347 vs 370
09-04-2012, 10:14 PM
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347 vs 370 I'm building a motor this winter and am trying to make a solid decision before I start slowly buying parts. I am on a budget like most people so I was thinking about just using my 346 that's in the car now and just putting forged internals in it to save money in place of sourcing a used block/crank ect. What would the power difference HP and TQ between 347 vs 370 assuming both have same brand forged internals besides stock crank, 317 heads mildly ported, blower cam, same compression and a D1 Procharger maxed out with Meth? I would assume the 347 would like higher RPM's more, is a slight bit lighter, would make more boost due to smaller cubes and would save me a little coin. Just curious on the power difference if there is one?
09-04-2012, 10:37 PM
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The 370 would have less boost and less flex and would seem to last longer. Sell the 346 to pay for a 370 you probably get more out of it complete to help cover your cost if the 346 is still running.
09-04-2012, 10:50 PM
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Easier to make the power with the 370, (not by much though) but both can make the same power. the limiting factor is the d1 procharger. I would personally just do the 347 over the 370 because 23 cubes isn't **** over the weight penalty. The aluminum block can handle more than what you can throw at with that d1 blower.
09-05-2012, 11:20 AM
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As was already said, both will make good power. I picked the 370 over the 347 for better overall efficency of the combo. With the 370, you take the bore size out to 4.030" vs a 3.905" for the 347. With the increase in bore size, you can run a better head with larger valves. With less valve shrouding, you increase your combo's efficency therefore making more power. How much power are you looking to make? I agree that the D1 will be your limiting factor before the motor itself, however if your planning to make more power later on you should take that into consideration now. Either are quite capable though and have proven to make good power.
09-05-2012, 06:58 PM
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Thanks for the input guys! I just don't want to make a descision on the motor now and regret it down the road. Im not one of those guys that say I have to have XXX amount of horsepower. I just want it to be strong and safe. I wouldnt mind trying to make 750ish on meth though. I will probably never put a F series blower on it but who knows. I will just be running a set of mildly ported 317 casting heads and could never see myself make spending a ton of money on aftermarket heads with bigger valves ect. I will be reusing my pushrods, cam and oil pump so the the motor wont be exactly complete if I do decide to go the 370 route and sell the stock motor. The stock motor that is in it now runs great and is perfect condition btw. All that being said, would a built 347 make say 750 while a built 370 make 800 with same pully and variables ect? Will the 370 at those power levels be that much safer? Am I overlooking something?
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09-05-2012, 11:08 PM
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If the engines are pullied the same and everything else is the same they won't make the same boost. You are really just over thinking a simple combo. 750 is cake with meth and around 10 compression. Is this car an auto or manual?
09-06-2012, 08:23 PM
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That's a lie. The blower is the major peak torque and hp determining factor. The bigger engine will have more power down low when off boost, but when the boost is built the power and torque is really close. You will notice the iron block more over the 23 cubes. Iron blocks these days just aren't all that necessary.
If the engines are pullied the same and everything else is the same they won't make the same boost. You are really just over thinking a simple combo. 750 is cake with meth and around 10 compression. Is this car an auto or manual?
If the engines are pullied the same and everything else is the same they won't make the same boost. You are really just over thinking a simple combo. 750 is cake with meth and around 10 compression. Is this car an auto or manual?
09-06-2012, 08:52 PM
#12
Boost is a measurement of restriction, the blower spinning at any given rpm will produce the same amount of CFM weather your feeding a 347 or a 370 CI. So the 370 CI is just less restrictive. Its like holding your thumb over the end of a hose, the hose isn't flowing more water the restriction just makes more pressure.
09-06-2012, 08:58 PM
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No...
Boost is a measurement of restriction, the blower spinning at any given rpm will produce the same amount of CFM weather your feeding a 347 or a 370 CI. So the 370 CI is just less restrictive. Its like holding your thumb over the end of a hose, the hose isn't flowing more water the restriction just makes more pressure.
