Quote Originally Posted by glennsexton View Post
Welcome to CHR!
I agree with most all of the above – especially the information about roller cams and the input from Tech, re; compression ratio and cam timing. Is this the original engine that came in this car? If so you may be sitting on a pretty sweet deal and not realize it. The reason I ask is that you also reference “L30” – which is the 275 HP 327 from 1968 and the prize is it had 10:1 compression ratio.

The rear end that would have come with the RPO L30 engine was RPO G94-15 which is a 3.31 radio (code DD). The highest numerical ratio available from GM for the 1968 Chevelle was 3:73 so in all likelihood the 4:11 is aftermarket.

The RPO M21 is the close Muncie with a 2.20 first gear versus RPO M20 with the 2.52 low gear.

You also said she runs like a watch – so… if it were mine, I’d not mess with the cam because the heads are truly a limiting factor here. I would do the following:
1. Holley Street Dominator – like this one on ebay for $75 - USED Holley Street Dominator intake Manifold 701R-28Z 300-28Z FREE SHIPPING
2. Remanufactured Quadrajet like this one from Summit: https://www.summitracing.com/parts/jet-35002/overview/ with a free breathing 3” air cleaner
3. HEI from Davis Unified Ignition – like this one: https://www.summitracing.com/parts/d...make/chevrolet
4. New 8mm wires and spark plugs – gapped at .050
5. Hooker Super Competition Headers like these - https://www.summitracing.com/parts/h...make/chevrolet with 40 series Flowmasters and 2-1/2 inch pipe all the way back to the rear bumpers (with nice chrome or stainless tips!)
6. Set timing at 12 degrees initial and 32 degrees all in.

I know it’s a bit over your budget, but it will bring a nice smile to your face when the Quadrajet secondaries come to life. If you drive this for six months or a year and find you want a bit more pizazz you can save your money for a big block.

Remember to have fun and be sure and let us know what you come up with. Pictures are good too..

Best,
Glenn
It is not the original engine to the car. I've run the #s and it came from an Impala. As far as the exhaust goes, I'm pricing headers and the cost it'll take to fit my current pipes to them. From the manifolds back the exhaust is brand new and exits in the stock location (no chrome or stainless tips for this guy). Part of the reason I'd like some more power is because the 4.11s have to go. Being that I live in the middle of nowhere, getting to a cruise or show involves highway driving. 4.11s with a 26" tall tire at 65mph is no fun at all. It's cheaper for me to buy a new posi carrier and new ring and pinion than to buy a LGT 700 5 speed transmission. I was thinking 3.55, 3.42, or 3.31. It'll kill the acceleration but it'll give me a tolerable cruise rpm.