97 PI cams (and whatever else) swap in to non-PI heads

GRWeldon

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Was redirected here last night. I wasn't aware of the...eh...changes at TCCoA.

A while back I bought a 97 T-bird in good shape except with milkshake oil. After tearing down the engine it appears that the freeze plug behind the timing cover (or water pump, can't remember) came out and destroyed all the bearings in the engine and heads. The cams were good and pretty sure all the other steel components are good as well. The head bearings were trashed.

I have a set of 95 heads that are in rebuildable condition. Is it possible to use the PI components out of the 97 and put them in to the 95 heads to use on the 97 engine? Sure would be cheaper that way...

Thanks...
 
I'm not super familiar with your setup or knowledge level, so please don't interpret any of what I'm going to say as condescending. I just want to be sure I understand and am giving you accurate advice, so I'm going to start at a basic level. :)

First - differences in the modular engine family. The modular was introduced in 1991 (Town Car) and remained largely unchanged through 1995. In 1996 the heads and top end were redesigned for a composite intake. In 1999, the performance improved "PI" cams/heads/intake came out for the Mustang, and by 2001 all modular applications were using the new PI design. A detail to note: PI engines for 1999-2000 were manufactured at the Windsor engine plant and have obvious differences to the 4.6 NPI engines manufactured at the Romeo engine plant. NPI engines were still manufactured at Romeo in 1999 and 2000 while Windsor was making PI engines. By 2001 Romeo stopped making NPI engines and had switched to PI. The easiest way to identify a Windsor engine is the oil fill cap is on the passenger valve cover; Romeo engines had it on the driver's side.

The most discussed and well-known change is the NPI-PI updates. These included a larger dish on the pistons, a smaller combustion chamber in the heads, larger intake ports and adjustments to the pathways, cams with added lift and revised duration, and longer runners on the intake manifold. However, the 95-96 changes are arguably more significant. The aluminum intake was scrapped in favor of the composite intake with longer runners and reduced heat soak and the top end was updated to support the new intake (fuel rails, EGR, cables, plenum etc.). The heads received longer valve stem guides to resolve a wear/oil burn issue, valve springs and seats were revised to allow for additional cam lift.

With these changes in mind, you can't install PI cams on NPI heads cast for 91-95 MY engines - the springs bind due to the added lift, and swapping the springs doesn't fix the issue. However putting the 95 heads on the 97 shortblock will work with NPI cams... just know that any future upgradeability is limited due to the early head casting.

Hope that answers your question.
 
Welcome!

I'd recommend replacing the heads and cams with PI heads and cams instead of "upgrading" non-pi heads.
 
Does the PI intake work on 95 heads or do those need to be swapped out?
 
The intake works just like it does on 96 npi heads, just goop some RTV on the two coolant passages and send it. The npi cams won't take much advantage of the PI intake though
 
I'm not super familiar with your setup or knowledge level, so please don't interpret any of what I'm going to say as condescending. I just want to be sure I understand and am giving you accurate advice, so I'm going to start at a basic level. :)

First - differences in the modular engine family. The modular was introduced in 1991 (Town Car) and remained largely unchanged through 1995. In 1996 the heads and top end were redesigned for a composite intake. In 1999, the performance improved "PI" cams/heads/intake came out for the Mustang, and by 2001 all modular applications were using the new PI design. A detail to note: PI engines for 1999-2000 were manufactured at the Windsor engine plant and have obvious differences to the 4.6 NPI engines manufactured at the Romeo engine plant. NPI engines were still manufactured at Romeo in 1999 and 2000 while Windsor was making PI engines. By 2001 Romeo stopped making NPI engines and had switched to PI. The easiest way to identify a Windsor engine is the oil fill cap is on the passenger valve cover; Romeo engines had it on the driver's side.

The most discussed and well-known change is the NPI-PI updates. These included a larger dish on the pistons, a smaller combustion chamber in the heads, larger intake ports and adjustments to the pathways, cams with added lift and revised duration, and longer runners on the intake manifold. However, the 95-96 changes are arguably more significant. The aluminum intake was scrapped in favor of the composite intake with longer runners and reduced heat soak and the top end was updated to support the new intake (fuel rails, EGR, cables, plenum etc.). The heads received longer valve stem guides to resolve a wear/oil burn issue, valve springs and seats were revised to allow for additional cam lift.

With these changes in mind, you can't install PI cams on NPI heads cast for 91-95 MY engines - the springs bind due to the added lift, and swapping the springs doesn't fix the issue. However putting the 95 heads on the 97 shortblock will work with NPI cams... just know that any future upgradeability is limited due to the early head casting.

