i am thinking of going back to stock exhaust manifolds for better appearance. could i open up the manifolds and have them port-matched and get big improvement over the stock air flow? or is it not worth the effort?

 

Is it a built motor or is it basically a stocker? My 68 RS was basically a stock 327 with Edelbrock Performer intake, 750 Q-Jet and Mallory Unilite ignition. One of my exhuast manifolds cracked. At the time I couldn't find an OEM replacement, so I switched to headers.

Not only did I not notice any significant performance increase, but the headers added heat, made it a pain to change the starter and looked like crap once the finish got a little ratty.

I now have a bone stock 67 RS with 327/210 2-bbl. I'm going to swap in an original 4-bbl intake and 750 Q-Jet, and maybe do a few other minor tweaks. The original 327 only has 103K miles on it, so I won't be rebuilding it at this time. I'm faced with a decision... keep the OEM exhaust manifolds and smog pump... or go with headers... everyone says headers, but I'm thinking "why"? It's basically going to be a weekend/fair weather cruiser. I'm not going to race it, I don't care if its fast, I just want it to look, sound and run good.

While the smog pump works, is disconnected because of a bad diverter valve. So either I find a diverter valve (not easy or cheap) or I cap the SMOG holes on the manifolds, or swap in headers or stock '68 non-A.I.R. exhaust manifolds (which are now available.)

If its basically a stocker and you want authenticity and a basically stock look... forget about headers.

 

Ported exhaust manifolds will give you a substantial increase in power over stockers, but not quite as much as a set of headers. Keeping the stock exhaust manifolds and porting them, will give you a stock appearance while still getting performance out of the engine. Theres a lot to be said for the sleeper look.

If you want to see what can be done with a totally stock-appearing engine, look at this website.

Cars in the 12s and 11s on stock factory tires.

 

Thanks Dirt.

I saw that on TV and was looking for a link to show some friends.

Sleepers are cool!

 

thanks for the feedback. i think this is the route i'll go (ported and port-matched stock manifolds).

by the way nice project...my 1st ride was a 76 Type LT Camaro with a GM 350 crate motor. brings back good memories. i've gotta scan some pics and post them on my web page

 

Glad to help.

 

Thanks for the words. I'm currently in the process of getting the rest of the engine put together. Hoping to get it all done within the next few days. The holdup was porting the Vortec heads, which took a few weeks. I'm hoping it works good once its up and running.

 

You can try to port them yourself(why not, what do you have to lose) or get them Extrude Honed or have them ported by Brysenki(I always spell it wrong) Racing. They port the stock log style manifolds for racers that need stock components and they see 20 hp gains easily over non ported manifolds. No heat problems and looks bone stock.

 

In Dave Vizard's book on intakes and carbs, he got a 350 with a ported stock cast-iron intake, and ported stock exhaust manifolds to make 390HP on the dyno. So porting *does* help a lot.

 

Here's the company I was talking about, I spell it wrong every time. I thought some dyno testing showed 15-20 hp increases, but they don't claim that much. http://www.castheads.com/exhaust_fol...haust_set.html The other option is to have them Extrude Honed which might cost less.

 

i posted two pics of my 76 Camaro taken in 1988 or 1989