[Jack Gifford]

Plenty of hemi-four repairs to keep me busy this winter:

> Center main bearing destroyed, main web & cap distorted, all piston skirts scuffed (two cracked), crank has .002" runout. I believe this all resulted from detonation on the engine dyno.

> Three cam followers destroyed, their guides bent, and their cam lobes scored, some bent valves. This must have all occurred right at the end of my last one-mile run a year ago. It appears to have been due to my faulty design of oil passages through the pivot studs- the passages stepped down from .110" to .052" diameter, which created sludge traps. The sludge in them appeared to consist of babbitt from the destroyed main bearing- no particles large enough for a filter to catch.

> One valve seat rotated and another fell out on disassembly. No clear reason, other than possibly too little interference fit.

I've got a good start on repairs, but it's definitely a winter project.

[Drag Star Le Mans]

Do you have a target date for the Salt Flats?

[sdbob]

Amazing your engine design and dedication.

[PAUL K]

Well that is definetly disappointing but seems fixable with a lot of work and a few parts.


Good luck with the repairs.

[Tom Vaught]

Sorry to read about your multiple engine component failures.
Both in cost and time spent to build another engine of that unique design.

Hang in there.

Tom V.

[Mr Anonymous]

Jack, keep after it. I'm sure you'll get it solved and back in business. IF you head to Bonneville, I'm in.

[Elarson]

Originally Posted by Jack Gifford

Plenty of hemi-four repairs to keep me busy this winter:

> Center main bearing destroyed, main web & cap distorted, all piston skirts scuffed (two cracked), crank has .002" runout. I believe this all resulted from detonation on the engine dyno.

> One valve seat rotated and another fell out on disassembly. No clear reason, other than possibly too little interference fit.

We got to be experts at autopsies on dead parts.

We had lots of piston scuffing and skirt cracking that we solved by loosening the piston-to-wall clearance beyond what had been suggested. Nitro hemis have really heavy pistons that don't growth thermally as fast as Pontiac wedge pistons; hence the need for looser clearance.

Talk to Mike about what valve seat interference he settled on (I think it was .007 or .008?)

Bonneville sounds like a road trip. Hey Mr. Anonymous...I'll bring the motel.

Eric

[mgarblik]

Jack, Let me know if I can help you with anything to get that engine back together. Have a seat and guide machine, and other specialty equipment. Not sure what to say about the main bearings other than only increasing the bearing clearance got us out of trouble. With enough oil pressure and flow, wide clearances were not an issue. Was just stunned to learn current top fuel engines run .008-.010" main bearing clearance. We ran .006-.0065" on the Boss Bird. Bearing issues went away.

[Sirrotica]

Originally Posted by Jack Gifford

Plenty of hemi-four repairs to keep me busy this winter:

> Center main bearing destroyed, main web & cap distorted, all piston skirts scuffed (two cracked), crank has .002" runout. I believe this all resulted from detonation on the engine dyno.

> Three cam followers destroyed, their guides bent, and their cam lobes scored, some bent valves. This must have all occurred right at the end of my last one-mile run a year ago. It appears to have been due to my faulty design of oil passages through the pivot studs- the passages stepped down from .110" to .052" diameter, which created sludge traps. The sludge in them appeared to consist of babbitt from the destroyed main bearing- no particles large enough for a filter to catch.

> One valve seat rotated and another fell out on disassembly. No clear reason, other than possibly too little interference fit.

I've got a good start on repairs, but it's definitely a winter project.

Jack, you sound like you have the perfect scenario to use a by pass filtration system. It will catch all the minute particulate that a standard filter will pass. Most filter near 99% efficient under 5 microns.

Sounds like you have a full time job for a few months correcting the carnage that your engine has sustained, good luck on the repairs.

[Dragncar]

We are all rooting for you. No better man to take something like this on.

[Jack Gifford]

Brad- I agree on bypass filtering... for normal-use engines. But the short running times of my race engine would not allow much bypass filtering to occur. And I'm not sure any filter element could catch the "gray slurry" I found in the stud bores.

Eric- Thanks for sharing info on piston & bearing clearances, etc.

Mike- Thanks for the offer of help- if I get "stuck" I may call you.
Things are falling in line pretty good. I had Ed Ide (who bored your IA2 oil passage) mill the bottom of my block true- had to cut it .024". And I had to mill #3 main cap .033". That amount of distortion could only result from detonation, not normal running. The 4-bolt billet main caps are 1" x 3" x 10" 2024T6 alloy for cryin' out loud!

The best news in a long time was finding that I actually have spare followers! I didn't remember having enough forethought to do that- the guy who CNC'd them apparently talked me into it. I've got spare wheels & clips for them, just need Ron Iskenderian to send me a few axles.

I believe the camshafts can be saved with a regrind to a slightly smaller base circle- maybe .020".

I'm machining new valve seats and the head to the same .006" interference fit that I used before. But I've devised a way to pin each seat in two places.

There's no way around paying Diamond to make me four new pistons. But that must wait for the block to be align-bored, to get a good deck height measurement and modify the pistons' compression heights accordingly. I also won't know the bore size until the block is bored. It can only go .022" over and stay in the same 'F' class, so I hope the sleeves will clean up okay.

[Steve Barcak]

Jack,
Sorry to learn of your troubles but, am confident you can handle whatever it may be. It sounds like you are already making progress to make it well again and even better. Best to you from Arizona! Wish we were closer

[Sirrotica]

Originally Posted by Jack Gifford

Brad- I agree on bypass filtering... for normal-use engines. But the short running times of my race engine would not allow much bypass filtering to occur. And I'm not sure any filter element could catch the "gray slurry" I found in the stud bores.

FWIW Jack, it will catch the stuff you describe. One filter will filter 1 gallon in under 4 minutes, not sure of your engines oil capacity. Eric and Mike tried a double setup on the Boss Bird, so 2 gallons in 4 minutes. You might want to ask Eric/Mike if that worked for them. I remember they did have some problems, can't recall exactly what it was though. Seems like the castings on the filters cracked due to vibration?

[Elarson]

Boss Bird had a full flow system on the scavenge back to tank....not a bypass system. We proved that without 100% filtration, torn up parts would contaminate the entire engine in less than 5 seconds.

Eric

[Tom Vaught]

Interesting post Eric.

Glad to see that your experiences with the Boss Bird, verified that in some applications you must have 100% filtration of the oil.

Tom V.

[Elarson]

We filtered the scavenged oil so the junk wouldn't contaminate the dry sump tank. Also we had such a hard time getting enough oil into the engine that we couldn't afford ANY restriction going in. 40+ gpm at 250 psi was way outside the typical oiling comfort zone.

Eric

[Jack Gifford]

Repairs are proceeding. Cylinder head is ready for valve seat machining. I've always disliked the "iffy" situation of brute force pressing valve seats into an aluminum head with .006" interference fit. So I tried a different (and new to me) approach. I rigged up a water heater to circulate through the head and keep it at 180 degrees F, which expanded the seat bores .003". With the head on the mill table and a new bronze seat on a spindle adapter, I held dry ice pellets (-109 degrees) around the seat for a couple of minutes. It worked like a charm! And I finished pinning all seats in place.

[Tom Vaught]

Excellent
Tom V.

[Scott Stoneburg]

Glad to hear its coming along Jack. 👍

[PAUL K]

Good job!