Insulating I6 Exhaust Manifold Photos

[Sharps40]

For prevention of post shut down fuel bowl percolation/boil over.

Has anybody here insulated their stock 230/250/292 intake/exhaust log against the low boiling point of modern fuels? i.e. to prevent post shut down percolation due to heat soak.

If so, post up pics.

I am running a test on John Lee, got the front 2/3 of the logs insulated with muffler packing to see if it helps. Temps in the bowl shot up to 105+ with the warm days this weekend....pretty much saturatin the intake plenum and leaking out the butterfly shafts.

This morning's run shows nothing but condensation on the outside of the carb and adapter after a 38 mile run.

We'll see over the next few days but if ya got somethin done that looks decent and works....show me! Please.

[T and S]

Do you have some type of insulator installed between the carb and manifold ? If not that may help.

[Sharps40]

Got the thick gasket that goes under the rochester/mono between adapter and manifold. About 1/4" thick. Dosn't help much. 10 minutes post shutdown and its perkin from radiated heat. When running, fuel bowl temps remain steady between 55 and 80 degrees F.

After shutdown, it rises to 100+ with 95ish being the boiling point of modern ethanol blends....not a problem for 40 psi fuel injection but a nemisis on carbed motors.

[TJ's Chevy]

I run 92 octane in my truck...I am using an edelbrock 4 barrel and I have headers which run a lot hotter then an exhaust manifold...most I have driven the truck is about 10 miles and no leak yet...course it hasn't been all that hot either....ah well..guess its time for dual electric fans! LOL! I remember the first edlebrock carb I put on was seeping fuel out of the carb gasket(the one that connects the top of the carb to the bottom. NOT the carb/intake gasket)...That may have been the issues was overboil of fuel...not sure...I'll see about digging up a picture...if I find on you'll have to look fairly hard. In the picture...look hard at the front center of the carb on the left and right front..you'll see a slight discoloration...that is fuel. It kinda looks orange in the picture. Since I put the other new one on(I returned the one that was seeping fuel) I haven't had this issue....we'll see what happens when temps are over 90.

[Sharps40]

I might have a line on this issue. Insulated the front half of the manifold, under the fuel bowl with exhaust packing. It helped. Slowed the temperature increase in the bowl from 10 minutes to about 30 minutes.....less perking and less fuel leaking over all but still not fixed.

Here is the max temp reached in the bowl, hood down, 30 minutes post shutdown....ambient air temp is 65ish degrees.



Got a wild hair a few minutes later and opened the hood and read the temperature of the adapter manifold interface....read at the adapter, above the 1/4 thick gasket....

Now this is with the hood open and things are cooling rapidly....



Immediately read the temperature of the outside of the bowl, midway up the side of the bowl....the side, most exposed to the cooling air.



Then read the temperature of the carb top, between the carb top cover and the air cleaner adapter.....the hood has been open now about 10 minutes after reading the max temp of the fuel in the bowl (hood closed for those readings)



Methinks this may be lots less about radiated heat from the manifold and bunches more about a lovely aluminum adapter transferring heat right straight up from the manifold and into the carb. At idle and immediately after a run the bowl is cool to the touch and often has a bit of condensation on it....not perkin or boilin till after it shuts down/air flow into the carb is stopped.

Betcha I need a phenolic insulator between the carb and the adapter.

[jayoldschool]

Make one out of wood to quickly test the theory.

[Sharps40]

Dayum fine ider! I got some oak inna shop.

[T and S]

A phenolic insulator was kinda what I was thinking about in my earlier post...

[Lugnutz65]

Originally Posted by Sharps40

Methinks this may be lots less about radiated heat from the manifold and bunches more about a lovely aluminum adapter transferring heat right straight up from the manifold and into the carb.

Correct me if I'm wrong, but you got the adapter and Weber carb from Tom Langdon, right? Ask him what he does to eliminate the problem. I have the adapter too but have not yet installed the Weber carb so mine is all still in the box with the carb rebuild kit you sold me. Remember?

[Sharps40]

Originally Posted by T and S

A phenolic insulator was kinda what I was thinking about in my earlier post...

Heck. I figgered a quarter incho paper was plenny! Ill havta gen up a spacer an see how it fairs.

[Sharps40]

Originally Posted by Lugnutz65

Correct me if I'm wrong, but you got the adapter and Weber carb from Tom Langdon, right? Ask him what he does to eliminate the problem. I have the adapter too but have not yet installed the Weber carb so mine is all still in the box with the carb rebuild kit you sold me. Remember?

I think k98al is runnin a weber too. We need his input too.

[ACK]

I was having a similar problem over the summer and put an inexpensive foil heat sheath on the gas line where it goes over the manifold and it made a world of difference. It's not as hot up here as Carolina, but it's worth considering.

[Sharps40]

Good Ider! I will add that. I'm thinkin a three part approach for early march.

1/4 to 1/2 inches of phenolic spacers for carb to adapter junction.

Metal heat shield backed by heat blanket and adapted to bracketry extending from the valve cover bolts.

Insulating heat sleeve on the fuel line.

Failing that.....under hood fan on a thermostat blowing across a bucket of ice and all aimed at the cabie!

[1963c-10]

Can always get one of those old fuel cooler cans they filled with ice.

[Sharps40]

Nah, the ice was a joke! still waffelin around about the large truck 292 exhaust or headers. New intake is on the way and I plan to flatten it out, open the plenum a bit and set it up on a 3/4" to 1" phenolic adapter....but for now gotta get this daily driver sealed up a bit so it smells pretty!

