Haven't tried it, but I have always thought it would the thing to do. Biggest bore possible, short stroke, and rev it hard. Seems like you could internally balance and take a lot of weight out of the crank doing this. I'm not sure how you would go about getting .250" less, but .100" could be done easily with a stock crank and chevy rods. It makes sense to me, because the block is the weakest link. Destroking it and getting a good internal balance should take a lot of load off the block, although I guess it would be added right back in as you pushed the RPM. Could you imagine such a setup with turbos? ________ MARIJUANA VAPORIZERS
Do you really want a sreamer with a 3.250 main? Sounds like disaster to me. I have an old Grumpy Jenkins 330 small block, that is a screamer,9500 rpm. Its a dog under 7000.
....along the same lines but in a diferent direction, why not a stroked 400 ?? Would the increase in cyl. wall thickness help with the block flexing - or is it too little to make a diff. ??
Bruce, I have thought about this quite a bit over the last few months. Gary Kubisch and I wonder if it wouldn't be an advantage if your going to run a heavy car down into the 8 second range. With a 4.320 bore and a 3.700 or 3.800 stroke you could build some nice power while keeping bearing speeds down which of course requires less oil to keep the rod bearings a float. I believe at some point you have to be able to turn these engines to 7500 plus RPMs or we will never get a naturally aspirated race car to run fast. I also agree with 10sec350 about the main bearing journal size so I would make bearing spacers for the top of the main journal and have billet main caps made. Here is a link to an Oldsmobile site that sells bearing spacers for the Olds. http://www.oldsperformanceproducts.com/products.asp At the bottom of this page you will see the bearing spacers. These will not work for us but it couldn't be to difficult to get a set made. Again... smaller bearing surface equals less oil needed to stop metal transfer. I also believe this would reduce the weight of our crankshafts quite a bit. I have also heard that an older nailhead crank may work. Has anyone ever compared a 455 crank to a 401 nail head crank? If anyone in the Cleveland area has a nail head crankshaft I would love to see it and compare it to a 455. Lets keep discussing these possibilities... maybe I will build a new engine. Later
401 and Destroke... Bob Gilland worked on putting a 401 steel crank in a 455 with billet caps but feel out of racing before he finished. Here's his e-mail and you can reach him at Performance Concept (706) 234-2414. I like the ideal of destroking as I am on the poweradder route but rpm makes et's. Without rpm you have to make more power and have more gears with less machanical advantage. I am going the route of 3.7 stroke on the new block and cutting the crap out of the deck to get the rod length down. Although I think a 3.800 stroke would help with oil control. THe less stroke, the less centrifugal force there is on oil at the rods thowing it out. SBC have oil problems on there 434 stroker setups with oiling. Not all but it takes a good engine builder to be able to control the oil in the engine and that is with a SBC. The large mains don't help things either. 3/4 groove bearing as with the added oiling holes in the top bearings are a huge help. I think that is a step in the right direction until there is a better/simpler solution to the oiling issue. Our heads don't flow enough for what we have or have the port cc's to support what we do. This is a big hurdle to make power over 6500 on strokers. They just run out of air. I'm sure Kevin will chime in on this as he is looking at the same approach and has some good ideas or maybe something in works??? :TU:
Yeah John, I was thinking of building a 494 but am not crazy about the idea of a longer stroke. Could be harder on the block. I have long considered the short stroke (compared to other big blocks) to be an advantage. plus a longer stoke motor is going to hit the tires harder (torque-something that I don't need more of) as my cat had a heck of a time digging it's claws in at Quaker. I figure if I'm going for a set of aluminum rods I might as well rev the thing and a shorter stroke seems to be the way to go.......but can the oil system keep up?
Bruce, Dont use any data collected from Quaker this weekend. The air was crap and the track was crap because of the air. I dont know if a longer crankshaft stroke is that tough on our blocks. I had a conversation with Mike T. about this and he says someone he knows had a computer program that showed the stresses go up with a long stroked crankshaft but I am just not sold on this. I think HEAVY components are much tougher on our blocks than stroke. My engine has over 80 passes and most of those were 7500 to 7600 rpms. Rick, I dont think there is a problem making HP above 6500 rpms with a 535 Buick. My engine is still PULLING at or above 7200. But again we have look at the weight of the components. I read an article from Reher Morrison about the use of titanium valves. They changed from SS to Titanium and the engine made additional power from 7200 to 7600 rpms. When starting to spin these engines above 7000 rpms you simply cant use the same components as used in a 6800 rpm engine. I just does not work. You also brought up the point of decking your new block. Our blocks having a 10.575 to 10.600 deck height is great for big cubes but horrible for small cubes. If your going to use a lightweight piston that has a compression height of 1.200 and a stroke of 3.700 then you need a connecting rod that is 7.500 plus in length. This is the biggest problem with small cubes in our Buick. For anyone building a Buick..... PAY ATTENTION TO THE OILING SYSTEM. Make sure you can do everything possible to improve oil VOLUME and oil CONTROL. Good conversation!!!!!
I have been doing some thinking on this whole setup.I want to destroke to a stock crank to 3.800 but with the pistons I have hear 1.330 compression height and a 10.550 deck height I will need a 7.300 rod to put the piston .020 in the hole.The thing that is holding me up is that long rod I know people have said pick a stroke and a compression height and order rods that fit.The 1.9+ rod to stroke ratio worries me.I think the piston speed will be to slow to allow the motor to work right down low.Now with a power adder I wouldn't care you have artificial torque.In Ricks case with the bulldog block (when we get it) We want to take the deck height to 10.300 or less This way we can take .250 out of the rod.We will also run between 1.3-1.45 Compression height so we can keep the ring package down farther in the hole and keep the wrist pin out of the oil ring.I don't like gl spacers and pin buttons add weight.The oil ring needs to remain stable oil in the chamber in a Nitrous motor is ugly :blast:. As for the heads running out above 6500 I don't see it happening on Hp alone but on Nitrous the volume of nitrous you need to push through the head to make big hp will limit us.The port volume needs to be 320 or so to use more than 300 hp worth of nitrous.We all know Rick likes his spray
John Brings up another point.Titanium valves would help alot in a buick :Brow: With the small base circle we are stuck with right now and the short rocker pivot length rocker arms the valve acceleration in these motors are astronomical So light components are required when you start going nuts with rpm and cam design.Valve train stability is very important in the quest for hp curently the buick valve train is very unstable.I would like to have the ability to spintron test a buick motor just to see how f'd up it is. The oil system on a high rpm buick needs to be either external wet sump or dry sump.This would allow you to control volume and pressure with out killing the cam bearings.
Hey guys. Just so you know , the deck height on my race stuff is about 9.200( close to small block). Its so short I have to use an external water pump. The bore is big(4.622) and the stroke in tiny(3.41). Of course it is dry sump oiling. The rod is comparitively long (6.600 long with Honda journals --1.880)and I keep a short piston (lighter) and this also keeps extra thrust off of the cylinder walls. We coat the piston tops and skirts. Although it is an interesting idea to do it with the buicks , you have got to spin a motor like this hard. Because you are killing the torque also everything would change (converter, gear, etc). Just some food for thought. George in DC
Jim Bell was destroking years ago.For roundy-round racing they had to keep cubes under 380",he destroked 430 and 400 motors,they screamed. gary
If I remember correctly Todd from GT Performance In Canada years ago used a nailhead crank in his 455's and they worked very well. Too bad no one is around who knows for sure o No: this is just what I was told Ken
