Just How Fast Are C2 Small Blocks?

[Joe C.]

Re: Just How Fast Are C2 Small Blocks?

Joe-------


Yes, with a modified engine and, possibly, drivetrain a lot of improvement is possible. But, what I'm talking about is pure stock.

Just answering the OP's request for stories, plus a bonus video for some people's enjoyment.

Also want to share with the OP what a normally perspirated 327 (well, OK, actually 331) can do when built RIGHT and with parts that work in harmony with each other. Wanna race your ZL1? Say, old chap, did you ever get that thing on the road?

Donny Brass runs a "pure stock" '66 with a 327/350 in PSMCDR in Michigan. He holds the class record, but of course, some cheating always goes on. His car is not streetable (at least in my opinion) since it uses a 4.56 axle ratio. The class allows suspension mods to transfer weight to the rear wheels. and lightening. The camshaft doesn't have to be stock, except for lift and duration at one lift value.....so "cheater" cams can and are used. His engine is WELL blueprinted and built with tight quench, which allows for aggressive spark advance and higher static compression (than advertised, not actual stock values) free from detonation. Probably makes around 400 honest flywheel HP. I believe street slicks are permitted as well, since he does a burnout before his runs.

He hooks perfectly and powershifts all gears, drives like a pro. His best run was 12.838 @ 106.8.

[Stuart F.]

Re: Just How Fast Are C2 Small Blocks?

No one in their right mind would venture forth to the drag strip, pay good money to enter, and run true and pure stock. That ain't no fun, and besides, you'd get ur butt whooped by all the cheaters. I'll admit, it was much easier to cheat back in the day. They'd measure your displacement with a ruler. The one and only thing they got me on at the end of the year was one guy was willing to pay the tear down fee (someone from out of state) and darn if some of my grind marks didn't show up in my port matched aluminum manifold - even after sand blasting! Just as well I didn't have to go any further. That was already a bad day as I dropped out my drive shaft at about 106 mph going through the lights and was going to have to tow home anyway. Do you know what a mess dropping a drive shaft out at that speed can make? Broke every ear of my tranny, the starter was hanging by the cables, and broke my distributor. Good thing was it shook loose all the dirt and grime from the underside.

Joe; In the video, did you go through the lights in 3rd? Man! With a good hookup and power shifting that could have been a super pass!

Stu Fox

[Don C.]

Re: Just How Fast Are C2 Small Blocks?

And another old guy (me) having fun and pretending to be 18 again. 13.2 at 107.7 MPH in a 65 with 327 (.040 over) and all GM parts (L82 cam advanced 4 degrees) plus headers. Since this video was taken I have swapped out the 461 manifold for an LT1 manifold, bumped the compression a bit (from 10.05 to 10.46) and increased exhaust valves from 1.50 to 1.56. dyno'd at 304 RWHP @ 6000 RPM in third gear with recent changes vs 290 at 5800 RPM when the video was taken. 3.55's and close ratio box don't help off the line! The secret is very meticulous build, lotsa work on 461 heads and minimizing exhaust back pressure. Quench is .035 and no detonation on 91 octane non-ethanol gas. I think I have come to the end of the end of the road on maximizing power with stock stuff........and it was certainly not cost efficient to do what I did for a few extra HP; but I just wanted to see what I could do.

https://www.youtube.com/watch?v=OQsi-DbKrr4

[Joe C.]

Re: Just How Fast Are C2 Small Blocks?

No one in their right mind would venture forth to the drag strip, pay good money to enter, and run true and pure stock. That ain't no fun, and besides, you'd get ur butt whooped by all the cheaters. I'll admit, it was much easier to cheat back in the day. They'd measure your displacement with a ruler. The one and only thing they got me on at the end of the year was one guy was willing to pay the tear down fee (someone from out of state) and darn if some of my grind marks didn't show up in my port matched aluminum manifold - even after sand blasting! Just as well I didn't have to go any further. That was already a bad day as I dropped out my drive shaft at about 106 mph going through the lights and was going to have to tow home anyway. Do you know what a mess dropping a drive shaft out at that speed can make? Broke every ear of my tranny, the starter was hanging by the cables, and broke my distributor. Good thing was it shook loose all the dirt and grime from the underside.

Joe; In the video, did you go through the lights in 3rd? Man! With a good hookup and power shifting that could have been a super pass!

Stu Fox

Thanks Stu. Yes, I did. If you look again, you'll see that the shift light comes on as I go thru the traps. It's set for 7250. It dynos at 412 RWHP @ 6400 RPM; 405 RWHP @ 7000 RPM. It's a wide ratio trans.

The car has a 3.70 axle and a RS600 5 speed, which makes for an awesome highway cruiser with the bonus of a nice, low 1st gear (2.79:1) which makes it very quick on the street (if I can keep the tires from going up in smoke). With a 4.56 gear, street slicks and somebody like Donny Brass driving, the thing would be in the 11's.

I agree with your reasoning about pure stock. It's not for me either.

[Joe C.]

Re: Just How Fast Are C2 Small Blocks?

Nice run Don!
Glad to see you enjoying yourself. And, like you, I "just want to see what I could do". Getting an engine to make more power is what it's all about. It's also fun to show C6s and C7s your taillights on the highway.

[Duke W.]

Re: Just How Fast Are C2 Small Blocks?