Boost is a measurement of restriction, the blower spinning at any given rpm will produce the same amount of CFM weather your feeding a 347 or a 370 CI. So the 370 CI is just less restrictive. Its like holding your thumb over the end of a hose, the hose isn't flowing more water the restriction just makes more pressure.
Makes sense
09-07-2012, 09:41 PM
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Do you have any upgrades to your engine now? I'm asking because I don't know why you would use all your old parts on the 370 if they are all factory.
The 370 would allow for better head selection in the future.
Either engine could meet your power goals but the supporting mods i.e. the rest of the drivetrain needs to be modified to handle the abuse that motor can put out.
You could sell your ls motor and tranny and buy a pull out 364 with an 80e to put back in and potentially have cash left over to put into internal upgrades.
If you want to keep the m6 you may want to set you hp goals lower or save up for a better built m6 because from what I have read on build threads is, m6 can't handle that amount of power.
The 370 would allow for better head selection in the future.
Either engine could meet your power goals but the supporting mods i.e. the rest of the drivetrain needs to be modified to handle the abuse that motor can put out.
You could sell your ls motor and tranny and buy a pull out 364 with an 80e to put back in and potentially have cash left over to put into internal upgrades.
If you want to keep the m6 you may want to set you hp goals lower or save up for a better built m6 because from what I have read on build threads is, m6 can't handle that amount of power.
09-08-2012, 05:11 AM
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Trans is built by tick performance, has a 1000hp aluminum driveshaft and a moser 9" with a wavetrac in it. Im not worried about the drivetrain and am not one of those that tries to make 1000hp and still have a 10 bolt. I will be reusing my cam, pushrods and retainers and locks. Like mentioned before, im useing stock casting 317 heads on either motor and wont be a need for upgraded bigger heads down the road.
09-08-2012, 06:30 AM
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Don't know if your building it yourself or not but, with the iron block your going to only have 2mounting holes for the procharger bracket on that side of the motor. iirc I think a saw a few guys weld a plate to the block n then welded a nut to the plate and used that as there 3 bolt hole for the bracket. Maybe someone else will chime in on this for sure.
09-08-2012, 10:29 AM
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Trans is built by tick performance, has a 1000hp aluminum driveshaft and a moser 9" with a wavetrac in it. Im not worried about the drivetrain and am not one of those that tries to make 1000hp and still have a 10 bolt. I will be reusing my cam, pushrods and retainers and locks. Like mentioned before, im useing stock casting 317 heads on either motor and wont be a need for upgraded bigger heads down the road.
Iron block will add approximately 100lbs to the front of your car. I went with the 6.0 because I figured that if something went wrong and the sleeves got scratched I could bore it out to repair instead of re-sleeving or purchasing a new block.
You can purchase 6.0 long blocks off Ebay for around 400 but could possibly buy a whole motor for 5-800 at salvage yards or craigslist.
I decided not to bore mine since the sleeves looks so great, I just had them honed and bought forged 4.005 pistons by SRP with -14.3 dish. I kinda wish I would have used flats because my CR is now 8.55 and from reading on here it will be a dog off boost.
09-08-2012, 01:03 PM
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Don't know if your building it yourself or not but, with the iron block your going to only have 2mounting holes for the procharger bracket on that side of the motor. iirc I think a saw a few guys weld a plate to the block n then welded a nut to the plate and used that as there 3 bolt hole for the bracket. Maybe someone else will chime in on this for sure.
09-08-2012, 08:24 PM
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I will have a machine shop do the machining and a buddy will clearance everything and assemble it. I won't be buying it already built if thats what you mean. I do know what your talking about with the mounting holes. I believe the spot is still there for the thurd hole, it just needs to be drilled and taped.
That hole may be there, for some reason I though I read a thread about j bracket mounting on the iron block. I could be wrong and if I am sorry for the miss info. Like I said hopefully bob or another vet will chime in on that