turb0racing

Im going to be turboing a GM 502 block. They come 4 bolt, forged crank and rods. Im going to start off with low boost stock bottom end. Then i plan to eventualy replace the rods and pistons with some ross pistons and eagle rods. Bore .02 over if the walls are good for it. And crank up the boost to the teens. I hope to have a 8 sec car so im going to need around 1k hp. I know its possble with this much displacment and airflow but can the cylnder walls take this much power? Are there any ways i can strengthen the block like with studs going from the outer blcok wall to the cylnder walls like the import guys do? Or should i be fine as is?

Damon

1000 HP is outside my expereince. I'll jsut note that there are a lot of guys running production BBC blocks into the 9s and faster. At least they claim it's a production block. Mods done to it? No idea. The BBC is a damned stout block even in stock production form. Fastest I even built a 454 was probably around 650-700HP on nitrous, going mid-bottom 10s in a fat pig street car. They thought of the block not being strong enough never entered my mind.

I would think that high RPMs would be a bigger problem for it than something that turns modest RPMs but with big bagfulls of torque (boost, nitrous). Vicious RPMs are uually what usually starts to make normally solid objects start to "move around" in unnatural ways.

rskrause

Those blocks are strong. I don't see any problems with what you have in mind. However, if you are buying new an aftermarket block isn't all that much more $$$.

Rich Krause

turb0racing

It's used and cheap. Thanks!

got_hp?

remember to take pics of the buildup and post them for us!

442olds

502 blocks have siamesed cylinders very strong. However if they are like the 454 Gen 6's the most the can be bored over is .060. So be carful how far you take them out. They already have a huge bore however 4.5" (I think). The blocks are strong but you may want to look at a few marine 502's and see what extremes they are being pushed too. I think there are some super charged and turbo'd marine 502's making well over 1200 hp! I don't think you'll have any problem reaching your goal as long as you keep a little cylinder wall in that motor. Put in some longer rods if your worried about it and reduce some of the stress the pistons put on the cylinder walls. You should try for at least a rod ratio of 1.75 or a little bigger if your going to be building a heavy breathin' drag motor anyway.

Another thing I forgot, if its a Gen 5 block your head choices are pretty small. Some aftermarket head companies have heads the are good for Mark IV, V and VI blocks. If its a Mark VI block you get just about any head you want and have no worries.

SStrokerAce

Yeah stock bore on that puppy is 4.470" so if you rebuild a 4.500" is a standard piston.

It should hold what you are looking at no problem.

Bret

1994B4C

1000HP with no worries about the block at all. I think the 502 came with a steel crank, 4340 rods and forged pistons. If so I wouldn't worry about any of that either with just a 1000HP. Maybe put in some good rod bolts and turn it loose.

LameRandomName

I am not certain if it's the same block, although I think it is, but GMPP just released a 572" BBC that has passed the 50 hour WOT durability test, so I have to assume that the block is fairly strong.

I know the 502's come with low tension oil rings, so you may want to change that.


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Well, I was wrong, the 572 uses a tall deck bowtie block.

Take a look.

That same site has info on the other GMPP crate engines, so maybe you want to look around a bit.

turb0racing

I wont go anywhere near .06 over. I mentioned im going to give it the mininal overbore .02 if possible. Im going to get custom Ross pistons anyways so it would be the same as geting more standared .030 over pistons. Pics for sure!

Van

I just noticed in your sig that you plan on using a t76 with your 502..... Are you planning a single t76 on that motor?

turb0racing

Well its not a T76 its a 76mm comp inlet dia holset turbo. I have no clue on the compressor map or if there even is one, but it seems to be a good sized turbo for a mild 502.

I used ray hall turbomap with the bigest turbo they have, the T72, the 502 maped out a bit small. But my turbo is 4mm larger and it has a massive scroll in the housing. And it might not be a perfect match with most of the powerband in the peak island. Its what i have and a $2-3000 aftermarket turbos are out of question for a JY turbo build.