Heavy Rod Headache
I was told by my machine shop that I shouldn't use Six Pack rods in my build because they are too heavy. I will be using TRW 2295 pistons, 906 ported heads, a solid lifter 509 camshaft, and roller rockers. Should I switch to LY rods or is this a real concern?Todd LangleyVia e-mail
The Six Pack rods are heavier, but they have thicker beams than the LY. They are a stronger rod, and with ARP bolts, I'd rather have the Six Pack rods than the LY's swinging those heavy 2295 domed slugs. Actually, the Six Pack rods are about the same weight as the typical aftermarket H-beams everyone is using these days, and no one seems too concerned about the weight of those, though admittedly the H-beams are considerably stronger. Your 440 parts list is exactly the kind of combo that was the hot setup 20 years ago, and back then the Six Pack rod was the ticket, and I still consider it a better rod of the two you mention, when used with heavy pistons.
Will My 340 Blow?
I have built and run a number of 340-based engines in the past without a problem, however, I am presently accumulating all the necessary parts to build a stroker combination that should produce well over 500 hp. I am told the production block I am planning to use will likely fail, even though it is only .020-inch overbored and has very little core shift. What is the practical horsepower limit for the passenger car block in a street/strip application? Should I buy a 340 restoration block and use it instead? Secondly, what is your take on the Schubeck composite lifters for long term use?
What ever happened to that 600hp 408 stroker that you built in 2001? Norman Connor Via e-mail
At 500 hp, your factory 340 block should hold up just fine. It's hard to pick a limit, since guys are always pushing power up, and what is acceptable life for one racer is unacceptable for another. Your real enemies to longevity are rpm and detonation. Keep detonation in check, and rpms within reason, and the engine will lead a long and happy life. With a stroker combo, you will need less rpm for a given power level, but the piston speed and thrust loads go up. Keep the reciprocating assembly strong and lightweight, and you've taken a major step forward towards longevity.
To put a number on it, I would feel perfectly safe with a factory block at 500-550 hp, if the bottom end is built with good forged parts. I know guys with 600-plus-horsepower stock-block small-blocks that have survived many seasons of racing without block issues. There are too many variables to put down a hard limit, but at 650 normally aspirated horsepower, I'd be getting concerned, and definitely would want aftermarket caps, studs, and the best internal components. What an aftermarket block buys is peace of mind and a good measure of insurance. Some guys just can't afford it and roll the dice. If the budget allows for it, the MP block would naturally be the first choice. In your particular situation, looking for 500 hp to run on the street, I wouldn't sweat it.
I have no personal experience with the Schubeck lifters, though most of what I hear is positive. Your best bet is to contact the manufacturer and ask about longevity in long-term street applications.
My 408 is on the stand. I gave up my W-2 heads to help out a friend who was in a health-related jam, and those heads eventually ended up in a former associate editor's car. I had a W-5 top end for the engine, which made about 670 hp with a tunnel-ram, but the valve seats in those heads wiggled after running on the dyno, causing valve leakage. I just never got around to recutting the seats and bolting it back together.