SB

iTrader: (1)

#1 for NA BBC with decent cam: http://diamondperformanceparts.com/home.php?cat=282

#2 : Stainless MArine

midwest272

Not to hijack , has anyone got any experience with the KE that Diamond sells ? Pulling a set of cmi sweepers off a side by side app. and would like to know the space left between motors . Those sweepers are a pain to get around and didn't hold up like price would suggest........ there E tops are pretty tough almost 15 years on a set no issues .

I would give away 20 hp a side to have piece of mind when it comes to exhaust manifolds

endeavour32

iTrader: (4)

The only thing you will be giving up is bling factor, I am willing bet my last dollar that the KE's make more power than the CMI'S. . I had them on a single so I can't comment on access with twins.

MILD THUNDER

iTrader: (3)

If you look at the chart i posted in post 3, youll see the eickerts outperformed the e top cmis.

getrdunn

iTrader: (7)

To OP I've had both exhaust in question. Lightnings were awesome and had a sound of their own and performed well. Had them on a 454 twin build with 502/465 hp cam with dart oval port heads. Engines made 480 plus hp and no issues with reversion what so ever. Gils are notorious for cracking etc and can lead to multiple problems if not caught right away. Not all of them of course however just a known fact. So in a nutshell between the two in question I would without a doubt go lightning. Easy to change plugs also.

On the other hand there is a few sets of stainless marine manifolds here on OSO for sale as well as on eBay and craigslist if I'm not mistaking. I do know anyone I've ever talked with who has had those really like them and seem to be trouble free.

Both Gil and stainless marine offer dry risers. Consider what cam your going with and go from there. Any of the manifolds/headers will perform well within your build and doubt you'd see much gains if your staying under 500 hp.

Craney

iTrader: (2)

How many threads have you read on here that my Stainless Marine exhaust are leaking!!!!

MILD THUNDER

iTrader: (3)

The exhaust system on a big block chevy, is a major player in power output. I used to think years back, that bigger better exhausts, were for high rpm only racing stuff, and usually, when installed on a fairly mild bbc, would kill torque. That is just not the case.

A good exhaust system can substantially increase midrange torque, by quite a bit (as well as upper rpm power). We spend what seems like an eternity here, arguing over intake port volume, a few degrees of camshaft duration, seeking a torquey engine combo. Spend money on cnc port work, trick valve jobs and bowl blending, for better flow. When in fact, the results of all that work on the intake side, could have been achieved by simply bolting on a better exhaust system.

I have stellings headers on mine now, but pretty certain my next mod, is going to be Stainless Marine GEN 3 manifolds.

I'd like to see if we can organize an exhaust shootout this winter. Seems like about everybody is building a 700HP N/A engine these days. It be interesting to see what changes in output are seen at that level, by trying various exhaust setups on the dyno. Maybe try some GIL's, Eickerts, Imco's, CMI's, Lightnings, SM's, etc back to back.

I've seen quite a few engines come off the dyno that were dyno'd with big race car headers at the dyno shop, and end up really rich in the boat when the typical short runner wet marine exhaust is bolted on.

Im pretty sure that at 700HP level, running a short runner manifold, like a GIL, into a 3.5" gas tube, especially if water is mixing in, is a power killer. I'd imagine water in the tube, is probably choking that pipe down to the 2.5" volume range.

getrdunn

iTrader: (7)

MT you are right it would be interesting to do back to back testing on the said exhaust on 700/750 hp engines. Regarding the OP's build I honestly doubt much gains would be seen from one exhaust to another on a 454/500 hp or less engine. We did testing but it was years ago on 496 manifolds and under 500 hp plus engines gains were very minimal if any.

Raylar did a bunch of back to back testing also and posted results on this forum some time ago.

SB

iTrader: (1)

NA, The collector (riser + added connection length + tailpipe) is just as important, if not more important, than primary length and this never, I say again, never, get's considered unless maybe in marine ' tractor header' applications.

edit in: Papasmurf just learnt this with his 'sleeper' Formula.

getrdunn

iTrader: (7)

Helps scavenging big time. We use to mess around with that back in the drag strip days when dynos were far and few in between. Results would always very but knowledge was always gained regardless.