Do you want to do a 3900 swap? whats stopping you

[Guest]

These 3900 engines are getting pretty cheap now. You can find low mileage ones for under $1k now, and medium mileage ones for 5-600.

I know a couple of mgb guys browse here as well as Fiero guys as well as other fwd setups.

If you had contemplated a 3900 in the past, what has stopped you from moving fwd with the swap? Is it the fitment issues you are worried about? The cost of the motor? Computer controls? Cost of the add ons to get it work with an obd1 setup?

[Guest]

I had a deposit on one at the wreckers years ago when basically the first one that ended up at the local wreckers showed up, I then saw a great deal on a truck at the time (at the same wreckers) and bought that instead.

I didn't go with the 3500 this past summer in my car due to having most of the parts already to go LX9, RWD timing cover, and other related parts that make a longitudinal swap easier. I had limited time to perform the swap in, so I went that route. Going 3900 would have meant that I would have needed to figure out other aspects, like belt routing and cam phaser control (though I have a plan for the cam phaser, that retains the functionality of the variable cam).

I'm still looking at it in the future when I get bored of the LX9, but that will be a few years off, I would suspect. The planned 500+ HP in a 2300 lbs or so car I have is going to be plenty ridiculous as it is, I don't see me needing more.

To summarize the issue is more of a fitment and control aspect that lays squarely on the variable cam aspect being the reason to have not gone that route, yet.

There's a 3900 at a semi local wreckers I can get for about $200, and might do so so that I can put it on a stand and start working out the details that I haven't yet.

[Forgotten User]

anyway to get the timing cover side to have a mount for a FWD setup?

[robertisaar]

why no 3900?

two reasons:

i was able to pick up a well-maintained 100K mile LQ1 and 4T60E for $100 within an hour drive
because the latest 3500VVT is looking more impressive

even then..... the next time i need an engine, the HFV6 lineup is on the table.

[ericjon262]

I've been eyeing up the later gen IV engines for other reasons than just increased displacement. i'm interested in the VVT setup, and possibly a custom cam for single cam variable LSA. it's a project that's still a ways out though. probably once I hit my next duty station I'll get started on it.

[Guest]

why no 3900?

two reasons:

i was able to pick up a well-maintained 100K mile LQ1 and 4T60E for $100 within an hour drive
because the latest 3500VVT is looking more impressive

even then..... the next time i need an engine, the HFV6 lineup is on the table.

If there was a 3900 for $100 in the same yard with the same mileage, would you have picked up the 3900 instead of the Dohc?

[Guest]

anyway to get the timing cover side to have a mount for a FWD setup?

Yes it will bolt on, There are a couple other things that need to be done but lets save that for a different thread if we could please.

[robertisaar]

If there was a 3900 for $100 in the same yard with the same mileage, would you have picked up the 3900 instead of the Dohc?

didn't get it from a yard... came from another forum member who kept up on it right until he swapped it out for a L67. it was taking up too much storage space, so i ended up with it.

if i came across a gen4 3500/3900 for $100 before or after after the LQ1, i'd still probably pick it up, it certainly couldn't hurt to have around.

[caffeine]

I might swap one into a drift camaro I recently acquired.

[Guest]

I might swap one into a drift camaro I recently acquired.

what do you forsee as being one of the more challenging aspects of the swap?

[ericjon262]

what do you forsee as being one of the more challenging aspects of the swap?

I would bet it's all the little custom parts that will come into play.

[caffeine]

Do you want to do a 3900 swap? whats stopping you

what do you forsee as being one of the more challenging aspects of the swap?

I already have a game plan. But the most challenging part will actually be finding a place for a power steering pump since the VVT water pump sits right where I would ideally put the power steering pump. Everything else is pretty standard...
- Flip upper intake
- Use V8/3.1 rad with 3.1 lower rad hose and yet to be determined upper hose
- Use 2.8 headers with new flanges welded on OR source a couple of car 3900 front manifolds with a custom y-pipe
- Custom solid 1/4" steel motor mounts
- Repin stock harness for '7730 and modify pigtails as necessary
- Custom external crank trigger (or purchase one and modify mount)
- Custom T5 front bearing retainer with HTOB mount and dual starter pocket 2.8 bellhousing (already made) (lots of alternative ways to bolt up a T5 as well)
- AFPR for for returnless rail OR vette/S10 fuel filter/regulator
- Notch front crossmember for oil pan clearance

[Guest]

planning to keep vvt?

[ericjon262]

I highly doubt it if he's gonna run a '7730. if he is, I would love to know how.

[caffeine]

I'm gonna try running the VCT as an on/off type of switch as opposed to continuously variable PWM. The alternative is locking the cam to one position or getting expensive custom cam bearings/bearing spacers made.