Quote:
Originally Posted by Cliff R
I don't know if there is a "proven safe lobe" to run in a stock block even with a brace in it. Keep in mind with the spring pressures required to control the valve action with these solid roller cams it's like having 16 fat guys standing on your pushrods. The side-loading is extreme with solid roller cams at the spring pressures we run on them aggressive profiles or not......IMHO.
Here I built ONE stock 455 block engine with a solid roller cam for full race duty and it last 11 runs before the lifter bores caved in and took out the entire engine.
Prior to that deal we had rebuilt and "upgraded" that engine half a dozen times. It came here first time with flat top SD pistons on stock rods topped with #48 heads and a Comp 292 Magnum cam in it. That engine BARELY busted the car into the 11's so the owner wanted some changes made to it.
The heads went to KRE for porting and they supplied a 260/260@ .050" flat solid for it. Added Crower rods and kept the SD pistons but put lighter pins in them. That put the car solidly into the 10's, but after a few years the owner wanted more so we went to a set of 330cfm early Edelbrock round port heads and a solid roller cam. That cam was 264/264 on a 110LSA but not overly aggressive. It really didn't run much faster than the flat solid cam so the owner opted for a larger solid roller cam 276/284 with over .700" lift. I did NOT like the change and insisted on a lifter bore brace, but it didn't help. We lost the lifter bores after 11 runs and took out the entire engine.
It wouldn't have mattered anyhow as the power level was exceeding the capabilities of the block. I found a couple of main cap dowel pins in the oil pan last time it was apart so the writing was on the wall before the lifter bores caved in.
We replaced that engine with a KRE 505 with High Port heads and it has survived nearly 20 years of HARD use with one set of springs and rod bearings rolled into it. We also had to upgrade to Crower Enduro rockers and 13 out of 15 of the Scorpion rockers were cracked.
Hard lesson learned with pushing the limits of the stock blocks. If I were still in the engine building business we'd very quickly go to an aftermarket block with that sort of engine. No solid rollers with PAC springs and super high compression would end up in a stock block for any reason, even if it was for drag racing purposes where it's only loaded 9 seconds at a couple dozen times a month. I'd just build an aftermarket block from the start and sleep a lot better at night.......
|
That sort of thing is always in the back of everyone mind who does this sort of thing with a stock block.
It would suck if it broke. I do have a IA2 with 80% of the stuff already bought.
What brace did you run ?
That cam was bigger than anything I would try in a stock block. No PAC springs either but anything can happen.
I tried to sell the block but no one jumped so I put it together with a few upgrades.
Not even going to try getting it into the 9s.
I was temped to just run the same UD cam I ran for years and years. This cam is just a tad bigger.
But IA2s exist for a reason.