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I was wondering, I know the base hp on the 4.5 is 180hp and the 4.9 is 200hp...... but when the 4.5 was used in the Allante, it had 200hp....equal to that of the 4.9...... what was changed to get this extra power? and can those parts be put on a 4.9 to get even more power?
 

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hehe, man your just like me when i first got my coupe. One of the biggest differances with the allante engine is the intake, its TPI insted of PFI, it also has more of a newer TB style unlike our carb looking TB. Iam not sure if thats where the 20hp comes from though. Also finding one would be really hard and wouldnt be cheap. That and i dont even know how hard it is to go from PFI to TPI. hey you still got 20hp on me, i have the 4.5 in mine, thinking about converiting it to a 4.9 some day.
 

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Yeah the 4.9 has 20 more hp and 20 more ft lbs of tourqe..... I perosnally don't like the nose/hood of the '87-'90 DeVille..... just not my type, I like the grille/hood of the '91-'93, but I think it can be switched over...

Are you sure that's not a picture of the HT4100 instead of the 4.5?

I dunno if the intake gave it the extra power or what, maybe someone else does?
 

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Panther said:
Yeah the 4.9 has 20 more hp and 20 more ft lbs of tourqe..... I perosnally don't like the nose/hood of the '87-'90 DeVille..... just not my type, I like the grille/hood of the '91-'93, but I think it can be switched over...

Are you sure that's not a picture of the HT4100 instead of the 4.5?

I dunno if the intake gave it the extra power or what, maybe someone else does?
I have some limited experience (I just finished rebuilding the 4.5 in an '89 Allante, but haven't yet started it). From checking www.gmpartsdirect.com 's catalog, it appears that many, if not most of the internal part differences between the Allante 4.5 and the "standard" 4.5 were incorporated into the 4.9 (except the rods, liners and crank, of course). The intake is the major difference between the Allante and the others. It is port injected, but I don't know if it is technically "tuned port injected", although since it has intake runners, like the TPI corvette, I suppose it is.

You may want to check some of the Fiero boards. A lot of those guys are swapping Cadillac 4.x engines into Fieros and they do a lot of part interchanging. Seems to me I remember something about there being some port differences between the heads and the intake on non-Allante 4.5 engines, but I think the 4.9's would work with the Allante heads.

One thing I find interesting is that the Allante intake is very similar in design to the Mustang 5.0 of the same era. Are those (Mustangs) considered TPI?
 

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Panther said:
Well, the 4.9 is PFI....Port Fuel Injection.....
kinda OT, but my friends said, "PFI, is that pretty F'n intimadating"
So how hard would it be to put an allante intake manifold on my 4.5?
 

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DeVillish said:
kinda OT, but my friends said, "PFI, is that pretty F'n intimadating"
So how hard would it be to put an allante intake manifold on my 4.5?
Physically, assuming the ports match up (see above), all you need to do is replace the lower intake with an Allante lower intake, then bolt the Allante upper intake to the upper one.

The problem/challenge is the ECM. I don't have a clue how it would react.
 

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I'm gearing up to swap an '89 Allante upper & lower intake manifold onto my crate 4.9 motor. Haven't actually started, just collecting parts & information. There are some issues which demand paying attention to year/make/model stuff. The h2o systems are a bit different, as are the emmissions air/vacum systems. However, it is a doable project.

One major difference is that the Allante has a high strength steel bridge which supports the valve rockers. The 4.9 bridge looks bigger, but it's aluminum. So it looks like the Allante bridge will go along with the manifolds, etc.

I looked at the differences in the ecm's with a friend. It looks like the Allante has more aggressive fuel mapping & a higher rev limit.....so I think the 4.9 ecm will work when the swap is done.

A few photos available at http://groups.msn.com/FieroCaddySwapGroup
just look for the thread Allante<-->4.9

David Breeze
 

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The difference in power between the standard 4.5 and the 4.5 in the Allante was cylinder heads with better flowing ports and the intake manifold. The head/port design was basically carried over to the 4.5 PFI engine (1990) and the 4.9 (1991-1995)....so....the basic HP difference between the 4.9 and the 4.5 Allante engine that made up the power difference was the intake manifold. The cam shaft and cam timing were both the same.

The 4.9 is a port fuel injected engine. The Allante engine is a tuned port fuel injected engine. The long, individual runners on the Allante intake manifold are tuned for more torque in the mid range giving the engine a broader torque curve than the "non-tuned" manifold on the 4.9.