[TJ's Chevy]

Yer more then likely gonna find a 292 2.5 inch exhaust manifold in a 63-70's C-40, 50 , or 60. The headers will make the biggest difference either way. And converting to dual shouldn't be to expensive...To convert mine to dual was like $240 and the mufflers were $75 a piece(Flowmasters are spendy anywhere). I think yer runnin glass packs...they are like $40 a piece and even as low as $20. lol If you do a dual exhaust dual 1 7/8 will be the largest you want to go. That will keep your torque, and leave it in the low range.

[NavyChief]

Sharps,

I am running the weber on a original intake with Langdon headers. Have not seen any issues and it runs nice even for my tires 250! What intake did you go with and are you going to use water heat for it?

[Sharps40]

Stock cast iron intake is inbound....later model as it has two bungs on the plenum for manifold vacuum source instead of one bung like mine. Currently have brakes and pcv joined at an F adapter on the outer center bung.

Once the manifold arrives I'm gonna look it over. Minimum engagement will be to swap it on to split the vacuum sources and help keep trash outta the brake booster lines. If the manifold is amenable, I'll flatten the top and open the plenum a bit. Goal is to mount the Weber 32/36 with the primary on the 3-4 runner (bowl forward) as it is now but bring it down much closer to the manifold and open the plenum or at least have a wider smoother flow from carb base into the plenum on a phenolic insulator plate/adapter. Moving that tall column of air on the tall but restrictive adapter is only good for about a few percent of power/torque and mostly in the upper rpm ranges. Better fit/flowing plenum should see a much better signal to the carb and put more power in the low to mid range where this heavy rig can use it most. I rarely break 3000 rpm now with the T5 and typically cruise in all gears 1900 to 2300 rpm. Even at 70 mph I'm only tachin 2450/2550 rpm.

Given the stock cam is the absolute best choice for idle and power in the daily driving range, I'm thinkin the exhaust is academic. For the $450ish it'll take to put on the high flow 292 exhaust or iron or tube headers and replumb, I suspect my choice will be to stay with the factory exhaust and build a nice looking sheet metal insulator for the log and part of the downpipe.

[Sharps40]

I'm a bit more likely to invest $200 in a Wideband O2 so I can have a blast tweakin jets on that carb and get instant feedback instead of drivin thru a tank o gas with each update.

For now, phenolic spacers for the current adapter are inbound along with some richer secondary main jets to pick up the 2500 to WOT response.

Just busted 18.6 mpg combined and the plugs look great/no lean hole on the secondary...so I think the main is in perfect for the new engine/trans combo. But the secondary builds power just a bit slow, which is an indication it could stand to be a bit fatter on jetting.

After the secondary and leak is fixed I plan to start changing total timing around to see what this engine prefers. I'm 4K miles into the new engine and ready for oil change #3 so its spring and time to get jiggy with the final tune.

[64chevtruck]

Originally Posted by T.J. MCCAULEY

I run 92 octane in my truck...I am using an edelbrock 4 barrel and I have headers which run a lot hotter then an exhaust manifold...most I have driven the truck is about 10 miles and no leak yet...course it hasn't been all that hot either....ah well..guess its time for dual electric fans! LOL! I remember the first edlebrock carb I put on was seeping fuel out of the carb gasket(the one that connects the top of the carb to the bottom. NOT the carb/intake gasket)...That may have been the issues was overboil of fuel...not sure...I'll see about digging up a picture...if I find on you'll have to look fairly hard. In the picture...look hard at the front center of the carb on the left and right front..you'll see a slight discoloration...that is fuel. It kinda looks orange in the picture. Since I put the other new one on(I returned the one that was seeping fuel) I haven't had this issue....we'll see what happens when temps are over 90.

Kool Headers TJ!

[TJ's Chevy]

Originally Posted by 64chevtruck

Kool Headers TJ!

Thanks!

[NavyChief]

TJ what kind of mileage are you getting with that setup?

Sharps do you have a specific phenolic insulator plate/adapter in mind. I also do not like the tall spacer and was hoping to work something out. You sound much more knowledgeable on this than me!

[TJ's Chevy]

Originally Posted by NavyChief

TJ what kind of mileage are you getting with that setup?

No idea...I reckon 15-17 cruising at 50-55...cause I'm barely touching the throttle.

[NavyChief]

Sharps after reading your post more thoroughly I am running the following:
Weber 32/36 Carb
Spacer/Adapter provided by Langdon
Stock intake with water heat
Langdon headers

With this setup I do not have a problem boiling over but actually the opposite. My spacer will accumulate a light coat of ice in cooler temperatures. I have not had the setup long enough to run it in the summer yet so not sure if it will clear up when it gets warmer. Not sure if this will help you or not.

[Sharps40]

I'll likely use 1" thick phenolic sheet on the new manifold. Got some milkcrate engineering to do.

I am on the langdon adapter exhaust valve closed on stock manifold. My set up condenses year round but never freezes. Boil over is due to heat soak on shut down. Prolly a combo of radiated and transfer thru the adapter.

I have the electric choke and it works great. Timed good to. It is wide open just when the cold loght goes out/thermostat opens. So no cold driveability issues. In fact I never warm it up. Hot idle is 500 and fast idle is 800 so I just key it and press the Go Pedal.

The 32/36 works like fuel injection. Perfect function but no computer