Burn patterns on piston and chamber

[1980RS]

My chambers on the L-29 heads and piston crowns looked super after using a burr finish in the intake ports and chambers. I am sold on doing the burr finish after testing it with 2 different sets of heads. Never had intake ports so clean after a few races.

I have never needed any reason to use a burr finish.Get your shape ,csa,correct and it all takes care of itself.You never see a burr finish in nascar stuff,I never see burr finish in anything that comes out of top shops in country,Foltz does as nice as work as anything I have held in my hands.I never see any type of burr finish from him.To each their own but I see it as a bandaid and nothing more.jmo

I can agree with you but after trying the burr finish my track numbers were better and after I dropped my jetting the car with the 1 set of heads I used the burr finish on went quicker and faster than I could have ever imagined. I do know that people don't believe in everything that everyone does. I just believe in what works the best at the track. Recently I had someone that told me I was slowing my car down buy using a 4 hole spacer and restricted air flow thought that was pretty funny as the spacer picked up a solid tenth that day with it. Nascar is all about high RPM top end and my stuff is all about torque in a somewhat low RPM environment as I do not spin my engines that tight but they work for me. I do however like the work you do.

[Lloyd klem]

My chambers on the L-29 heads and piston crowns looked super after using a burr finish in the intake ports and chambers. I am sold on doing the burr finish after testing it with 2 different sets of heads. Never had intake ports so clean after a few races.

I have never needed any reason to use a burr finish.Get your shape ,csa,correct and it all takes care of itself.You never see a burr finish in nascar stuff,I never see burr finish in anything that comes out of top shops in country,Foltz does as nice as work as anything I have held in my hands.I never see any type of burr finish from him.To each their own but I see it as a bandaid and nothing more.jmo

I can agree with you but after trying the burr finish my track numbers were better and after I dropped my jetting the car with the 1 set of heads I used the burr finish on went quicker and faster than I could have ever imagined. I do know that people don't believe in everything that everyone does. I just believe in what works the best at the track. Recently I had someone that told me I was slowing my car down buy using a 4 hole spacer and restricted air flow thought that was pretty funny as the spacer picked up a solid tenth that day with it. Nascar is all about high RPM top end and my stuff is all about torque in a somewhat low RPM environment as I do not spin my engines that tight but they work for me. I do however like the work you do.

That's why we try things and that's why we race.I don't believe what I do is the only way or the correct way in everything.If you find something that works for you,that's all that matters.plenty of people have been successful doing things differently.

[Lloyd klem]

With burr finish in ports and chamber.
Should I try burr finish on the piston too?

Erland

That chamber and plug both show me plenty of oil introduced into the burn there.That being said I wouldn't want the base threaded area hanging into that combustion area with that much oil in the burn.That plug alone shows me this engine needed assistance way before it got to point it did.I see guys so worried about what head ,what intake is best,when what I truly see is not that.What needs to be addressed is getting back to basics of good valve job and most importantly ,ring seal.There is nothing in that chamber pic that even resembles a happy engine.I have worked on dozens of engs with same perimeters you guys are and when they are happy even on pump piss they have nice even burn across 90 percent of chamber and piston top.Light gray or tan is what you want.Even a little light dusty off white will work.But it shouldn't look like raw sewage !!

Just curious, what type of racing do you do? Class racer?

I like heads up drag racing but I have been involved in most types of racing on engine building,design etc.I don't even care for racing that much now days.I do things to learn and improve .

[Erland Cox]

With burr finish in ports and chamber.
Should I try burr finish on the piston too?

Erland

That chamber and plug both show me plenty of oil introduced into the burn there.That being said I wouldn't want the base threaded area hanging into that combustion area with that much oil in the burn.That plug alone shows me this engine needed assistance way before it got to point it did.I see guys so worried about what head ,what intake is best,when what I truly see is not that.What needs to be addressed is getting back to basics of good valve job and most importantly ,ring seal.There is nothing in that chamber pic that even resembles a happy engine.I have worked on dozens of engs with same perimeters you guys are and when they are happy even on pump piss they have nice even burn across 90 percent of chamber and piston top.Light gray or tan is what you want.Even a little light dusty off white will work.But it shouldn't look like raw sewage !!

Just curious, what type of racing do you do? Class racer?

This is an endurance racer that I play with on track.
Block should be 97.00 but was 97.09 to 97.12 so it was a bit worn.
And what is worse is that the ring pack is 1,5mm top and second on a 86mm stroke.
Revving to 8500 is to far with that ring pack so there will a new engine in the future.
But I had other issues to fix first and past them I will have new block and pistons.
Even if it was worn out it ran very well and consistent.
And it is not the extra play that is the problem, it is the ring width.
Plus it cracked a cylinder before it was disassembled and that probably does not make anything look better.



