The intake can be cut perfectly flat but still be cut at a different angle from how it mounts on the head. I know this because my 1st 4.9 died and I thought it was the gasket, 2 motors later a new intake fixed it.

I'll shoot myself before trying to mod another 4.9 ...

Quick question...
Is it possible that the damaged cap and the combustion gas "remnants" in the cooling system were caused by the previous engines, and that there is nothing wrong with this one? And you just "got lucky" and the (possibly previously damaged) cap let go when you tapped it?

After what I've seen with these engines, I can't believe that the aluminum rocker supports would survive any kind of coil bind. Certainly not enough to lift the head.

quote Originally posted by FriendOfYours: The other two motors used the steel bridge, this motor was the factory aluminum

When the time comes, you should inspect the aluminum bridge for signs that the rockers bolts are pulling out. These aluminum bridges are very weak, so it probably isn't cam related if the bridges survived. But since this is still a customer car and 3 bad engines, you should verify everything before putting the 4th engine together.

quote Originally posted by FriendOfYours: The springs are factory

Keeping stock springs with a higher lift cam, especially on and engine modified with the intent of higher RPM is a very, very bad idea.
If you have the lever type valve spring compressor and a dial indicator set it up and measure the distance to coil bind, or retainer contact with the valve guide boss. Then use a dial indicator on the pushrod to check the actual lift on the camshaft. Only with these two numbers will you know if everything is OK from a binding perspective. I am making the assumption there is no piston to valve interference, since you had the heads off at least one of the other engines and you would have seen the contact dimpled in the pistons if there was any.

quote Originally posted by FriendOfYours: The intake is perfectly flat. I checked it with the same starrett I use on heads, blocks and everything else I machine. It isn't twisted either

I am not concerned with the bottom of the intake, I am concerned with the faces where it mates to each of the heads. Prior to installing the intake on the next engine, I would suggest installing it w/o gaskets first. Snug one side and then use a feeler guage to check the gap on the other side an "actually measure" how close the two are. I am pretty sure they will not be the same to 0.000" and will have some normal variation... the key is how different they are. While the one side it tight, also check the gaps at end and see how much they vary from edge of bank to edge of bank. Only after you have done these checks and they all come out within spec will you know this isn't the issue.

quote Originally posted by FriendOfYours: The engine is mounted at 4 points on the bottom, it barely shifts without the dogbone.

The upgrades you have done to the 4.9 should easily produce more than 300 lb-ft of torque. With the 5 speed getrag, the mounts will have to resist 3790+ lb-ft of torque at the axles during first gear acceleration. As you try to shake the engine from the top (about 24" from the axles), you would have to apply about 1500+ lbs of force... to check the actual deflection and I doubt you have done that.

If you really want to know what is happening back there, remove the decklid, disconnect the dogbone, and have a buddy drive the car hard while you watch for movement. Of if you are working solo, take a sharpie marker and make a bracket that presses it against the side of the strut tower (with some slight pressure). Then remove the dogbone and wail on it. The sharpie will mark the strut tower with how much movement you have.

If you have the typical 4.9 mounting method with one of the engine mounts pretty much under the oil pan... that one is doing very little to resist torque since the torque originates from the axle and both engine mounts are on the same side of the axle. To maximize the benefit of 4 corner mounting, the two in the rear must be behind the axle and the distance between the front side mounts and the rear side mounts needs to be as large as possible. The reason for this is the further the mounts are apart, the lower the forces they will see and the less they will deflect.

Most of the "transmission" mounts I see people use as engine mounts are not designed for any significant upward loading. Some of the poly ones have a metal retainer, but it is probably less than 1/8" thick and will bend as it is overloaded. Once it bends, then it has a larger range of motion and will allow more movement. If you are going to use rubber for your mounts, then use round suspension or cradle bushings. The rubber is pressed into the sleeve and are stiffer to start with and they are fully encapsulated and will not break free.

quote Originally posted by FriendOfYours: The tune has been rewritten nearly 50x now and it was done with a wideband and a knock mic.

50 writes of the tune is just 50 chances for something to not take. The very large assumption you are making is that your tuning package is 100% accurate and that every change you make in your software (TunerCats I assume) is actually changed in the chip program & the change was the precise amount you requested. The Caddy is far from 100% hacked and the tuning options you have with it are no where near everything that happens within the chip, and no one is doing anything to make the available software better. Rockcrawl was one of the early fiero pioneers and tuning expert on the 4.9 and he had difficulty tuning some of his engines simply because the stock ecm would not respond correctly with some of his programming changes.

