Critique Chamber Burn Pics

[RyanJ]

Just looking for some opinions on chamber burn on set of heads I just ran on dyno. It's a W8 Mopar head originally designed by Chapman specifically for the 2000-2001 Chrysler Lemans Prototype program. It is NOT his normal Intake Port/Chamber. The exhaust port is standard W8/9 Chapman. Seats are 45* IN/EX done by Chapman, I think it has a 65*bottom, 38ish top. Was ran on pump gas. A/F was in mid 13's. This motor has a -30 CC reverse mirror dish CP piston. Nothing wrong with motor, I just pulled drivers side head to look at the burn.

Here are some general pics:

#7 Chamber: http://board.moparts.org/ubbthreads/upl ... 0_6146.JPG

#1 Chamber: http://board.moparts.org/ubbthreads/upl ... 0_6148.JPG

#7 Chamber: http://board.moparts.org/ubbthreads/upl ... 0_6156.JPG

#7 Chamber: http://board.moparts.org/ubbthreads/upl ... 0_6157.JPG

#3 Chamber: http://board.moparts.org/ubbthreads/upl ... 0_6164.JPG

And here is what I really want an opinion on.... Someone please explain to me exactly what is happening with the exhaust side of my chamber and exhaust seat/port in these pics. All 8 cylinders were "cleaning" the chamber and the same spots on the Exhaust seat/bowl/short turn in the exact same pattern. The entire Ex port is nice dry carbon, and the clean streaks are kind of wet, It does'nt seem like oil, or fuel or assembly lube or anything I can think of.... A buddy of mine says he has seen the same clean streaks in 410 Sprint Car Ex ports (dunno if they were All Pro or Brodix heads), so I'm hoping someone on here can explain to me exactly what this is and why it is happening. It's just driving me nuts not knowing.

#7 Ex Seat/Bowl: http://board.moparts.org/ubbthreads/upl ... 0_6150.JPG

#7 Ex ST Streak: http://board.moparts.org/ubbthreads/upl ... 0_6153.JPG

#7: http://board.moparts.org/ubbthreads/upl ... 0_6155.JPG

#1 Ex Port: http://board.moparts.org/ubbthreads/upl ... 0_6152.JPG

The 2 clean streaks come together mid way up the port wall and narrow up to a sharp point at the port exit. Could it really be fuel wash? I just find it hard to believe THAT much fuel is puddling over on that side of the chamber, but perhaps it is??? It is certainly very consistant chamber to chamber. That is really the only thing I can think of...

[RyanJ]

I just went back and looked at an old pic of this head I took after I sprayed some dykem down it on flowbench way back when... (don't laugh at my rudimentary wet flow testing, I have actually found it usually works pretty well when looking back at heads after they have actually been ran, and yes I sprayed a little bit too much in this pic, but hard to gauge how much you are spraying) Now I'm thinking this very well could be fuel "wash" Look at how much fuel was puddling right where the clean spot is at in chamber on Ex side. That is certainly what it looks like, raw fuel trailing over the seat out the Ex port, and if ALOT of fuel puddled in that area of the chamber, I suppose it would keep it cool enough and covered enough in active moving raw fuel that no carbon could develop.... Or am I on crack?

Dykem pic: http://board.moparts.org/ubbthreads/upl ... 0_5125.JPG

[Nwguy]

Possibly the exhaust overscavenging the chamber and pulling raw fuel out the exhaust??

REAL late ex valve closing?

I had not seen the second post when I put this up.

[RyanJ]

I think you might be onto something there.....I thought my VE was a little high for this combo, 116's., and the cylinder press seemed lower than we expected. I will have to look at cam card tomorrow and doublecheck my cam timing in motor. This head is a 12* valve angle and has exceptional low lift intake flow. We know with the dykem, where the majority of fuel wants to go, and if the cam has too much overlap, I suppose the scavenge in the exhaust could be sucking the raw fuel right out.

[MadBill]

Although it would hardly be the hot tip from a power standpoint, seems like if, by way of diagnosis, one was to advance the cam maybe 10 degrees (intake valve/piston clearance willing), it would significantly reduce any over-scavenge, as signalled by exhaust port 'gulley washers' and unrealistic V.E.s
An exhaust system deliberately mis-tuned for the relevant RPM might serve the same purpose. (both easier than sourcing a new early EVC cam strictly for evaluation)

[Fatman]

Ryan

Not helping here but just a quick question.
Did the intake bowls come with that texture/finish from chapman?
If not, are there any before/after results you could share?

Thanks

[racing97]

Question
Were the pictures taken on a clean cut,as you would a plug check?

Best regards

[SStrokerAce]

If it was fuel was you think you would see that in EGT and BSFC numbers.... any idea there?

Bret

[RyanJ]

When I got the heads they just had CNC lines, I sand rolled chambers/Ex ports and chattered up intake seats under the 65, all way down to bowl to roof transition with carbide.

Dyno headers had no EGT bungs, so no EGT #'s, BSFC looks ok.

The motor made last pull came down from 7400 was idled for ~5 seconds and killed. Was never ran again before pics, but no it was not high RPM, kill ignition, Nascar style plug check.

I do have unusually deep valve reliefs, and it has a belt drive on it, so when it gets re-dynoed I do plan on playing with cam timing. It was a 108 LSA cam in at 104. 11.4:1, I have .036" piston to head.

[Unkl Ian]

The thing that catches my eye is all the exposed threads
on the spark plug holes.

[k-star]

Just as a stupid question.... what typ of lube did you put on the valve stem when you assembled the heads????

Keith

[XR8TED]

I used that Dykem trick with my airbrush worked pretty good...

[SStrokerAce]

It either is a wet flow issue (most likely) or a situation where the overlap is too much. Maybe a more aggressive lobe off the seat with the same specs.... it just seems like you could really improve the BSFC numbers here by limiting that problem. I really can't think it would be anything other than fuel going up and out the exhaust port to cause that.

Bret

[LilRacr]

The thing that catches my eye is all the exposed threads
on the spark plug holes.

Just as stated above, what reach plugs are you using and what reach is required per the head?

A too short plug reach will really screw up the combustion burn.

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