Mars inspired me 3900 engine
 

seeing how well Mars did with his engine it motivated me to make the swap. I looked for cam bearing spacers but not much luck so I said screw it and had them made up myself.

I am using a set, keeping a backup, and had a couple extra made in case anyone else wanted to do this swap.

Re: Mars inspired me 3900 engine
 

Re: Mars inspired me 3900 engine
 

I started a thread in the for sale section for the extra sets of bearing spacers I had made up to partially fund my WOT cam purchase. I would like to go with a custom turbo grind. I like the specs of the LS9 cam, and am hoping it can be reproduced. Should provide a good idle, little overlap, but good duration and lift numbers.

I had -12an fittings made for the heads as I will eliminate the factory water manifold on the lz9. I will prob weld them in when all is said and done. I am thinking epoxy will work though.

75mm TB adapter from TCE will be going on a lz4 upper intake with an 5.3 truck LS throttle body.

I have tried several local welders and so far none have wanted to tackle welding the SS flange onto the cast exhaust manifold. I might have to figure something else out.

Re: Mars inspired me 3900 engine
 

use a mild steel flange to weld to the manifold , the stainless expands to much and will cause cracks .

were u located at maybe i can weld it up for ya

Re: Mars inspired me 3900 engine
 

the flange is only available in stainless, noone offers it in mild. think tial vband exhaust housing. in florida.

getting a stainless flange cut, then bolt that to the factory manifold, then weld the turbo flange to the newly cut stainless piece, might be the best way to go.

Re: Mars inspired me 3900 engine
 

what size is the vband , i bet we can find u something in mild steel that will work , except for the amount of heat u have to put into the cast ur going to warp the vband anyways , so making it a bolt on deal will be much better

im on the other side of the country so i wouldnt be of any help to u for getting it welded up

Re: Mars inspired me 3900 engine
 

pretty sure its a 2" vband. I always forget how its measured. The outside edge of the ring is almost 3 inches, but the opening of the flange for the exhaust flow is only 2 inch opening.

https://cimg0.ibsrv.net/gimg/www.thi...fa08e90982.jpg



I went down to the parts store today and bought a gasket, going to drill out the broken studs, then have a stainless plate made, weld the flange to that, then bolt it to the exh manifold. Should be hassle free then.

Re: Mars inspired me 3900 engine
 

Bigcheese, good to see you made it over here.

Re: Mars inspired me 3900 engine
 

Definitly following this thread.

Re: Mars inspired me 3900 engine
 

so i figured I would at least gasket match the heads while I had them off. It ended up being a full "port" so to speak.

I raised the roof by about .1 of an inch, blended the valve guide boss, smoothed the short turn radius, and also blended the valve seat. not sure what it is going to do for flow, but I am going to send them off to Champion racing heads in Palm Coast to do the valve job and associated bits. I will also have them flowed to see what they do just for knowledge sake. Not expecting big improvment in numbers, I just want a number for me so I know.

Gonna purchase all new valves, and have Champion do the valve job on new valves, most likely all new guides, TI retainers, and stronger springs. Gonna have to make a purchase with WOT tech soon.

https://cimg6.ibsrv.net/gimg/www.thi...6882f78417.jpg

Re: Mars inspired me 3900 engine
 

Before you send the heads to Champion, may want to look up some reviews. Seems that many people have had significant difficulty reaching Tom, and some have claimed poor turn around times, like months late in some of the worst cases I've read. At the very least I would call Tom and inquire. Source for most of the complaints are located at turbobuick.com.

Re: Mars inspired me 3900 engine
 

Why not have a local machine shop perform the head work?

Re: Mars inspired me 3900 engine
 

google searched and only pulled up a few threads about issues with CHampion. They were older threads too. I didn't get on the buick forums and do a search there though

Champion is close enough for me to consider being local.

Re: Mars inspired me 3900 engine
 

Yeah if youre close enough then at least you can drive over there and jump on his desk when he doesn't answer the phone.

Re: Mars inspired me 3900 engine
 

just posting a pic of the torn down 3900 that I have been using for test fitting parts, and the 8k mile engine on the left going in.

https://cimg9.ibsrv.net/gimg/www.thi...a66afc2874.jpg

Re: Mars inspired me 3900 engine
 

for those third gen guys with a 2.8 or even maybe a 3.1 with a distributor, if you turn the 3.9 upper intake around(which is needed to be done in a fbody) a modified distributor will fit. This makes swapping easier, and just a computer tune away from bolting this in.

https://cimg7.ibsrv.net/gimg/www.thi...3f9a4fcdfc.jpg



https://cimg4.ibsrv.net/gimg/www.thi...2a230aabf0.jpg

Re: Mars inspired me 3900 engine
 

picked up some parts from WOT-tech to go along with the cam bearing spacers

camshaft, manley retainers, pac 1218 springs and cam bearings.. I still have to measure the pushrod length before ordering custom ones. here is my cam card. its a fairly mild cam I think

https://cimg6.ibsrv.net/gimg/www.thi...c91f941c7a.jpg

Re: Mars inspired me 3900 engine
 

Nice. The cam I have is close to that. Its not split so much though. 224/228 dur@.050

Re: Mars inspired me 3900 engine
 

Bumping this back up for the awesomeness. I might skip the 3.4 and jump straight to the 3.9 with the ease of the dizzy swap.