The rocker arm support bar on the 4.5 Allante engine was incorporated to add robustness to the valve train for extended high speed running. It doesn't add any power per se and probably will do little or nothing for performance....BUT...if any more agressive cam/stronger valve springs are added it is essential as the aluminum bar will become the "weak link" you will discover.

You can drill and tap the side of the aluminum rocker arm support bar for bolts and bolt some small aluminum tabs to it that can then be heliarced to the intake manifold for stiffening.

Be aware that the Allante intake manifold is of three varieties...it is not just all the same tuned manifold. The 4.1 in the 87-88 Allante had EGR provisions in the upper intake manifold plenum. This can be plugged or blocked off as long as you are aware of it. The 89-92 Allante upper intake had no provisions for EGR... Also, the intake ports on the Allante engines for 87/88 and the 89/92 were different shaped from the standard production 4.1 and 4.5 TBI engines and the same as the 4.5 PFI and 4.9 PFI engines in later years. In other words, the heads on all the allante engines had the ports that were later used on the 4.9. I believe that any model of lower intake will fit the ports on the 4.9....BUT....there is a significant change in the coolant passage on the lower intake manifold to fit the revised cylinder head design on the 4.9. This change occurred aobut late 88 so there are some 88 Allante lowers with the change and all 89-92 lowers should have the change. If you wanted to put an Allante intake on a 4.9 AND have the EGR work so that the PCM calibration will function as it does in the normal application you need a later edition lower intake (from mid 88 on...look for the coolant passage that is "half sized" or flat on one edge) and an early model 87-88 upper intake with the provisions for EGR.. I think, but cannot say for certain, that even the early lower intake may work OK if you are carefull at assembly and use RTV at the coolant passage to make sure that it will not leak due to the port mismatch.

Good luck.
 

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BTW....before you start putting an Allante intake manifold on a 4.9 make sure that it is going to clear the brake booster. There was a very tight clearance issue when putting that intake on the standard passenger car Cadillacs with the 4.1/4.5/4.9 engines. The intake and throttle body would clear but there is little or no room for an air duct to get past the brake booster/master cylinder. Not even enough room for a K&N cone or anything.
 

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You are right on with your observations reguarding the variety of physical differences. Since I have an '89 Allante motor and a '90 Crate 4.9, I am expecting the coolant ports at the heads/lower intake manifold to match up. If they don't I have a machinist lined up to weld/fill/machine the excess void to make the match work.

The only reason I haven't begun disassembly of the engines is I'm not sure how to proceed on valve rocker removal. I got an Allante factory service manual. It suggests removal of the entire rocker assy...attached to the bridge....is the preferred method. And I've heard it's easy to break either the bridge or the rocker girdles by careless removal techniques. That's why I joined this forum, I need some hand holding here.

Your also right on about the Allante "power" coming from the intakes, which is why this seems to be a "factory" upgrade almost for the 4.9.

This is going into a Pontiac Fiero, which BTW I'm doing a 4" chop top on, so clearance issues are of a different flavor. FWIW, Im matingthe motor with a 4t60e trans, not the Allante trans.

David Breeze
 

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opm2000 said:
You are right on with your observations reguarding the variety of physical differences. Since I have an '89 Allante motor and a '90 Crate 4.9, I am expecting the coolant ports at the heads/lower intake manifold to match up. If they don't I have a machinist lined up to weld/fill/machine the excess void to make the match work.

The only reason I haven't begun disassembly of the engines is I'm not sure how to proceed on valve rocker removal. I got an Allante factory service manual. It suggests removal of the entire rocker assy...attached to the bridge....is the preferred method. And I've heard it's easy to break either the bridge or the rocker girdles by careless removal techniques.

David Breeze
You are correct that it is easy to break the rocker arm support bar and/or the rocker arm pivots. The most common problem is stripping the rocker pivot bolts out of the arm if you are not carefull ..... and if you don't break the pivot in the process... or both... LOL

The ONLY way to disassemble the rocker arms is to first take the 4 small bolts out of the projections on the arm that stabilize it. Next break loose the 5 large hex nuts that hold the bar to the stud headed head bolts. Loosen the 5 large nex nuts about 1 turn at a time moving down the bar sequentially until the bar is completely loose. Re-assemble it in the same way. Install the rocker arm support bar onto the head bolts , install the hex nuts and gradually pull them down in sequence until the bar is seated and then final torque them. Believe the service manual.....

