Rear wheel drive DOHC 3.4

[Mad Max]

I am looking into buying a complete factory long block DOHC and running it in an S10. Motor mounts are not an issue, I can fab them, the engine comes with a manual flywheel, I will use the 5 speed in the truck.
Here's where things change: I have 3 sets of Weber down draft carbs which I plan to fabricate an intake to bolt to the heads. I will have to fabricate headers which shouldn't be too difficult, and the kicker is going to be the ignition. Since there is no way to put a distributor on this engine, you know where the distributor hole is... I will have to have a crank fired ignition that does not use a factory computer (stand alone) I've looked at alot of these motors, they aren't much different (space wise) than a 2.8 although the heads are mangous big. It should be almost a bolt in to an S10. The problems that will be a little tricky are the coolant outlet / inlet, which still shouldn't be too bad, everything else looks straight forward. I think the 2.8 oil pan even has the same mounting bolt pattern. I figure a set of well tuned Webers, headers and a good exhaust will most likely help this engine to 225HP.
Somewhere I read that these were originally 275 HP, but the cheesy 700 r4 couldn't be considered reliable so they detuned it to be less dangerous to the auto tranny. Effn cheap auto trannies.

[mrl390]

275hp, no.

700 R4? Where did you read that? There has never been a 700 R4 bolted behind the 3.4 DOHC.

Good luck

[Mad Max]

I will have to find the link and post it. You are probably right about the tranny, I think I incorrectly said the 700R4. I think it was more likely the cheeser FWD t250 or something. The article that I read said that GM had developed this engine for substantial power increase for performance oriented driving in FWD higher end cars. They managed to get 275 reliable HP out of the engine, but the Hydramatic boys couldn't develop a FWD tranny to handle the power, so they detuned it to 220HP rating. I've never heard of a RWD application, although as I said earlier, it doesn't look like it would be too tough to adapt.

[Superdave]

the 275HP is a myth.


Sounds like a fun project!

[IsaacHayes]

Just get the PCM that comes with the DOHC, and wire that in, that way you don't have to worry about a distributor, and carbs/etc. Carbs will not make as much power, and the drive-ability won't be as good.

Headers will help the engine out a lot if you can make long tube equal length. Then if you get the PCM tuned to dial it in, it will really be nice.

Where the starter mounts on the block could be an issue with your trans. I think there is some year combination or other vehicle that the belhousing will accommodate it though.

[pocket-rocket]

If you are dead set on carbs, a distributor can be bolted down. You would probably want to use one out of an older 2.8 RWD vehicle. Then just remove the distributor plug and install the dizzy. Good luck with the project, it sounds interesting even though I would have to go with what Isaac is saying and stick with fuel injection.

[RedZMonte]

doesnt the rear head cover the Dist hole? hence the reason its a PITA to change the leakey "O-Ring". if thats the right spot for it i don't see how a dist could go in there without trimming the head. I too would suggest staying FI and run the stock ECU... you don't have to have everything hooked up, just the main sensors for opperation, the other items can be deleted in the ECU.

S

[Mad Max]

doesnt the rear head cover the Dist hole? hence the reason its a PITA to change the leakey "O-Ring". if thats the right spot for it i don't see how a dist could go in there without trimming the head. I too would suggest staying FI and run the stock ECU... you don't have to have everything hooked up, just the main sensors for opperation, the other items can be deleted in the ECU.

S

Thanks for the input guys. Actually, the Weber carbs are about as close as you can get to multiport injection. They are tuneable through out the fuel delivery band. They have 40 mm venturis, an have an individual barrel for each cylinder - plus- they look the bags and make a crazy intake sound.

You are right about the dizzy, it will not fit in the proper location because the passenger head obscures the hole. The problem with the ECU is that I don't have a donor rig and will be purchasing a new factory long block without anything attached to the engine. I am going to try to show all engine with minimal wiring and stuff on the heads/block. Electromotive Ignition makes a stand alone crank fired ignition system with separate coil packs that is completely programmable by laptop interface. It has 2 step rev limiter, tuneable advance/retard throughout the RPM band and can retard timing through a boost sensor. It can also trigger methanol injection.

The one big issue I neglected is the starter motor is on the driver's side. I will have to custom cut and weld a bellhousing to fit the starter. I am pretty sure the blocks are not starter ambidextrous.

I haven't rulled out a complete ECU controlled engine, but it seems like that will be almost as much work as what I described earlier.

http://www.angelfire.com/ca2/34Performance/dohc.html BTW - for all of you guys doubting the 275 HP rumor, READ THIS.

[Mad Max]

the 275HP is a myth.


Sounds like a fun project!

http://www.angelfire.com/ca2/34Performance/dohc.html

Sorry for the double post.

[bszopi]

Give me a few hours and I'll post up a website on a free webhost that says it actually had 343hp when originally produced...

Or, you can just read this...

http://60degreev6.com/forum/f101/anyone-hear-of-the-3-4dohc-having-275hp-t28369

[bszopi]

And since everything on the internet is the truth, I guess I need to believe this as well http://www.apfn.org/apfn/flight77.htm

[robertisaar]

the LO northstars made ~275HP with roughly the same engine... just with an extra pair of cylinders and set at 90*(ideal for a V8 compared to the ideal 60* for a V6) bank engles...

so, let's assume the LQ1 is actually a LO N* with 6 cylinders. a HO LQ1 would bump up from ~215HP to ~235HP if the same ~9% bump in power was engineered from i think different cam profiles alone(possibly a compression bump as well, but i'm not too sure of that).

[pocket-rocket]

doesnt the rear head cover the Dist hole? hence the reason its a PITA to change the leakey "O-Ring". if thats the right spot for it i don't see how a dist could go in there without trimming the head. I too would suggest staying FI and run the stock ECU... you don't have to have everything hooked up, just the main sensors for opperation, the other items can be deleted in the ECU.

S

Right, right. I forgot about the rear head. It *might* fit with trimming, but it would be really close. At least I was right on staying with fuel injection The joys of too much to do and not enough time to do it/keep it all strait.

[RedZMonte]

wow there is a blast from the past! i havnt seen that page in YEARS (~10).... the original engine concept may have produced that kind of power but by the time it made it to production it is nothing like what we have.... it has potential if you have the time and resources to do the work (porting, custom piston compression, Rods, Cams, Valves, custom intake manifolds, ect...) but realistically without a major mods, staying N/A it will take a bit to get you there, not saying it cant be done i would love to see it done.

as for finding a wireing harness and ecu www.car-part.com is a great place to find them... I have a full OBDII swap for ~$150 bux... the stand alone is nice if you don't mind tuning a complete engine 100% from scratch.

as for the V6 N* talk.... Its called the 3.5L LX5 "ShortStar" 215hp 230tq..

http://en.wikipedia.org/wiki/GM_Premium_V_engine#LX5

[robertisaar]

as for the V6 N* talk.... Its called the 3.5L LX5 "ShortStar" 215hp 230tq..
http://en.wikipedia.org/wiki/GM_Premium_V_engine#LX5

which was roughly what the LQ1 was rated for... depending on year and tranny. considering the near identical bore/stroke, they're roughly the same idea. except the 3.5 has a chain instead of timing belt and was cast with a 90* bank.