Re: Mars inspired me 3900 engine
 

The dizzy swap is not as easy as it sounds, the dizzy that you have seen is not a stock dizzy, it's much taller than stock.

That being said going DIS is not that difficult, and is a superior ignition system to dizzy anyway.

Re: Mars inspired me 3900 engine
 

I agree 100 percent. Switching over to dis was something i will always have on my camaro.

Re: Mars inspired me 3900 engine
 

Yes the dizzy is longer than stock. I will have to check my notes but I think I had it extended 2-2.5 inches. somewhere in that range. Not hard to do though.

Yes DIS is a superior ignition, however the distributor has worked on several 400+ hp engines I have built so far with no issues. If your goal is 400 hp and both ignitions can support it, some might not want to make the switch.

keeping the dizzy makes the swap into a camaro with a distributor that much easier. No wiring changes, no buying new sensors, no swapping computers no buying or using old coil packs. You can use the stock computer, but have the timing and fuel maps used for a 3.1 gen 2 cavalier. will it make max power with that tune? No but it will start and run and the final tune will just have to be done just like any other swap.

I built that dizzy as a proof of concept and it does work. Obviously this could work for those that have an old S10 or GMC truck that had the v6 originally too or any other RWD platform where the upper intake needs to be turned around.

Re: Mars inspired me 3900 engine
 

I though the dis swap was easy. All the wires were exactly the same from the old dizzy set up, the ecm 7730 was easy to change to dis. I run $59 and it only required 4 changes in the bin file. No repining or anything. And its nice to have a hacked file that has a 3 step rev limiter as well which works great on DIS.

Im not trying to say that you must go dis im just saying its not very hard if any other viewers are wanting to attempt the change. The only hard part was the crank sensor and such. I bought the external kit from BCC 3 years ago which made the swap cost me 160 bucks but literly only took 20 min to install. Funny that now i have a 3.4L that has knotches on the crank and a spot for the sensor.... oh well I didnt know at the time that I would be running a 3.4.

I will admit though back 3 years ago if I could have used the dizzy when i did the hybrid swap, I would have because I was scared that the dis would be a pita to do and or not work right.

Re: Mars inspired me 3900 engine
 

I just think it's cool to have another viable option, instead of being forced to run the DIS. I know eventually I'd swap over but this setup would work great in the mean time

Re: Mars inspired me 3900 engine
 

no big news but a while back I had dropped off a 3900 to my local machine shop. since that time its been hot tanked and the bearing spacers and bearings on the middle two cam journals have been installed in the block. The two outers need to be installed.

after that, measurements of the crank throw, rod length, deck height, and pin diameter need to be done, so I can order the correct pistons. I have a JE piston in mind, but have to confirm the measurements to get the proper compression height for a decent quench. the pistons I am looking at will be under $500 for forged pistons, and have about a 10.8 compression. I'll have some pics once the machine work is complete.

Re: Mars inspired me 3900 engine
 

RobertFrank, since you're in the SL valley, if you ever need to reference a running stock DIS 3.4, my '94 Camaro is sitting here doing nothing since I need my Ranger most days.
The cost of the aftermarket dizzy is probably more than the DIS conversion, and as much as I like mechanical distributors in general, I gotta admit the DIS gives a lot more precision, and a lot more tuning flexibility. My only gripe with my DIS is really the fault of the OBD1.5

Re: Mars inspired me 3900 engine
 

Ever think of swapping to a 7730? I know its sorta a step back but from my experience with OBD 1.5 and a 7730... a 7730 is way better and if you work with the right mask such as a $59 and yes you can run that with a N/A car, that code has tons of options and damm is it easy to use in most areas.

Ive been using $59 for 5 years now and DIS with it for 3.

Re: Mars inspired me 3900 engine
 

That would be awesome to come and check it out, maybe bounce around some ideas of different aspects of what I want to do. I do have a 7730 computer from my 91 L98 car. I just need a harness and a MEMCAL to make my life easier.

Re: Mars inspired me 3900 engine
 

just dropped my pistons off at teh machine shop today. progress is slow obviously as I haven't provided all the parts.

JE forged turbo piston for ls1. 3.905 bore

Re: Mars inspired me 3900 engine
 

I heard these engine could run an LS piston. That's cool

Re: Mars inspired me 3900 engine
 

Nice.