The secret is very meticulous build, lotsa work on 461 heads and minimizing exhaust back pressure. Quench is .035 and no detonation on 91 octane non-ethanol gas. I think I have come to the end of the end of the road on maximizing power with stock stuff........and it was certainly not cost efficient to do what I did for a few extra HP; but I just wanted to see what I could do.

https://www.youtube.com/watch?v=OQsi-DbKrr4

There is more left if you install a LT-1 cam. Not much more peak, but it will extend the useable rev range to 7200 with carefully setup OE valve springs, so average horsepower delivered will be greater, which should increase MPH and cut ET a tenth or two.

You still have the best flowing heads in my library of head flow data, and IIRC they still have the 1.94/1.50" valve set.

Duke

[Joe L.]

Re: Just How Fast Are C2 Small Blocks?

Say, old chap, did you ever get that thing on the road?

Joe-------


Not quite yet.

[Joe C.]

Re: Just How Fast Are C2 Small Blocks?

Joe-------


Not quite yet.

I'd be happy to fly out and help you.
Say.................we can even grab a few dozen lobsters, you know, for a light snack.

[Don C.]

Re: Just How Fast Are C2 Small Blocks?

Hi Duke
The intake is still 1.94 but the exhaust is now 1.56. I experienced excessive valve stem wear on the 1.50 valves (no wear on the bronze guides, which surprised me) and discovered that the machine shop did a bad job on concentricity, to which I attribute the side wear. I used the my son's portable valve grinding set and opened them up myself to accommodate the 1.56 valves ......... and they are now concentric. Yeh, I've followed all your various threads on the LT1 cam and I agree it would give me a bit more. I do however like the protection afforded by valve float at 6700 RPM considering I am using 1966 OE rods (the stronger ones).

[Duke W.]

Re: Just How Fast Are C2 Small Blocks?

"I have swapped out the 461 manifold for an LT1 manifold, bumped the compression a bit (from 10.05 to 10.46) and increased exhaust valves from 1.50 to 1.56."

Don, do you do any dyno pulls before the above changes? Everyone would be interested in knowing about how much top end power the LT-1 manifold makes compared to the 327 SHP manifold. I can back out the increase from the CR and the exhaust valve size increase is not signficant.

Breaking 300 SAE corrected RWHP with vintage OE components is excellent, and I agree on the revs. Even with reworked second design 327 rods, I would not recommend revving much over 6500.

Duke

[Joe L.]

Re: Just How Fast Are C2 Small Blocks?

I'd be happy to fly out and help you.
Say.................we can even grab a few dozen lobsters, you know, for a light snack.

Joe-----


...at least a few dozen. I'll be back in New England in about 7 weeks and I'm starting to salivate already.

[Don C.]

Re: Just How Fast Are C2 Small Blocks?

Here ya go. I don't like that I sacrificed mid range power, which surprised me. I was hoping the slight increase in CR and valve size would compensate; but that didn't happen.
I copied the two dyno runs from the dynojet (WINPEP7) software. I hope it comes through. I am thinking of reinstalling the 461 manifold and seeing the dyno result of that retrograde swap and if it delivers more area under the curve
I am interested in what your analysis shows Duke

Red=461
Blue= LT1
461 LT1 comparison.jpg

[William F.]

Re: Just How Fast Are C2 Small Blocks?

Back to original thread. When's the race?? Keep us posted! When the flag drops, the BS stops.

[Duke W.]

Re: Just How Fast Are C2 Small Blocks?

Here ya go. I don't like that I sacrificed mid range power, which surprised me. I was hoping the slight increase in CR and valve size would compensate; but that didn't happen.
I copied the two dyno runs from the dynojet (WINPEP7) software. I hope it comes through. I am thinking of reinstalling the 461 manifold and seeing the dyno result of that retrograde swap and if it delivers more area under the curve
I am interested in what your analysis shows Duke

Red=461
Blue= LT1
[ATTACH=CONFIG]60815[/ATTACH]

The LT-1 manifold with 0.4 more CR makes about 5 percent more peak power than the 461, but 2.5 percent less peak torque. The increased CR is likely no more than about 2 percent, so that gives the LT-1 manifold with the same CR a maximum advantage of 3 percent peak power, but 4.5 percent less peak torque. Over the entire rev range from 1500 to 6500 the LT1 probably makes marginally more average power. The 461 makes more average power from 1500 to 4000, which is the normal road driving range, including accelerating onto a freeway and passing on a two-land road, but the LT-1 has a definite advantage in the 5000-6500 range, which is were the engine is running shifting at 6500 through the gears.

The LT-1 appears to achieve 80 percent of peak torque at about 2100, which is close enough to my high performance road engine requirement of 80 percent at 2000 to be okay. Since the 461 test didn't begin until about 2500 there is insufficient data to draw a conclusion. If you install and retest the 461 make sure the pulls start an no more than 1500 and 1000-1200 is better.

So the LT-1 manifold is probably not worth it unless you are doing some serious racing and want to exceed that "magic" 300 SAE corrected RWHP on an OE 327 that looks like OE to the casual observer.

I've always maintained that about 15 of the 20 horsepower rated difference between the LT-1 and L-46 is the manifold and only 5 is attributable to the camshaft, nothwithstanding the extended rev range of the mechanical lifers; 1.03(350) = 361, so your data says it's about 50/50.

The bottom line is the 461 is probably best for someone who wants maximum torque bandwidth for a responsive SHP road engine, but the LT-1 manifold is better for serious racing. All things considered, the LT-1 manifold is likely not worth the expense and loss of originality for most owners. A Flint-built L-79 makes about 220 SAE corrected RWHP and 280 peak torque. The L-46 cam advanced four degrees or LT-1 cam along with massagaed heads and 10-10.5:1 true CR yields a good torque bandwidth 327 that looks OE, but with substantially more power in the upper third of the rev range with little to no loss of low end torque.

Duke