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DevilDogge

Power Difference - 345 Vs 392 @ 15psi

So, as John L suckered me into buying his blower, I can't get a pulley large enough to spin it slow enough to keep it at 8 psi or so.  I'm going to use that excuse to make the pitch to my wife as to why I have to get the forged engine, and of course, I'll be sure to lay the blame squarely on John's shoulders lol.  

 

 

The only thing I think I know is that I want the 2618 pistons and ARP head studs.  Other than that, I'm torn whether to save a bit of coin and stick with the same sized displacement (345), or to pony up and bore it to 392. I'm not playing at Muzza's status financially, so keep that in mind.  

 

What is the potential power difference between a 345 and a 392 at 15 psi?  Is it worth the extra money to go bigger now?  Do I have the essentials down  for a safe daily driver at 15 psi (2618 pistons & ARP head studs)?  School me, please. 

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Obviously you will net more power per pound of boost. The blower will also top out at a lower boost number. If you're not planning on running more than 15psi then just go with the larger cid motor. An F1d can easily make that much on a 392 (or 426).

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You've got a centri blower.  If you always plan to stay centri, or turbo for that matter, get the 392.  They won't bore it much, the rod length is what is different to give it the extra Ci.  What this means is the motor will be more of a torque motor rather than fast revving high rpm horse power.  Not a bad thing at all for a street/strip car, just something to note.  You're a stick car so that torque will make more challenges getting off the line, but I think not a big deal with a centri or turbos since they build boost with RPM.

 

My recommendation would be different if you ever planned to go to a PD blower.  They make instant torque so having more stroke, a 6 speed, and a PD blower wouldn't be what I'd recommend.

 

As for what you need:

 

You already mentioned the 2618 pistons and ARP studs.  Definitely get both.

Cometic head gaskets

Decide what compression ratio you want.  I'd suggest 9.5:1 or close to that for a good compromise in power and safety on pump gas for the street.  This will have some effect on the head gasket used.

Fuel system?  Arrington has some excellent options now for this.

Fuel rails with front and rear crossovers

Tuner (device and person) - I think you have a Trinity right?  So that's covered.

You already got a clutch, so you're good there.

If you want a cam do it now while the motor is being assembled with appropriate push rods and springs to match.

Head work again isn't as important on a blower car, and is a bit pricey, so I'd skip that and do it down the road if you wanted it.

Gauges - at least AFR, I personally like boost and AFR with a fuel rail mounted fuel pressure gauge.

 

If you think the max you'll want is 15psi build the motor to take 20.  I can promise you 15psi won't do it forever lol

 

That's all I can think of.  Very cool wife lol

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You've got a centri blower.  If you always plan to stay centri, or turbo for that matter, get the 392.  They won't bore it much, the rod length is what is different to give it the extra Ci.  What this means is the motor will be more of a torque motor rather than fast revving high rpm horse power.  Not a bad thing at all for a street/strip car, just something to note.  You're a stick car so that torque will make more challenges getting off the line, but I think not a big deal with a centri or turbos since they build boost with RPM.

 

My recommendation would be different if you ever planned to go to a PD blower.  They make instant torque so having more stroke, a 6 speed, and a PD blower wouldn't be what I'd recommend.

 

As for what you need:

 

You already mentioned the 2618 pistons and ARP studs.  Definitely get both.

Cometic head gaskets

Decide what compression ratio you want.  I'd suggest 9.5:1 or close to that for a good compromise in power and safety on pump gas for the street.  This will have some effect on the head gasket used.

Fuel system?  Arrington has some excellent options now for this.

Fuel rails with front and rear crossovers

Tuner (device and person) - I think you have a Trinity right?  So that's covered.

You already got a clutch, so you're good there.

If you want a cam do it now while the motor is being assembled with appropriate push rods and springs to match.

Head work again isn't as important on a blower car, and is a bit pricey, so I'd skip that and do it down the road if you wanted it.

Gauges - at least AFR, I personally like boost and AFR with a fuel rail mounted fuel pressure gauge.

 

If you think the max you'll want is 15psi build the motor to take 20.  I can promise you 15psi won't do it forever lol

 

That's all I can think of.  Very cool wife lol

 

That she is, Jay.