The rocker arm pivot bolts should NEVER be removed when the rocker arm is under load. Those bolts are self thread rolling bolts that screw into the aluminum bar. The self threading bolts make a very tight, strong thread and form a self locking thread when they seat. If the arm is under load and the bolt is removed it will strip as the threads will reach the end before the valve spring load is relaxed and the bolt will pull out. There is really need to remove the rocker arm pivots from the bar unless something is broken so I would leave the assembly intact. Removing the self threading bolts repeatedly will weaken the threads.

If you can get a pair of the forged steel bars they are totally bulletproof for about any kind of cam/spring loads. Those were also installed on the European "export" engines if you are looking up part numbers.

BTW...the 4.1/4.5/4.9 engines are all "net build" valvetrain engines that are not adjustable..so..if you are milling the heads, changing cams or such you will need to have some custom pushrods made to the correct length. I have heard of people shimming the rocker arm pivots but longer bolts would be mandatory if you do that and I would not expect that assembly to be strong enough to handle much load if the pivots are not direct mounted to the arm.
 

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BTW....you want to use the 4.9 intake gaskets with the spring loaded bolts when you use the Allante intake.

look at the allante intake you have and look at the water crossover passage. The later model versions have a "flat" side to them that is roughly horizontal. The earlier engines and intakes had a much larger cross-section water crossover. The earlier manifolds can work on the later heads as the water passage will just lap over onto blank material....as long as the intake manifold gasket seals around the perimter. You may need the intake gaskets from the earlier Allante or the early 4.1/4.5 transverse engines that had the matching water crossover cross-section in them. Just look at the water crossover passages in the manifold and the head carefully and make sure they match and if they don't make sure the intake gasket you are using covers the perimeter of the larger opening so that it will seal.

Use the spring loaded intake bolts (they have a short stack of belleville washers for loading) regardless and use the later model bolt tensioning specs and sequence.
 

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Wow, thanks for that, it's just the kind of info I'm looking for. I've never seen a valve train with a bridge on it like that.

I'm really curious to find out what the water ports on the Allante look like, and then compare them to what I have on the 4.9 crate motor. I'm prepared for the situation of non-similar port shapes....but the Allante heads have the same part number as the 4.9 crate heads, so I'm still holding out hope.

The one thing holding me back from starting to pull the valvetrain is this: Of the five main studs holding the bridge, one has a nut that is directly between two valve rockers so tightly that I can't get a socket on it. And that would also be a problem when reassembly & torquing time come. The only thing I can see here is that one or both of those rockers have to be removed or at least loosened first, then a socket would fit. Hopefully there is a simple answer which I haven't thought of.

You mentioned that the export motors also had the high strength steel bridge. That may be the case with my 4.9 crate motor, as it is tagged "export". I haven't even pulled the valve covers off it, just waiting to get my ducks in a row.
 

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I used a deepwell socket on that nut (may have been a six-point). The walls are thinner than a standard socket. It had to be wriggled in, but it fit (I'm using off-the-shelf Craftsman metric tools).
 

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opm2000 said:
Wow, thanks for that, it's just the kind of info I'm looking for. I've never seen a valve train with a bridge on it like that.

I'm really curious to find out what the water ports on the Allante look like, and then compare them to what I have on the 4.9 crate motor. I'm prepared for the situation of non-similar port shapes....but the Allante heads have the same part number as the 4.9 crate heads, so I'm still holding out hope.

The one thing holding me back from starting to pull the valvetrain is this: Of the five main studs holding the bridge, one has a nut that is directly between two valve rockers so tightly that I can't get a socket on it. And that would also be a problem when reassembly & torquing time come. The only thing I can see here is that one or both of those rockers have to be removed or at least loosened first, then a socket would fit. Hopefully there is a simple answer which I haven't thought of.

You mentioned that the export motors also had the high strength steel bridge. That may be the case with my 4.9 crate motor, as it is tagged "export". I haven't even pulled the valve covers off it, just waiting to get my ducks in a row.
If it is an export engine then it may have the steel bars. After the Allante engine was replaced by the Northstar in 93 the steel bars became relatively rare so I'm not sure they were used on service engines and how long they were released for the export 4.9 engine. Just have to look and see.

That center hex nut is tight to the rockers. Don't force a socket in there as the pivot can be broken that way. Find a thin wall deep socket and it will fit fine. If you have access to a lathe you can ususally turn down a normal deep socket to get the clearnace to fit.
 
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