Burn patterns on piston and chamber

[Erland Cox]

Lloyd. Now when you are taking your engine apart for refreshing it would be interesting with some pictures of a perfect burn pattern.
And some tuition to how to get there would be great too.
But to get a true burn pattern, shouldn´t the engine be run at wot and turned off instantly?
I looked at all of my heads and they were all shiny so I think it has more to do with them running on idle than anything else.
But I would like to make it better if possible.

Erland

[BobbyB]

He is using ms109 fuel. Makes what ?1.5hp per cube . Highly doubt anyone could make more with parts being used.

That burn pattern or lack of tells me there is quite a bit left.A good running engine has a nice even burn across 90 percent of piston and chamber.It should have a light gray/tan light dusty texture if right.When you have a sludge look across 1/3 of your piston and no even heat or cover across the rest ,you are leaving pretty good power behind.Could be cyl prep or ring type issue but I see allot of room in the valve job in that pic that needs addressed also.It will taking going to a bigger valve to get all the cuts sharp and correct again,it don't look like it could be fixed any other way.jmo.No disrespect to anyone involved but I see allot could be improved on.I never put a engine together without roll radius the sharp edges and laying some texture on top of piston to help with a even burn.im no fan of flattops to get a nice mixture motion,if that's used your valve job and head and ring seal needs to 100 percent on point.

Appreciate everyone feedback and no my feelings are not hurt lol.i am here to learn and any constructive criticism is fine by me.
Just to clarify-
Heads 165cc ported to 186cc
2.10" avg csa
1.94" - 1.5" valves
89% throat on intake
Bowl 100% of intake valve.
I done valve job with stones as that's all I have.
40,50,60,70,82
I ported heads,intake and built engine.
The block was honed using profilometer by my machine shop I use,they honed to JE recommendations.
Cam is a comp roller
240 - 256 @ 0.050 "
406 lobes
1.7 - 1.5 rockers.
Ran best ET,mph at track 109 ICL,109 LSA.
Made 522 ft/ lbs @ 5300rpm
570hp @ 6600rpm
Down 5 hp @ 7000rpm.
3620 pound Streeter
1.46 in 60ft
6.71 @ 101mph
10.62 @ 124. 65mph.
So I have some work to do by the sounds of it, I wonder if the MS109 fuel is not suitable for 11.4 compression?
I used it because of the short cam worried about cylinder pressure.
This year it had 20 dyno pulls,30 passes at track and maybe 500 miles of street, so not alot of work.
I have plenty to think about.

When you say “bowl is 100% of intake valve” Are you saying the CSA of the bowl is 100% of the CSA of the outside diameter of your 1.94” valve?…2.95 square inches?

[KnightEngines]

Super Stock engine off the dyno.

Chad,
Are you using leaded fuel??

NHRA has a list of fuels. Tried them all. It made the same power with VPc12 and I like the smell. Brings back memories!

Chad - dunno if you've tried it, but give VP C85 a shot, I've never seen that stuff not pick up power.
It's ethanol base, not sure if you can use an alcohol fuel?

Makes better HP than meth & rpm's better, tho not quite as much tq.
I'd go out on a limb & say it'd match the old leaded roo16.

Earlier this year I had a 383 holden on the dyno, maxxed out tune on E85 made 687hp, poured in the C85, no tune changes at all - 723hp, 36hp pour in.
With tweaking to suit the fuel that could easily have been 50hp, but we didn't have enough to play around.

[Lloyd klem]

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?

I have always put a texture on piston when radius work on edges done.I have never saw a light carbon trail across entire piston not work.Nobody likes their comb chamber shiny smooth?
I always have made power with light dome on piston over flattop.If I have to crowd a chamber down so hard to make comp with a flattop I can't get a valve in it I want.If I'm going to trouble and expense to build an engine ,I'm going after every aspect!Now if a guy can't seal his motor then a piston of any roughness isn't gona save it.