 

 

Thanks for the advice.  It all makes sense.  I have the Arrington comp fuel pump already, so I think that should suffice, but I'd definitely need bigger injectors.  Never thought about the fuel rails with dual crossovers.  If Arrington does the install, they'll be doing the tune as well. I'm leaning toward the 392.  Just trying to get all the costs accounted for.  

Might as well add a nag1 to the list. 15psi, 10psi, won't matter. It'll still be 11s lol

lol we'll see

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You've got a centri blower.  If you always plan to stay centri, or turbo for that matter, get the 392.  They won't bore it much, the rod length is what is different to give it the extra Ci.  What this means is the motor will be more of a torque motor rather than fast revving high rpm horse power.  Not a bad thing at all for a street/strip car, just something to note.  You're a stick car so that torque will make more challenges getting off the line, but I think not a big deal with a centri or turbos since they build boost with RPM.

 

My recommendation would be different if you ever planned to go to a PD blower.  They make instant torque so having more stroke, a 6 speed, and a PD blower wouldn't be what I'd recommend.

 

As for what you need:

 

You already mentioned the 2618 pistons and ARP studs.  Definitely get both.

Cometic head gaskets

Decide what compression ratio you want.  I'd suggest 9.5:1 or close to that for a good compromise in power and safety on pump gas for the street.  This will have some effect on the head gasket used.

Fuel system?  Arrington has some excellent options now for this.

Fuel rails with front and rear crossovers

Tuner (device and person) - I think you have a Trinity right?  So that's covered.

You already got a clutch, so you're good there.

If you want a cam do it now while the motor is being assembled with appropriate push rods and springs to match.

Head work again isn't as important on a blower car, and is a bit pricey, so I'd skip that and do it down the road if you wanted it.

Gauges - at least AFR, I personally like boost and AFR with a fuel rail mounted fuel pressure gauge.

 

If you think the max you'll want is 15psi build the motor to take 20.  I can promise you 15psi won't do it forever lol

 

That's all I can think of.  Very cool wife lol

 

 

The rod length is not what changes displacement. Rod length has zero affect on displacement.

 

If staying under 1000hp, stock head bolts and stock head gaskets will not fail. Definitely 2618 pistons as well as steel rings and potentially 9310 wrist pins.

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The rod length is not what changes displacement. Rod length has zero affect on displacement.

 

If staying under 1000hp, stock head bolts and stock head gaskets will not fail. Definitely 2618 pistons as well as steel rings and potentially 9310 wrist pins.

 

Should have qualified that to say with the crank.  Thanks for the correction.

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Haha, love the text string

☺ ...with the buy-in from Natasha, I expect now is the time for a few extras. The blown engine thing is what I needed to get a green light.

 

I totally agree with Speedy that at some point you will want more power, so good to try for 392 if you can. Arrington did have some good deals on long blocks, so push for any sale price they offered, then some - I have found them good on working with you there... but do price check any items outside of the engine - there were a couple of good mark-ups I noticed after the fact. ☺

 

Wasn't there a string about gauges on the fuel rail that Mani kept putting his foot in his mouth? ????????

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I respectfully disagree with this statement. Stock head gaskets at that power level make me very nervous, but stock head bolts at that power level i would never trust

 

If staying under 1000hp, stock head bolts and stock head gaskets will not fail

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Stock head bolts will hold fine with stock head gaskets at 15psi. I ran mine for two years at 21 and a 250 shot before the gasket let go. The studs aren't that expensive any way so it's not a big deal either way.

 

Thanks for making her hate me lol I'm gonna have to hide out now at the track when I see her coming.


oh yea send me your address again and I'll send you my old intercooler and the beefed up boxes

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Might as well add a nag1 to the list. 15psi, 10psi, won't matter. It'll still be 11s lol

 

 

Wanna bet on it. lol

 

 

I respectfully disagree with this statement. Stock head gaskets at that power level make me very nervous, but stock head bolts at that power level i would never trust

 

If staying under 1000hp, stock head bolts and stock head gaskets will not fail

Seem to remember this discussion not to long ago in my build thread.

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