rallysport92

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

Stephen 87 IROC

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.

MachinistOne

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

rskrause

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

rallysport92

Is it possible to go any bigger with the stroke?

Stephen 87 IROC

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.

byrons1502

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

rallysport92

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

ulakovic22

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.

rskrause

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

rallysport92

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.

ulakovic22

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.

rskrause

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

ulakovic22

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.

rallysport92

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?