TheSamba.com :: View topic - A request

Mon Mar 29, 2021 12:22 pm

Hi everyone. I'm designing an intake manifold and need someone to take meassure how hot the intake base on the cylinder head gets at operating temps. If someone could get that number for me that would be awesome.

God bless

Mon Mar 29, 2021 2:09 pm

I can check, but how hot when? The hottest I can get it? How far do I have to drive? What time of day? Where at the base? Under a manifold nut? I have a 67 Bug. Do you have a Bug? Obviously my numbers wouldn't matter if I had a Bus.

Mon Mar 29, 2021 2:14 pm

Are you ultimately looking for the temperature resistance/tolerance of joining methods such as silver solder vs braze vs weld?

Mon Mar 29, 2021 2:24 pm

bugguy1967 wrote: I can check, but how hot when? The hottest I can get it? How far do I have to drive? What time of day? Where at the base? Under a manifold nut? I have a 67 Bug. Do you have a Bug? Obviously my numbers wouldn't matter if I had a Bus.

Hello, I'm looking for the temperature of the intake flange on the head so like you described you would probably have to meassure the temp of the nut and or stud that holds the intake manifold to the cylinder head base/flange. I have a bug but still no running engine which is why I ask. I'm looking for how hot the flange can get on conditions at or above driving temps. So maybe warm the engine up and drive up a hill or two?

If you could get me those numbers I would be extremely grateful!

Mon Mar 29, 2021 2:26 pm

Rome wrote: Are you ultimately looking for the temperature resistance/tolerance of joining methods such as silver solder vs braze vs weld?

Hi, I'm 3d printing an intake manifold and need to select a material that can withstand the heat without wraping and or melting is why I ask. It's something I've been thinking about for a while and now that I have the carbs and heads u can start making them in cad.

Thanks
Aiden

Mon Mar 29, 2021 2:32 pm

Peak temperature at base, up to 160 degrees C minus the thermal barrier of the gasket used.

Mon Mar 29, 2021 4:00 pm

I think heat soak after shut down should also be considered.

Worst case scenario like a fully loaded bus going up a steep grade, CHT is reaching 400+ and you are forced to shut down and pull off the road. I would hate to fix whatever got me to pull off just to find my manifolds warped and are now leaking badly.

Mon Mar 29, 2021 4:22 pm

I would say with all the factors involved you'd need to use a material that is rated to atleast 350⁰F, but 400⁰F or 450⁰F would be ideal.

The intake flange will reach the same temperature as the head temp.

The heat soak factor could actually make it hotter than the heads are at when running.

Mon Mar 29, 2021 4:29 pm

Consider the Type 3 "bakelite" manifold gaskets, used in place of the steel gaskets used on Type 1/2 engines. Anyone know the temp tolerance of that material?

Mon Mar 29, 2021 4:40 pm

KTPhil wrote: Consider the Type 3 "bakelite" manifold gaskets, used in place of the steel gaskets used on Type 1/2 engines. Anyone know the temp tolerance of that material?
Alot, it doesn't melt (I've tried), eventually it just catches fire. As already mentioned heat soak is the big concern, I'd plan for 500 degrees + just in case.

Mon Mar 29, 2021 5:50 pm

Not really a quesion of "how hot", rather how hot for how long.
JB weld can take 500 degrees F......
once
but 300F for a LONG time, with a little gasoline spray, it slowly transforms into a "old turd-like" consistency and crumbles. I don't think you will be satisfied with the long term performance of any plastic bolted to a aircooled head besides phenolic.

I predict you're going to make them out of steel as soon as you realize you can do it and it's just a matter of time. And it may or may not be influenced by how long the plastic ones last :wink:
Have made manifolds from 3/4 thick phenolic too, you can drill and even tap it, although it's not ideal for this job.

Mon Mar 29, 2021 5:55 pm

Wow. I didnt think this subject would get this in depth :) heat soak is a factor for sure. And heat cycles. And duration as Modok mentioned. So if I resen print or 3d print a set, it looks like I'm gonna need the best of the best as far as strength and heat resistance goes.

It seems nearly every modern engine, including LS engines, use a nylon based manifolds. So water cooled heads simply just not get as HOT?

Thanks for the replies and help, I will start researching which plastic MAy be a good candidate.

Mon Mar 29, 2021 6:05 pm

Yep and they get wrecked if the engine is overheated.

I guess when it comes to plastic there is a big difference between 250F and 350F

It IS possible, but I don't think it would be strong enough to hold up the carb AND attach to the head the normal way. The way VW has the manifold attached to the SP head, is a PITA, even aluminum is questionable.

Mon Mar 29, 2021 6:18 pm

PEEK (Polyether ether ketone) is possibly a good option for an intake manifold.

I think it's very expensive tho

Mon Mar 29, 2021 6:22 pm

Ask your local foundry, maybe you can print out of a low temp wax to use as a meltable plug for sand casting in aluminum.

Mon Mar 29, 2021 7:49 pm

KTPhil wrote: Consider the Type 3 "bakelite" manifold gaskets, used in place of the steel gaskets used on Type 1/2 engines. Anyone know the temp tolerance of that material?
Never seen that!

Or do you mean the bakelite spacers that held the injectors in place? The ones that were always cracked then you took the injectors out and had to be replaced. They weren't gaskets.

Mon Mar 29, 2021 8:25 pm

i planned to drive my baja to work tomorrow, if i can remember ill hit the intake runners with the thermal gun and give u a few readings. its a boosted 2021 so my iat will be higher than a n/a, and ill run the piss out of it too.
i dont think these heat numbers as are high as u guys are thinking, ive checked my drawthrough 2276 after running the piss out of it on a 100 degree summer day and i believe my runners were upper 120's. even measuring the head right at the exhaust was only about 380 degrees i think.
and yeh heat soaks and evens out through the metals but its not going to increase in temperature without a heat source.
and plastics have come a long ways .. its almost scary the amount of plastics used on engines these days. granted there no fuel running through them but try to find a new car that doesnt have a plastic intake. all radiators have plastic tanks, and there's plastic thermostat housings, valve covers, fuel lines, injectors, and im sure numerous other things i dont know about as im a body guy and not a mechanic. and also, the new vehicles run hotter than the old ones used to...
chickensoup, if you figure out the plastic for this id be interested in commissioning you to print something for me, if your interested? its and old v8 turbo intake piece that was used to convert n/a to drawthrough so itd have to be fuel resistant too

Mon Mar 29, 2021 9:41 pm

oprn wrote: KTPhil wrote: Consider the Type 3 "bakelite" manifold gaskets, used in place of the steel gaskets used on Type 1/2 engines. Anyone know the temp tolerance of that material?
Never seen that!

Or do you mean the bakelite spacers that held the injectors in place? The ones that were always cracked then you took the injectors out and had to be replaced. They weren't gaskets.
Some had a... about 6mm thick insulating spacer between the manifold and head. I have a few, some are brown and some are black.

Mon Mar 29, 2021 9:46 pm

The guy making my DBW induction in Norway 3D prints his intakes. Not sure what the material he uses is. All I remember is carbon fiber something something.

He's logged a bunch of miles with his 2,3L. My TBs are splayed outward, and will use brackets to support them.

Mon Mar 29, 2021 11:02 pm

Get some garolite sheet from McMaster (1/2+ inch thick) and make a spacer in addition to the manifolds. It could reduce the heat soak significantly or entirely. It may allow you to use a material for the intakes that doesn't need to be quite as heat resistant.