MoMo

I've got a beautiful 1968 Corvette convertible that I am putting a 427 big block in. It originally was a 300 horse 327 but with the original engine long gone. I wanted this Vette to be my version of the ultimate dream car. But being a big block, it's not your daily driver type of car.

I am just finishing warming over an 86 IROC-Z to be my daily driver until my daughter goes to college in 3 years, then it will be hers.
And there are new cars, but nothing I'm real hot over. So I'm already making plans for a future daily driver, and I wanted to see what you guys thought of the idea.

I have a 400 small block, hot tanked, overbored, and magnufluxed, in my garage. I was thinking about destroking it to a 377 using a forged 350 crank and long 6" rods. I'm also thinking about getting back into forced induction, and I prefer turbos. But because turbos and 377's like more rpm's than smog-friendly cams will allow, it would be ideal to find a pre-74 that needs a good home. This time, a T-top coupe.

I'd build it into a 377 twin turbo, and fuel injected engine with a redline around 7500 rpm. I'd use an LT-1 or miniram fuelie system and a couple of fairly small turbos that spool up by around 3000 and pump hard to 7000. Like maybe a pair of Garrett T04's. There's lots of room for turbos and a good exhaust system. Definitely sidepipes. Also tons of room for a huge intercooler. And I'm thinking a Muncie 4-speed with 3.55 gears would be about right. ROD would be perfect, but I'd lose my license with so much potential (...if I still have my license after finishing my 427 roadster).

What are the average prices for rough to moderate 73 coupes?
And what do you guys think about that plan for a daily driver?
The only thing better than a sweet high-revver with snarly sidepipes, is one that has twin turbos whistling under the hood.

Let everyone else buy the C6, I'm not done having fun!!!
:D

Corvettes White

Sounds good, but why a '73? Now and then I see a beater for 7000 or so but chrome starts about 10,000 from what I have seen but have not been shopping for a few years now.

You can always buy a new car but the real fun is in building your own. Go for it.

George (w/ a Bowtie aluminum small block, B&S to 383, LT-1 clone dream car '69 in progress)

Flareside

630 out of a 427? What's the redline and off-idle torque like? Makes an L88 sound mild!

-Joe

PatsLs1vette

man that sounds good to me a 377 high reving 73 go for it. :cheers:

ZD75blue

sounds like fun... i would pick up another c3 and go full out cusom with a sweet motor

i too would like to know the secret to this 630 427 :cheers:

ZD

MoMo

Well here's the lowdown on the 427. It's actually a destroked 4-bolt 454, because 427 blocks are getting rare. Physically they are the same, only the serial numbers differ.

It is all forged parts, crank, shot-peened and polished forged pink rods, and forged pistons.
The motor is built to 435 horse 427 specs, except 0.030" over. Even on the factory 435 horse 427's, the 435 horses appeared at a lower rpm and were not the actual peak numbers. One article I read had it more like 514 hp at 6000 rpm.

So add a modern solid roller cam to that and a set of race-prepared heads with enormous 2.30"/1.88" valves and a good set of Hooker Supercomp headers, and you get the 600 lb-ft and 630 hp figures, according to Dyno2000. I'll have to get it on a real dyno to confirm those numbers.

Basically, I've build a modern L88, except instead of getting the power from 12.5:1 compression, I'm getting the power on 11:1 compression and a modern solid roller cam. I'm still going to have to use a witch's brew in the gas tank so that I don't detonate this still-high compression engine, but I wanted to have a home-built L88 type performance Corvette roadster.

I plan on doing a lot of racing with it in SCCA events and various timed events in the west, such as the Silver State Classic and Pony Express 100.
That's the only way an engine like this can stretch its legs, without the f*@king cops on my butt all the time!

The redline is actually higher for a forged 427 with good forged rods that have been shot-peened and polished, ARP rod bolts, and 4-bolt mains with ARP studs, but on a set of race-ported and bowl-blended oval ports with big valves, about 7400 rpm is all I'll be able to breathe. The closed port heads HAVE been unshrouded, increasing their combustion space from 105cc to 109cc. That's why I'll be at 11:1 instead of 11.4:1.

Part of the redline determination is due to piston speed. A 427 with a 1.64 rod/stroke ratio has a lower piston speed than a 454 with a 1.53 rod/stroke ratio. This allows you to rev it up higher. 6400 rpm is max on a 427 with cast internals. That's why I went with all forged to get the extra 1000 rpm. And then a cam to match. RPM is an important multiplier in the HP formula, so if you have a cam that holds the torque to higher rpms and an engine that'll breathe at those rpm's, the horsepower will climb higher too. Naturally, I'm running a single plane.