Makes sense for building compression without combustion chamber compromises. What about flat tops for engines that don’t need big compression such as a 10.5:1 deal?

Two schools of thought on piston top finish are having a smooth top (sometimes smooth and shiny) to avoid carbon build up and reflect heat from the piston and back into the chamber and the other is to do as you do and texture the piston to purposefully get a layer of carbon as an insulator to the piston and keep heat in the chamber. As a hypothetical, with identical combustion events occurring on both of these piston finishes wouldn’t we see a different carbon pattern?

I see carbon deposits as the poorly burnt excess hydrocarbons that we have in our A/F ratio for making power to ensure all oxygen that is drawn in is consumed (excess fuel has that cooling effect too). It’s the hydrocarbon molecules that didn’t have enough oxygen molecules to consume it. On Steve’s low mileage engine it looks like deposits are beginning to form around the area of combustion initiation that’s imperfect and not long after that better combustion eventuates. Also carbon is sticking around the hottest areas first. The carbon can’t yet stick to all the clean smoothish surfaces but will likely spread over time. Barely any coloring on the cylinder wall above top ring but it eventually would have. The wet look of the carbon area could be fuel gum and varnish due to oxidization of partially burnt fuel. Running rich mixtures are not often going to be perfectly homogeneous either with rich and lean pockets with each combustion event. Rich pocket = carbon pocket. In such a low mileage engine as Steve’s I’d be concerned if incomplete burned fuel was all over the combustion space already without a rougher texture on components for it to adhere to. But like you said we can be successful with different experiences so I certainly accept where you’re coming from.

Tell us more about your 383 street/strip combo running 8s and 150? That’s one kick ass combo that can be driven to and from the track.

I don't know how to say it any clearer,I won't run flattops in any engine regardless of compression.We had a 572 from wj clear back in 80s.I saw how his pistons were manipulated and textured and I started looking at that on my stuff.Everything we did improved.The whole idea is to get it lit and try and even heat out across most area you can.imo this is a positive and has proven to me to make power.I have taken flat tops to Mill or lathe and completely changed top layout.It always made power,it lets me change things in comb chamber also.As far as my 383,it's nothing extreme at all.Moderate compression ,55 mm cam nice lifters ,rockers and big pushrods make it stable.23 deg raised runner allpro heads.Sheetmetal intake I made and huge carb.Just all basic stuff .My car works nice and our clutch program is decent.

[Lloyd klem]

200,000 mile stock LS head ,did this test years ago, and it's spark plug. 1st thing I noticed was black on plug is exactly where the blue hit the plug on bench. All 8 old plugs had same black spot.
Sanded carbon off before flowing so I could see where the dye hit

You ever knock that knob clear out of there and go to short thread plug?I have picked up power many times in those heads with complete chamber remod.

[Lloyd klem]

Back in early to mid 90s we worked on and ran a pavement late model class.Short track.360 was max allowed.Factory iron head or dart 2 was it.No porting just what you could get at with valve cutter and cutter for throat.10.00 to1 rule.We started with flat tops and made more power with a slight reverse dome.Then we were tore down and that outlawed.Then gave us 3 flat top piston numbers we could run .We started altering the top a bunch.They let it go for 2 yrs and outlaw that.This was Victor Jr intake only class.Had to be a 2 barrel 500 Holley,no mods.We learned to move carb forward on intake.This was hyd flat tappet .550" lift max.We learned allot about not every cyl got same plug gap,valve jobs or piston alterations or something as simple as punch peen marks to alter burn rate.We dynoed several guys engines.Most made 450-460.We always made 495-515.It was a tough class with crap rules but that is a great way to learn.Every detail needs looked at to progress whole program!

[SpeierRacingHeads]

Chad,
Are you using leaded fuel??

NHRA has a list of fuels. Tried them all. It made the same power with VPc12 and I like the smell. Brings back memories!