Im sure they are cheaper then my forged ones. I got raped for my 3400 diamond pistons...lol I paid a tick over 700 bucks for mine to the door.. freaking nuts. That's like 120 bucks a piston.

Re: Mars inspired me 3900 engine
 

about $480 for a set of 8 is what I paid. That was the cheapest I could find from Real St in Orlando The rings were $92.

I will need to open up the rod bushing .002 to fit the slightly larger pin(.943 stock vs .945).

I thought my Cr was going to be closer to 11:1, but since the factory piston sits so deep in the hole(.040) These will still sit about .008-.018 down in the hole pending on final assembly and if the deck needs squared up. That will put the CR anywhere from 10.22 up to around 10.55:1 which isn't terrible for boost.

JE 321238 is the part # I used

I also found a straight bolt in piston that has a 5cc valve cutouts that will give about a 13:1 CR which I might try later for a NA build on e85. I think 350hp at the crank is possible. DSS makes that piston 1810sx I think is the pn. DSS also has a piston with a 15cc dish that is a drop in on the stock rod too. thats 1813sx. that would prob be a good compression ratio for a street motor on 93 octane.

Re: Mars inspired me 3900 engine
 

Yea thats a good deal for some forged pistons. My rings were 140 bucks as well. It added up fast when it came to the pistons rings rods mls gasket and head studs..

10.5:1 isnt bad at all. 93 octane and solid tunes and it will be fine. I did fine with the E85 running 12.5:1 and boost for a bit but it was pretty radical as i had to run a massive cam to get the dynamic compression down to better levels. I feel that the 12-13:1 area is a awesome option for a N/A set up but for boost its just not, no question about it.

Look forward to seeing your engine come together soon!

Re: Mars inspired me 3900 engine
 

Well I'm glad I could be an inspiration.

I wish I had enough motor to actually use my turbo to its' full potential... I'm still on stock head bolts.

Maybe sometime (after I see how yours goes) I'll build a motor for boost.

Untill then, I have a spare 250$ low mileage motor ready to swap in when mine blows up...

Nice find on the pistons.

Re: Mars inspired me 3900 engine
 

If you guys want to check out a wicked 3.9 turbo build this dude over in the fiero forums has built a "stroker" 3.9. Looks nuts and very detailed.

http://www.fiero.nl/forum/Forum2/HTML/107886.html

Re: Mars inspired me 3900 engine
 

last post for a bit. I dropped off the rings and I picked up some arp rod bolts from wot tech at the machine shop. Not sure how long it will take for them to do the machining and assembly. ill update then.

here is a pic of my cam bearing spacers in the block with replacement 2.8 cam bearings and a flat tappet cam for test fitting. everything spec'd out.

Re: Mars inspired me 3900 engine
 

Everything is back from the machine shop and I have been slowly working on it. Cleaning everything is my priority right now. Pistons fit but still need to verify deck height once assembled. Ill have all that data when things start getting assembled

https://cimg6.ibsrv.net/gimg/www.thi...366669d6d3.jpg
https://cimg9.ibsrv.net/gimg/www.thi...e294c67904.jpg
my cam bearing spacers fit good

Re: Mars inspired me 3900 engine
 

Looking good. I look forward to your block being together!

Re: Mars inspired me 3900 engine
 

its slow going. found a pit in one of my crank bearings so I have to get a new set. I mocked up cyliner 2 piston in the bore and a close up of the cam spacers installed with the cam bearings.

https://cimg2.ibsrv.net/gimg/www.thi...80cedbe39d.jpg


https://cimg5.ibsrv.net/gimg/www.thi...0ee3059560.jpg

Re: Mars inspired me 3900 engine
 

thinking about .022 top ring and .024 second ring. thoughts? turbo use with e85 and about 14 psi, or a 150 shot. haven't decided yet. Bore is 3.905

Re: Mars inspired me 3900 engine
 

Top ring gap is at .022


second ring is at .021


main clearances are about .015 for all journals.


Piston sits about .005 in the hole.

Re: Mars inspired me 3900 engine
 

Long time no post. I was doing some googling and came back across this old thread.

So update on this engine. I had a valve seat fall out of it and it trashed every piston and bits got sucked back up into the intake runners and then back down into each cylinder. So I trashed that engine.

I bought an 8k mile junkyard 3.9 and put in a lnj camshaft for an 09 equinox. It's a straight bolt in, no spacers needed. GM parts direct has the cam. I kept stock rods and pistons

I tuned that engine on 15 lbs and made 520 whp and 500 tq to the wheels on a bone stock engine. I tried turning the boost up to 20 lbs and was dialing in the tune, and it lasted or a short while but it broke a rod and bent another. It was probably around 600 whp and 600 whtq. So that's prob the limit of this engine on stock internals.

So now I bought some Pauter aftermarket rods and using ls1 pistons again. And doing an upgraded camshaft. Should make 700 HP no problem now and be reliable.