Al
Please keep us updated. Especially any REAL numbers You end up with. Also pictures are a real bonus. Might even start a thread for your build in the sixers gallery or Virtial Dragstrip.
Thanks,
Frank

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

Sure will Frank - I'll just post them in my Profile in Slixer's Gallery
http://www.slantsix.org/forum/viewtopic ... highlight=

and on my personal website.

_________________
Cheers!
Al T

Well 3 years have gone by since I started this engine build. What resulted was, as the title states, a story of frustration, self doubt, embarassment and now hope. My story is long but I documented it in hope that others might learn from it.

As stated earlier in this thread, my idea was to create maximum torque under 5000 rpm to create a driveable 4000+ lb highway car while improving fuel economy. I wanted to see if I could extract more power from each stroke and minimize underhood temps without sacrificing daily performance or manners.

At a high level, here's what I specified:
- '72 block bored to accept Wiseco 3.445 pistons
- K1 7.005" rods
- ported '76 head with Ford valves I=1.735", Ex 1.5"
- Erson custom cam where: Intake closes late, Ex Opens late and overlap is negligible
- Aussie permaseal head gasket

(Click on pic to see details full size)



I spent a hour with the builder reviewing my ideas, gave him copies of all my paper work (dimensions, compression ratios, cam specs, etc)

My first warning came when I picked up the engine and my builder stated that " he'd used a steel shim gasket instead of the one I'd given him and he'd put a bit of advance into the cam". I should have put my foot down there but my business was very busy, time was in short supply so I gritted my teeth, took it home and installed it.

In summary, performance was dissappointing -very similar as before but now I heard what I thought might be detonation starting around 2psi. I say "might" because taking into consideration that the car's exhaust system needed replacing, the blower makes some noise, my hearing is not so good and I'd never actually had the sound of detonation pointed out to me before. Frustration and self doubt set in. I didn't have the time or will power to investigate so I drove Big Red occasionally without regard for any of the noises it made. . . until this spring.

I took time off from work and began to systemically investigate.
In addition to the above symptoms, I was loosing coolant and the car ran too hot.
- I pulled the plugs (NGK-UR5's) and noticed that the gaps were around 0.060" rather than the 0.035" I'd set them at. Number 4 plug had no electrode at all.
- I pressure tested each cylinder and sure enough, air bubbled up into the rad from several of them.
- cranking compressions appeared to around the 90 lb range but I was having trouble keeping the gage in
At this point doubt and embarassement is setting in at the "dumb ass" who kept pushing the car when he knew something wasn't right.
Well, I knew the head would have to come off so I got at it.

Here's the sight that greeted me at piston 4. (Click on pic to see details full size).


Now I see where the spark plug electrode went. I also see excessive pitting on each piston on the cylinder wall side of the intake valve. I push on the pistons - each is quit loose.


There is no ridge in the cylinder wall and the top of the holes appear to be in the 3.445" dia range. Obviously, the pistons have taken a sh** kicking.

I turn my attention to the head. The steel gasket doesn't shown a obvious point of failure. From a "distance", things don't look too bad.



I dissassemble and find out that 4 exhuast valves have pits that look like this.


The intake valves are fine but the head casting seats have almost dissappeared in the area above the piston pitting. (Click on pic to see details full size).




So now I know what pre ignition/detonation does to an engine. The question is why did it happen. I'll cover my analysis in my next post.

_________________
Cheers!
Al T

I started by taking some measurements. Here's what I found.
1. The deck height was not 0.168 as expected (from builders measurement). It was 0.160"
2. The head chambers looked small. I checked the volume. It was now 40 cc, not the planned 44.
3. I degreed the cam (as built). I drew the wheel on the PC, cut it out and mounted it on my pulley with 3M Spray Mount (PostIt Adhesive)


I checked TDC and made an adjustment to my indicator tab to make sure it was right on.


The truth of the builders words "I put a little advance in it for you" were shown. The adjustable JP Performance cam crank sprocket was installed at the 0' slot but the valve events were actually advanced about 5' from advertized.



The Exhaust was opening early, but more importantly, the intake was closing 10' too soon.

The net result of these collections of deviations was:



In summary:
The combination of
- shaving the head excessively
- the incorrectly measured block height/deck height
- the substitution of the thinner steel shim gasket
had bumped the static compression from 9.3 up to 10.3

The intake earlier closing together with the increased static compression ratio had bumped the DCR from 7.82 to 9.08. This is well beyond the 8.2 which I believe is kinda' a rule of thumb. Now add boost on top of these numbers and detonation was inevitable.

Now that I knew what had happened and why it had happened, a flicker of hope returned. The engine as it was built was not what I had designed. The builder had done what he'd have done on a stock NA build (more compression, advance cam). Perhaps my design would work after all. I decided to see if I could salvage the engine with some remedial action to at least test my concept albeit perhaps temporarily. I'll put that story in my next post.

_________________
Cheers!
Al T

First I tackled the head. I spent a few hours with valve compound and the drill to re-establish seats for the intake valves and take out the pits on the exhaust valves.



Next I retarded the cam about 5'. (See last column in table). The instructions accompanying the tming gears from JP were not helpful but I was able to establish the valve events where I wanted them.


Reinstalling the head with the 0.040" Permaseal gasket now produced a static compression ratio of 9.75 and with the later closing of the intake valve, the DCR is down to more acceptable 8.18.



I installed colder plugs from a NGK-UR5 to a NGK UR6

Lastly, I dumped a bottle of octane boost into the tank of premium fuel and outfitted a new, quieter exhaust system.

So here's where I'm at now. After some initial adustments to the EFI to compensate for some changes to the engine, I've driven about 60 miles.
- That noise, which I now recognize as detonation, is gone.
- The power is noticably better (smoother and steady) on a local 6% mile long grade.
- I need to reprogram a considerable portion of my fuel maps to compensate for this change in cam.
- I believe I can hear those loose pistons.

Finally, I've got renewed hope in my theory for how to build a blown "highway cruizer" slant.

Lessons Learned:
- make sure your builder understands exactly what you want to do. I thought I had but obviously it got lost in the mix somewhere. In my case, I'm not sure what I could have done differently.
- perhaps ask for final "as built" dimensions and test results
- re-emphasized: engines are systems and the cummulative result of how all the pieces work together. What appears to be a small change can cascade into something much larger
- get your hearing fixed
- just because circumstances suggest that you are crazy doesn't mean that you are.

_________________
Cheers!
Al T

Did you ever cross-check the calculate the DCR (dynamic compression ratio) with cranking compression readings, on the combo that was detonating?
DD

Thanks for the rundown, Al.

I am into my boosted/EFI/MPG rig now, and it is working pretty well so far. I am about to install a knock sensor so I can lean on it harder and have some feedback there. Water/meth inj is recently installed and it has pulled some ~310 HP runs and 24 hwy MPG. My near/medium term goal is a reliable 330-370 HP and 25+ MPG. I blew one composite head gasket at 6000 miles due to an aggressive tuneup and a fire ring exposed to combustion chamber. Static comp is 8.7:1 and MP 244 cam at 103-104 deg centerline.

http://slantsix.org/forum/viewtopic.php?t=45187

Lou

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Home of Slant6-powered fun machines since 1988

Unfortunately I did not. However I have tested it now:

1-did not test as alt in the way
2-105
3-110
4-95
5-95
6-100

With a DCR of 8.18 and atmospheric being 13.2 at 3000 ft ASL, the theoretical pressure is 108 psi

_________________
Cheers!
Al T