I'm thinking about buying a large bore bow tie, but have a question as to how much stroke can these blocks accept. From what I've seen GM says they're set up fo a 3.75" stroke. Can a 4" or larger stroke be run in these blocks w/o issue? I can put my hands on one of these blocks for a decent price, but I'd like to see if I can get away with a 4" or 4.125" stroke before I lay out the $$$$... a decent price still isn't cheap, LOL.
I need a good place to bolt the new Brodix heads...
Steve...

 

I guess it depends what you mean by "w/o issue". The Bowtie accepts a 3.875" out of the box. Using a 4.00" crank will typically requiring clearancing the pan rails and/or the rod bolt heads. Longer than 4.00" would not be "w/o issue" to my way of thinking.

Rich

 

Good point Rich, I should clarify "issue"... for me that means hitting jacket water. I figured on taking some metal out of the block. I'm just wondering what folks are getting away with in the stroke department.
Steve...

 

Steve,

A 4.0 will go with very little work. 4.125 will require machining down on the counterweights. In my opinion, 4.0 is the largest I would put into a "standard" sbc block. For the record... there have been standard sbc's with 4.250 stroke cranks in them and this was many years ago. So yeah it's been done but don't do it.

If you really want to push things up then why not go to a sprerad pan-rail block like the iron eagle or rocket? A 4.0 is a drop-in with these and a 4.125 is plenty feasible.

-Mindgame

 

MG: doesn't the Rocket have a raised cam bore to go along with the spread pan rails? Not that this is a terrible thing, but it does add another level of cost and a certain amount of complexity to the buildup. Ditto for the cam bores, which are also larger than standard if memory serves. To me, the best place to start a big displacement smalkl block is the Motown. 4.250" x 4.000" and you have a big-bore 454ci small block without having to touch the block.

Rich

 

I thought about the other blocks, but I'm trying to keep the build up cost within reason... for once, LOL. The block that I can get is a new large bore bowtie that has 90% of the machine work done on it such as cutting lifter bores, align hone, etc... All I'd need to do is massage the rails and hone the cylinders to final size. The bores were even sonic tested. I'll be staying in the 4" range on the stroke to keep the camshaft out of the clearance picture. The $$$ saved on initial block cost, machine work, custom oil pan, and a few other items will help off set the cost I'm looking at on the custom intake and custom exhaust.
415" SBC with Brodix heads and a big turbo should get me those 11 teens I'm looking for.
Steve...

 

You're right Rich, larger cam bore (BBC size with more strength), raised cam, spread rails...

It does add a little more cost but then again, there are alot more manufacturers building stuff for these blocks now. The timing chain is not much more than a std hi-quality timing set ($60-100)... the cam is ~$50 more, the oil pans are all over the place with a lot more guys building them now besides just Stefs... so we're talking $350-750 or more.

So they're not really THAT much more expensive to build. Not as expensive as they were when they came out that's for sure.

The nice thing about the Rocket is that a 4.0 crank is pretty much a drop-in and 4.125 is very easy. A 4.25 is doable and the bores can go as large as 4.2" before you need to sleeve it. That's a huge smallblock built on a bulletproof bottom end. Of course you pay for it but chasing big cid in a small block has never been so cheap.

The Motown IS a nice alternative but for the ultimate sbc build I still like the Rocket and Iron Eagle better. Especially for an all out solid roller street build. Mild cammed blower or nitrous and I might just go Motown.

Now Steve here is going to a turbo!?!... geez, I'm starting to feel puny with my big NA sbc ideas. Everyone's going to superchargers and turbos these days.



Sounds like a deal you can't pass up Steve. For your goals I think you might not need a raised cam block anyways.

Good luck.

-Mindgame

 

Mindgame,

Don't feel bad, even though I'm doing a couple of "helper" motors now, I'll always be a NA kind of guy at heart.

Steve,

A 4.0" fits in the Bowtie pretty easy, like clearancing a standard SBC/LT1 for a stroker crank. I agree with MG and Rich that a Motown is a dam nice way to go too.... You might want to look at a 3.800" stroke crank. You can use off the shelf 400 pistons (depending on what Brodix heads you are talking about! There are even 17/18* off the shelfers now) with that stroke and end up having the motor zero decked for you. Saves both piston cost and more machine costs and the turbo is probably not going to notice the 20 cubes difference. Still a 427/434 SBC was a certain aura too it vs. a 414 cube SBC.

Bret

 

Bret, I'll be looking at a set of custom slugs unfortunately. The heads I have are 12* and the only off the the shelf pistons I've found are by Diamond, but are 13.5:1 NA stuff. I'd like to run the 4" stroke, but at the same time I need to start figuring rod length & compression height into the picture. I plan on running well over 20 psi, so I need to do some homework on the ring package here. I really appreciate all the input guys! This should be a pretty interesting project when it's all said & done...
Steve...

 

That's probably gonna want a good sized dish then because most 12* stuff i've ever seen doesn't have the largest combustion chamber. Even for a high CR on a turbo you'll still have a good amount of dish there. Probably looking at a 5.85-5.70" rod on that puppy just to get enough compression height for the dish and ring pack.

Bret

 

Haha, and all youre looking for is 11s?

 

I was actually surprised at the chamber volume on these heads... 67cc according to Brodix. I should have them in my hands next week, but it will be a while before I'll have a chance to cc them.

jonaddis84, I just want to be sure that I can hit 11's year round...
Steve...

 

With that engine pushing over 20psi you'll be pulling those times year around in REVERSE. I guess you're building a monster there steve... most ~400 cubic inch SBCs i see pushing around 20psi are usually hitting over 900rwhp (with 23* heads). Dan millen has a 375 cubic inch windsor with a 104mm turbo pushing 27-28psi of boost. As you can see he in the high 6s at over 200mph in a damn near full-bodied 99+ mustang (there was an in-car video of him driving it down the road and then through a burger king drive-through on LS1Tech)

I'm definitely going to be watching your progress on this build. 415", 12* heads, and 20psi will make insane power... i'd bet on 11-1200rwhp under 7500rpm. Good luck man