Thread: Big block motor build help

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Oh i can use a 454 crank in this engine? I never knew that Like i mentioned i`m new to the BB chevy stuff. Could the rods fro ma 454 work as well?

thanks
pat

Originally Posted by 80 BB stepside

Oh i can use a 454 crank in this engine? I never knew that Like i mentioned i`m new to the BB chevy stuff. Could the rods fro ma 454 work as well?

thanks
pat

any rod that is 6.135 long thats std for a big block so from a 366 to a 502 will work with the KB pistons or have a set of custom made and you could go to a 6.385 rod but what i think would be a wast of good money or you can buy a H or I beam but the stock rods work good if you can get them recond and use a sps or arp rod bolt the press pin rod like the scat I beam is good to

Well i`ll keep you informed if the guy i emailed if he is willing to take the offer + shipping. Is this a good setup or should i go to the 454 rotating assembly?

thanks
pat

Also would you reccomend a 700r4 behind this? Its got a 12 bolt 3.73 rearend in it and i`m gonna use it sometimes so RPM`s can stay low and not be screaming with a 3 speed auto.

thanks
pat

Couple other things to consider.

Number one – bigger pistons shorter stroke makes more power. The main reason is that when the stroke is increased, the pistons (and there by the rings) travel further up and down in the bore which results in a loss due to friction. In addition, the piston must accelerate and decelerate faster with a longer stroke within the same time, specifically one revolution of the crankshaft. This also requires energy. On the positive side (and why stroking is usually done) is that this increases the cubic capacity which increases the torque produced by the engine. A longer stroke will make more torque, due to the increased displacement. When you increase displacement with stroke versus bore, both torque and horsepower peeks occur at a lower RPM.

Number two – installation of a 454 crank in a 396/402 block with stock length rods will require a non-stock set of pistons. Keith Black has a piston for this application (KB893) that sell for $400-500 per set. These pistons are made for 4.125” bore (stock 402 motor) and a 4” stroke (454 stock crank) and net 434 cubic inches. While it may appear a good idea initially to stroke your 402 block, the cost of the pistons needs to be factored. It’s probably less expensive to find a 454 short block and rebuild it with standard 454 pistons.

Number three – the 454 crank is externally balanced. This means that you MUST use a 454 damper and flexplate/flywheel. I would recommend having the assembly professionally balanced at a reputable shop as the vibration caused by a mismatch will result in a very expensive chunk of useless metal bolted between the fenders of your ride.

Number four – while the 454 crankshaft will bolt nicely into your 402 block, there may be clearance problems with the rods at the base of the cylinders. Some machine work will, in all likelihood, need to be accomplished for proper clearances. This is again, a job for a professional or a seasoned engine builder that knows where and how much to grind out.

There is also a temptation to bore your 402 to 4.250” to allow the use of standard 454 pistons. Be real sure your block will be able to withstand such before attempting. The walls need to be thick enough and there is always the possibility of not being able to perfectly align crankshaft to cylinders once the bore has taken place. I am painfully aware of this after finding a “bind” during a rebuild that required significant rework and new balancing of already expensive rods. (Fortunately before firing up the motor and hurting anything!)

All said, do what your heart (and checkbook) tells you! As you have probably surmised, this site is full of great information and people like techinspector and pat mccarthy are venerable pros who have a lot of years of buildin’ under their belts.

Bottom line is that this whole hot rod thing can be a lot of fun if you remember to go slow and easy, learn from your mistakes (and the sage advice of those who’ve gone before you) and have a blast getting elbow deep in building special memories.

Regards,
Glenn

Originally Posted by glennsexton

Couple other things to consider.

Number one – bigger pistons shorter stroke makes more power. The main reason is that when the stroke is increased, the pistons (and there by the rings) travel further up and down in the bore which results in a loss due to friction. In addition, the piston must accelerate and decelerate faster with a longer stroke within the same time, specifically one revolution of the crankshaft. This also requires energy. On the positive side (and why stroking is usually done) is that this increases the cubic capacity which increases the torque produced by the engine. A longer stroke will make more torque, due to the increased displacement. When you increase displacement with stroke versus bore, both torque and horsepower peeks occur at a lower RPM.

Number two – installation of a 454 crank in a 396/402 block with stock length rods will require a non-stock set of pistons. Keith Black has a piston for this application (KB893) that sell for $400-500 per set. These pistons are made for 4.125” bore (stock 402 motor) and a 4” stroke (454 stock crank) and net 434 cubic inches. While it may appear a good idea initially to stroke your 402 block, the cost of the pistons needs to be factored. It’s probably less expensive to find a 454 short block and rebuild it with standard 454 pistons.

Number three – the 454 crank is externally balanced. This means that you MUST use a 454 damper and flexplate/flywheel. I would recommend having the assembly professionally balanced at a reputable shop as the vibration caused by a mismatch will result in a very expensive chunk of useless metal bolted between the fenders of your ride.

Number four – while the 454 crankshaft will bolt nicely into your 402 block, there may be clearance problems with the rods at the base of the cylinders. Some machine work will, in all likelihood, need to be accomplished for proper clearances. This is again, a job for a professional or a seasoned engine builder that knows where and how much to grind out.

There is also a temptation to bore your 402 to 4.250” to allow the use of standard 454 pistons. Be real sure your block will be able to withstand such before attempting. The walls need to be thick enough and there is always the possibility of not being able to perfectly align crankshaft to cylinders once the bore has taken place. I am painfully aware of this after finding a “bind” during a rebuild that required significant rework and new balancing of already expensive rods. (Fortunately before firing up the motor and hurting anything!)

All said, do what your heart (and checkbook) tells you! As you have probably surmised, this site is full of great information and people like techinspector and pat mccarthy are venerable pros who have a lot of years of buildin’ under their belts.

Bottom line is that this whole hot rod thing can be a lot of fun if you remember to go slow and easy, learn from your mistakes (and the sage advice of those who’ve gone before you) and have a blast getting elbow deep in building special memories.

Regards,
Glenn

well some good points BUT.... you should not and i would never tell you to bore out your 402 out to 4.250 bore the KB pistons are not to bad 500 a set ? your 454 crank damper and fly wheel will all be 454 ex bal so your 402 will be a 454 with a smaller bore it will be ex bal .. .it not a bad job to bal the mass did one not more then drill some holes no heavy metal or any thing like that . yes there could be a very small bit of work to get the crank to swing thru so you could say just build a 454 ?? the pistons are cheaper but if you can find a 454 crank your going to buy parts ? so the 402 with a 4.00 stroke would not be top on my list BUT there was a time were 402 blocks were cheap and now there is more 454 cranks out there guys are putting in 4.250 strokes and you can buy a new cast steel crank for a good price .i built many 4.00 to 4.750 strokes bbc so i do not see this small bit of work much if you take your time .for bore to stroke the big piston is the way to go BUT you can only go so far on bore the dart. pro. block. donovans about 4.600to 4.625 is about it so bigger stroke it is if you want a big cid engine bigger piston with the rings working on the bore take power to i bore blocks all the time if its is there to bore out i will.. my f2b rottler is not happy less it is boring a big holes

Well i was going to sell it but now i think i would have a sence of pride if i took this block and built it and made a good street motor out of it rather then sell it and regret i did.SO its back on the front burner o build it and i think it`ll be just fine making 450hp out of this 402 block.

thanks
pat
p.s. now the hunt begins for the rotaating assembly as the 427 slipped away