Hey all,

First, let me apologize for this post, alot of you are going to be saying I should have searched better. I did, but I just want a comprehensive answer to a few questions I have that I cant find a clear answer to doing searches. As some of you know I have a 1996 PI with at least a bent rod in the engine and definately some oil leaking past the rings. I have decided, (after several discussions with my wallet as to what I can afford) that I am going to just re-build the engine myself. What I would like to know is this: what are some good mods I can do (while I have the engine out and apart) that are fairly good budgetwise and would give me the best amount of power. I know this much at least, I need new suspension ( which can come after Im done with the engine) new exhaust (at least new cats, one is leaking like its going out of style and the other one isnt too far behind) and new mufflers (all of it hi-flow) what else can I do? and where do I go for it, remember that I am not that good with technical stuff about the engine so plain old english helps , my father and some friends will be assissting me with the re-build so hopefully everything goes smoothly, also tips for any of this will be appreciated. As always thanks for the help, sometimes I dont know what I would do if it wasnt for CVN.

Paul

Paul,

You are looking at about $500 for pistons and rings, plus at least one rod. If you go to www.corral.net you can find those parts for a little less.

Get good forged STOCK size "floating" ROMEO pistons, with rings, and a set of forged rods. At that point, the block is pretty much ready for anything.

The stock pistons have about a 9cc dish, anything less of a dish will increase your compression ratio (CR) and improve economy and power potential. Now, if you opt for a pair of good used "PI" heads, you CANNOT use any pistons with a dish that is 9cc or SMALLER. If you send out your heads for porting (a VERY good option), you could go with a smaller dish for improved performance. I think "flat-top" pistons are going WAY too far however.

DO NOT hone the cylinder walls, and DO NOT remove the crank or bearing caps unless it is absolutely necessary (you have bad main bearings). Just install your new parts and run it.

Good pistons and rods coupled with fully ported stock heads should net you somewhat over 210 RWHP on pump fuel. With NO external changes.

SVO:

Your reasons for not removing crank aside from cost of new fasteners? I like to eyeball and measure bearings and journals when things are apart anyway....

Paul:

How many miles on this beast? if >100K, I'd be replacing the timing chain(s) and possibly the timing gears, too. A little slop there will screw your performance.

Getting the heads ported & polished is definitely the way to go. It shouldn't be too expensive, and you'll see a marked improvement in performance. Remember to send your exhaust headers and intake manifold with the heads so they can be matched to the ports. No sense in having the heads ported unless they match the intake/exhaust!

If you have the old 'all plastic' intake manifold, get the Ford replacment unit with the aluminum first (water) crossover. A wrecking yard intake will work fine if you don't damage it while installing it.

I'd have the exhaust headers porcelainized or powder coated as long as they're already out. They always seem to be the worst-looking components under the hood! Powder coating should run you less than $50.

As long as you have the engine out, now's a good time to get it cleaned. Find a shop with a steam cleaner to remove any exterior dirt BEFORE you open the engine up. Also, they can flush out any interior oil/water passages to ensure good fluid flows.

As far as NOT honing the cylinders or removing the main bearing caps, I'll have to admit that I don't know why JohnG says not to. I'd find out the reason, but apparently he knows something I don't!

Above all, use your resources here to help you do the job right. You can save mega $ and irritation by listening and understanding and doing it right the first time!

In most of my recomendations, I assume the reader is not intimately familiar with performing an engine overhaul. Therefore, some things are better left untouched. Sort-of, "if it ain't broke, don't fix it" kinda thing.

Pulling the mains without cause on a modular engine can only reduce it's life. If you accidently over or under Tq any main bolt, you will fail the bearing(s)/crank. A risk, IMO, not worth taking.

Now, if the oil is milky, and you know it was operated with water or coolant in the oil, then it NEEDS new bearings. That is not an option.

You have to hone the block to fit forged pistons. If you leave it alone, you'll end up with an expensive paperweight. Piston clearance is absolutely critical, and different with forged vs. cast, as are straight cylinders.

I've found that quality forged pistons and rings run closer to $800 if you use an off-the-shelf dish size. Eagle rods at least are "cheap" at $420 or so.