It could very well be that the changes this engine needs to run well, the stock caddy ecm simply will not accept from the available tuning software. The nice thing is the caddy ecm and the 7730 use the same ECM connectors, so with some repining, splicing the injector wires together, adding a legitimate knock sensor, and converting to IAC control with a TB swap... you could be running an ecm that is 100% full understood and there are custom bins available with multiple times the resolution in the spark and fuel tables to help dial the swap in. It is what the best 4.9 guy in the fiero world (Rockcrawl) did...You just can't do it if you want to run the 4T60E...

[This message has been edited by fieroguru (edited 01-12-2013).]

FOY I know the last think you want to hear is criticism especially from me right now, but at what point were you going to tell me the car you were going to deliver to me today did not have the steel support beams in it, that I asked and paid for?

The steel ones from what I understand are threaded and can be re-used, the aluminum ones are not and should not be reused once removed.

Raydar, there is little to no chance its a fluke, he said that when he fired it up today, there was air screaming out of the resivour tank.

Guru Thank you for taking the time to read through and make all your responses.

Everyone else I really appreciate the support, it has been a crazy roller coaster of a ride with this car.

Just another thought, are the heads being swapped over? If they are, have we checked to make sure that we don't have a cracked head?

The cylinder that failed on motor #2 is it the same one that failed on the 3rd motor. (I am calling my motor number 1, the first one you put in number 2 and the so on.) Can we check and see if its the same one that failed on this last motor.

It if is, at least we will have an idea of what area to look for the issue.


Hey Steve are you still reading this topic. If so we need to get in touch.

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857GT Part 85GT Part 87GT Part Caddy, 93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Now with Nitrous. Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.

[This message has been edited by Capt Fiero (edited 01-12-2013).]

If there is too little lift, the bridges would be fine and we'd still have this problem.

Stock springs with this cam has been done by myself and many others numerous times with no issues

The bottom of the intake is not what I was referring to, I was talking about the mating surfaces. They are completely uniform and are not the issue.

Not by hand. I drove it without the dogbone on the first motor with maybe 2" of deflection, 1" either direction from centerline at the TB. I have 60k miles on my 4.9 with no dogbone and these same mounts

No knock and egts were good. Dead on at 14.7 afr at partial and tuned to 13.5 at WOT. Only reason to cause headgasket failure and they were fine.

Thanks for taking the time to write it up

If the specs were off on the cam, you should see odd cranking compression numbers- how did that thing register when you first put it together?
More than 200psi cranking usually spells problems on pump gas (I'm at that threshold with my combination of static compression and cam grind in my 2.5)

quote Originally posted by Capt Fiero: .... Raydar, there is little to no chance its a fluke, he said that when he fired it up today, there was air screaming out of the resivour tank. ...

Sorry. Missed that little detail.

Okay... back into lurk mode.

I don't even know what to say. I feel bad for everyone involved. Maybe it's time to do a full rebuild?

no offense to the caddy purists but i think its time to swap in something a bit more reliable. ive never heard much good from those powerplants on stock form, seems they are made of glass parts and highly fragile. these are very mild modifications to have all these problems. IMO, this thread should be deleted and a new one started from scratch. ever thought of a SBC? a 305 would be more reliable than the 4.9 lol, but thats my $0.02

We had a SBC V8 5spd Getrag Fiero and just sold it, as I actually preferred the 4.9 as a daily driver. When FOY said they could keep it at the high 20's for MPG and possibly wring out close to 300hp from it, I jumped at the chance. Our Small Block was a carbed 305 and was great above 2500rpms, however did not have the cruising torque or the smoothness of the Caddy motor. Our SBC Fiero also had Coil Overs, poly, Corvette brakes, poly suspension with rear sway bar. We had 5 Fiero's and had to let 2 of them go. The V8 was the first to go and our only duke will be the 2nd to go. I am keeping my 88GT, my 87GT and Lisa is keeping her 85 2M6 / GT Clone show car. On top of the 3 Fiero's we are keeping, we also have a 96 AWD Blazer and a 2000 Pontiac Grand Prix GTP.