Erland

[Erland Cox]

That chamber and plug both show me plenty of oil introduced into the burn there.That being said I wouldn't want the base threaded area hanging into that combustion area with that much oil in the burn.That plug alone shows me this engine needed assistance way before it got to point it did.I see guys so worried about what head ,what intake is best,when what I truly see is not that.What needs to be addressed is getting back to basics of good valve job and most importantly ,ring seal.There is nothing in that chamber pic that even resembles a happy engine.I have worked on dozens of engs with same perimeters you guys are and when they are happy even on pump piss they have nice even burn across 90 percent of chamber and piston top.Light gray or tan is what you want.Even a little light dusty off white will work.But it shouldn't look like raw sewage !!

Just curious, what type of racing do you do? Class racer?

I like heads up drag racing but I have been involved in most types of racing on engine building,design etc.I don't even care for racing that much now days.I do things to learn and improve .

What is your idea of what the accelerator enrichment is for?

Erland

[Lloyd klem]

We were running like 9.04-9.06 and 148 mph.We were just altering some poor fuel to find a little more power.Our timing was on edge for fuel being used ,it got me my 8.98 and 150 mph ticket tho.We had made enough attempts and realized I probably didn't have enough fuel to drive back home 55 miles.So I loaded it on buddies trailer.Its been sitting his shop since.I figured I pull plugs today and set valves and drive it home.

[juuhanaa]

Just curious, what type of racing do you do? Class racer?

I like heads up drag racing but I have been involved in most types of racing on engine building,design etc.I don't even care for racing that much now days.I do things to learn and improve .

What is your idea of what the accelerator enrichment is for?

Erland

At 2018 Arctic rally we didnt need a accelerator enrichment after the throttle got stuck wide open. It was interesting to note how well it accelerated out of corners by releasing the brake, so im not sure where we need that.

[HQM383]

I did a test with both EFI and carburetors on 2 manifolds, one 60 grit and the other burr finished.
The head was burr finished and only the manifolds changed.
Not even with EFI was it possible to get good accelerator enrichment without overshoot on the 60 grit manifold.
It had to have so much fuel that it always went rich at the end of enrichment.
No such problems with the burr finish manifold.
So I would like to ask the experts if they know why we need acceleration enrichment?
The reason is quite eye opening and it is not what you have been taught.

Erland

I do experience with carbs (Holley type) that different amounts of enrichment are required with a different amount of emulsion and mab. Reduced density and wall adhesion with more emulsion allows for faster booster/mainwell response time - less required acceleration enrichment. So with carbs booster lag is one reason. But I assume there is more to it if you are referring to efi?

[Erland Cox]

Both EFI and carbs.
They hade the same difference with the 60 grit versus the burrfinish manifold.

Erland

[bob460]

We were running like 9.04-9.06 and 148 mph.We were just altering some poor fuel to find a little more power.Our timing was on edge for fuel being used ,it got me my 8.98 and 150 mph ticket tho.We had made enough attempts and realized I probably didn't have enough fuel to drive back home 55 miles.So I loaded it on buddies trailer.Its been sitting his shop since.I figured I pull plugs today and set valves and drive it home.

Must be making around 900hp NA................impressive for only 383ci, driving to and from track.

What's peak rpm's?

[brentry]

I would agree on 90% color
I assumed op had to run it longer.

[HQM383]

You could pull a bunch of fuel out of that.Your pistons don't have near enough coverage imo.Need to get some texture too them.

If he added texture to the pistons would that allow more incomplete combusted hydrocarbons to adhere to the piston with no real change to the status quo? Piston top would read different than with a shiny top that carbon is less susceptible to stick to with no difference in outcome?

What do you find unfavorable with flat top pistons and in what application?

What’s the preference over flat tops?

[HQM383]

Both EFI and carbs.
They hade the same difference with the 60 grit versus the burrfinish manifold.

Erland

Burr finish, less de-atomization due to boundary layer needing less enrichment. More golf ball effect than 60 grit.

[steve cowan]

"Spark plug wetting seems to be an issue for a lot of early OEM type cylinder heads."

Not if carb is set up correctly.
Looks like fuel wash/overly rich AFR. ( probably at part throttle )
I assume this is a street/strip engine. The mistake (racers ) most people make is setting up AFR for WOT and calling it a day.
What about idle/off idle and cruise AFR?
Even racers will have a happier engine if you take care of that. For a drag racer , having an engine that runs strong at part throttle can pay dividends on the return road to the pits.
For circle track racers , fuel consumption can be a factor in winning.
Do you use an AFR gauge ?

Engine came off dyno and went in my car showing 12.5 AFR @ WOT.
I have used 2 other carbs but worked on the 12.5:1 at the track
950 hp (750) 850 annular.
Idle afr is 12.5
Cruise on transfer slot is 15.0
WOT steady 12.5.

[steve cowan]

Super Stock engine off the dyno.

Chad,
Are you using leaded fuel??