340 turbo questions.

[clbitting]

I have a 1970 340 block that is in great condition. I would like to run small twin turbos or even a descent single turbo, but can't really find any info on what needs to be done engine wise so I don't ruin a good block. I already have the 416 stroker kit, but I haven't sent the block off yet. Any idea what compression needs to be ran to run about 10-12lbs of boost? Any tips or pointers would be greatly appreciated!


THANKS!

 

[moparleo]

Save the 340 block. When you say great condition, does that mean never bored, no scored cylinders ? Really the 340 casting is pretty thin compared to the 360 and good ones are rare. There are millions of 360's out there and so will be cheap to buy a good one. You want a strong bottom end, good crank,rods, forged pistons if you are going to run any boost all of the time. Extra oiling is a plus, upgrade your cooling system, it will generate more heat. Really before you spend more $ I would contact the turbo manufacturers and see what they recommend. They have a dog in this fight and probably won't steer you wrong. They know what blows up engines on purpose so you don't blow up yours by accident.

 

[clbitting]

No the block has not been bored yet. Didn't want to waist money if my stroker kit wasn't a good setup for a turbo. Better oil pump and water pump will be used for sure. From what the turbo manufacture said I can run decent boost if I have no higher than a 10:1 compression. Thanks for the input!

 

[Adam]

Leo is right about the heat. I had a single turbo on a Chevy 350 back in the 80s. The Turbo is a huge heat sink; it baked the paint off the hood right above it; that kind of heat is hard on everything, oil, fuel, cooling, etc. Have you looked at the belt driven superchargers?

 

[moparleo]

There you go. They sound better too!

 

[burntorange70]

I think Maddart over on ForAbobiesonly was working on a turbo SBM build.

 

[Chryco Psycho]

The stroker kit you have will not work in a 360 block , the crank journals are different or a 318 block the bore size will be wrong for the pistons .
I would want to be around 8:1 if you want to use pump gas & have close to 1 atmosphere of boost

 

[Challenger340]

remember here....
there are differences in Piston alloys used in "Forged" Pistons ?

Most Stroker Kits use a 4032 Alloy Forged Pistons.....
Most Manufacturers DO NOT recommend any more than 6 lbs Boost on their 4032 Piston Alloys ?

just saying.... before contemplating ANYTHING in the way of Boost for the kit you have... might be a good idea to phone the piston manufacturer used in your Kit... and find out what Alloy Pistons you have ?

generally speaking here....
* 2618 Alloy Forged Pistons are for Boost/Nitrous applications

* 4032 Alloy Forged Pistons for only the absolutely lowest Boost applications(6-8psi MAX), or maybe just a 100hp shot at most ?


You are very welcome Neil... knowledge from actual EXPERIENCE should always be free ?

 

[moparleo]

Super charging is much easier do than running a turbo. No special exhaust plumbing, excessive heat under the hood. You can change boost with a pulley change. Put your money into the bottom end and cooling system. You will also need a carburetor built for a super charger, and a good exhaust system. Remember that an engine is only a combustion powered air pump. You can only get as much air in as you can get out.

 

[moper]

I think you don't see it much because of the pricing associated with doing it right (or even wrong). IMO - there's no point in boosting with a belt driven anything. It sucks away a ton of the power it makes so you can do much better with a smaller turbo setup. Like was said - talk to a turbo manufacturer and be honest with them - turbos are a lot like cams - bigger is not usually better. Talk to a piston manufacturer (I like CP) and get a sset made for your setup. Limit it to 8:1. Prepare for running head studs, and find a fabricator for the exh manifolding work (or buy a TiG). Also do some research into engine management systems. I like FAST products but it's been a long time since I used one. Custom intercoolers are a design drawing and phone call away. Do the piping mock ups, then the powder coating. Ready to run you're probably looking close to $20K for something good, solid, reliable, and powerful.

 

[74chlngrTT5.9]

I agree supercharging would be easier to set up. I also agree with moper that the parasitic drag that comes with them is always there to some degree whether on the go pedal or not. This also translates into a loss of fuel economy. (To appease any responses to this opinion, Yes I know the newer designs are much more efficient than they have been in the past.)
I have chosen to go the turbo route for 2 primary reasons.
1) With superchargers you get the instant seat of the pants acceleration with a limited effective RPM range. Turbos are a more gradual increase to the power and properly sized ones will provide a longer power cycle. This more gradual increase IMOP also will be less destructive to all areas from the motor through the drive train given equal HP/torque ratings.

2) Unlike superchargers that are always on, the turbos can help the motor run more efficiently during light throttle cruising. I plan on fuel injecting mine to further the cause because there will be many miles put on it.

Also:
Heat is generated when the air is compressed via supercharger or turbo. IMOP again neither one is better or worse than the other.

IMOP x3 Even though you have the 340 stroker kit, I suggest you go with the above mentioned 360. Dime a dozen motors to test the turbo waters with as I am doing.

Good luck with any direction you choose to go.