This build has actually given the 4.9's a bit of a bad wrap, I know 3 guys with modded 4.9's that have been racing them for years and not had any problems. I know a dozen more with daily driver 4.9's that don't have problems. There is some part in this build or some issue with how it is being put together causing these motors to blow up. FOY is going to have to go back to Basics and find out what it is, if he even wants to attempt to complete the build.

Go to nthe junk yard, get a stock intake. Change the head gasket. Test it, test compression etc.. Then when you know it's 100% fine. Swap your intake on. That way you know for sure what is ir is not causing the problem.

Good luck.

[This message has been edited by Purple86GT (edited 01-13-2013).]

quote Originally posted by 34blazer660: no offense to the caddy purists but i think its time to swap in something a bit more reliable. ive never heard much good from those powerplants on stock form, seems they are made of glass parts and highly fragile. these are very mild modifications to have all these problems. IMO, this thread should be deleted and a new one started from scratch. ever thought of a SBC? a 305 would be more reliable than the 4.9 lol, but thats my $0.02

Do YOU have a Fiero with a 4.9? It would appear that you do not.

The STOCK 4.9 in a FIero is extremely dependable.

I never had these problems with my 4.9. I rebuilt my 4.9, ported the heads, had a delta cam, steel rocker supports, ported Allante intake, tune, MSD ignition parts and poly engine mounts. When I rebuilt it I took every cylinder sleeve out, replaced the o-rings on the cylinder sleeves, cleaned the threads in the block for the head bolts then put it all back together. It dynoed at around 190HP and 280TQ at the wheels and I never had one problem with it. It was not driven lightly and it never left me stranded. The only thing that ever left me stranded was when my Isuzu transmission would explode.

quote Originally posted by pdemondo: Do YOU have a Fiero with a 4.9? It would appear that you do not. The STOCK 4.9 in a FIero is extremely dependable.

I dont recall stating that i own a 4.9 powered fiero, so whats your point? im suggesting that there IS other options out there to meet the intended goal of power and reliability.

quote Originally posted by 34blazer660: I dont recall stating that i own a 4.9 powered fiero, so whats your point? im suggesting that there IS other options out there to meet the intended goal of power and reliability.

And those of us with 4.9 Fieros have heard about all of those options. Ad nauseum.

But thanks for your input.

quote Originally posted by Raydar: And those of us with 4.9 Fieros have heard about all of those options, Ad nauseum. But thanks for your input.

understood. i suppose i would be sick of hearing about better options too.

Naah. There is always a "better" option. No matter what someone is building.
Just tired of self-proclaimed experts repeating the same old sh!t that we've been hearing for years.

quote Originally posted by Raydar: Naah. There is always a "better" option. No matter what someone is building. Just tired of self-proclaimed experts repeating the same old sh!t that we've been hearing for years.

PHEW! im glad im not a self-proclaimed expert! LOL

for this situation, it looks like the engine work may need to be outsourced to a professional engine builder who knows these engines, since everyone else has no issues with their 4.9.

Wow, did you read any of this thread or have seen the other builds we have done?

Between my father and myself we've owned 50+ Fiero's, have built a dozen 4.9s, 8 3800(SC), 4 3.4TDC, and 3 quad4s

We are a full time machine shop shipping 10s of thousands of dollars of custom built parts every month all over the country. First motor was a motor that was previously turbocharged and in our '91 Civic. I figured the threads had just become weak. Second motor had already been improperly helicoiled before I purchased it. This newest motor was a great runner I pulled myself. This is called shitty luck

[This message has been edited by FriendOfYours (edited 01-13-2013).]

quote Originally posted by FriendOfYours: Wow, did you read any of this thread or have seen the other builds we have done? Between my father and myself we've owned 50+ Fiero's, have built a dozen 4.9s, 8 3800(SC), 4 3.4TDC, and 3 quad4s We are a full time machine shop shipping 10s of thousands of dollars of custom built parts every month all over the country. First motor was a motor that was previously turbocharged and in our '91 Civic. I figured the threads had just become weak. Second motor had already been improperly helicoiled before I purchased it. This newest motor was a great runner I pulled myself. This is called shitty luck

this is exactly why i felt this thread needs to be completly deleted. there is nothing "proper" about this build except how to hastily slap an already flawed boat anchor together and make excuses to why 3 of them were destroyed. ive been following this thread the whole time wondering if you even know what you are doing. apparently im not the only one who has doubts. if you built a dozen 4.9's then i feel the is almost no room for mistakes. if you want to call it bad luck then delete this thread before all your credibility goes out the window. why am i running my big mouth you ask? lack of "proper" attention to details, broken suspense dates, poor excuses backed up by a pissing match. apologies to Capt....

