Piston discussion

[powerstrokenstang]

At what point are some of yall doing bowl work and decompressing. What are the benifits of having to lip still there. We decided on mine to only do valve reliefs since its a single charger heui. Lol kinda nice having a puller thatll start at 45 deg unassisted.

 

[Big Bore]

Did you relieve the edge at all?

 

[powerstrokenstang]

No not decompressed at all other than the slight amount from the fly cuts. Lip is all there and after 17 pulls at 2200+ deg and 6 at about 1800 they still looked great when i stuck em in the new block a few months ago. Compression makes power so why give any up unless you need the room for mad fuel? I am interested in what the lip does to combustion and flame front, anyone care to share some knowledge?

 

[UNLIMITED_DIESEL]

FWIW, we made the call to leave as much as possible in there. We might not have done it to an engine build that was going to see a lot of miles, but as Jason stated, after several pulls and several degrees of EGT there did not seem to be any issues with the pistons. Also just for consideration, Jason was having no issues carrying RPM down the track either, which is one reason some people lose some compression to help turn more RPM.

I think you have to look at the whole setup, not just the pistons. The cam, head porting, and everything else seems to all be playing well together.

The only regret that I have is not putting billet rods in your engine from the get go. I don't think we would have lost your last engine if the rods would have been a little stronger. I guess we will never know.

It will be interesting to see how she does this year!

 

[powerstrokenstang]

Never know worked out for the best gettin rid of that block though lol. I wondered about rpm and compression too, so decompressed does turn up a lil better? I dont regret leaving compression alone, it runs good and pretty clean and was holding 3500 down the tack last year w a 11.15:1 final drive and a compressor cover that rubbed on the wheel. Hopefully itll run even better this year. I just started this to see what some others were doing and wanted to learn about bowl design. Is just cuttin junks out of a piston the best thing for the engine and power.

If you wanted to decompress why not cut the cone out instead of opening up the bowl? I know w the lip gone you can run more timing and get it in the bowl, but does that really matter a whole lot? If the fuel gets mostly in btdc and its not washing dow the cyl walls then is being in the bowl a big deal.

 

[Hotrodtractor]

Think wide and shallow.... keep the compression up, get the spray into the bowl to promote mixing and to improve combustion turbulence....

 

[UNLIMITED_DIESEL]

Never know worked out for the best gettin rid of that block though lol. I wondered about rpm and compression too, so decompressed does turn up a lil better? I dont regret leaving compression alone, it runs good and pretty clean and was holding 3500 down the tack last year w a 11.15:1 final drive and a compressor cover that rubbed on the wheel. Hopefully itll run even better this year. I just started this to see what some others were doing and wanted to learn about bowl design. Is just cuttin junks out of a piston the best thing for the engine and power.

If you wanted to decompress why not cut the cone out instead of opening up the bowl? I know w the lip gone you can run more timing and get it in the bowl, but does that really matter a whole lot? If the fuel gets mostly in btdc and its not washing dow the cyl walls then is being in the bowl a big deal.

The spray should never be out of the bowl on your engine. We conquered that with some tweaks to the heads...

 

[powerstrokenstang]

Think wide and shallow.... keep the compression up, get the spray into the bowl to promote mixing and to improve combustion turbulence....

Sounds like cummins pistons.

The spray should never be out of the bowl on your engine. We conquered that with some tweaks to the heads...

Indeed, my spray looks better than alot of stock engines ive seen of any brand. I was just wondering if outside the bowl btdc was alot better than drawin injector out late to stay in the bowl.

 

[NyCowboy87]

Not sure if your going to round out or radius the edges arount the valve reliefs, if not you had better think about doing it. The shop that built the engine I bought didnt and well all 8 cracked, with one breaking in half and effing the cylinder along with the rod.

 

[cfdeng7]

Not sure if your going to round out or radius the edges arount the valve reliefs, if not you had better think about doing it. The shop that built the engine I bought didnt and well all 8 cracked, with one breaking in half and effing the cylinder along with the rod.

Yupp sharp corners are stress risers. They also become hot spots. This is a lot of the reasoning behind radiusing the lip on the bowls.

 

[PowerstrokeJunkie]

15:1 with only bowl work

 

[02BigD]

Is that you old motor Kris?

 

[PowerstrokeJunkie]

Yessir.

stupid ass mistake :doh:

 

[powerstrokenstang]

So where is the trade off. On a gas motor more compression is always more power and compression is compression gas or diesel. More compression should spool a lil faster too shouldn it?

My valve reliefs are not radiused but no probs have arised. I will decompress one day but not till huei gets its break through or i manage to go mech. Lol its far too late to change my setup now i am goin pullin tomo. I am just lookin to learn about the piston design and how things get changed with maching.

 

[NyCowboy87]

My valve reliefs are not radiused but no probs have arised. I will decompress one day but not till huei gets its break through or i manage to go mech. Lol its far too late to change my setup now i am goin pullin tomo. I am just lookin to learn about the piston design and how things get changed with maching.

Well hope you have better luck than I did haha.

 

[powerstrokenstang]

Lol yea me too.

 

[obspsd]

how'd it do at the pull?