Hope that answers your question.
Thank you for this detailed explanation. First off, a question or two. Are the cam's in a 97 Bird the same as the cams in a 95 Bird? Second, are the heads from a 95 the same as heads from a 97? Third, will the composite intake from the 97 fit on 95 heads? If the answer to all is "yes", then I have the information I need. I'll be able to put my "good" 97 cams into the 95 heads and be good to go. If the answer to either is "no", then I'll have more questions.

In any case, I'm not looking for anything more than a drivable T'bird. In total I've owned two 95 Cougars, a 94 5-speed SC (still own), a 95 4.6 LX, a 96 4.6 LX and a 97 4.6 LX (still own). I love the cars, do ALL my own mechanic work, have rebuilt one 4.6, starting work on another. I'm not an expert but I'm not a novice either. My professional career has been a progression from Machinist to Manufacturing engineer. I'm now retired.

The engine in the 97 that I own was ruined by a freeze plug (behind the timing cover) that just fell out when the previous owner was driving it. I don't know if they stopped immediately but the bearing journals in the heads were trashed. The rod and crank bearings faired a bit better but need to be replaced. The driver's side rear cylinder has some pitting in it due to coolant sitting in it for quite a while. I had the block cleaned about 2 years ago and am now considering rebuilding. I really would like to the the block bored to remove the pitting but I can't afford new pistons and rings and the machining cost. I haven't really measured the bores or the pistons yet, maybe it's not feasible to put the original hardware back in it but that's the plan. It's really difficult to determine exactly how deep the pitting is on that one cylinder (is it #4 or #7, not really sure of the numbering order). It may only be a few thousandth deep or it may be more than .030. Not really sure how to measure. In any case, I'm sure there would be degraded performance on that cylinder but I don't think it would cause a miss. Like I say, I just want to put it back on the road. I bought it for $500 back in 2017. I have all new standard size bearings and rings on-hand. Bought the new parts before I retired, now I can't afford to put any more in to it. Just trying to make due with the components I have on hand from the 97 Tbird and the 95 Cougar I parked for parts years ago.

Again, thanks for your reply. Look forward to your answer...
 
Yes 97 cams will work in 95 heads, they don't have as much lift as later PI cams where the 95 and earlier heads become an issue. 95 and 97 are both npi, the 95 npi is just the earliest form of it with some nuances. Composite intake is a direct fit too, as are valve covers, manifolds etc.

The only issue with using the 95 heads if you're not concerned about performance is the valve guides are prone to excessive wear with miles and oil consumption is increased.

Having said that, I'm not sure this is worth the trouble, its one thing if all you're swapping to get it working are the heads but doing a full bttom end rebuild on a similarly roached block to me would be a sign to find a good used engine from a salvage yard for the time and money
 
Yes 97 cams will work in 95 heads, they don't have as much lift as later PI cams where the 95 and earlier heads become an issue. 95 and 97 are both npi, the 95 npi is just the earliest form of it with some nuances. Composite intake is a direct fit too, as are valve covers, manifolds etc.

The only issue with using the 95 heads if you're not concerned about performance is the valve guides are prone to excessive wear with miles and oil consumption is increased.

Having said that, I'm not sure this is worth the trouble, its one thing if all you're swapping to get it working are the heads but doing a full bttom end rebuild on a similarly roached block to me would be a sign to find a good used engine from a salvage yard for the time and money
Sorry it took me so long to get back here and read your message. I got involved with another project, had to rebuild a couple of hydraulic cylinders and the 4-valve bank that operates the functions on my backhoe. Seems that I have many projects on-line and you never know which one will be the priority at any given time!

The info about the 97 cams is exactly what I wanted to know. I was under the impression that 96-97 heads were PI heads, so thank you for correcting me there. In the time between my last post I measured the cylinders of the original 97 block that I was intending to rebuild. I didn't want to buy new pistons so I was hoping for a usable nominal block. The cylinder that was pitted turned out to be .005 over after removing the pits with a hone. I have another engine from a 95 that needs to be torn down and inspected. Not hoping for much on it, I know for a fact that it had 266K miles on it.

I don't know, but maybe this is the proper place to ask... Are normal 4.6 block able to be bored oversize? I've had a few of them, even rebuilt one but never had any machine work done. Just thought I'd ask...
 
The 4.6 can’t be bored out as much as the old 302s, but people routinely go .020” over with them, and you can buy replacement pistons and rings in that size. However I have torn apart multiple 300k mile plus 4.6s and found zero cylinder wear, and even still having a cross-hatch, so unless you are upgrading to forged pistons and stronger rods for a power adder, for the price of machine work and new pistons, rings, and bearings, it would be cheaper to just find a good complete used engine for $500.
 
+1 Oversize pistons alone will cost that, not to mention the machine work.

They can be bored, but no more than .030 over(at least safely), but you really need a machine shop that does 4.6s and uses a torque plate.
 
