Pure Stock Muscle Car Drags

[Old Sage]

Zilch, based on comments attributed to Duntov, the ZL-1 Corvette production number of 2 is probably bogus. That's how many were sold, not how many were built.

As a neutral observer, I looked at the rules on http://www.geocities.com/psmcdr/rules.html. They seem to meet the spirit of factory stock. To be honest, 11.54 for a heavy N/A non-nitrous L-88 Corvette is impressive by any measure, let alone with the tire limitation.

[zilch1]

Zilch, based on comments attributed to Duntov, the ZL-1 Corvette production number of 2 is probably bogus. That's how many were sold, not how many were built.

As a neutral observer, I looked at the rules on http://www.geocities.com/psmcdr/rules.html. They seem to meet the spirit of factory stock. To be honest, 11.54 for a heavy N/A non-nitrous L-88 Corvette is impressive by any measure, let alone with the tire limitation.

L-88s ran mid thirteens when they were brand new - and with 9" slicks in place (see vintage HOT ROD test elsewhere in this thread).

They don't tear down the engine in "the pure stock drags" unless it's "certified stock," so no-one but the owner knows how "stock" the L88 your referred to actually is. Even "certified stock" permits a host of modications.

What the rules don't say is often times more important than what they do say, as every winning professional racers knows. Consider the following:

The 1971 Pontiac Lemans in the link below now runs mid twelves (and managed one "corrected" high 11 second pass) in the "pure stock drags." Look at the mods; the stock CR was 8.4:1; now it's 9.5:1. It was a 455 when new, now it's a 462. It uses aftermarket forged rods and crank. Even the cam is custom ground (much tighter LSA and more lift) and is significantly hotter than the "068" cam it came with from the factory.

The owner/driver of that car is Dan Jensen, who is also the organizer of the "pure stock drags."

That car would have had a hard time getting out of the 14s and breaking 100 MPH through the traps when it was new - on ANY tires. And Dan is forthcoming about his mods; many others aren't.

http://www.highperformancepontiac.co...ensen_t37.html

[nota]

Fwiw I have an original 1967 magazine (Hot Rod iirc?) stored somewhere on the shelves which includes a road-test of a new L-88 Tri-carb 4speed convertible. Theirs did a 13.8

[zilch1]

Fwiw I have an original 1967 magazine (Hot Rod iirc?) stored somewhere on the shelves which includes a road-test of a new L-88 Tri-carb 4speed convertible. Theirs did a 13.8

The hottest tri carb engine was the L71; it became the L89 with aluminum heads.

The L88 was 4 barrel only.

The L88 was "for off road use only" according to GM literature. It made ~ 35 more HP than the L71/L89 because it had higher compression, more cam and better flowing heads. The cars themselves were stripped and weren't suitable for street driving. They required 103 octane MON gasoline per the sticker on the center console.

Despite that, they couldn't get out of the 13s - with ANY tire - in bone stock condition.

The L71, L72 and L89 were better "daily drivers," although they also lacked hydraulic lifters and required frequent valve lash adjustments.

None of those engines (or the ZL1) made more than 376 SAE NET HP as they rolled off the production line when new. The 376 HP figure is for the ZL1 (per owner dyno testing). The L88 made a few HP less and the others made less than that.

A new LS2 (364 cid base 'Vette engine) makes 400 SAE NET HP and only needs 93 octane PON. Tire for tire, it is faster than ANY vintage Corvette in "virgin stock" condition.

[Old Sage]

To be fair to that gentleman, his L-88 was torn down and it was stock and the bore must have been within 70.

Any discussion on the ZL-1 is not complete without mentioning GM's test#3 or P/B 5th test. Don't get me wrong, the LS2 is a great engine, but it's no big block Chevy.

[zilch1]

To be fair to that gentleman, his L-88 was torn down and it was stock and the bore must have been within 70.

Any discussion on the ZL-1 is not complete without mentioning GM's test#3 or P/B 5th test. Don't get me wrong, the LS2 is a great engine, but it's no big block Chevy.

How do you know it was "stock?"

The "pure stock drags" permit a HOST of engine modifications. I just showed you an example of a 1971 Lemans that's owned and raced in the "pure stock drags" by the event organizer, Dan Jensen. Here is it again:

http://www.highperformancepontiac.co...ensen_t37.html

Do you really believe that a 1971 Lemans ran mid twelves at 110 MPH off the showroom floor when new? His does because of all the pure stock LEGAL MODIFICATIONS he made to it. He's running a 9.5:1 CR (stock was 8.4:1) a cam with more lift and a much tighter LSA, an overbore, forged rods, forged pistons, a modern, low restriction exhaust system, etc., etc., etc.

