440 motorhome build- 30 degree intake seat?

[mgoblue9798]

30 seats can work well if the valve lift is very low.
Can also work well when the valve shrouding is too "open" but these heads i don't know if they qualify for that.

Why is it 30 or 45? The angle can be anything you want. 37 is a nice angle

There is .150 between the edge of the intake valve and the closest part of the unmodified chamber wall.

[modok]

Not that side, the other sides.
But the valve being closer to the chamber wall does allow you to open up the other sides a bit more. Ideal shrouding is a nice cup all the way around.
I mean like the 440 open chamber heads it's almost totally flat chamber around most of the valve, that's "too open". I don't know about your industrial heads but they must be but better than those.

Some flowbench testing would tell. All I would say for sure is that a 37 seat seems worth trying because of the low lift.

[mgoblue9798]

[modok]

That chamber sure makes the valves look small.
Looks better than the open chamber. Does seem like larger valves or 37 seat COULd work, but, I really don't know just educated guess.

[Geoff2]

If memory serves me, the 1.88" int valve was used on the early 1958-on Chrysler 350/361 BB engines. The early 60s saw the size increased to 2.08" in 413 engines. This engine is bigger, so a bigger valve should help power everywhere, even though it is a low rpm engine. The 30* seat is a good idea & makes good sense if the valve size is increased because new seats will need to be cut.

[Mummert]

Adding low lift flow to a head will act very much like adding low lift duration to the cam. If you think the seat duration on the camshaft is too small flatten the seat angle. If you think the cam has to much duration at the seat steepen the valve angle up.
In my experience with tow and motorhome engines is that you can't put a short enough duration cam in them to pull drive on a long grade, and once you pull them down into second it doesnt matter much anyway.
California is the graveyard of tow engines 10-15 mile 7% grades, 100F temps on the desert floor, 50mph head winds
I'd forget about the valve seat thing and start looking at tri y or long tube headers and an oil cooler, and a good radiator and something other than a ThermoQuad. These things help tow and rv engines.

[BCjohnny]

Second goal is budget

They also have sodium filled exhaust valves and hardened seat inserts from the factory. Exh valves, seats and guides are in excellent shape and will be reused. I am open to changing the intake and will have to do so if I use a 30 degree seat on the intake

If you're determined, keep the existing exhaust (I'd personally go larger to what comfortably fit the insert) and do what you can with the throat

I'd step up to the 2.08 intake aiming for around 88% throat diameter with 30-37/45*/60/75 angles, and hand blend

Lose the fixation with 30*, there may be minor or theoretical benefits, but ..... with what you are trying to achieve ...... don't overthink it

JMO

There is no reason to use a 30 degree seat ....... It’s all about the shape. And a 30* seat has a horrible shape

[Powertrip]

A proper valve job with a back cut intake valve will give you most of the benefit of a 30 degree seat without any of the headache.
Or expense, as you need a good valve job anyway.
Those heads and valves are oddball compared to normal BBM stuff, so replacing valves could get expensive.

[ClassAct]

There you are!
I was waiting for you once again to make your no merit comment disparaging 30 degree seats!
I and many others ( by means of iron heads no less ) have produced well over 650 hp while running 30 degree intake seats , so I hope you don’t mind that myself and others continue to do so when we care to and not listen to you!

Stop misguiding people when there just looking for a simple motorhome up grade build

Who cares? I knew you’d be here, making claim after claim about a 30 degree seat. I know you live and die by flow bench numbers. I do not. The shape of the 30* seat is horrible. Just horrible. I wouldn’t use a 30* seat on a lawn mower. It’s not even worth it for that.

So stop misguiding people with bad advice. Once again, a 30* seat is NEVER an upgrade. Ever. In fact I find it hilarious that Vizard doesn’t even harp on that junk seat like he used to. I have called him out here, on ST about the end of a series of articles he did in the best car magazine ever, Super Stock and Drag Illustrated. He used a Quadrant Scientific flow bench and a 30* seat on a 400 Chevy. The last article never came out. That was long before Hot Rod killed the magazine.

The 30* seat is bad. The shape is horrible. If you love flow bench numbers then by all means, you’ll love a 30* seat. Otherwise you just forget about that valve job and step into the 1970’s.

[mgoblue9798]

Adding low lift flow to a head will act very much like adding low lift duration to the cam. If you think the seat duration on the camshaft is too small flatten the seat angle. If you think the cam has to much duration at the seat steepen the valve angle up.
In my experience with tow and motorhome engines is that you can't put a short enough duration cam in them to pull drive on a long grade, and once you pull them down into second it doesnt matter much anyway.
California is the graveyard of tow engines 10-15 mile 7% grades, 100F temps on the desert floor, 50mph head winds
I'd forget about the valve seat thing and start looking at tri y or long tube headers and an oil cooler, and a good radiator and something other than a ThermoQuad. These things help tow and rv engines.

Thermoquad will be used, already have one with the altitude compensator to help at elevation. Also have long tubes, coolers, giant stock radiator from the 413. Trans cooler as well, and a misting bar across the front of the radiator to help cool things down when needed. Also will be running a gear vendor's overdrive so I will have the ability to split gears for at least 6 forward, possibly 8 if I combine it with a 518 overdrive.

[mgoblue9798]

Second goal is budget

They also have sodium filled exhaust valves and hardened seat inserts from the factory. Exh valves, seats and guides are in excellent shape and will be reused. I am open to changing the intake and will have to do so if I use a 30 degree seat on the intake

If you're determined, keep the existing exhaust (I'd personally go larger to what comfortably fit the insert) and do what you can with the throat

I'd step up to the 2.08 intake aiming for around 88% throat diameter with 30-37/45*/60/75 angles, and hand blend

Lose the fixation with 30*, there may be minor or theoretical benefits, but ..... with what you are trying to achieve ...... don't overthink it

JMO

There is no reason to use a 30 degree seat ....... It’s all about the shape. And a 30* seat has a horrible shape

No fixation with any particular valve job angles, just asking a question with an open mind and trying to learn from other's experience.

[mgoblue9798]

If memory serves me, the 1.88" int valve was used on the early 1958-on Chrysler 350/361 BB engines. The early 60s saw the size increased to 2.08" in 413 engines. This engine is bigger, so a bigger valve should help power everywhere, even though it is a low rpm engine. The 30* seat is a good idea & makes good sense if the valve size is increased because new seats will need to be cut.

Believe it or not all the 413 RV engines used these small valves all the way to the end of prodiuction in the late 70's.

[CamKing]

Using Mike Jones's RV cam made for the 440 202 @50 and 450 lift. Would this combo benefit from a 30 degree intake seat and slightly larger intake valve?

With that cam, and your application, stick with 45 degree seats

[mgoblue9798]

Using Mike Jones's RV cam made for the 440 202 @50 and 450 lift. Would this combo benefit from a 30 degree intake seat and slightly larger intake valve?

With that cam, and your application, stick with 45 degree seats

Thank you for chiming in Mike. Have you had customers run your RV cam with a 413 or 413 heads? About what rpm would max torque be with your cam?

[CamKing]

Thank you for chiming in Mike. Have you had customers run your RV cam with a 413 or 413 heads? About what rpm would max torque be with your cam?

I'm not sure about those heads, I would have to check with my customers.
From memory, I think peak torque is right above 3,000 rpm.