372xp port timing numbers??

[Jake Dykstra]

So after cutting base and squish band I'm at 103/130/80 .024
Thoughts on how it run? Thought I might run it first before I grind on it. I unshrouded the lowers and cleaned up the in and out.
just curious if anyone has ran numbers similar to this as mostly peeps run 100/120/75 or thereabouts.

 

[huskihl]

I wouldn’t raise the exhaust if I didn’t have the ability to raise the transfers. Your last numbers will work fine if you can raise them, although the intake will be closer to 79 after machine work

 

[farminkarman]

So after cutting base and squish band I'm at 103/130/80 .024
Thoughts on how it run? Thought I might run it first before I grind on it. I unshrouded the lowers and cleaned up the in and out.
just curious if anyone has ran numbers similar to this as mostly peeps run 100/120/75 or thereabouts.

As Kevin said, you gotta raise the transfers.

 

[Dolkitafreak]

Ditto on what was stated previously. 100-120-80 is a very solid set of numbers in a 372 provided it is all grinded well.

 

[Mastermind]

102/122/78 is what I have in my notes.

 

[Kiwioilboiler]

102/122/78 is what I have in my notes.

Your notes work well in my saw.

 

[Jake Dykstra]

Sound good. Thanks fellas. Figured some one has tried the longer blow down numbers. I'll get the grinder fired up!

 

[Mastermind]

Sound good. Thanks fellas. Figured some one has tried the longer blow down numbers. I'll get the grinder fired up!

I've noticed that tighter transfers like longer blowdown. Big open two port engines can run fine with 14° or so. Four port motors....22° or more. With stratified engines, forget all that. LOL

 

[huskihl]

28° bd in a 372 turns about 16k no load but drops to 9k in the cut.

Vs 18-20° bd tuning at 14.5k and running 11k in the wood

 

[Mastermind]

28° bd in a 372 turns about 16k no load but drops to 9k in the cut.

Vs 18-20° bd tuning at 14.5k and running 11k in the wood

Yes sir. 28° is 7900 numbers. LOL

 

[Jake Dykstra]

28° bd in a 372 turns about 16k no load but drops to 9k in the cut.

Vs 18-20° bd tuning at 14.5k and running 11k in the wood

Yep. Just went out and buried it in a 30" log and I would say that describes it perfectly. Sounds like a real ripper with no load but falls on its face under load. Ah well now I know.
Thanks fellas

 

[huskihl]

Transfer-raising hell

 

[farminkarman]

Transfer-raising hell


View attachment 383531View attachment 383532View attachment 383533

Let the grinding begin!

 

[huskihl]

Let the grinding begin!

Let it finish!

 

[farminkarman]

Let it finish!

View attachment 383537

That is top notch grinding there. I wish mine looked that good.

 

[cuinrearview]

That is top notch grinding there. I wish mine looked that good.

https://www.amazon.com/Strength-Strengthener-Exerciser-Training-Extension/dp/B0BVVLTN5L/ref=asc_df_B0BVVLTN5L/?tag=hyprod-20&linkCode=df0&hvadid=652391490384&hvpos=&hvnetw=g&hvrand=17108814207763653589&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=1019144&hvtargid=pla-2005804346595&psc=1&gclid=CjwKCAjw-7OlBhB8EiwAnoOEk1L83xlqsy8xHJDgMHhuYSYgWJM4eyDLmObXTCkvzhllOO_P6rEwfxoCWRwQAvD_BwE

 

[Ketchup]

Yes sir. 28° is 7900 numbers. LOL

Do you think 7900 likes more blowdown because of the longer stroke?

 

[farminkarman]

Do you think 7900 likes more blowdown because of the longer stroke?

I would think of it more in terms of case compression. The 79XX saws have fairly small & tight transfer tunnels and fairly wide upper transfer openings. This means the 79XX saws can get away with the upper transfer opening later and still filling the cylinder. Being that these saws are limited on exhaust port width, the temptation is to raise the exhaust above 100....but they can run pretty well if you keep the exhaust and the transfers lower. The 372's have pretty big transfer tunnels and need more open time to get the charge moving and fill the cylinder.

 

[huskihl]

7900 also has a narrow exhaust. If the transfer charge let go too early, it would go out the exhaust.

 

[DOHC20]

Ok, so i have a bit of a noob question. In the case of the OP, if the transfers were at the correct timing numbers after base cut.....could you lower the bottom of the transfers to make them larger to flow more since they cant be raised to make them larger?? will it have any detrimental effects? ive never come across this scenario when ive ported so i thought id ask. ive also never seen anyone lower the base of the transfers for more size.