Am I expected to pull the heads off every motor to check the head bolt threads before I put a motor in? Of course not. Go back and look at the pictures. Perhaps this last motor could have been saved, if the cam ends up being the issue, but the previous motors were already flawed and I had no way of knowing. Look at the engine bay, does that look like something that was hastily thrown together? Every nut and bolt on was meticulously torqued, all gaskets replaced and I was very careful to ensure the motor never knocked, went lean or severely overheated.

I have never asked him for a dime past our agreed amount, I have covered everything and have spent a lot of time on this. I am done with all the negativity projected towards me when I have been upstanding and hard working throughout the entire process. I will no longer be responding. PM if you want to talk, I'll be in contact with Capt and he can post updates.

FOY - keep your head up, you haven't stopped working to make it right - it doesn't go unnoticed. Anyone that has done custom work knows that unexpected stuff happens.

quote Originally posted by 81 4.9L X-11: FOY - keep your head up, you haven't stopped working to make it right - it doesn't go unnoticed. Anyone that has done custom work knows that unexpected stuff happens.

Seriously. Ignore the trolls.
I tend to agree with you. You have just had a run of extraordinarily bad luck. You are not reinventing the wheel, here.

quote Originally posted by 34blazer660: IMO, this thread should be deleted...

There's no need to erase history, here or anywhere else.

You're relatively new at PFF. Threads aren't allowed to be deleted in this forum on a whim... fortunately.

Despite the disappointment and set-backs for everyone involved, there's plenty of worthwhile info in this thread for future reference.

One way or another this situation will be resolved, and it will be chronicled right here in this thread.

quote Originally posted by 34blazer660: I dont recall stating that i own a 4.9 powered fiero, so whats your point? im suggesting that there IS other options out there to meet the intended goal of power and reliability.

We all know there are other options, so what is your point?
If you do a search, you will find out that there have been MANY discussions of the pros and cons of various engines swapped into a Fiero. It seems that the originator of this thread, and most other participants, are well aware that they not limited to the 4.9.


What engines you swapped into your Fiero that you would recommend?

quote Originally posted by pdemondo: We all know there are other options, so what is your point? If you do a search, you will find out that there have been MANY discussions of the pros and cons of various engines swapped into a Fiero. It seems that the originator of this thread, and most other participants, are well aware that they not limited to the 4.9. What engines you swapped into your Fiero that you would recommend?

the main point is to introduce BETTER powerplants, OP has to start all over again anyway. but im done beating that horse....

quote Originally posted by pdemondo: We all know there are other options, so what is your point? If you do a search, you will find out that there have been MANY discussions of the pros and cons of various engines swapped into a Fiero. It seems that the originator of this thread, and most other participants, are well aware that they not limited to the 4.9. What engines you swapped into your Fiero that you would recommend?

I have to say that I personally don't understand why anyone would want a V8 Fiero. It just seems to me that low-rpm power in a light car just makes for a lot of wheelspin and breaking weak links in the drivetrain.
IMHO the most ideal V8 would be the Northstar because of the more high-rpm powerband.

All that being said IMO the 3x00 engines make a great Fiero swap; they make plenty of mid-rpm power, are good on gas, very simple to swap in, and respond well to mods. You might not make the tire burning low-rpm torque of a V8 but 200whp is pretty easily achieved and if you do want to burn some rubber it's not a problem. Traction is there when you want it too. My 3500 Fiero ran a 13.6 with a stock engine, stock Fiero muffler, and a hastily thrown-in 75 shot of N2O in 2nd, 3rd, and 4th using a button mounted in one of the ashtrays haha (making it tricky to shift and then reach for the button). I think it could easily do 13s with an F23 swap and still a stock motor.

No disrespect to the OP; it sounds like the 4.9 makes a decent dd engine, but for me a V8 is just a bunch of extra work for similar power.

quote Originally posted by bcampbell: I have to say that I personally don't understand why anyone would want a V8 Fiero.

Call me a dinosaur, but for a daily driver I'd love to have a V8 Fiero... for the sound. Yes, for the sound.

