I currently have a 306 getting a twin kit that uses twin Grand National Turbos. (Sorry I havent found the exact specs yet). These parts are going on a stock block with TFS cam, intake and TW heads. I figure I should be able to get 500 to the tires with it but also want to keep it alive. When the time comes for a new motor I will definitely be going with a dart block set up. However my question is...347? Or would these turbos support a bigger inch motor. Maybe step to a 9.2 deck motor??? 393? 408? 427? I know I would need to rework a few things but as long as the turbos are in good shape why not use them. I just dont want to slap two really small turbos on a big inch motor and end up choking it out. Heck if I new I could put these things on a well built 460 I would as long as they werent to small..know what I mean Verne?

 

Anybody??? 44 views and not even a go to h e double hockey stick post??

 

the search button is your friend here - since the gn guys ditch their stock turbos to make more power, I would say that 2 would probably be fine for a mild build like your 306, but not much more.

 

It will work for a 302-347 nicely. GN turbos probably will respond well.

 

I have searched but didnt see anyone do anything with TWO GN turbos. I think my 306 with these turbos should be capable of 500+ but not sure. I gotta tune it to stay safe but I am hoping for 500RWHP with this setup. Upgrade to a Dart Blocked 347 hopefully soon.

 

Go to the Chevy section and find the thread "How long until it grenades?" the thread originator used twin GN turbos on a junkyard 350 and it ran very impressive.

 

I didnt search the chevy section before. Thanks.

 

Motor size is part of the deal BUT hp.
How hp will a pair of GN turbo support?

If you are going to build a custom motor build a custom motor.
Don't fall into the off the shelf trap of the common 331,347,393,408,427.

Do it right. 380 or bigger depend on head flow.

9.2" deck
4.125"+ bore
3.500" Stroke

 

What I am looking at doing is swapping short blocks at a later date and I want to make sure I am not going to have to spend another 2500-3k on a new turbo set up. I am running a 306 in a stock block now and want to think about a dart blocked stroker later..SO do I stay with a 302 based motor?? or go to the 9.2 deck and do a 393??? 408? Would those turbos support a 393 / 408 I guess is what I am asking. If not... I would probably stick to a 347. For a street car I figure 6-700 hp out of a 347 is plenty.

 

Well a 302 isn't going to hold 700hp.
A W is an option, don't bother building it if Dart is in the future.
If you Go Dart use the motor above.

 

i have a 306 stock block afr 185, f-cam. with two stock g/n turbos @ 20#. i went 10.8 @124. yeah i run race gas and timing is locked at 26 deg. but i do drive it on the steet also. also have a c-4 with 327 gear. car is 3220 with me in it too. i suppose a 347 would be nice with these turbo's also. good luck.

 

20#'s on a stock block? holy cow man.