I'm leery of running a 6" rod 383 (vs. 5.7" rod) due to the oil rail support required on the piston. (The oil rail support is necessary because the additional rod length is compensated by moving the pin up - into the oil ring groove).

My intentions with the 383 are a 95% street car. I'm shooting for 8.5 compression (64cc head) so I can run cheap gas now and be able to add a blower or turbo later (boost is definitely in this engine's future). The only forged pistons to fit my needs are the JE -28cc inverted dome (6" rod) or -31cc (5.7" rod).

The rest of my combo is the Vortec Heads (for now), 268AR solid roller Comp Cam (ground on a 112 LSA) & Holley single plane mpfi (parts I've gathered so far). Eagle told me I can specify the inverted dome piston in one of their rotating assemblies - so I'm leaning towards that assembly (plus I get a discount through work).

What are your thoughts on the oil rail support? with boost? N2O?

Thanks,
Chris

 

The support is only on the oil rings- not the compression rings- thankfully. I've built a couple of long rod motors and all I ever did was what the piston manufacturer told me to do. Worked fine. I can't say whether it was still working fine 20,000 miles later since I didn't have the engine that long. No problems in 5000-6000 miles I owned them, though.

If you expect to get 50,000 street miles out of the engine I would probably be a little wary, but for a weekend warrior that's not going to see a daily commute I wouldn't worry about it.

If you're building for boost or nitrous follow the piston manufacturer's recommendations for ring gap. Build it from day one as if it's going to see boost/nitrous.

 

There's no such thing as "build it N/A now and add it later". Too many critical things need to be optimized for either the one application or the other. It's essentially impossible to compromise sufficiently to keep the engine happy under both conditions. Either build it for boost, and realize that it will be crippled N/A; or build it for N/A, and rebuild it for boost.

In particular, a cam profile that works well with low compression and boost, will result in a N/A motor that's about as lazy as a L48.

Here's one of the standard approaches to dealing with the problem. http://www.jepistons.com/pdf/2002-je38-43.pdf Scroll all the way to the bottom.

 

Yeah, what RB said about picking a combo.

And FYI, there are pistons for 6" rod 383s that have full ring grooves for all of the rings.... Ask me how I know (hint: Ross). I would bet that they make something that would work for your application too....

 

Thanks for all the responses!

Damon: I don't plan to daily drive the vehicle, but I'd like it to be possible should I want to - or even take it on long trips. I want to build a solid short block that can last 50k+. Given that criteria, maybe the potential pitfalls outweigh the gains from the extra .3" rod length?

RB83L69: I've finally found the single turbo kit pieces I was looking for (good timing). You're not the first person to tell me I can't build an engine that will perform well NA & with boost. I think I'll listen and build this engine for boost from the ground up. I didn't know about the pin buttons - that's an interesting solution.

Matt: I will look at Ross - thanks!

Chris