Keep in mind that from the time I was 17 years old (back in '73), I was driving a V8, and some pretty nice ones at that, like a 4-spd '67 Chevelle SS396 with a lumpy cam and a free-flowing (loud) 2.5" true dual-exhaust. I didn't require all the power, and I very seldom used much of it (relatively speaking), but I was able to listen to that sweet music the whole time the car was running.

It wasn't until I bought my first Fiero in the mid 1990's that I owned a car which didn't have either a small or big block Chevy V8. I adjusted, but...

On the other hand, I also autocross my 5-spd '84 Fiero... with a duke. I'd love to have more power on the track, but I wouldn't want a heavy V8 in the back. The handling would just suck. This is where a potent 4-banger like a Quad4 would be nice, or yeah, even a built up 3500.

I gotta agree with Patrick on this one. I could have put anything in my fiero but chose the 4.9. I still have some bugs to work out but I just love the sound! My first car was a 66 mustang with a 289. then a 65, then a 67, then a 67 convertible, then an 87 2.4 4cyl. mustang. I've missed the V8 ever since. The 4.9 just sounds fantastic! I didn't find it that difficult of a swap either.

I am amazed however that some people have such a strong opinion as to what is "worth while" swapping into a fiero. Most automotive friends of mine are of the opinion that I should start with a car worth swapping an engine into. Let's face it, the fiero resale value is not very good and if "worth while" refers to return on investment, I'd buy another classic mustang and do it up right. I think most of us like and drive fieros for what they are...a great little affordable car with an excellent platform for "personalized" modification. Not too many people out there in the market for a concours correct 84 fiero they're willing to spend big dollars on...yet.

quote Originally posted by bcampbell: I have to say that I personally don't understand why anyone would want a V8 Fiero. It just seems to me that low-rpm power in a light car just makes for a lot of wheelspin and breaking weak links in the drivetrain. IMHO the most ideal V8 would be the Northstar because of the more high-rpm powerband.

Pretty much any of the common V8s (SBC, LS(x), N*) can have an idle to 7000 rpm power band and be built to have 300+ whp... with the exception of 4.9. It is all in using the right intake, cam, heads and exhaust for the power band you want.

quote Originally posted by bcampbell: I have to say that I personally don't understand why anyone would want a V8 Fiero. It just seems to me that low-rpm power in a light car just makes for a lot of wheelspin and breaking weak links in the drivetrain. IMHO the most ideal V8 would be the Northstar because of the more high-rpm powerband. All that being said IMO the 3x00 engines make a great Fiero swap; they make plenty of mid-rpm power, are good on gas, very simple to swap in, and respond well to mods. You might not make the tire burning low-rpm torque of a V8 but 200whp is pretty easily achieved and if you do want to burn some rubber it's not a problem. Traction is there when you want it too. My 3500 Fiero ran a 13.6 with a stock engine, stock Fiero muffler, and a hastily thrown-in 75 shot of N2O in 2nd, 3rd, and 4th using a button mounted in one of the ashtrays haha (making it tricky to shift and then reach for the button). I think it could easily do 13s with an F23 swap and still a stock motor.

quote Originally posted by fieroguru: Pretty much any of the common V8s (SBC, LS(x), N*) can have an idle to 7000 rpm power band and be built to have 300+ whp... with the exception of 4.9. It is all in using the right intake, cam, heads and exhaust for the power band you want.

Ditto.

My Northstar pushed 255 RWHP/267 RWTQ stock with a bad tune and ran 12.86 @ 106. My new engine pushes 300 RWHP and 288 RWTQ, still with a bad tune. I broke an axle going for a hard launch at an 1/8 mile strip, but later trapped 112 on a soft launch at a 1/4 mile strip.
It also will accelerate from 32 mph at 1100 RPM in 5th easily. The long block weighs just a tick over 300 lbs. It also sounds fantastic, even moreso now that I have an X-pipe on it.

So, again, how does a 3500 that needs N2O to get down to 13.6 compare?
The V6/60 engines are great swaps in that they are VERY easy and are still a significant upgrade over stock.

If someone wants a 4.9, and understands/recognizes the potential of the engine relative to the alternatives, then that's his choice.
The 4.9 is lightweight, cheap, sounds good and gives about the same performance as your 3500. Built 4.9's have pushed mid/low 2's to the wheels.

