I have begun looking around for cylinder head porting information that is simple, and accessible.

This guy's approach seems do-able, and uncomplicated. He also seems to lack a massive ego, and know-it-all attitude which I find more tolerable to to watch than some who want to show the world something.

What are your thoughts, is this approach as reasonable as it appears?

How did you begin your cylinder porting for the first time adventure?

https://www.youtube.com/watch?v=rHI_8ssElms&t=121s

I started grinding away removing obvious boogers.
After finding water jackets I realized how thin slant heads are in a few places.

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Hyper_pak

I hear that, and have read here that others mention that they are very thin in spots...

I doubt I will even use a larger valve to begin with..

valves are not the thin parts, ports are the thin side.

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Hyper_pak

I guess I have only ported Slant 6 heads, but I have felt there is quite a bit of meat in most places. You can use stock valves, but you are giving up a fair bit of power. 1.70/1.44 is the minimum I would use personally. I have used 1.72/1.50 SBC valves mostly (cheap) and Mike Jeffrey's favorite sizes for a hipo head were 1.76/1.50. The main place to NOT hit hard with the grinder is the port wall between the I and E on each cylinder.

All of this said, you do not need to remove tons of material to really wake up a Slant head. Bowls under the valve are the most critical part...

When I get time, I'll try to look at this guy's video.

Lou

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Home of Slant6-powered fun machines since 1988

Here is a cut head, very interesting walls.

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Hyper_pak

Thanks Lou. I appreciate your experience, and perspective behind the information you have offered.

Would you still recommend 1.72/1.50 valves if my redline is realistically about 4500, and probably more importantly RPM is 3200 at cruise?

My main interest in doing any porting is to have excellent torque and to have it carry out across the RPM range, rather than have a torque Peak and then slump. IF bigger valves are the ticket, I will go there..

Stan, do you have a uncompressed copy of that picture that you could send or email to me?

Greg

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http://www.youtube.com/hyperpack

Yes, i will send you what I have.

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Hyper_pak

Concerning the horizontally sectioned head that Hyper Pac posted.
The port wall thickness and the general shape where the head was sectioned looks inconsistent because the saw cut across the head is not level. Look at the material above the spark plug bores. The cut was inconsistent concerning height across the head. The port arm walls are not vertically flat, they have a curvature to them. The bowl (or valve guide area port) walls have a lot of curvature. What is shown on that sectioned head is the effect of cutting through a radius at different heights.
Also concerning improving port flow, as one moves away from the valve seat, the importance drops significantly.

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Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

DadTruck is right about the port flow and the seat/bowl area being most important.

Greg, please fwd me a copy of that pic when you get it.

Jase, if you are only looking for power up to 4500, then you do not need much porting. However, as far as "losing" low end torque by porting, I have never seen that. Probably you can port all you want and put in bigger valves and you will just gain power over the whole range. The cam (combined with CR) will have more effect on low end loss.

It is good to decide and state your goals and it looks like you are being honest about that. If you do the porting, you will gain up top too and I see no reason not to twist any Slant (unless in really poor shape or with very low compression and stock cam) to 5000 RPM. Food for thought, anyway. Can you say more about what you are expecting this car/truck to do and what kind of performance you are seeking? This could be a dragstrip time, or a net HP number (often dicey to interpret), or a comparative factory car (of any era) that you want to match in all around driving? This can help with giving advice about how far to go and what combo of parts to use.

Thanks to all and good morning!

Lou

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Home of Slant6-powered fun machines since 1988

Will do..

Just waiting on Stan..

If you need my Info Stan, let me know..

I am pretty sure you have my cell#, maybe email?


Greg

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http://www.youtube.com/hyperpack

Understood, and relieved as that tends to keep things simple..
Dodge M37 with my first engine swap. '77 Slant 6, NP435 Wide ratio four speed. Stock 35" tall tires, and stock 5.83 to 1 gears. Truck weights about 6000 with me in it, and fuel in the tank.

My interest in "porting" comes from the understanding that a "good cylinder head" does everything better than a fair cylinder head. It is my perception that I could get a better torque "curve" and more of a plateau with less cam, from a cylinder head that that flows a bit better... I would be happy to trade some peak #s for something that starts strong, and carries across the RPM range.

The engine will spend time lugging along at 1000-2500 when plowing my uphill driveway. ALSO it will spend time singing at 3200 and it would be nice "Peak" torque or Really good torque in the 2700-3200RPM, I am aiming for that b/c I have read-understood that Peak torque is often closely associated with Peak VE, which also coincides with good fuel economy. Overdrive is not really an option, and fuel economy is relative. No data for fuel economy with the slant 6 yet, but with the original engine the best I ever saw was 12 MPG.

Finally the desire to have the engine run and pull well up to 4500 is for pulling a hill when loaded, as 4500RPM is about 45 MPH in 3rd gear. If the RPM window could extend out to 5000 with out loosing low end, I am fine with that, the reality is that I don't expect to spend a lot of time on the high side of 3500.

I am expecting to cut the cylinder head for additional compression, and presently thinking 87 Octane is the goal.. Even in stock form the 225 is doing ok, but I will at some point pull the head for additional compression and efficiency. Why not improve the head flow at the same time? Realistically the truck might see 500-1000 miles a year.

Any and all perspectives welcome and appreciated, even the reality check type opinions.

When setting the specifications for all of the components going into an engine build, I cannot say that any one item is more important than any other, as they all need to work together. However I do believe that the camshaft specifications has more impact on the ‘personality’ of the final motor than any other single item.
If the goal of your build is low RPM torque, the right cam is what is going to make that happen.
You want a small cam, around 200 degrees of duration or smaller, medium lift. With an upper RPM cap of 4500 rpm, I would stay with stock sized valves, do some minor bowl clean up and invest in a good multi angle valve job.
To maximize performance you need to maximize compression and the ignition curve.
For the compression: get knowledgeable on Static and Dynamic compression.
For the ignition curve: a heavy vehicle usually won’t take a lot of initial timing, but with the right springs you will be able to bring the mechanical advance in as the vehicle starts rolling.
Remember, you are working with a small displacement engine and a large vehicle, be prepared to be underwhelmed.
In summary, it is understandable that you want to maximize low end torque, a good flowing cylinder head can help, but it is not at the top of the short list of things that make low rpm torque, which are:
1) large displacement, which you do not have
2) camshaft profile-one with an early closing intake valve to build dynamic compression
3) compression, static and dynamic
4) ignition advance, mainly when the mechanical advance comes in and how it ramps.

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

I done sent it.
Anyone else want a copy?

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Hyper_pak