Fiero 3.5 Cadillac Short Star or 3.6VVT.

[Anchor]

I am planning to do an engine swap to my 1988 Fiero Gt with a 5-speed this summer. I am currently trying to decide on the best value for the buck. My research currently indicates that a 4.9 PFI Cadillac is a good candidate. I have had difficulty in finding information on a 3.5 Cadillac Short Star V-6 or the new 3.6 VVT. Does anyone out there have any information.

Please advise.

Thanks, Anchor.

[bszopi]

This should provide you with all the info you want on the 3.6 VVT...

http://www.60degreev6.com/index.php?p=sections&sid=32

[Jeff]

bszopi, Hey there I saw one item you posted about the 3900 V6...can you tell me if this will work in a 88 Fiero GT?

[bszopi]

The 3900? Don't see why it wouldn't work in a Fiero. You would either have to use the PCM from it if you wanted all of the electronics of it (fly-by-wire throttle, variable runner size, etc), and then you'd have to figure out a way to overcome the tranny controls in the PCM. Or, you could stick on some other parts and possibly use a high end standalone ECM that might have outputs which could possibly control some of the other functions. Or you could just get rid of all of those electronic extras and just have a higher displacement engine with 3400 top end parts.

[Jeff]

bszopi, Hey there again, this is Jeff just wondering more about the 3900 in the Fiero. From any info you have, can you use an existing 5 speed Getrag Tranny out of the 88 Fiero GT and can you us the same head and plenum off the 88 2.8 V6? Also are there any pics of this engine available to look at? Sort of want all the options but that may get tricky so can I stay with my 88 computer or do I need the one for the 3900? I do have a performance chip in my computer right now and have had good luck with it, just wondering if I can keep that and if I do, will I loose a lot of the power of the 3900 or just some of the electronic goodies? Whenever you have time I would really like to hear from you regarding this and what my best plan is to obtain one of these engines. Can I just order a short block and have my 2.8 head and plenum put on and how much might a short block be or if I went ahead and got a long block and computer for the 3900? Can't wait to hear back from you.......Jeff

[GPXSS]

Im going to be putting a 3900 into my 86 GT 5spd when one comes available (05' is the targeted release) It has the exact same bolt pattern as your existing 2.8.. so anything that fits the 2.8 will fit the 3900. The block is also basically the same, so you shouldn't have any problems putting Iron head stuff on there.. although the fiero 2.8 intake may be very restrictive to such a large V6.

I plan on using the 3900 as it is and either adopt the PCM it comes with so that I get Displacement on Demand and Variable Valve Timing, or I will use an OBD1 ECM and tune it myself (which will lose all the above features).

[Manitcor]

Im consdering this swap myself, though ive been curious about being able to drop the DOD but keep the VVT part of the engine. My idea, and please correct me if I sound nuts, would be to use 3500 heads and intakes ported as much as possible for NA in place of the 3900 topend so I remove all the DOD stuff but keep the enitre bottom end. Then use something like the Haltech line of ECUs to control the engine and take advantage of the VVT.

To my understanding there is nothing about the 3900 head desgin that effects the VVT features but Im not entirely sure.

If you remove the VVT you are going to be cutting into the engines capaibilty to maximize its power band based on driving conditions. I would not be surprised if a decent portion of that ~250hp advertiesed power is from the use of VVT. Though even if you kill off VVT you still have a huge V6 that im sure would put out a good amount of power though not ~250hp. Of course you could always jut put in a hot cam grind.

[GPXSS]

the DOD stuff is in the lifter valley, and it may need to be kept in place to seal the oil passages. The VVT is just a phaser bolted to the front of the cam. I don't think there is a diff. between 3500 and 3900 heads, its all in the block.

[bszopi]

IIRC, the 3500 uses DOD as well... At least from earlier press releases from about a year ago, it was supposed to. Jeff, if you look in the OFF TOPIC area, I had a post about the debut of the 3900 and there are several pictures of it in that thread.

[Manitcor]

IIRC, the 3500 uses DOD as well... At least from earlier press releases from about a year ago, it was supposed to. Jeff, if you look in the OFF TOPIC area, I had a post about the debut of the 3900 and there are several pictures of it in that thread.

I read about that too, but any of the recent press releases make no mention of it.

??

[quantum110]

Re: Fiero 3.5 Cadillac Short Star or 3.6VVT.

I have had difficulty in finding information on a 3.5 Cadillac Short Star V-6 or the new 3.6 VVT. Does anyone out there have any information.

The 3.5L isn't a Caddy motor, maybe thats why your not finding any info. 90*V6, Pistons Sleaves, no aftermarket....the 3.4L DOHC beats this by for in bang for the buck, mainly because your still going to probably have to pay 3k and above for a used one.

[quantum110]

IIRC, the 3500 uses DOD as well... At least from earlier press releases from about a year ago, it was supposed to. Jeff, if you look in the OFF TOPIC area, I had a post about the debut of the 3900 and there are several pictures of it in that thread.

The current 3500 does not use DOD, it is suppose to debut w/ either the 3900 or one of the V8's not sure which.

[brian89gp]

I have heard that the 3.5 shortstar and the 4.0/4.6 Northstar motors use the same engine mounting positions, so if you want a 3.5 you might consider getting a V8 of it .

[brian89gp]

Just noticed you had an 88, that sucks. There has been 1 person I think that managed the swap (over on www.fiero.nl ) but it required some cutting.

Since the N* is out I would wait for either the 3900 or 3.6VVT if you want to stay in the 60v6 family, otherwise I would choose the 4.9.

The 4.9L's, at least around here, can be gotten for dirt cheap, both the 3900 and 3.6VVT I bet are going to be quite expensive for a while not to mention the wiring mess you will have to deal with.

[sspeedstreet]

Try http://www.fiero.nl/cgi-bin/fiero/se...ve%3A+TD+%26+Q and http://www.fiero.nl/cgi-bin/fiero/se...+%26+Questions

He's the one putting a 3.5 in an 88 Fiero. Lots of threads to look through, but I think he has most of the bugs worked out.