Foreign object in cylinder. What to do?

[Anonymous]

Hello everyone,

I woke up on Friday to the sound of the phone ringing, apparently Dad was broken down in the Mav, he told me it rattled very loudly in the turn lane and just cut out and wouldn't restart, and when rolled it out of the way he popped the hood and noticed the air cleaner nut was completely free and that the stud to hold the cheapy cleaner on was gone...

Sorry about the quality of the picture:

It beat up the #6 piston a lot, but didn't put a hole in it, thankfully. There's no damage visible (to me) on the cylinder walls though. There was low compression (90psi) however, so it might have damaged valves too.

The block hasn't had any machine work before, just rerings, so should I just take advantage of the situation and do a rebuild with oversize pistons?
Any other suggestions?

Thanks a million,

Levi

 

[xctasy]

It's an in-tact 250 Maverick. Think about a realistic budget, get the Ford Performance book, and get some extra words of wisdom from some others here.

In my opinion, a 250 is a very,very good engine to rebuild with 2.3 HSC pistons and 2.5HSC con-rods. The bearings and pistons and rings should be simple to set up, and, so long as you have a disciplined budget and have it in your mind to keep the Mav for a long time, you'll be happy. The latter unleaded post 78 head has good valve sizes as an upgrade.

My Aussie 250 suffered a similar problem to yours...the detonation is quite common when a rusted head gasket allows the two adjacent cylinders at the back to over heat.

The rod bearings will be shot, with no temper, and no clean surface. The hammering from detonation is very violent, and creates serious damage.

If a quote on a non-standard upgrade rebuild lookes to much, then look at just a stock rebuild. Just because we are Ford Six Performance doesn't mean it has to be a hottie. A 250 has so much low-end grunt, and there is no shame in doing minimum to just get it back on the road.

But with an engine as big as the 250 is very responsive to the right modifications. Check the cross-flow Chronicles on Jacks old pre-cross-flow US 250. That fairly stock engine kicked some butt.

 

[Anonymous]

Thanks for the good advice, XECUTE.
Sorry I didn't explicitly mention that it was mechanical damage from an ingested foreign object, originally a 2" long stud of mild steel. Now its two 1" pieces of metal

I'm pulling the engine today to inspect the lower end, and am going to order the performance handbook.

Thanks again,

Levi

 

[simon]

In my opinion, a 250 is a very,very good engine to rebuild with 2.3 HSC pistons and 2.5HSC con-rods.

I knew about the tempo pistons, but never heard about the tempo rods.

I´d like to learn more about that.

Any suggestions of compression ratio and head milling, i.e. how far I could/ should mill when using mixed&matched HSC tempo intestines?
is crank journal grinding necessary? what bearings to use?

thanks in advance

 

[MandarinaRacing]

I believe somothing similar happened to another forum member, maybe you should change the topic tittle and sorta grab his attention...

Alex

 

[xctasy]

um, sorta went of on a tangent, ooopsie....

I've not seen an engine tough enough to swallow steel parts.


As for the HSC rods, the 2.3 ones are 5.45" long, and the 2.5 HSC ones are 6.00", perfect for a 250. The original 2.5 pistons are a little too tall, but the 2.3 HSC pistons are almost perfect. You may need toi use a thicker composite gasket, not the thinner steel one.

The original US 250 had rods with a centre spacing of less than 5.88", 1.955" throw crank (3.91" stroke) and shallow 1.53" pistons all in a 9.469" deck, leaving the piston over 100 thou down in the bore at top dead centre.

With 6 inch rods, 1.955" throw and 1.53" pistons, thats 16 thou popping out of the deck. With a nice thick gasket or some closed and ground rods or decked pistons, you'd just fit them in without taking the head off. That improves the rod ratio a little, and gives you more modern components which allow a 6000 rpm rev range to be explored.

Back to your regular program. I'll try to read your post before replying next time LimeMaverick brother :roll:

 

[MustangSix]

You'll have to watch the compression ratio carefully with that rod/piston combo.

Figure a Felpro composite gasket compresses to about .050" and the chamber is 64-66 cc. You could be looking at some pretty high CR with that combo, perhaps too high.

If going that route on a 250, I'd keep the stock pistons with ~6.5cc dish just to help manage the CR. You'll still need a bit of chamber work to get the CR down to pump gas levels.

 

[Anonymous]

Update:

Got the piston out, and I think its been deformed.
The top compression ring is pinched in the groove, and the wrist pin is binding. The top and bottom surfaces of the rod bearing have been wiped shiny in spots (theyre fairly new, what a shame), and the crank journals look to be in need of cleaning up.

Sounds the 2.3 piston/2.5 rod setup is a interesting idea, but this will be a daily driver. Would it be a better idea for me to go with stock pistons/rods, and deck the block/head back to stock specs using a composite gasket.