A used pi engine is easy to find cheap. Thu need two engine stands; you take the stuff off the front, the oilpan, and the valvecovers off our engine, and put them on the new one. Look at the timing chains and tensioners; the 2003 to 2007 engines had iffy tensioner sliders that were prone to breaking. Also, Change the plastic tensioner actuators with the mn12 iron ones. You'll want to disassemble the tensioner, by removing the roll pin. There are no rings, it's designed to leak.Look at the teeth on the crank gear; you might want to get new gears and chains, depending on what the teeth look like. Swap the old cast trigger wheel for the stamped one, and make sure it has the washer with it.
I did all that stuff, and put in a high volume oil pump.
 
A used pi engine is easy to find cheap. Thu need two engine stands; you take the stuff off the front, the oilpan, and the valvecovers off our engine, and put them on the new one. Look at the timing chains and tensioners; the 2003 to 2007 engines had iffy tensioner sliders that were prone to breaking. Also, Change the plastic tensioner actuators with the mn12 iron ones. You'll want to disassemble the tensioner, by removing the roll pin. There are no rings, it's designed to leak.Look at the teeth on the crank gear; you might want to get new gears and chains, depending on what the teeth look like. Swap the old cast trigger wheel for the stamped one, and make sure it has the washer with it.
I did all that stuff, and put in a high volume oil pump.

The iron tensioners are the only thing I'd save from a 94-5 motor. My 03 DOHC has my cars factory original 1994 timing set except for the better later crank sprocket and secondary chains.
 
I mounted the plastic ones on my fail board. That design is a fail as designed. on the 03 engine I bought 725 miles, already had broken bottoms on the plastic pieces, which were stuck to the screen on the oil pump pickup. There were grooves in the crank gear from the chain. The plastic tensioners lack two oil squirters that lube the chains; that whole design is a fail. I had Nick send me the right parts to replace it all. I wish I'd picked his brain more about porting. He was such a nice guy. He had patents in modern speaker design, especially the voice coil.
 
They don't have those ratchet pieces either, where you can use a paper clip to lock them in the compressed position, which are very useful for reinstalling the chains/guides
 
I was told to be careful installing them, if you get then too tight it will wear the front cam bearing journal quickly.
 
I was told to be careful installing them, if you get then too tight it will wear the front cam bearing journal quickly.
Nothing you can really do to overtighten them during install, once you release the pin they'll just take up the chain slack. With oil pressure more slack gets taken up. I've heard of the potential they can overextend but it seems to be more of a possibility with high power turbo cars with 2 steps, not something I'd worry about. Could probably grind a few teeth off the ratchet piece if that is a concern though
 
The last step putting them in it to tighten the chain by extending the tensioner. Don't overextend it, is what I'm saying. I had the chain too tight the first time; it made the engine hard to turn. The sliders will wear in pretty quick, and the ratchet will extend as necessary. The plastic ones don't have a ratchet, so the chains flop around until you get oil pressure. Between that, and the lack of squirters, they are a fail.
 
Both mmr and Modular headshop sell iron ones.
 
Both mmr and Modular headshop sell iron ones.
You can still get the iron tensioners at Ford. Bought them for my sons 97 PI build in the spring.
 
My boss' 06 5.4 snapped a chain due to a failed tensioner. They put in a reman engine, that was notable for the list of stuff fixed in remanufacture.They even helicoiled the heads.
 
The last step putting them in it to tighten the chain by extending the tensioner. Don't overextend it, is what I'm saying. I had the chain too tight the first time; it made the engine hard to turn. The sliders will wear in pretty quick, and the ratchet will extend as necessary. The plastic ones don't have a ratchet, so the chains flop around until you get oil pressure. Between that, and the lack of squirters, they are a fail.

There’s no setting the tensioner, just pull the holding pin and release, the internal spring takes up the slack. Oil pressure takes up whatever’s left

An 06 5.4 would have the plastic tensioners, no? Those style don’t use the ratchet setup that potentially overtension. The problem with the plastic ones is the opposite!
 
Thanks for all this good information. When I rebuilt the engine that lasted 33K miles afterward, plastic timing chain tensioners were in the rebuild kit, so I used them. That was 19 years ago...I can claim ignorance...which would be true. As for boring, I don't really want to, just not sure what I'll find in the block I have. BTW, there's no place around here (Central Alabama) that you can get a $500 PI 4.6 unless you want to pull it out yourself at Pull-a-Part. I'm over 60 and don't quite intend to go through the process of pulling one at a junkyard. Did that for an 03 Acura TL transmission once 6 years ago. I won't do it again. I'm not under 30!
 
I get that, but pull a parts are even cheaper than that, I got my 03 DOHC for $350 flat, and that yard actually did the pulling for you at that time, I just had to arrange transportation.

