Reply to "Stroker Motor Questions by Dave F #5972"

Dave, Welcome to the DTBB!

your kind words are appreciated, thank you. I'm sorry to read that Katrina impacted your life, for that you have my wishes for your continued recovery from the devastation.

My first thought is a fuel injected all alloy 427 Clevor sounds pretty BITCHEN! Way to go Dave, I'm sure there are many owners that would love to have the same motor in their engine bay.

The Eelbrock heads are so new, I just don't know what their capabilities are out of the box. I've yet to read any feedback from an owner running those heads. The flow figures certainly aren't as good as those of the Australian AFD / CHI 2V heads. In general, Edelbrock heads for any motor have a reputation for not being the top heads out of the box, but head porters are normally capable of porting & extracting much more performance from them. Your performance goals seem modest enough that I'm sure one way or the other, out of the box or ported, the heads will be capable of making a good compliment to your motor.

Don't be self conscious about wanting that magic 7 liter displacment. Who wouldn't?! From what I read & hear from other owners, you are not alone. The issues with stroker motors in a Cleveland or Windsor package tend to boil down to rod length to stroke ratio (R/S ratio) and the wrist pin intersecting the oil ring groove, as you have alluded to. The piston is pulled pretty far out of the hole at BDC, but I'm not aware of any kits where that has become an achilles heel.

The R/S ratio issue is a non issue according to some very very highly respected engine builders. There are others however that believe it is important. So there are skilled practioners on both sides of the issue, all with mechanical engineering degrees. In a conversation with a well respected engine builder a while back, he kindly put it this way: the R/S ratio is an issue, but not the most important one, there are other issues that supercede it, it is not given the importance in regards to high rpm race engines it once was. With the advent of inexpensive Chinese stroker cranks the industry has blown the past rules regarding R/S ratio out of the water.

One example of this is the new Z06 Corvette motor. It's 427 cubic inches, with a 4.125" bore & 4.00" stroke. The SBC motor has a shorter deck height than the Cleveland motor. I haven't read how long the rods are in that motor, but I feel safe in writing the R/S ratio of that motor must be less than 1.5:1, yet that motor has a 7000 rpm red line (if my memory is correct).

I know of a fellow Pantera owner who has hired a very big name engine builder to build his 4" stroker motor, and this builder is going with a 6.2" rod because he comes from the school that R/S ratio is important. When I built solid lifter Cleveland engines, I always stuffed 6" rods in them because the engines seemed to run better above 6000 rpm. Small block Chevy guys did the same thing. I had it drilled into my head that the R/S ratio was important. Members of the camp that place more importance on the R/S ratio normally want a minimum ratio of 1.55:1.

The other side of the coin is that when the wrist pin intersects the oil ring groove, the motor burns oil. Some people don't mind dumping a quart of oil in their crankcase every so often, some don't drive their cars very often or for long distances, these folks don't think oil burning is an issue to sweat over. Speaking solely for myself, if I built an expensive high performance street motor, the last thing I want to see it doing is burning oil. Additionally, I drive my Pantera long distances, I don't want to have to tote along several quarts of oil on my trips.

For a reliable, smooth running street motor as you have described, I would place more importance on the location of the wrist pin, than I would the R/S ratio. The normal 4.00" stroker kit for a 9.2" deck height block and pistons with Cleveland valve notches includes a 6" long rod. The R/S ratio of these kits is 1.5:1, and the wrist pin intersects the oil ring groove. The 3.85" stroker kits have the same length rod, the crank throw is only 0.075" shorter, yet the wrist pin misses the oil ring groove. So it would seem your choices are to either build a 427 cubic inch motor and tolerate oil burning, or build a 411 cubic inch motor and avoid oil burning.

But I have a twist for you. Spend the extra money for a set of custom sized rods, and order them in a length of 5.925". Use them with a 4" stroke crank. You'll be able to use a piston with the same compression height as the 3.85" stroker kit, therefore the wrist pin will miss the oil ring groove. The R/S ratio of this combination will be 1.48:1, which I bet is better than the Z06 Corvette motor, it is the same as the R/S ratio of the production 400 cubic inch small block Chevy, which had a 3.75" stroke crank. This should be acceptable for a street motor with a red line of 6000 rpm to 6500 rpm.

Before you think that's a brilliant solution, price the rods, but don't throw any bricks at me, OK? lol................

Your friend on the DTBB