[BLACK70GTO]

Hey anyone hear of a 521 ci. built from a 400 ?? It is supposed to have a 4.750 stroke,Sounds like a lot of cubic inch

[WARPed]

Originally Posted by BLACK70GTO

Hey anyone hear of a 521 ci. built from a 400 ?? It is supposed to have a 4.750 stroke,Sounds like a lot of cubic inch

If it was to be used a just a grocery getter it might hold up. Can you say split the block? I would reserve that much stroke for aftermarket blocks.

[71 Ventura II]

IMHO The factory deck height is way too short to even think about running a 4.75 stroke. It would require a rod length of 7.5"+++ to get a 1.57 or better rod stroke ratio. Which brings to light the piston ring lands! If you had a 7.5" rod on a 4.75 stroke there would be no room left for the rings on the piston, with the factory deck height, since the pin would be in the middle of the ring lands! JD

[BLACK70GTO]

Pontiac lover's this is the last 521cid shortblock I have assembled,no wimpy 462 this is 521 cid of pontiac power and torque.These will make 670lbs plus of torque and are the most street friendly motor you have ever owned.Great idle and vac. flat tappet,roller,iron or alum. heads it likes them all.This is for the short block only,but can finish to any level you wish.The block is a 1967 casting that was baked,blasted,magged,linehoned,decked,arp main studs,brass soft plugs and durabond cam bearings.The crankshaft is a forged 4.750 stroke riding in speedpro bearings,rods are hbeam with arp2000 bolts,pistons are custom JE forged with coated skirts,duel pin oilers,tool steel pins,wire loc's compression is 10.1 with a 85cc head valve reliefs will .630 lift cams the assembly is balanced total seal gapless rings to keep the gas were you need it.Yes they are as happy on the street as they are on the strip.For about the same $ as a 462-472 you can have a 521cid ground pounder Pontiac!!

[71 Ventura II]

Originally Posted by BLACK70GTO

Pontiac lover's this is the last 521cid shortblock I have assembled,no wimpy 462 this is 521 cid of pontiac power and torque.These will make 670lbs plus of torque and are the most street friendly motor you have ever owned.Great idle and vac. flat tappet,roller,iron or alum. heads it likes them all.This is for the short block only,but can finish to any level you wish.The block is a 1967 casting that was baked,blasted,magged,linehoned,decked,arp main studs,brass soft plugs and durabond cam bearings.The crankshaft is a forged 4.750 stroke riding in speedpro bearings,rods are hbeam with arp2000 bolts,pistons are custom JE forged with coated skirts,duel pin oilers,tool steel pins,wire loc's compression is 10.1 with a 85cc head valve reliefs will .630 lift cams the assembly is balanced total seal gapless rings to keep the gas were you need it.Yes they are as happy on the street as they are on the strip.For about the same $ as a 462-472 you can have a 521cid ground pounder Pontiac!!

I wouldn't touch this engine with a 10 foot pole. If you got it to run with those evidentally short rods good for you. Can you say "Bomb"! I thought you could. JD

P.S. What he doesn't reveal is how short the rods are and that you can't rev the engine much above idle! LOL

[440GP69]

Rod length and r-s ratio is Overated IMHO Just make sure you leave some piston in there to avoid rock, If you used a shorter but Common 6.535 BBC rod and used everyday 468 pistons 1.295-1.31 CD "Might need to cut down the Counter weights" you could do this easy and Fill the block half way, Milodon or Program Center Splayed caps and LW BME rods and LW pistons its possible to build this and have a good street engine But I wouldn't revvv past 55-5800!, A set of SD's Alum D-ports and a T2 intake with a 245-252 at .050 Hyd roller could be some Fun! BUT Build at own risk and Know that you can never replace the IA2 just because you have cubes, JMO

[71 Ventura II]

Originally Posted by 440GP69

Rod length and r-s ratio is Overated IMHO Just make sure you leave some piston in there to avoid rock, If you used a shorter but Common 6.535 BBC rod and used everyday 468 pistons 1.295-1.31 CD "Might need to cut down the Counter weights" you could do this easy and Fill the block half way, Milodon or Program Center Splayed caps and LW BME rods and LW pistons its possible to build this and have a good street engine But I wouldn't revvv past 55-5800!, A set of SD's Alum D-ports and a T2 intake with a 245-252 at .050 Hyd roller could be some Fun! BUT Build at own risk and Know that you can never replace the IA2 just because you have cubes, JMO

1.375 rod/stroke ratio and 5500-5800 rpm with massive side loading of the pistons!

