Deciding between 3400 and DOHC

[Sinister_Z]

Hey folks

I'm considering either the 3400 or DOHC for my next project. I just need to find the basic engine weight for boths engines. Also can anyone tell me which engine gets the better gas mileage? Thanks

Shay

[96mcls]

i say 3400, because it's easier to work on/modify than a 3.4 DOHC, and is very reliable and gets better gas mileage, plus now it has a growing aftermarket. as for weight i'm not sure about the DOHC but a 3400 weighs in around 350-380 lbs with all brackets... but i'm sure the 3.4 DOHC weighs alot more.

[Guest]

What vehicle will this be going in?

[Sinister_Z]

What vehicle will this be going in?

This daunting project is for my 67' Chevy Corvair 140 4 speed. I like both engines and have been able to take a close look at CodeRed's 3400 out in my garage. I also think that a 3.4 DOHC engine would make a very impressive statement in the engine compartment when I popped the hood. The engine will be heavier than the all Aluminum flat 6 that's in there now. So I'm trying to take the increased weight into account for my center of gravity and rear suspension setup.

Shay

[firechiken]

If your just looking to make a statement, I think the DOHC would be the way to go. And making headers to fit in there would be easy. Otherwise, it would be a tough call, arguments could be made for both.

[Guest]

The Corvair will surely have enough room for the DOHC, though hight may be tight.

But have you though about engine rotation? The Corvair uses a reverse rotation engine (counter clockwise when facing the belt end), so this will have to be taken into account when you swap this over.

Guys that swap in SBCs usually get a reverse rotation cam, and regrind the lead in gooves in the cranks, along with custom oil pumps, for the reverse rotation.

I'm not sure what you could do with the 660, 4 custom cams would be hella expensive.

Swapping a different transaxle in would probably be easier, cheaper and work better, say something from a Porsche, a mid to late '70s 911 transaxle can usually be found rather in expensivly.

I guess another option would be custom gears or mabe just final drive in the Corvair transaxle. It's been a while since I looked at one, but my Grandfather has one sitting in a frame he built back in the '60s or '70s for a mid engine project that was never completed. He was going to mate a SBC to the Corvair transaxle with the transaxle turned around, so that the engine faced "the right way". :P The adaptor plates are STILL hanging on his wall in the garage.

[Sinister_Z]

But have you though about engine rotation?

Like I mentioned "A Daunting Project". So far I have seen a SBC, a Aluminum Buick 215 V8 and a Buick 3.8 V6 converted to reverse rotation for the Corvair platform.

http://www.corvair.org/chapters/v8vairs/images/StatlandJessica/JessicaStatland.htm

http://www.corvaircorsa.com/brekke01.html

I could go the easier route and track down a Crown or Kelmark midengine kit and parts. But i like my back seat plus I'm 6'3" and need the leg room. I've been planning this swap on and off again for the past year. I almost went the route of a Marine SBC reverse rotation but decided I wanted to keep it more of a driver just with reliability and better fuel ecomomy than my old 140. Bottom line is that there are a lot obstacles to clear. One being going from a aircooled engine to a liquid cooled engine and not cutting up my trunk for a radiator. If got lots of ideas and plans. Right now they're still on the drawing board but I hope to get started soon this winter.

Shay

[Guest]

But have you though about engine rotation?

Like I mentioned "A Daunting Project". So far I have seen a SBC, a Aluminum Buick 215 V8 and a Buick 3.8 V6 converted to reverse rotation for the Corvair platform.

http://www.corvair.org/chapters/v8vairs/images/StatlandJessica/JessicaStatland.htm

http://www.corvaircorsa.com/brekke01.html

I could go the easier route and track down a Crown or Kelmark midengine kit and parts. But i like my back seat plus I'm 6'3" and need the leg room. I've been planning this swap on and off again for the past year. I almost went the route of a Marine SBC reverse rotation but decided I wanted to keep it more of a driver just with reliability and better fuel ecomomy than my old 140. Bottom line is that there are a lot obstacles to clear. One being going from a aircooled engine to a liquid cooled engine and not cutting up my trunk for a radiator. If got lots of ideas and plans. Right now they're still on the drawing board but I hope to get started soon this winter.

Shay

I'll check those links later.

Have you thought about the Porsche transaxle? I'm pretty sure they use forward rotation engines, I know there is a member here working on installing a genII 3.1 in his Porsche, but I can't remember if he flipped teh transaxle or not.

[Guest]

Ok, here is the 914 thread, very cool. http://www.60degreev6.com/index.php?...hlight=porsche

I can't tell from the pics, but he may have flipped the axle, the last one kinda makes it look that way, seeing as you can see the tail lights. I didn't re-read the whole thread just now, but I thought I'd post here for you anyway.

[geoffinbc]

I have never seen a Corvair trans axle but on our dune buggy you can simply flip the ring gear to the other side of the pinion providing reverse rotation. We did this to our Car transaxle when we installed bus axles with gear reduction hubs

But why are you ditching the air cooled 6? It is what makes the Corvair a Corvair.

[Sinister_Z]

I can't imagine that you could flip a corvair differential very easily. And if you could I again would be losing my back seat. The way the V8 guys do it is remove the stock Corvair transmission and directly bolt a TH350, for example, to the differential minus the tail shaft.

I read the 914 thread a lil while back. Good stuff.

I haven't open up the guts of the differential. But it is a Corvair specific unit and I'm not too sure other common methods of thought could apply. I will be opening mine up here in upcoming weeks to see what lies beneath. I munched the Passenger side yoke so it's coming out to see if it can be saved or to see if i need to find a new unit.

WHy am I getting rid of my 140 flat 6? Ahh that's the real question isn't it? Well I have lots of reasons. The 140 is a great enigine in it's own right but I desire an engine that can deliver all weather reliablity and better fuel economy to start. I want an engine that tunes and manages it self and provides me a motor that parts are more available as well as more inexpensive then the original engine. Plus it would be nice eye candy to look at when I pop the hood.

I want to make a real nice driver out of her. I new fuel injected V6 and T-5 in place of her old 5 speed and I'll have no quams about taking out for long distance drives at all.

Thanks

Shay

[Guest]

If you want cheap parts go 3400, if yuo want to pay an arm and a leg, go DOHC. DOHC would definatly be cool, but by no stretch of the imagination are they chepa to buid/rebuild and there is a very limited number of aftermarket parts for them.

[geoffinbc]

Lots of guys put mega squirt systems on their VW's they work great and really make a driver out of the car. New megasquirt systems have ignition control too.

I just think it would be easier to keep the engine and trans than having to modify the hell out of the car to fit something forein to the chassis into it. Plus keeping the super light aluminum 6 would keep the car nimble and light. Also you would not have to worry about water cooling.

[SappySE107]

Since you want a nice daily with good milage and easy to find parts, stop thinking about the DOHC. Parts can be found but they aren't that cheap. The timing belt must be checked every oil change (well it should be at least), and replaced every 60k if not sooner. Gas milage is also lower than the pushrod.

Id take a 3400 over the 3.4 iron head as well

[Sinister_Z]

So what are we talking comparetively on gas mileage? What are the figures for both motors, in town and highway?

I was actually thinking about differential issue today. Just say for a second that you could flip the diff over and now the rotation of the engine and the direction of the wheels are as they should be. The only problen so far that I've seen with that is that the trans is directly bolted to the diff case and now would essentially give me 4 gears in reverse and 1 forward gear. I really need to open case up and see what can be done.

Shay
____________
Semper Fortis