Small Bore = Big Power Cheap?
 

I have been thinking about this combo for a while and I think that there is a lot of power to be had cheap with a turbocharged 350 Pontiac. Here is my thought: the early blocks have a lot of cylinder wall thickness and the small bore will greatly reduced head gasket issues. They are also as cheap as landfill.

Forged pistons for these engines are now readily available and the valve shrouding issue shouldn't be a significant problem in a forced-induction situation. You could mess around with valve chamfers but I doubt you'd even need to.

I think a '72 350 with the 1.96/1.77 valve combo would be a great start. Add the aforementioned forged pistons with some cheapo forged rods, stock crank and an 067 or 068 cam you'd have a pretty stout foundation. Round it out with a Tomahawk intake, Holley carb and a set of Ram Air III exhaust manifolds and I think that you'd be well on your way to 600+ horses with the right turbo. I think a BW S475 would be a good choice, provided the exhaust turbine wasn't too big.

Has anyone tried anything like this?

I have not tried it but have thought of it many times... specially after looking at the 350 deck next to a 455 block. Massive amount of sealing surface along with very beefy casting everywhere.

Locating stock logs that you could flip forward like I did on my S15 would be a smart move.

600 horses on low boost setting...

350 under boost!
 

I think Jeff -aka-- 69turbobird---was running a 350 stock and got it to run 11. e/t ---1/4 mile, but i am not 100% sure, I am too lazy to look for his post--look for him and I am pretty sure you will find more info...he sells turbos, turbo headers and relate items...

I think you could get 700 hp out of it on pump gas if you intercool it and maybe add a water/meth kit... just be sure you got strong pistons/rods and maybe better main caps. (splayed 4 bolt)

An s475 would work great. I have one on a 351w it starts to spool around 2200 and about 10psi at 4000.

Sounds like a very workable combo to me, but turbo and cheap don't really go together. LOL
Once a turbo spools you have huge torque so a 600 HP turbo engine is going to do a lot of work.
I think it was Firechicken that had a 068 cam and went mid 10's, but don't remember at what C.I.

I'd prefer two smaller turbos so you have boost just off idle.

I thought the same thing but unfortunately the bolt pattern is asymmetrical. Needs to be fabbed.

Sorry for the confusion..... Use a RH log on the left side and the LH on the right side... If you have a big pile of Pontiac logs and big chassis chances are that you might get lucky with some manifolds.

Some Pontiac exhaust manifolds are center and/or near center outlet. No big deal makin a u and going back up or if goin fwd meetin under the pan somewhere(ala single exhaust crossover or if twin turbo makin an x under the pan) If motor mounts werent in the way long branch manifolds could be swapped side to side(fwd facing vs rear facing) Ram air logs arent bad either.

subscribbing

Don, you could always go twin turbo and make some power.

Twin turbos

:D

Would have been neat to see you use them John... Not a bad deal either. 1200+ in your dragster is serious fast... Sub 7's at 2000 lbs... Heck a 3200 lb door car could go bottom 8's with them.

I'm not so sure I would want boost down that low as the engine will be going in a mostly stock '66 A-body chassis. I would like to make sure the tires are firmly planted before the boost comes on. This will be a street car that will see a few trips to the track per year.

While it will certainly be easy to make more power with a larger bore engine, I am looking for a durable stock block combination that won't have an appetite for head gaskets, yet will have enough power to get a full-bodied car into the 10s. I think it is doable.

The problem is (other than getting it to the ground) going into boost kills your MPG. I know this isn't a high mpg build but...

You want it to start building boost just above your normal cruising rpm.

That is exactly what I was thinking of perhaps getting a converter that is just loose enough to build boost against while power braking at the starting line. Being in boost all of the time would also make for a very difficult car to manage on the street.

Took the first test drive tonight in my 1970 turbocharged 350 Lemans wagon. It is going to be fun!(once I finish installing body panels) Pulled really hard for a completely stock 350, buying up parts to build the replacement engine currently :) Forgive my horrible video editing skills.

http://www.youtube.com/watch?v=MXUd1TmB2Vk

LOL.. all stripped down and hammering the country roads.... I like your style!!

Love it- please send more photos/videos!

Thanks! I won't have anymore videos until later this fall when I get paint and some body panels on it. I could not resist taking it out for one blast down the road :). I will start my own thread when I get some better pictures and have time to write down more details of the build. Highlights of the build are cheap Chinese gt45 turbo, completely stock 350(for now), lots and lots of fabrication and using parts the way they were never intended!

[IMG]http://i1150.photobucket.com/albums/...ps9724d57e.jpg[/IMG]

[IMG]http://i1150.photobucket.com/albums/...psdf1088ab.jpg[/IMG]

[IMG]http://i1150.photobucket.com/albums/...ps96d76528.jpg[/IMG]