I lost my motor a couple weeks ago and am weighing my options for replacements. Unfortunately I live in one of those states with pretty strict emissions regulations but I would still like to get the best performance I can while staying clean. I'm considering going to either a 383 or 396 while using the same cam (.533in .544ex, 222-230 on a 112) and heads (stage 2 ARE ported factory castings). What I need to know is what affect a stroker will have on emissions...better or worse, and if the cam I'm using now is too small, is there another cam that anyone can recommend that will improve performance while still passing the sniffer test. Is it worth the effort to increase cubic inches without increasing cam size? Are there worthwhile gains to be found? Are there any cons when considering a 396 over a 383? Thanks for any help/info you guys can give.

 

Stroke the engine and leave the same cam.... it won't make much more hp but it will make a good deal more torque. You'll need head porting and a cam to extend the rpm and make your hp.

Emissions.... well I don't really know for sure but it seems to me that having a larger stroke in itself doesn't change a whole lot. More compression will make for more hydrocarbon output but the combustion chamber is still the same. If you improve the quench height, that might have a tendency to improve things a bit emissions-wise. Then there's the air/fuel ratio... so there a lot more to running clean....... well I should say that the things that really matter are not necessarily tied in with the increase in stroke. I'd say it plays a minimal part.

-Mindgame

 

more compression puts out more hydrocarbons?
you mean nitrogen oxides or did i miss something?

 

I don' t think that is the case...I think Jimmy hit the nail on the head.

In any event, I went with the stroker and passed Mass. emissions with no problems.

 

From an article on the LS6:

Maybe GM is wrong but I couldn't find anything on the subject online..... just stuff on diesels.

-Mindgame

 

Thanks for the replies. I really would prefer to install the larger cam when I put the new motor together but really don't want to go through the problems I did last year with the emissions. I would hate to spend all that money on the upgraded parts for the motor without being able to see the added benefits of the extra cubic inches. If it were easier to change the cams in the lt1s it really wouldn't be much of a problem.

 

according to those PR statements (for example) the viper v10 engine is close kin to formula one
...now i'm a big fan of domestic pushrod engines but uh...... formula one..... sorry, lol

also i think we all know gaining .4 compression does not take huge development and research.... just a minute or two on a milling machine


still i'd like to know more about if it just spits out nasty NOx compounds or anything else

 

More cubes will clean up the cam a bit, but dont bank on putting a monster cam in and passing.

 

Here is my guess,

Going to say a 230/240 cam up from the 220/230 and putting it on a 114 LSA so you tighten up the overlap should be o.k. on a 383. It's just a guess but cubes always eat up runner volume and duration.

Bret

 

That quote wasn't from GM...but rather GMHTP. BIG difference. Good possibility of the author making an error there. I know for a fact the NOx emissions rise due to the increased cylinder temp/pressures of a higher compression ratio. Maybe someone else has some more info on this?

 

Just judging by that article and how they "cleaned" it up with another set of cats points to NOx. That is the purpose of catalytic converters, to clean up the NOx emissions. They may have also squeaked by under some loop hole allowing a little higher HC for less NOx. The EPA is full of illogical concepts like that. Ex. emissions trading

 

To my knowledge, contemporary catalytic convertors contain integrated beds that can promote both reduction (NOx -> N + O) reactions and oxidation (CO->CO2, HC->CO2 + H2O) reactions. You would have to find out if the "pup" pre-convertors are for reduction or oxidation. Logically, you would put the reduction convertor in front, so that the liberated O2 could be used in the main cat to oxidize CO and HC.

 

Hey Big Dave I've got a stock shortblock for sale from a 97 SS for $550 if you're interested in getting your car back on the road right away. Call Dale 301-333-8094 or 301-526-4605, sorry to hera she broke, what went?

 

Well Josh,
If you want to be technical... it was actually McMullun Argus Publishing Inc.. This particular publication happens to be "Super Chevy" magazine which I bought just for the LS6 article... although I'm sure other publications ran the article.

Anyhow, considering the fact that the author of this article interviewed and quoted head engineer John Juriga, cylinder head designer Ron Sperry and a few others.... I'd say that he was most likely paraphrasing the information he had gathered. Maybe you know for sure??
And there's always a "possibility" for anything.

-Mindgame

 

Actually, when you know what they did to the combustion chamber to gain that .4 point of compression, you'll understand that there was a bit more involved than just "milling the head". What I gather, is that the change in combustion chamber shape also changed the bowl and port of the head. I believe Chuck has posted on the differences in another thread... maybe you can strike up a debate there.

-Mindgame