[This message has been edited by Will (edited 01-14-2013).]

quote Originally posted by FriendOfYours: Am I expected to pull the heads off every motor to check the head bolt threads before I put a motor in? .

Yes you should. I know many people who will pull apart a crate engine and re-assemble it because they leave nothing to chance
Anytime I ever do a swap I always pull apart the engine and inspect eveything and replace all gaskets and bolts. I stopped doing swaps for others because they complained of the additional cost involved, but none of my swaps have ever failed because of it. When you install a used engine you have no idea what the condition of anything is unless the engine is pulled completely apart and inspected, from there I throw away all gaskets and bolts and use new. Takes more time, yes, but avoids many problems.

quote Originally posted by 34blazer660: the main point is to introduce BETTER powerplants, OP has to start all over again anyway. but im done beating that horse....

Oh Yeah, all that any of us know about is 4.9 swaps. Nobody has ever really looked at the Northstar, 3800, 3500, LS1, small block chevy,
quad 4, ecotec, or others. Thanks for letting us know. I guess we are all not as eligntened as you so we swap this horrible motor in.

PLEASE, what motor have you swapped into your FIero?

What a surprise I found upon finally opening this thread. Happy New Year to all and hope this gets better soon.

quote Originally posted by Will: Ditto. My Northstar pushed 255 RWHP/267 RWTQ stock with a bad tune and ran 12.86 @ 106. My new engine pushes 300 RWHP and 288 RWTQ, still with a bad tune. I broke an axle going for a hard launch at an 1/8 mile strip, but later trapped 112 on a soft launch at a 1/4 mile strip. It also will accelerate from 32 mph at 1100 RPM in 5th easily. The long block weighs just a tick over 300 lbs. It also sounds fantastic, even moreso now that I have an X-pipe on it. So, again, how does a 3500 that needs N2O to get down to 13.6 compare? The V6/60 engines are great swaps in that they are VERY easy and are still a significant upgrade over stock. If someone wants a 4.9, and understands/recognizes the potential of the engine relative to the alternatives, then that's his choice. The 4.9 is lightweight, cheap, sounds good and gives about the same performance as your 3500. Built 4.9's have pushed mid/low 2's to the wheels.

I think my point was that I put pretty much no effort into making my car fast and it actually surprised me. I didn't mean to imply that V8 Fieros don't make good track cars, its just that you don't see very many fast V8 Fieros on a track putting down good numbers. Making the power is one thing, putting it down is another. Did I mention I was running 205/45/r16 street tires? Like I mentioned I believe it would have done 13s without the N2O with an F23 swap, and I'll test that theory this year. While we're at it , I should mention that the top speed was 102MPH which is pretty comparable to yours.

I have nothing against V8s. I had an LT1/T56 89 Firebird and it was a blast to drive. I just wouldn't put it in a smaller car. Traction was difficult enough with the stock LT1.

quote Originally posted by pdemondo: PLEASE, what motor have you swapped into your FIero?

What are you trying to prove here?

quote Originally posted by bcampbell: I think my point was that I put pretty much no effort into making my car fast and it actually surprised me. I didn't mean to imply that V8 Fieros don't make good track cars, its just that you don't see very many fast V8 Fieros on a track putting down good numbers. Making the power is one thing, putting it down is another. Did I mention I was running 205/45/r16 street tires? Like I mentioned I believe it would have done 13s without the N2O with an F23 swap, and I'll test that theory this year. While we're at it , I should mention that the top speed was 102MPH which is pretty comparable to yours.

102 is still 40 HP down from 106... I did run 13.2 at 102 my first visit to the strip with an open circuit IAT.
Yeah, the V6's are cheap and easy... not arguing that at all.

Boy people like to argue over which engine they like or think is the best when in the end it boils down to what the guy that owns the car wants period that is it. As for checking heads of every engine well if they are known for having problems then yes I would say check them, especially if you are supplying the engine. Every 3800 that leaves my garage that I have supplied has been upgraded to the aluminum lower intake gaskets and the newer valve cover gaskets. Not because they were leaking but because they are known to be a problem so why not fix it before installing the engine while it is a lot easier to work on and prevent any possible problems that might have occurred if I had not replaced them.
I would rather put in a little extra work on the engine before installing to prevent a lot of work later on. Dan

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Over 10 years of full 3800 swaps and harnesses and still going.