[440GP69]

LOLOLOL! Why not Chubby guys been doing it a Long time!, I also never said its the Best way or it will live a Long happy life, All i said was its Possible to do

[Jim Zeek]

I have a 502 from a 67 400 block. 4.211 bore x 4.500 stroke. Filled with 4 bolt caps, forged crank, GRP rods and ross pistons. Roller cam (.726 lift) lifter bore brace.

[lust4speed]

The side loading point is definitely valid; but if rod/stroke length really made that much difference, then the 400 would be king over both the 428 and the 455. There is certainly an optimum rod length, but additional stroke and cubic inches trumps the theoretical stuff. Granted that if we were starting out with a clean slate designing our engine parameters, then a minor addition to horsepower would be obtained with longer rods.

That said, I would reserve the 4.75" stroke for aftermarket blocks and people willing to take big risks. My personal level of comfort stops at a 4.25" stroke with the 400 block.

[440GP69]

Another Point, Pontiac cylinders are probably not long enough for a Short rod and 4.75 stroke so Maybe what I said earlier is BS and wouldn't work with 6.535 rods,IDK I'd never build a 400 with more than 4.5 stroke Period, BTW SD Just built a 10.5:1 330e-head 498cidStock block engine, Made 700+hp and 640tq so There is merit to the 4.5 stroke But I Wouldn't even put a 4.75 in my IA2 let alone a stocky FWIW, Its possible But not the Best or Least expensive route!

[Wareagle]

Originally Posted by BLACK70GTO

Pontiac lover's this is the last 521cid shortblock I have assembled,no wimpy 462 this is 521 cid of pontiac power and torque.These will make 670lbs plus of torque and are the most street friendly motor you have ever owned.Great idle and vac. flat tappet,roller,iron or alum. heads it likes them all.This is for the short block only,but can finish to any level you wish.The block is a 1967 casting that was baked,blasted,magged,linehoned,decked,arp main studs,brass soft plugs and durabond cam bearings.The crankshaft is a forged 4.750 stroke riding in speedpro bearings,rods are hbeam with arp2000 bolts,pistons are custom JE forged with coated skirts,duel pin oilers,tool steel pins,wire loc's compression is 10.1 with a 85cc head valve reliefs will .630 lift cams the assembly is balanced total seal gapless rings to keep the gas were you need it.Yes they are as happy on the street as they are on the strip.For about the same $ as a 462-472 you can have a 521cid ground pounder Pontiac!!

Cool -- the F.A.S.T guys are getting 500 cubes out of their 400's .

[Half-Inch Stud]

521 cubic PMD Sounds reliable enough with the forged crank. Just open the EXH valve just past 90 ATDC.

[Polar-Pontiac]

Tick,Tick,Tick,Tick,Tick,.....

[TIN TIGR]

too many guys think like bracket racers here..if the crank and pistons fit, run the thing..

i like the stock 4.21 stroke, 3" main, and just wind the pee out of it better, but everyone has a preference

[BVR421]

could be cool for stock appearing class with minimum vacuum requirement. iron heads and qjet, mild solid roller, shift at 5500

my mind is wandering to a 4.75 crank in my old 63 389 sedan for a lazy street motor with a big highway gear
who am I kidding I cant even afford a tank of gas for my everyday car much less a thirsty 521

[goquick]

I guess the 5.050" stroke Pontiac crank combo someone I know has must have been a time bomb for the 6 years he ran it? He turned it 6300-6500 rpm every time he made a pass. 3500 lb car with RAIV heads ran mid 9's. He also tore alot of rear bumpers off it before he finally put wheelies bars on. He had 6.535" rods from BME in it too. Torque monster!

[TIN TIGR]

thank you go quick..the bbc tall deck is the same height(near enuf) as the yak, and nobody thinks 4.5 inch strokes are big..thats a std customer item for me..i wouldnt hesitate to drop a bigger crank in if it was what they wanted..

[440GP69]

So the 6.535 would work with the 4.75, Its definatley outside the box thinking But i kinda like it in a nice 400 block.

[Jack Ferris]

Originally Posted by BLACK70GTO

For about the same $ as a 462-472 you can have a 521cid ground pounder Pontiac!!

This is the only part of the initial post I personally agree with but who am I to say anything. Torque is wonderful until it becomes greater than what the car can possibly do to effectively plant it to the ground. At that point your a$$ is being handed to you on a platter as you burn the tires to the ground sitting in one spot. I agree with tin tigr and that is the power made up the rpm range is a lot friendlier than the Caddy making torque off idle. But this is a world of choices and the freedom to choose to do what ever the hell you want with your motor. Heres to being different (Im toasting as I say that).