UPDATE: Cracked piston...questions?

[stuck]

Okay I have '69 351W that I bought already rebuilt so I don't know the specs on it.

I cracked a piston so I am planning to replace them with forged or hypereutectic. What do you guys suggest? I also want to bump up the compression a bit and replace the dished pistons that were in it. I know the 69-70 have a lower deck height causing clearance issues with some pistons. What are my options? Also, I assume I should go with ARP rod bolts when I do this....any thoughts? I am running factory heads and I may do a little porting to them before they go back on....

Also, stock size bore size is 4 inch , but what is the actual piston size, there has to be tolerances. I measured the piston last night and I think it was around 4.020 or so. Is this typically marked on the piston somewhere? I just need to reorder the same size. I assume its .030 over but it may be less...

A 4.030 bore would have a piston of what size?

Thanks,
Ryan

[Flyin_Freddie]

Forged pistons are generally more for race applications and, naturally, more expensive. Not out of the ballpark more, but there is usually a couple hundred bucks difference. Hypereutectic pistons are sorta the 'middle of the road' - not really suitable for all out race applications, but will work for occassional racing. More expensive than stock pistons, not as expensive as forged. I'm running Keith Black hypereutectic pistons in my 392" stroker from RDI, as installed at Olthoff's Racing. I run my car at track events, but no wheel-to-wheel all out racing. I'm confident the hypereutectics will hold up to my driving style with no problems.

ARP con rod bolts are definitely what you want. Superb quality for just a few bucks more - isn't everything always "...just a few bucks more"?

Oversize pistons are usually marked somewhere....but you need to know the 'code'. I've seen some marked as '+1' meaning they were for cylinders that were bored .010" over...'+2' for .020" over, and so on. And, I've seen some marked '+.010', too...just depends on the manufacturer, I'm thinking. But, your parts guys should be able to help. If your block is standard bore, and not been over size bored to clean it up or anything like that, I'd just mic the currently installed pistons, and match up the new ones. I seem to recall you need at least .020" difference in the cylinder bore and piston size...more for aluminum pistons as they expand more when heated.

Be sure and send your rotating assembly...crank, rods, pistons, etc. ... to the machine shop for balancing and blueprinting, and not just assume it all balances. The cost is worth the performance. It really makes a difference in the finished product.

I'm sure someone else with more experience than I will weigh in on your questions, too. And your machine shop will have MUCH more experience, too, so use them as a resource as well.

Good luck, and let us know how it all turns out.

[Mr.Fixit]

New pistons = new rings = fresh hone job on the bores. You will need to rebalance the whole rotating assembly, so your machine shop can tell you what your bore size is and what your deck height is. Using that information, along with your cylinder head chamber info, you (or better yet the machine shop) can order the correct pistons for your setup. Then they should balance the pistons to each other, then balance the rods to each other, then balance the crank to your piston/rod weight. They'll want the flywheel and balancer(dampner) to do the crank balancing. Since you are doing all that, it's a good idea to have them resize the rods and put new ARP bolts in them.

[stuck]

How much does balancing cost? I have a baby due in a matter of days so I will be lucky if I even have the money to put it back together.

I planned new hypereutectic pistons, rings, ARP rod bolts/bearings and the hone...but balancing...hmmm! Damn this is getting expensive....

Anyone know a good local(Austin/San Antonio) source for machine work....I do graphic artwork so maybe we can make a deal?

Thanks guys,

[Scott Mc.]

I would highly recommend Mike Bowman of Bowman Technologies. Number is 348-0288. He did work on mine (for the previous owner) and is a super guy and loves cobras. Tell him I sent you over!

E-mail me if you want more info.

Dumb question here....how do you crack them??

[stuck]

Detonation....! In my case anyway....long story...I'll fill you in later...over a beer, because I sure need one.

[ERA600hp]

You can Pay me now or Pay me Later!!

The later is the more expensive!!

Don't short cut, take your time, if necessary wait and do it right, it will cost you more later!!

Flyin Freddie, Good answer, and I though you were just anouther pretty face??

The Royal Rhubarb

[427Aggie]

Ok might not be an option but something to think of...find out what the cost to fix is and then look up what a new shortblock will cost from somewhere like Jegs, summit, ford racing...you may find that the cost isn't a whole lot more for a new block and stuff...then you can take your time on the old block and do it up right..then you have a spare engine

Matt

[mustangmendez]

How fast do you want to go =How much do you want to spend $$$ .Then what is your weekest link then theres a traction problem and so on as you know your engine was fast, so go from there.
Tony

[Clois Harlan]

Tony,

To answer your question on how much does it cost to balance an engine.