Yes, you should replace all the timing gear (chains, guides, tensioners). You should also have a valve job done and the crank measured and polished (or ground) for new bearings. You need to make sure that crank isn't hurt after bending the rod.

It sounds like you haven't done this before. Be careful. If you make any mistakes it will be an expensive lesson.

Properly rebuilding a 4.6L isn't particularly cheap. It may make sense to consider a new Ford engine. If you consider labor and machine work costs, it starts to look pretty attractive especially with PI heads. The only advantage to DIY is you get a tough forged engine. No cost advantage at all. Forged pistons don't wear as long as cast either, but they sure take abuse.

Please do not suggest other hone their cylinders if you are not aware of the damage it can do, and do not warn of how easily that can happen.

Having rebuilt dozens of engines, and been to school on dozens more, I have a unique "accross the board" factory education on service procedures, and the why's of them. The fact is, it is very common to get forged slugs pre-sized for standard bores, in which case the sizing only needs to be verified, not altered.

I stand squarely by my suggestions, and without reservation.

OK, the bores should be honed to match the pistons by a non-idiot using torque plates and the correct finish to match the piston rings. Better? I wasn't listing every last detail. There's an interesting torque procedure on the main bearings I didn't mention either...

Pre-sized slugs do exist, sometimes they're even correct in size. As an experienced engine builder, you should know that it typically is not done this way. Rather the bores are honed to match individual pistons. Given that .0005" is enough to make a huge difference in fit, and the fact that bores wear, the most correct and longest-lasting result will be obtained with NEW bores honed to match the NEW pistons.

Why buy a set of new pistons and throw them in a worn bore? Waste of good parts and engine lifespan.

How exactly will the "back-yard" mechanic get all that honing grit outta the mill?

Answer........They won't, consequently they will wear out the rings and/or bore much earlier than if they'd just leave it alone.

The answer is you don't rebuild an engine by yourself. Hire a competent machinist to provide you a correctly honed, washed block. Same goes for the crank, valve job, and rod bushing fit.

Boy, I would hope someone isn't honing in their backyard. Definitely take it to a machine shop for prep work(cleaning, honing/boring,etc). My machinist only charges a $100 to assemble, so that would be the best thing for an inexperienced DIY'er. How do the new rings seat without honing?

John,
I hate to be a pain, but even a STOCK bore, if you replace it with stock sized pistons, forged or cast, still needs honed or rings will NOT seal... I don't forsee a weekend mechanic doing this... this is a major undertaking, and someone who is familiar with honing cylinders will have all the equipment to do it right in the first place... otherwise, they will take the block to the local machine shop to have it done. Advocating that bores should NOT be honed when replacing pistons is worse advice than telling someone to just run a hone on a drill thru the cylinder... at least with the glaze broken and a crosshatch pattern on the cylinder, the new rings will seat...

David,

The idea that rings will not seal on an un-honed bore is just as valid an old wive's tail as that they won't seal if you use synthetic oil.

Two years ago, I may well have said and thought just as you do. Having seen numerous piston replacements on "used" and un-honed bores as prescribed by the applicable FSM has definately shown me that what I had thought about such things was inaccurate at best, and that unless there is bore damage, just re-ring and run.

Well, I hate to say it, but I have seen re-rings done on a bore that still checked out within tolerance, and those that didn't have a hone run to break the glaze pumped oil past the rings and were eventually torn down again and honed... then they seated and ran fine... Even fords own service manuals state a glaze breaker hone MUST be run thru the bore for new rings.

In reply to:

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... As some of you know I have a 1996 PI with at least a bent rod in the engine and definately some oil leaking past the rings....

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Regardless of the hone/dont hone argument, the original post poses a couple questions.
A. Who verified it has a rod bent? Is the rod knocking or is it a noise caused by something else like exh leak, lash adjusters or timing chain tensioners when cold? If a rod is knocking not necessarily a bent rod either.
B. If it does have bent rod, think what caused it. Betcha that particular crank journal is shot.


If it needs that much work I think the best monetary wise course would be a used engine.