What is this telling me?

General engine tech -- Drag Racing to Circle Track

Moderator: Team

TMSJoe
Expert
Expert
Posts: 535
Joined: Wed Dec 29, 2010 8:53 am

What is this telling me?

Post by TMSJoe » Tue Feb 11, 2014 7:06 pm

I have a 400 SBC with AFR 235 heads. About 13.2 to 1 compression. 4150 4bbl 950 CFM I'm told. The engine has a season of racing on it and it is in my shop to find out why it's not fast.

One thing I found is there is piston to head contact. This seemed to have shined up the bottom of the piston skirts. They measure correctly at the gauge point but Diamond could not tell me what the size should be at the very bottom.

Based on the pictures I'm thinking I don't like the intake roof swirl lump. It seems to be directing the fuel to one side of the head.

Thoughts?
AFR235(0).jpg
You do not have the required permissions to view the files attached to this post.

User avatar
MadBill
Guru
Guru
Posts: 12624
Joined: Tue Nov 15, 2005 10:41 am
Location: The Great White North

Re: What is this telling me?

Post by MadBill » Tue Feb 11, 2014 7:21 pm

How about some piston pix, tops and skirts?
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.

lorax
Guru
Guru
Posts: 1778
Joined: Fri Aug 24, 2012 1:00 am

Re: What is this telling me?

Post by lorax » Tue Feb 11, 2014 7:24 pm

Pig fat and fuel wash. How do you start to determine there is something wrong with the heads or pistons until that is fixed. I have no doubt its a slug.

User avatar
BrazilianZ28Camaro
Guru
Guru
Posts: 3792
Joined: Mon Feb 09, 2009 10:52 pm

Re: What is this telling me?

Post by BrazilianZ28Camaro » Tue Feb 11, 2014 7:26 pm

Seems way too rich.

Check the compression ring land, probably the piston to head contact distorted it and the ring is stuck ,leaking cylinder pressure to the crank case.

The clean area of the chamber is the absence of fuel.
'71 Z28 Pro-Street Camaro
Pump gas -T-ram - All motor SBC 427"
3308 lbs- leaf spring/Caltrac Car
29x10.5 Hoosiers
New best 1/8 mile ET
1.45 60' / 4.12 330' / 6.38@109mph :D

BigBlocksOnTop2
Pro
Pro
Posts: 385
Joined: Thu Mar 21, 2013 12:03 pm
Location: Chancellorsville Battle Field, Chancellorsville, Virginia

Re: What is this telling me?

Post by BigBlocksOnTop2 » Tue Feb 11, 2014 9:09 pm

lorax wrote:Pig fat and fuel wash. How do you start to determine there is something wrong with the heads or pistons until that is fixed. I have no doubt its a slug.
X2 Fix the carb. Blown power vlv., leak, too big jetting.

bigjoe1
Show Guest
Show Guest
Posts: 6160
Joined: Thu Aug 24, 2006 8:16 pm
Location: santa ana calif-92703
Contact:

Re: What is this telling me?

Post by bigjoe1 » Tue Feb 11, 2014 9:19 pm

I bet he was READING his plugs


JOE SHERMAN RACING

CNC BLOCKS
Guru
Guru
Posts: 4657
Joined: Thu Jul 01, 2004 6:34 am
Location: NORTHEAST
Contact:

Re: What is this telling me?

Post by CNC BLOCKS » Tue Feb 11, 2014 9:46 pm

Fuel wash not a very good burn pattern, I would say that the engine is over fueled.
Website is up and running
http://hinksonautomotive-cncblocks.com/
Machine shop tour
http://hinksonautomotive-cncblocks.com/shop-tour/
Monthly Specials
http://hinksonautomotive-cncblocks.com/specials/
55MM babbit cam bearings with 1 hole

lorax
Guru
Guru
Posts: 1778
Joined: Fri Aug 24, 2012 1:00 am

Re: What is this telling me?

Post by lorax » Tue Feb 11, 2014 9:53 pm

bigjoe1 wrote:I bet he was READING his plugs


JOE SHERMAN RACING
If he was, he did it in the dark with his eyes closed. I can read the one plug in the head on an I phone and know its stupid fat.
What was he reading? The name & numbers on the plug?

TMSJoe
Expert
Expert
Posts: 535
Joined: Wed Dec 29, 2010 8:53 am

Re: What is this telling me?

Post by TMSJoe » Tue Feb 11, 2014 10:58 pm

lorax wrote:
bigjoe1 wrote:I bet he was READING his plugs


JOE SHERMAN RACING
If he was, he did it in the dark with his eyes closed. I can read the one plug in the head on an I phone and know its stupid fat.
What was he reading? The name & numbers on the plug?
The spark plug in the picture is not from the head. That is my flowbench spark plug. I didn't take any piston pictures but they look a lot like the head. Wet carbon on the dome and clean around the edges. Too cold to get pictures tonight but I will add some after work when I have to be there.

cspeier
Guru
Guru
Posts: 2478
Joined: Thu Mar 31, 2005 5:31 pm
Location: Hays Kansas
Contact:

Re: What is this telling me?

Post by cspeier » Tue Feb 11, 2014 11:03 pm

No matter how fat the engine is/was, your still going to get that goofy burn pattern look.

However the intake port is nice and clean.

dieselgeek
Guru
Guru
Posts: 2248
Joined: Tue Sep 09, 2008 4:51 pm

Re: What is this telling me?

Post by dieselgeek » Tue Feb 11, 2014 11:13 pm

Is that all fuel or is there oil contamination as well?
Calibration Engineer
www.DIYAutotune.com

williamsmotowerx
Expert
Expert
Posts: 711
Joined: Sat Feb 10, 2007 1:24 pm
Contact:

Re: What is this telling me?

Post by williamsmotowerx » Tue Feb 11, 2014 11:17 pm

BrazilianZ28Camaro wrote:
The clean area of the chamber is the absence of fuel.
have to be careful with that statement... fuel does wash carbon away

TMSJoe
Expert
Expert
Posts: 535
Joined: Wed Dec 29, 2010 8:53 am

Re: What is this telling me?

Post by TMSJoe » Wed Feb 12, 2014 12:04 am

dieselgeek wrote:Is that all fuel or is there oil contamination as well?
There may be some oil mixed in. Several pistons hit the head good enough to shine the top and leave dark carbon edges where the chamber pad ends. My thoughts are the piston was knocked out of square at TDC and probably the ring seal was compromised. The quench of the head didn't show contact but the small pad under the spark plug left marks on the piston crowns. The head has dark carbon but the piston was clean AL in the same spot under the plugs.

JoePorting
Guru
Guru
Posts: 2457
Joined: Mon Jun 14, 2010 3:16 pm
Location: Lake Elizabeth, CA

Re: What is this telling me?

Post by JoePorting » Wed Feb 12, 2014 1:16 pm

Could also be a weak ignition/electrical system. How was the motor running overall. Missing? Popping? Surging?
Joe Facciano

lorax
Guru
Guru
Posts: 1778
Joined: Fri Aug 24, 2012 1:00 am

Re: What is this telling me?

Post by lorax » Wed Feb 12, 2014 1:32 pm

JoePorting wrote:Could also be a weak ignition/electrical system. How was the motor running overall. Missing? Popping? Surging?
I was thinking the same thing. Very weak ignition, or very late timing, possibly due to wrong timing tab.
Or all of the above.

Post Reply