gasket job and am wondering what your preffered method of applying the gasket and sealants is. This attempt I layed red rtv around every opening and once tacky I layed the metal gasket that had been sprayed with copper rtv on both sides. I then only put rtv on the top side of metal gasket around water passages. I let everything get tacky for about an hour before resting the manifold back in place and tightened in intervals following the inward out pattern.






Any success stories fishing out things dropped into an intake? For the record I covered everything while it was exposed and thought I did a good job, but anything is possible and since I have a leak, I figure I should go fishing.

[PwrWgnDrvr]

I have rebuilt more poly's the last 50 yrs than I can count. NEVER have I used silicone like that and NEVER have I had a leaky manifold - neither before, nor after, rebuilding. I'm not surprised that the silicone goober job failed. Seemed like a method for those with no understanding of the science of engine building. If it was so great, they would come from the factory like that.
Fish with a magnet I guess.
I always install manifold gaskets with "hi tack" on the head surface and gasket surface that faces the head. Nothing on the side of the gasket that faces the manifold, nor on the manifold. I place a thin layer of silicone on the foam end gaskets and set them on the block. I let that set up for an hr or so, then place more silicone right at the ends of the gasket and a thin layer on top. Then I set the manifold in place and bolt it down. Has worked every time, without fail.

[Wildergarten]

NEVER have I used silicone like that and NEVER have I had a leaky manifold - neither before, nor after, rebuilding.

Agreed about the method shown. What it can do is squeeze stringy blobs of silicone into the intake that can then go into the cylinder. Not good.

If it was so great, they would come from the factory like that.

Unless I'm mistaken, silicone gasket sealant was not commonly available when that engine was made. Nor would there be time for it to skin over on an assembly line.

I place a thin layer of silicone on the foam end gaskets and set them on the block. I let that set up for an hr or so, then place more silicone right at the ends of the gasket and a thin layer on top. Then I set the manifold in place and bolt it down. Has worked every time, without fail.

Correct. The biggest cause of leaks is when the foam gasket on the manifold ends squirm during assembly.

[Hobcobble]

I have rebuilt more poly's the last 50 yrs than I can count. NEVER have I used silicone like that and NEVER have I had a leaky manifold - neither before, nor after, rebuilding. I'm not surprised that the silicone goober job failed. Seemed like a method for those with no understanding of the science of engine building. If it was so great, they would come from the factory like that.
Fish with a magnet I guess.
I always install manifold gaskets with "hi tack" on the head surface and gasket surface that faces the head. Nothing on the side of the gasket that faces the manifold, nor on the manifold. I place a thin layer of silicone on the foam end gaskets and set them on the block. I let that set up for an hr or so, then place more silicone right at the ends of the gasket and a thin layer on top. Then I set the manifold in place and bolt it down. Has worked every time, without fail.

https://www.permatex.com/products/gaske ... t-sealant/

John

[Hobcobble]

So I just finished up the intake manifold gasket/carb rebuild/tune up. I feel mostly defeated.
Could it be a stuck valve?

Thread Starter Quote:
"Hey guys I am getting ready for a cross country drive in my ‘64 S400 bus with a 318 poly. Engine has been running smooth until lately. "

Seeing as you had the engine running smoothly for a period of time, I wouldn't think
that its a valve issue.

Take Terry's suggestion/methods as described in his recent post and install
the intake manifold accordingly. Put the carb back on and see what you have.

John

[Grodr625]

I have rebuilt more poly's the last 50 yrs than I can count. NEVER have I used silicone like that and NEVER have I had a leaky manifold - neither before, nor after, rebuilding. I'm not surprised that the silicone goober job failed. Seemed like a method for those with no understanding of the science of engine building. If it was so great, they would come from the factory like that.
Fish with a magnet I guess.
I always install manifold gaskets with "hi tack" on the head surface and gasket surface that faces the head. Nothing on the side of the gasket that faces the manifold, nor on the manifold. I place a thin layer of silicone on the foam end gaskets and set them on the block. I let that set up for an hr or so, then place more silicone right at the ends of the gasket and a thin layer on top. Then I set the manifold in place and bolt it down. Has worked every time, without fail.

Lots of interesting things said here.

Hear me out-

Having never replaced an intake gasket, I extensively research this process here and all over the web since my shop manual had no write up for this that I could find.

