Stupid Big Block Question

Does anyone know how much a gen 5 big block can be bored and how big can I go with the stroke?

Mark IV and Gen V blocks can be safely bored to 0.060" over

A 4-1/4" stroker crank can probably be installed but as with any production block, clearances need to be checked.

The 4.25" cranks fit fine in the late model blocks.

Weren't there some Gen V 502 blocks that had siamesed bores? If it's one of those it can be bored to 4.500". Otherwise don't go more than 60 or 70 over. 60 over (4.310" is preferred by many engine builders.

Rich

Is it possible to go any bigger with the stroke?

With a stock 454 Gen V block? Probably not. To clearance the block for more stroke, you risk hitting a water jacket. Going longer than 4.250" stroke usually means also going to a tall deck block so that the wrist pin stays out of the piston rings.

If you want a really long stroke, buy an aftermarket block. Going to a much longer stroke means having the pan rails clearanced and the bottom of the cylinders clearanced. All the good aftermarket blocks are already clearanced for a stroker crank and are cast differently so more clearancing doesn't cut into water jackets. The alternative is to fill a production block with blok fill.

A 454 block has a 4.250" bore. The 502 blocks are 4.470" and can be bored to 4.530". I don't think there were any production 502 Gen V engines.

4.25 cranks are an easy fit when done correctly. the blocks can be bored more than .060 but need sonic checked first.

So no recommendations for anything over 505ci on this stock block? I will take this advice thanks for the info. It seems I have a different motor and motor question every week and u guys take the time to answer all of them. Thanks

Personally I'm running a Gen V 502 block that is bored .100 over. Need to sonic check them for sure. Recommened max bore on mine was 4.5 which was only .030 over, but it wasnt' big enough for me :) What are you looking for because you will have no rebuilds in the block if you go big.

Personally I'm running a Gen V 502 block that is bored .100 over. Need to sonic check them for sure. Recommened max bore on mine was 4.5 which was only .030 over, but it wasnt' big enough for me :) What are you looking for because you will have no rebuilds in the block if you go big.


That's what I thought (that there are Gen V blocks with siamesed bores). But unless it's a siamese bore block, 70 over (4.320) is about as far as you want to go. Only exception is some of the early, rare truck blocks.

Rich

I wanted to go as big as I can possibly go right now. In the future once I get a little more driving experience under my belt (and more money) then Ill go huge. Im trying to break into the drag radial/stock supension circuit so I was gonna hit it with a pretty big shot of nitrous after I get some bracket time.

Depending on your bore size you can go anywhere from 496-510 approx. unless you want to go aftermarket block. That can get expensive though. If you can fit it, get a tall deck block and then you can run a 4.375 or 4.5 stroke :) Of course those would be earlier Mark IV blocks, not a Gen V. Also Gen V have no provision for a mechanical pump, just FYI.

Keep the overbore to a minimum if you are going to be making your hp with the juice. A good ring seal will be worth more than the gain from boring. Go 30 over (4.280") with a 4.25" crank. That's 489ci with a nice, thick cylinder wall and you can use a shelf piston. I prefer a short rod with big nitrous to decrease dwell at TDC and keep peak cylinder pressure down a little, but that is an endless debate.

This is assuming a stock, non-siamesed block.

Rich

I haven't done too much research but short rods are good and bad. Stock is too short and tends to push the walls out, but I've read that a lot of builders want a shorter rod because they tend to build torque early. Those same builders also say that if you don't start getting your torque in by 2000-2500 then your motor will be a turd, lol.

Wat kind of pistons should I go with? Do I absolutely have to use nitrous spec'd pistons or can I use any forged piston?

I haven't done too much research but short rods are good and bad. Stock is too short and tends to push the walls out, but I've read that a lot of builders want a shorter rod because they tend to build torque early. Those same builders also say that if you don't start getting your torque in by 2000-2500 then your motor will be a turd, lol.

I probably shouldn't have opened that can of worms. I think the hp difference between long and short rods is minimal. But with a blower, or especially nitrous I think anything you can do to limit peak cylinder pressure near TDC is useful for longevity, not for hp. Also maybe a trivial difference, but if (as I believe) the power comes out the same why not?

A high rpm NA motor should have a long rod. Again, not for hp. In this case, keeping the reciprocating weight down (longer rod = lighter piston greater than the increase in rod weight) will lower stress on the rods and rod bolts at high rpm and it may accelerate a little faster (in a car, not on the dyno).

Rich

Right now since funds are limited I rather go with longevity...

I wanted to go as big as I can possibly go right now. In the future once I get a little more driving experience under my belt (and more money) then Ill go huge.

Might as well do it now instead of doing it twice.

You've never said what the bore size is of the Gen V block. 4.25 or 4.5(ish). Go big now and get a 4.500" bore block. A short deck block with a 4.250" stroke makes a 540 and will fit anywhere a smaller BBC will fit. The 540 can be bored out to a 565. Going bigger than that requires more stroke and a tall deck or a 5" bore spacing block which cause more problems fitting it into many cars. 572 and 632 are the next most common large sizes although they have engines even bigger than that which are technically Promod engines. I don't have the $70,000+ for a 700+ cubic inch engine that can make 1500 hp NA.

Well going with any other motor at this point is not gonna happen unless it just comes outta nowhere (school is taking ALL of my money) so I have to ease into it. The bore is 4.25 (454).

Easiest and cheapest way is to just put a 4.25 crank in there and hone the cylinders for a stock sized piston again if the cylinders haven't been pushed out too much. If you can afford it get at least a +.250 rod and you should be able to easily find a light off the shelf piston. Not sure how much is a big shot for you, for me 200 is a big shot, while for others 400+ is normal. I would think that anything less than 200 you can run a normal N/A piston. Anything larger and you would have to step up your piston/ring combination. Probably worth it to just get a nitrous piston in the first place as long as it gives you the compresson you want.

Yeah its gonna be a 200 shot for me. A standard bore coupled with a 4.25 stroke would give me 477ci? All of the cylinders in the block along with the crank and rods look extremely clean and if I wanted to just put the bottom end back together and drive it on the street, I could just get some higher compression pistons and use some closed chambered heads I have and call it a day. The cylinders dont even need to be honed.

Yeah its gonna be a 200 shot for me. A standard bore coupled with a 4.25 stroke would give me 477ci? All of the cylinders in the block along with the crank and rods look extremely clean and if I wanted to just put the bottom end back together and drive it on the street, I could just get some higher compression pistons and use some closed chambered heads I have and call it a day. The cylinders dont even need to be honed.

Do it.

Rich

Agreed, if you have all the parts in good shape then use what you got and spend the money you have set aside on things that make horsepower like better heads.

I also have a 383 I thought about swinging in until I get the 454 done. And I also have a 402 block sitting around that I thought about throwing the 454 crank into but finding stroker pistons for this weird combination sucks. Im just all confused on what to do right now

Just run the 454 for now, it's an easy combo that will give you good power for very little investment.

Got ya, thanks for the help everybody

...The cylinders dont even need to be honed.If you are putting new rings in, you will want to put a new hone on it. Two reasons: 1) Bust any glaze on the walls, 2) Your new rings won't seat properly with out it. Do it right the first time.

Thanks I will do that. I would hate to put it together and have those types of problems.