I spent $400 to internally balance a 428.

Clois

[rdorman]

You can balance your rod/piston/ring assembly yourself which is fairly easy (time consuming) and will save you some money.
Rick

[Boudy]

What if you bought a rebuilt shortblock? Well you would spend about $450 exchange. It would have cast KBs and new bearings. All used parts.

What if you rebuilt what you have?
Vat, M Flux Block, Cam Bearing & Freeze Plugs $140
Bore & Hone $88
Press Pistons $24
Stock Rebuild Kit $350
Assembly $300 w/gaskets

Upgrades:

Balance $150
Surface Block $100
Line Bore $100
Nitraite Rotating Assembly $150
Hyp KB Pistons $250
Resize Rods w/new ARP Bolts $180
New Cast Crank $300
New I Beams $200
C & A Rings $150

These are just some numbers to chew on......

Boudy

[stuck]

Here's the skinny...I am not exactly poor, but I might as well be because I have been spoending way to much money on this car and my wife isn't happy about it. I'm lucky to pay for gas and insurance at this point...

The motor only has 1200 miles since rebuild! I am not redoing everything again! I am doing what it takes to get it back on the road plus minor upgrades(KB pistons and ARP bolts). But, what's this about resizing for the ARP bolts...aren't there some that are direct replacements?

Anyway...nothing crazy here...this is not a race motor...and I don't typically torture it too hard. I simply want it back on the road....

[rdorman]

You may be able to save some money. If the assembly was balanced before you may be able to balance the new parts. That you can do yourself. Some one jump in here! Don't bore the engine larger unless you have to, just more money. If there is no damage to the block and you can just balance the new pistons (should come fairly close as is) you may be able to get away with spending about $400. It may have the ARP bolts already in it! If so, replacing the nuts isn't a bad idea.

I think Fixit was refering to where you cut the cap a bit and rebore the rods for proper bearing fit.

Let the experts chime in on this. I am just throwing out food for thought.

Rick

[Boudy]

Resizing the rods doesn't have to be done to accept ARP bolts, the two are just usually done together. Sorry if I my post was misleading. Bolts only will run about $100.

Boudy

[Mr.Fixit]

You're gonna have to replace the pistons, might as well resize the rods and replace their bolts then. Yes, they cut the parting line and then hone out the big end. You do NOT need to bore the block, just a "glaze break hone" which can be done with a ball hone. Since you have new pistons, you will NEED to rebalance the crank ($100) which may include getting all your pistons matched in weight along with the rods. New rings, gaskets, and if you have the money, bearings. The machine shop will tell you your bore size, combustion chamber volume, rod length and deck height so you can get the right pistons. You do not need : hot tank, cam bearings, a bore job, line hone, decking, torque plate honing, new rods, new block. If you didn't keep track of exactly which lifters came out of which bores, you need new ones so it's a good time to try a different cam. There are advantages to more machining, and some aftermarket parts, but they are not necessary and out of the question if you can't spend the money on them.

[kountzecobra]

If the bores are fine, replace the pistons, rings, and bearings. Balancing is not a must, but if you replace the rod bolts, always resize the rods afterwards. The ARP bolts will fit tighter and will egg-shape the big ends of the rods. Save a few bucks, pacify pregnant wife, and rat-hole money to build a "Double-Throw-Down-Big-Ass-Honking-Stroker-Windsor" at a later date.

[james-w]

Ok so I will ask the REALLY dumb question but can't you just buy an exact replament piston, balance it to the same weight, hone the cyl and add new rings on that piston. We are talking about a new motor that has 1200 miles on it. Tell me why this would not work. Ryan your car is a play toy and you are not out racing it. (stop light to stoplight does not count)

James

[fordnut]

Ryan,

Just take the broken piston to Hamilton's machine shop, He is the best Ford engine guy in San Antonio. He can identify the piston and order a match. All of this talk about ARP rod bolts and resizing the rods is a bunch of bull. ( We are not talking NASCAR here) You will only be turning the engine about 5500 or at best 6000 RPM. If you take another undamaged piston they can match the piston weight and no other balancing will be needed. You will have the same enging that you have been driving. You can put it back on the road for less than $400 bucks. Save Your money and buy a 351 stroker next year for your kid's birthday.

P.S. make sure you do not have block damage ie, scrapes and scratches

Hamilton's Shop is at Mission auto parts 2918 Roosevelt Av. Phone 921-2803

[joe garland]

Ryan, The last three suggestions all make good common sense, and I would go with their line of thought.