General consensus amongst hot rodders I could find is that the foam end gaskets are junk. Many many references on the web that call for making the end gaskets out of pure RTV. The old gasket was leaking heavily from this area.

There are also threads on this forum that talk about using red rtv. I believe a user on here likes to backfill the steel gaskets with red rtv and makes the end gaskets out of the same.

The instructions that came with the gasket acquired from Fel Pro specifically call for use of silicone sealer I applied under and over the steel gasket around the water ports
“Now apply 1/8” continuous bead of silicone sealer around each water port on cyl heads” the gasket set comes with a tube of black RTV labeled “Black RTV Silicone”

I know GM has been using ultra grey rtv on assembly lines for years and years.

Now that I’ve defended myself and shown the conflicting info avalilable, I am going to do it as you described above. I am nervous about leaks from the water passages, but you guys seem confident that all the steel gasket needs is some tacky sealant and nothing more with a dab of rtv where it meets the foam.

My final question: do I use thread sealant on the intake fasteners? I have some high temp Permatex handy from a transmission flush on my subaru.

[wally426ci]

How is the project going? You shouldn't need thread seal if there is sealant everywhere else. The front and back cork gaskets also help with spacing - without them, the weight of the intake could push the intake down and not allow for perfect alignment everywhere else....

[Grodr625]

Well this weekend will be round 3...

Second attempt stripped out already questionable threads in the cylinder head. Was left with a vacuum leak that is only overcome on high idle.

The water passage ports have lots of corrosion and pitting and I have learned this is why Fel Pro recommends a bit of rtv around them. Others on the H A M B have claimed great success filling pitting with epoxy ala JB Weld. Short of replacing my heads, how would any of you tackle pitting around the ports?

Tomorrow I will attempt to helicoil the hole and put everything back together. The foam gaskets worked well the second time, so I will be using them on the third install.

Also found out the PO had the wrong plugs in the engine that I refreshed with new incorrect autolite 45s. When I picked up the correct Champion 129s (318-3 engine with 18mm plug holes) I realized how much longer the 45s were. There was definitely contact with the piston as the insulator on plug has broken off and the gap was fully closed. I believe this was my rattling as I combed through with a magnet pulling the oil pan looking for a highly unlikely stray bolt with no luck.

Fingers crossed the helicoil and some sort of coolant passage voodoo seals her up.

[Grodr625]

Update: heli coil repair a success. Intake bolts took full torque. No more coolant in oil. Still a slight hissing sound.

Engine still struggling to idle, revs just fine. Fuel pump replaced, fuel lines blown out, carburetor needle checked, float level checked (brass float replaced), new coil, reman distributor installed (“new” points that came with were not closing flat and replaced) New Cap/rotor, vacuum choke removed from carb- port plugged, manual choke installed. Start and run wiring completely replaced from switch to ballast firewall connector bypassed- terminals heat shrunk wrapped.

Engine was having a hard time starting. I pulled the “new” condensor the distributor came with and replaced with an orange wire NOS unit and the engine fired right up, but only stayed alive above ~1200 rpm.

Engine idles rough right before it stalls and only stays alive throttled or with choke partially closed. Timing light shows mark bouncing around 3-5 degrees intermittently. At this point I figured timing chain or worse. With only a few days before a long drive I sent her off to a truck repair shop.

Mechanic confirms he also believes it is a timing chain with too much slack or some damage. Says timing holds steady under load, but bounces at idle and dies. He’s tearing into it this week.

Any timing chain stories to reaffirm me of this? Possibility of engine damage- valves? He believes it will be a quick job and get me going very soon. Fingers crossed nothing else is out of whack.

[Grodr625]

After a timing chain/gear replacement, another rebuilt carburetor, a new fuel line and pump, and we are off. Roadtrip started Tuesday and we are creeping though South Dakota en route to NJ via Madison>Chicago I-90>I-80. No real issues thus far. Thanks for all the help on this one. It feels great to hit the open road in the 400.

[soopernaut]

That would be a sight to see, an old Dodge bus on the freeway.

[wally426ci]

GREAT NEWS! So you were not crazy, there was that other problem. Best of luck on the trip!!!

[Wildergarten]

Good to hear!

Brings to mind The Who from Live at Leeds...
https://www.youtube.com/watch?v=TmfQQC1bsf4

Give me a hundred!
95
I won't take under
95
It's a bus age wonder, She can haul like thunder!!!