Chad - dunno if you've tried it, but give VP C85 a shot, I've never seen that stuff not pick up power.
It's ethanol base, not sure if you can use an alcohol fuel?

Makes better HP than meth & rpm's better, tho not quite as much tq.
I'd go out on a limb & say it'd match the old leaded roo16.

Earlier this year I had a 383 holden on the dyno, maxxed out tune on E85 made 687hp, poured in the C85, no tune changes at all - 723hp, 36hp pour in.
With tweaking to suit the fuel that could easily have been 50hp, but we didn't have enough to play around.

This is the fuel list

[Roundybout]

We learned allot about not every cyl got same plug gap,valve jobs or piston alterations or something as simple as punch peen marks to alter burn rate.We dynoed several guys engines.Most made 450-460.We always made 495-515.It was a tough class with crap rules but that is a great way to learn.Every detail needs looked at to progress whole program!

I’m a firm believer in treating every cylinder in a multi-cylinder engine on its own. It’s silly to think that each cylinder is maximized to its fullest potential without treating them as single cylinder combined with the others. Tuning the A/F ratio for example for the worst case cylinder or optimizing timing for the worst case cylinder leaves a lot on the table in some cases. Tons of trial and error on port shapes, piston design, timing, fueling, gaps ect on a carb based engine separated a good engine from a great engine.

Now with EFI and all the simulation software available there is still old school stuff that can be done to optimize each particular engine combo and cylinder. I can only imagine the man hours involved in perfecting that in say a NASCAR/F1 program.

[Old School]

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.

I think Erland Cox has a great idea. Let us see pictures of your pistons and heads burn pattern when you refresh the engine. I am sure we could all learn from your example and an engine that is making close to 2.5 hp per cubic inch, especially one that can be driven on the public highway for transportation. I would be interested in head pics and cam specs if that is not secret. However, if you are selling the engine nothing will be secret long.

[Bigchief632]

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.

I think Erland Cox has a great idea. Let us see pictures of your pistons and heads burn pattern when you refresh the engine. I am sure we could all learn from your example and an engine that is making close to 2.5 hp per cubic inch, especially one that can be driven on the public highway for transportation. I would be interested in head pics and cam specs if that is not secret. However, if you are selling the engine nothing will be secret long.

I'd settle for some pictures of the car, engine, maybe some videos or even time slips would be cool.

[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.

I think Erland Cox has a great idea. Let us see pictures of your pistons and heads burn pattern when you refresh the engine. I am sure we could all learn from your example and an engine that is making close to 2.5 hp per cubic inch, especially one that can be driven on the public highway for transportation. I would be interested in head pics and cam specs if that is not secret. However, if you are selling the engine nothing will be secret long.

2.5 hp? Not sure what math your using.lol. I bet it's no where near there.The guy picked up engine and is getting put in his car and headers made and hood scoop mounted.When it gets pulled down this winter I will see how it looks.

[brentry]

Never tried to knock nob completely out. I do like your thoughts on get it lit and using the area. I think maybe alot guys favor flat top more. Like others have said. It would be interesting to see some of your pics and see how you manipulate it.

[Lloyd klem]

When I tear it down I can get pics of chambers.Heads and cam is nothing exotic or not used many times before.
Heads are 2.200 -1.585 .Int is 52 deg and 91.5 throat.Upper csa at flange is 3.020".6mm intake valve.
Cam is 27.5 ,69.5 int ..on ex 82 ,28.
114 lsa in on 111 icl. .865 lift int..820 ex.Manifold is sheet metal 4.600" in plenum open down to 3.025. Has 3.750" runner.

[Ishiftem]

How do I modify this chamber to improve the burn pattern ?

1734268D-E6C8-4994-858A-0D6F203A5C7B.jpeg

[DCal]

How do I modify this chamber to improve the burn pattern ?

1734268D-E6C8-4994-858A-0D6F203A5C7B.jpeg

I'd be happy with that. It's better than most I've seen. Not that my opinion counts