Carburetion is courtesy of Barry Grant, on a Gold Claw double pumper with 775 cfm sleeves. (I'm at high altitude). The sleeves are interchangeable, so I can bump that up if I race at lower altitudes.

The reason I thought of a 73 is for a couple reasons, actually. It has the 5mph front bumpers, which are better for a daily driver. It still has the gorgeous Kamm-effect rear that the early sharks have. It is pre-74 so that in Colorado at least, I can build it as wild as I want without worrying about emissions. And being a 73, which has a little bit of a reputation for low hp, I can get one for a better price than the earlier chrome-bumper sharks.

I have nothing against the later sharks either, they're nice and cheap. But then I'd have a major problem trying to keep the high-revving 377 emissions legal, because then I couldn't put the cam I really want in it.
Also, I prefer the removeable rear windows with T-tops in the shark coupes.

But if I do find a killer deal on a 74-82 shark, I'd have to consider it. I'd just have to be a lot more careful how I build the 377. For example, making it a 6500 rpm engine instead of a 7500 rpm engine, just because of the smaller cam I'd have to use. And also dual exhaust with cats!

Flareside

I gotta tell you MoMo, I was very sceptical of your engine configuration claims, so I plugged them into DD2000. You're right, you can make over 600 with a roller cam (I used the Comp 288AR), but low end torque is a little lacking. Compared to the ZZ502 profile I've got, you're down over 150 foot pounds until up around 3500 rpms. Drivability sounds marginal. You better bring some steep gears to this party. Peak HP is over 6500!

I couldn't make over 600 HP with any oval head I've got, but I could with a few heavily ported rectangulars. Which casting are you using, 215 or something similar? Which cam are you planning? Supercomp 2.125 or 1.875 headers?

-Joe


[Modified by Flareside, 2:17 PM 12/15/2001]

MoMo

I have no doubt that a 427 with a big cam is in the neighborhood of 150 lb-ft less than a 502. For one thing, it's 75 cubic inches less. The 502 also has a quarter inch longer stroke (same as a 454). Plus if you use a milder cam, you'll get more torque.

The reason I chose a large oval port head and then had my machinist hog the snot out of it, bowl blend it, put large valves in it and then unshroud it, was because I needed the torque advantage of an oval port head in the midrange, yet with the rpm capability of 7000 or a little more. Here in Denver, according to my machinist, many racers running 427 engines are using this configuration, and they are a lot faster and quicker than the guys running the rectangle port heads. I guess we'll see.

I also wanted the midrange to upper range torque stronger so that I can come out of the curves without so much torque that I've got serious traction problems at the lower speeds, but then with an awesome ramp-up in torque as I come out of the apex. This is more of a road racer than a drag racer.

I had a good friend who was a drag racer that was trying to talk me into a 502 crate motor. I wanted the 427 because of its superior upper rpm response and its smaller bottom end torque. Maybe with slicks, that 150 lb-ft would make for an awesome launch on a drag racer, but this isn't a drag racer.
And besides that, DD2000 is showing the 427 having 440 lb-ft at 2000 rpm. That's much better than the small block that was in there, even at the small block's peak. So if the M20 with 3.36 gears felt "not too bad" launching with a 327 and 350, why would I need super steep gears with a torquier 427?

If I had the close ratio M21 or M22, yes, steeper gears would help. But 1st on an M20 is 2.52:1, which is like a close ratio on 3.90 gears in 1st.
Will the M20 live? I don't know. We'll see. The best I can do is rebuild it and try it out. If it fails, I'll have to look at stronger options.

The cam I'm using is a Crane solid roller, p/n 138601. It has duration of 246/254 @ 0.050" with lift of 0.615"/0.636" intake/exhaust, respectively. LCA is 110 degrees, and is installed straight up.

Here are the flow numbers on those oval port heads, at 25" H2O pressure drop using a Superflow model 600:

Intake:
CFM: Valve Lift:
63.9 .100
132.5 .200
198.5 .300
232.8 .400
261.4 .500
272.9 .600
272.9 .700

Exhaust:
CFM: Valve Lift:
52.4 .100
104.8 .200
137.1 .300
169.8 .400
192.3 .500
201.9 .600
208.2 .700

Maximum exhaust flow is 76% of max intake flow.
Not bad for an oval port head, huh?

I should have started a thread on the 427. That's okay.



[Modified by MoMo, 7:29 PM 12/15/2001]

Corvettes White

Fair reasons to select a ’73. I would also stay away from the ’75 and later cars for their cats and also they have a steel floor pan.

George