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Hi guys, I'm doing some investigating trying to decide on a head and cam combo for a shortblock that I've recently assembled, but before I can do so, I need to decide on an ideal rpm range for my application. I'm running a GM sbc 400 block, 509 casting 2-bolt with main studs. GM steal 3.480 stroke crank, H-beam rods, with forged HRC 6.7cc domes. (all balanced). My car as sets weighs in at 3200lbs with me in it. Could be anywhere from 3100-3300lbs when finished. My thoughts were to begin building power in the 4000-4500rpm range with a peak at or near 8000. Does this sound right? I'm taking in consideration that 377s don't produce a whole lot of grunt in the lower rpm range, and this heavy car is definitely going to need some help out of the hole. Is that taking this block and crank too far? An aftermarket block and crank are in my future but I'll have to settle for what I have for the time being. Please share your thoughts.
Thanks, Chris.
 

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That block will not live at that rpm ..and if it was well preped your still taking a chance..
For the cost off the block and prep ...you would be better off with at minimum the Dart SRP block
They can handle 700 +HP easily...
 

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Hi guys, I'm doing some investigating trying to decide on a head and cam combo for a shortblock that I've recently assembled, but before I can do so, I need to decide on an ideal rpm range for my application. I'm running a GM sbc 400 block, 509 casting 2-bolt with main studs. GM steal 3.480 stroke crank, H-beam rods, with forged HRC 6.7cc domes. (all balanced). My car as sets weighs in at 3200lbs with me in it. Could be anywhere from 3100-3300lbs when finished. My thoughts were to begin building power in the 4000-4500rpm range with a peak at or near 8000. Does this sound right? I'm taking in consideration that 377s don't produce a whole lot of grunt in the lower rpm range, and this heavy car is definitely going to need some help out of the hole. Is that taking this block and crank too far? An aftermarket block and crank are in my future but I'll have to settle for what I have for the time being. Please share your thoughts.
Thanks, Chris.
I'm not too sure on that Block but I would at least convert it to a 4 bolt main or find another Block. 8000 rpm is no big deal with a good head and valve train. The head and intake will determine where the power falls off at. I ran my old 355 to 7800 on the shift and 8000 through the traps with a Chevy factory steel crank and Pink rods. I thought 8000 was max rpm to stay together so 9.00 et @152 was it with a 4.88 gear. I still have the short block assembled from years ago, I decided to build a 383 with the heads for my small motor.
 

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Discussion Starter #5
That block will not live at that rpm ..and if it was well preped your still taking a chance..
For the cost off the block and prep ...you would be better off with at minimum the Dart SRP block
They can handle 700 +HP easily...
So, what are you suggesting to be a safe rpm? I need to tailor my combo to this short block, because unfortunately an aftermarket block isn't in the budget. I have other areas of the vehicle to attend to as well. I'm hoping next winter, for a new block and crank.
 

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I have a similar GM 509 block based build. My setup is good for 8200 rpm. But I shift at 7400 rpm and go through the traps at 7600 rpm. That, combined with the fact it is built properly, has allowed it to live a long life. This has been in my Camaro for 3 years and before that the block spent 12 years in my Chevelle bracket car with a 13.5:1 Shafiroff 434 combo for over 1500 passes. I totally agree with the gentleman above who said be careful spinning these over 8000 rpm. Cap walk is bad. Good luck.
 

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Discussion Starter #7
It is a complete engine combo which will dictate the RPM range.
Do tell us more. What exactly do you have and whats your goal.
Oh yeah budget?
The motor currently sits as followed. 509 casting 2-bolt main, studded, aligned bored, decked to 9.005, with the steam ports filled. GM steal crank, Eagle H-beam rods, forged HRC 13.6:1 pistons.(static at 9.000 deck). The rotating assembly is balanced. Dart Pro 1 215cc 2.05, 1.60, valves as cast. Professional Products Hurricane intake as cast. 950 Prosystems 4150 carb. Crane Energizer Gold 1.5:1 rockers with Comp Cams Magnum push rods. Comp Cams 306S solid camshaft 3000-7000rpm. The car currently weighs in at 3100lbs. 4.56 gear, 28" tall tire, Leaf springs, and if all goes well will have Caltracks, split mono leafs, and double adjustables with slider boxes. I will be running head studs this year with Cometic MLS gaskets. 400 turbo on foot brake. The car will be used primarily for 1/4 mile drag, with little street use.

I do have a NOS cheater kit, but spraying it can wait for a new block and crank. I hope this gives you a better idea. As, far as budget, I can't afford to invest in a block quite yet, with attention needed in other ares of the vehicle, but next winter brings a dif story. I would like to invest in a good roller set up to transfer over next winter. Thanks, Chris.
 

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Discussion Starter #8
I'm not too sure on that Block but I would at least convert it to a 4 bolt main or find another Block. 8000 rpm is no big deal with a good head and valve train. The head and intake will determine where the power falls off at. I ran my old 355 to 7800 on the shift and 8000 through the traps with a Chevy factory steel crank and Pink rods. I thought 8000 was max rpm to stay together so 9.00 et @152 was it with a 4.88 gear. I still have the short block assembled from years ago, I decided to build a 383 with the heads for my small motor.
JB, I went with a 2-bolt because when researching the 400, I discovered that incorporating the 4 bolt main cap on a GM 400 block actually weakened the structeral integrity by taking material out of the webbing that supports the caps. Not so much an issue with the 350. Hearing good stories of GM steal cranks and blocks definitely ease my mind. lol! Thanks, Chris.
 

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Discussion Starter #9
I have a similar GM 509 block based build. My setup is good for 8200 rpm. But I shift at 7400 rpm and go through the traps at 7600 rpm. That, combined with the fact it is built properly, has allowed it to live a long life. This has been in my Camaro for 3 years and before that the block spent 12 years in my Chevelle bracket car with a 13.5:1 Shafiroff 434 combo for over 1500 passes. I totally agree with the gentleman above who said be careful spinning these over 8000 rpm. Cap walk is bad. Good luck.
Thanks gearhead. My intensions are to take my internals and switch them over to an SLP or even a Little M or Iron Eagle next winter. I'd like to run a roller set-up this spring, but I fear investing in everything twice in order to accommodate both blocks. I'd rather invest for the future and short shift, then buy twice. I've already put myself in that position by listening to word of mouth around town, and not doing my homework. There has been some pretty good luck around here with going fast on GM blocks, but those that did eventually upgraded. Some horror stories too. That's great to hear you got that lifespan out of your block, I'm definitely hope to be that lucky. lol! Would be nice. Chris.
 

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Discussion Starter #10
Oh, Paul. I did forget the exhaust. 1 7/8" primary to 3 1/2" collector with Flowmaster Deltas. Thanks, Chris.
 
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