Howdy boys & girls,

I'm looking for some quantifiable results from someone having made similar modifications on their big block car. Please feel free to make suggestions or offer advice.

I've built a number of big block hot rods over the past 40 years, with drag strip performance in mind. Now, the nearest drag strip is 2+ hours away, so my focus has changed to street driving, and maybe trying my had at autocross. If not, terrifying small children and farm animals will have to do...

My 68 coupe presently has a 71 454/365, bored + .030. The engine only has 1-2 thousand miles on it. The intake is the stock high rise, cast iron intake from a 454 or 396 Chevelle. Carb is a rebuilt quadrajet and ignition a high voltage HEI. My new exhaust (installed this weekend, thanks to "66 Racer" way the heck out in Tucumcari New Mexico), is a pair of Hooker Sidemounts.

The cam is the oddball. It is a high lift, long duration cam probably intended for a rectangle port motor. lift is 540/540, duration 230/230, with a 109 degree centerline.

With the M21 2.20 first gear, and a 3.55 rear, it lacks low end power.

I'd like change the cam, intake, and carb to a contemporary design which can make the best of my 9:1 compression ration. Its a big motor with lots of stroke, so making a bunch of low end torque should be easy enough. I don't expect that I'll be doing to much driving at 7,000 rpm any more.

So folks, what do you suggest? Anyone have any real dyno results for an oval port motor?

Thanks in advance for your suggestions.

Doug

 

Will trans always remain? That 2.20 low will always be an issue for really great butt-o-meter fun with 3.55's.

Doesn't sound like you want a radical screamer. Any idea about bottom end build? Did you do it? Pistons? Deck height? Block or head milling? Head gaskets?

Are heads stock untouched with 2.06/1.72 valves?

What hood? Do we have room for a taller intake?

Any preference on cam? HR/SR or solid flat tappet? A good solid cam is a blast in an oval port motor. Valve adjustment is very infrequent these days with right parts.

Does it have A/C, PS and PB to deal with?

What size headers did you just install? Still got Hooker mufflers?


Oval port big blocks are a LOT of fun....


JIM

 

Will trans always remain?

Yes, I plan on keeping the M21 for the foreseable future.

Any idea about bottom end build? Did you do it? Pistons? Deck height? Block or head milling? Head gaskets?

I didn't do the motor. Block not decked. Head gaskets look to be steel, not composite.

Are heads stock untouched with 2.06/1.72 valves?

This is my bet.

What hood? Do we have room for a taller intake?

L88 hood. The Chevelle intake is pretty high, much moreso than the Vette intake.

Any preference on cam? HR/SR or solid flat tappet? A good solid cam is a blast in an oval port motor. Valve adjustment is very infrequent these days with right parts.

Solid or hydraulic are fine. I've owned a 65 396 vette, 1 68 435, and 2 69 435's, so solid cams don't intimidate me. Hydraulic rollers are a bit pricey.



Does it have A/C, PS and PB to deal with?

None of the above.

What size headers did you just install? Still got Hooker mufflers?

Sidemounts are 40" x 2 1/8" primaries, a 10" collector, and 40" sidepipes. Mufflers are the spiral's, so they should flow pretty well.


Doug