Check car-part.com, there's a bunch in your state sub $500 and these yards do the pulling for you. I just put in 04 grand marquis for the search criteria but you can find PI motors in every 02+ Panther platform car and E series van up to their discontinuation in the 2010s, Plus 02-04 Explorers(those have aluminum blocks which is a plus), F series pickups up to 05 and of course 99-04 Mustangs, it's actually a lot easier and probably cheaper to find PI engines than it is the older non PI stuff.

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Pulling one and rebuilding it is possible, but it's the same deal; once you pull it out, you can just as easily drive in the new engine on a truck
Paying a jy to deliver is probably cheaper than paying a shop. But, I'd call some shops and see what they want to do the swap for you. Junkyards deliver to shops all the time.
 
If it has less than 200k I wouldn’t bother rebuilding it, I’d just give it a good looking over, regasket it and send it
 
The engines I've had apart were all within oem tolerances when I tore them down. The red cougar got a valve stuffed hard enough to crack the head, but you can still see the cylinder crosshatching at 233k miles. I pulled the mark motor apart to inspect it, but I never should have touched it. I have new stuff to put it together with.
 
First - differences in the modular engine family. The modular was introduced in 1991 (Town Car) and remained largely unchanged through 1995. In 1996 the heads and top end were redesigned for a composite intake. In 1999, the performance improved "PI" cams/heads/intake came out for the Mustang, and by 2001 all modular applications were using the new PI design. A detail to note: PI engines for 1999-2000 were manufactured at the Windsor engine plant and have obvious differences to the 4.6 NPI engines manufactured at the Romeo engine plant. NPI engines were still manufactured at Romeo in 1999 and 2000 while Windsor was making PI engines. By 2001 Romeo stopped making NPI engines and had switched to PI. The easiest way to identify a Windsor engine is the oil fill cap is on the passenger valve cover; Romeo engines had it on the driver's side.

The most discussed and well-known change is the NPI-PI updates. These included a larger dish on the pistons, a smaller combustion chamber in the heads, larger intake ports and adjustments to the pathways, cams with added lift and revised duration, and longer runners on the intake manifold. However, the 95-96 changes are arguably more significant. The aluminum intake was scrapped in favor of the composite intake with longer runners and reduced heat soak and the top end was updated to support the new intake (fuel rails, EGR, cables, plenum etc.). The heads received longer valve stem guides to resolve a wear/oil burn issue, valve springs and seats were revised to allow for additional cam lift.

I have a specific need for my '95 Thunderbird such that I really want to keep it as-is NPI (iron block). From what you're saying does that mean that the latest, greatest Romeo version of the 4.6 would be a 1999-2000 engine? And would this engine be basically indistinguishable from a '95 motor not counting the different intake/fuel rails/EGR/etc.? I understand the heads would be better/slightly improved but they would be otherwise exactly the same as the '95 heads in terms of intake/exhaust port shape, valve cover bolt number and location, yes? The blocks would be externally identical, exact same timing covers and accessory locations, bolt bosses and whatnot? Is there a recommendation as to what cars are the best donors for a Romeo NPI engine or are the engines all the same? I had assumed that the best option was a '97 MN12 donor but that seems to be way off now.

I would want to build one with a forged crank and rods (and possibly pistons) but I don't suppose any stock NPI 4.6s came with any of that, correct? Are there any stock forged crank options or is that just more straightforward to buy aftermarket?
 
I have a specific need for my '95 Thunderbird such that I really want to keep it as-is NPI (iron block). From what you're saying does that mean that the latest, greatest Romeo version of the 4.6 would be a 1999-2000 engine? And would this engine be basically indistinguishable from a '95 motor not counting the different intake/fuel rails/EGR/etc.? I understand the heads would be better/slightly improved but they would be otherwise exactly the same as the '95 heads in terms of intake/exhaust port shape, valve cover bolt number and location, yes? The blocks would be externally identical, exact same timing covers and accessory locations, bolt bosses and whatnot? Is there a recommendation as to what cars are the best donors for a Romeo NPI engine or are the engines all the same? I had assumed that the best option was a '97 MN12 donor but that seems to be way off now.

I would want to build one with a forged crank and rods (and possibly pistons) but I don't suppose any stock NPI 4.6s came with any of that, correct? Are there any stock forged crank options or is that just more straightforward to buy aftermarket?

Any npi from 96-01 is virtually identical as far as longblock, the valve cover differences come from Windsor vs Romeo assembly but I don't believe any npis except for the earliest Navigators(5.4) were Windsor assembly. 94-95s have a different timing cover pattern from 96+ iron blocks, but oddly have the same pattern as Aluminum blocks(both Teksid and WAP), its just that one bolt below the water pump. A PI engine is indistinguishable from a npi engine on the outside unless you have the intake manifold off

Forged crank is dead weight unless you're spinning to 8000 RPM or making 600+ horsepower, which aint happening on a npi lol
 

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