RTV on lower intake manifold to head?

danielwd · Dec 9, 2017

Red RTV on both sides of felpro gasket for lower intake manifold to head?

Or not...just felpro gasket with no RVT?

What about upper intake manifold to lower manifold? RTV + gasket or not?

Felpro's website says no way...just use gasket.

Any suggestions?

Thanks in advance.

ericbphoto · Dec 9, 2017

I haven't built many engines. But I'll chime anyways. I would think that a reputable manufacturer should know the proper way to install a product that they designed. If Felpro says no goop, I would avoid the goop.

Eric B

Mark_88 · Dec 9, 2017

If this is the newer head with no water passages through the intake then you do not need anything on the gasket as mentioned.

If there is a water passage like the older style heads had, then you should only put a small coating of gasket sealant around the opening for the water passage.

I think they stopped that coolant routing after 92 on those Lima heads but I'm not sure...there was a post showing the intake ports on different heads but I don't recall if they showed what year that was modified.

danielwd · Dec 9, 2017

Thanks everybody for the input. This is a 1994 Ford Ranger 2.3 L. I apologize for not mentioning that.

There is a 'jacket' that butts up against the lower intake manifold that allows coolant to dissipate some heat...I guess. I really don't get how a little opening like that would help rid heat, but whatever.

I would also add that there is some scarring from me attempting to remove 23 year old gasket material from the intake to head surface. The head came clean fairly easily; however, the lower intake manifold was no fun. I went through many cans of intake cleaner, and it still needs some more scrubbing. The gasket material would not come off, and I fear that I pitted the surface trying to get it off. The couple of groves aren't deep, but they are evident. I've read that lightly applying JB weld over the surface with a razor blade and sanding can fill the pits.

Would this change everyone's opinion on the matter?

And would red RTV be okay? That's what I have on hand, but its for high-heat application.

Mark_88 · Dec 9, 2017

On the intake side with the water passthrough the idea is to seal against the coolant entering the intake/combustion and to prevent air into the mix because it would be like a vacuum leak and cause really rough idle and error codes.

Worst case scenario is you have to remove the intake side of things and redo the seal with the RTV...I would leave it off except around the water inlet.

The water inlet is actually for fuel atomization from what I heard...the heat helps to keep the fuel atomized so it burns more efficiently...but I'm going from what I was told in carburetor applications where the fuel needs to be warmed...and the intakes were designed so that the hot coolant passed under the fuel entry part of the intake and was affected by the higher temperatures...

tomw · Dec 10, 2017

If you have deep scratches, using JB Weld to fill, and then sand should restore them for use. Use a metal straightedge across the surface to check for flat, dips and high spots. You should not find significant variation.
The coolant passage was to help heat the incoming air(actually the manifold) to make fuel atomization better. Previous models had a small coolant hose routed around the back side of the head to one of the heater hoses and used a tee into the hose to connect. Coolant was circulated the same as through the heater core.
I would not use sealants if the surfaces are clean, dry and smooth. My experience is that even a thin coating of sealant, except on bolts that pierce the water jacket, tend to produce loose fasteners as the sealant oozes out from between the gasket & metal. That leads to leakage. I don't know how many front covers I used sealant on that developed leaks over time, with the fasteners not tensioned because the sealant 'moved'. I vote no, if you are counting. If you want to know for sure, get the shop manual for the official words.
tom

danielwd · Dec 12, 2017

tomw said:
If you have deep scratches, using JB Weld to fill, and then sand should restore them for use. Use a metal straightedge across the surface to check for flat, dips and high spots. You should not find significant variation.
The coolant passage was to help heat the incoming air(actually the manifold) to make fuel atomization better. Previous models had a small coolant hose routed around the back side of the head to one of the heater hoses and used a tee into the hose to connect. Coolant was circulated the same as through the heater core.
I would not use sealants if the surfaces are clean, dry and smooth. My experience is that even a thin coating of sealant, except on bolts that pierce the water jacket, tend to produce loose fasteners as the sealant oozes out from between the gasket & metal. That leads to leakage. I don't know how many front covers I used sealant on that developed leaks over time, with the fasteners not tensioned because the sealant 'moved'. I vote no, if you are counting. If you want to know for sure, get the shop manual for the official words.
tom

Thanks for all your advice. I have been researching, considering input here, and mulling things over. Time to get it done. I have decided to place Red RTV (high temp) around the water jacket because that is the area that received the most scarring and is pitted the most. I have applied jb weld and lightly sanded with fine sandpaper. It seems to have filled in some crevices. But the surface still looks a little rough to me.

I'm going to apply a very thin bead around the water jacket on the head side and intake manifold side.

We shall see how it goes! I will report back in some time with results.

Thanks!

Mark_88 · Dec 12, 2017

I've never used JB Weld on a head but I did use Liquid Metal on an exhaust leak and it worked great for about two years. It started to crumble and break away eventually so I just redid it when it started making noise.

This was on the outside and not pressed into place so much more likely to crumble and fall out. The question I would be asking is does the JB Weld stand up to the temperatures in that area like Liquid Metal or similar products. The JBW may be liquid metal rebranded or vise versa and that is why I was asking...

Do they indicate heat ranges for that to work in? Liquid Metal gets harder with higher temperatures so it is ideal for exhaust side head work but the intake side probably gets close to the same temp range.

danielwd · Dec 14, 2017

I use Muffler Weld from autozone on anything post-cat...not sure if it can withstand anything pre cat. Thankfully, my exhaust manifold looks like it is doing okay - it is original.

Updating my truck - I did install the lower intake and gasket. I also changed my mind and used a very thin (paper thin) coating of red RTV on the gasket to head surface. I allowed it to set up for 30 minutes or so, then I applied another very thin layer of red RTV to the gasket itself and installed the intake. I didn't feel anything slip.

I allowed the truck to sit for 24 hours and buttoned everything else back up.

Started up without evidence of exhaust leak. I ran it around the block, and it is driving spectacularly.

I will post back if anything else changes.

Thanks for the input guys, and we can let this thread die off!!!!

Mark_88 · Dec 20, 2017

The Red RTV is OK on the intake side and I've plastered an intake mating surface with it once when I had a leak under my carburetor. It doesn't hurt anything...unless it breaks off and gets into your float bowl somehow...but you won't have to worry about that.

Good work on fixiing it and sounds like you're off to the races... :icon_thumby:

mavereq · Dec 21, 2017

I normally just hit the gasket with some copper spray and slap it on.

RTV on lower intake manifold to head?

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