E-mail Dan and ask him about the mods that are permitted in that series. Here is his contact information:
http://www.geocities.com/psmcdr/contact.html

The engines in the "pure stock drags" can be blueprinted to NHRA "stock class" specs, which are very different than how they left the factory. That means 3 angle valve jobs, overbores, cc'd to minimum chambers and aftermarket valve springs. They are also allowed to run forged cranks, rods and pistons and cheater cams (which retain close to stock total lift and duration, but feature tighter lobe angles and "fast ramping" lobe profiles.)

You don't understand the ACTUAL rules of the "pure stock drags" and are basing your opinions solely on the name of the series.

A bone stock LS2 makes more "as installed" horsepower than ANY "old school" 427 Chevy in "as it left the factory" tune.


Here are actual dyno test results of a production line stock ZL1. It made 376 HP in its "as installed" state. EVERY other 427 Chevy made less:

http://www.camaros.org/copo.shtml

[nota]

The hottest tri carb engine was the L71; it became the L89 with aluminum heads.

The L88 was 4 barrel only.

The L88 was "for off road use only" according to GM literature. It made ~ 35 more HP than the L71/L89 because it had higher compression, more cam and better flowing heads.

Thanks for the info, and clarification. I haven't re-read that mag for some time. From memory that Vette was listed as 435hp ..?

[zilch1]

Thanks for the info, and clarification. I haven't re-read that mag for some time. From memory that Vette was listed as 435hp ..?

That's the L71. It made about 340 SAE NET ("as installed") HP, which puts it on the same level as the earlier ('97 - '99) LS1 Corvette engines.

Here's an actual engine dyno test of a ZL1, which was the absolute hotted of all the production line 427 Chevy engines. It required 103 octane per the factory sticker on the center console. It made 376 SAE NET HP in its "as installed" state:

http://www.camaros.org/copo.shtml

Here is a dyno test of a second ZL1:

http://members.cox.net/harddrivin1le/ZL1DYNOTEST.JPG

Here is a little (346 cid) LS1 making 503 HP with nothing more than an mild (.525" lift) aftermarket GMPP cam, LS6 valve springs and a CARBURETOR!

http://www.superchevy.com/technical/...s/0409sc_gmpp/

[Old Sage]

How do we know it is stock? You mean when they said it was stock, how do we know? How do we know Jim Morrison is dead? Some people would have to be called liars. Are you ready to do that?

I'll make you a fair offer, you post the entire ZL-1 dyno test, I will show you why quoting the baseline in this case is disingenuous.

[zilch1]

How do we know it is stock? You mean when they said it was stock, how do we know? How do we know Jim Morrison is dead? Some people would have to be called liars. Are you ready to do that?

I'll make you a fair offer, you post the entire ZL-1 dyno test, I will show you why quoting the baseline in this case is disingenuous.

"Stock" in the "pure stock drags" means MODIFIED per the rules of the pure stock drags, which invoke NHRA tech bulletins (i.e. blueprinting specs). It doesn't mean "stock like was when it was new."

Can you grasp that?

L88s were lower to mid 13 second cars when they were new and made ~ 370 SAE NET HP.

Here is the fastest documented test of a known production line stock L88. It ran a 13.56 @ 111 MPH - on 9" wide aftermarket slicks. The trap speed (which is largely unaffected by gearing) indicates potential high twelve second ETs with steep gears.

http://members.cox.net/harddrivin1le/HOTRODL88.jpeg

Elevens ain't happening without MODIFICATIONS.

[Old Sage]

I grasp you can't understand 100% stock means just that.

Now let's move along with the ZL-1 dyno results, I look forward to your post.

[zilch1]

I grasp you can't understand 100% stock means just that.

Now let's move along with the ZL-1 dyno results, I look forward to your post.

It only means that to those who don't know any better. Still don't believe me?

E mail Dan Jensen and ask him. Dan is the ORGANIZER of the "pure stock drags," so he's the best authority on this subject. Here is Dan's contact information, as posted on the "pure stock drags" site:

http://www.geocities.com/psmcdr/contact.html

Here is Dan Jensen's "pure stock" 1971 Pontiac Lemans, which he campaigns in the "pure stock drags:"

http://www.highperformancepontiac.co...ensen_t37.html

What was an 8.4:1 455 when new in 1971 is now a fully blueprinted, 9.5:1 462 fitted with a hotter, custom ground cam, aftermarket forged rods, aftermarket forged pistons and rings, a modern high flow, low restriction exhaust system and various other modifications. Hence, what was a 14 second/100 MPH car as it rolled off the showroom floor is now a 12.5 second/110 MPH car because of those CLASS LEGAL modifications.



The "stock" L88 you're referring to competes in the same "pure stock drags" events and was undoubtedly MODIFIED - LEGALLY - in a similar manner. But it's still "stock" according to the class rules. It's just not PRODUCTION LINE STOCK. Most casual observers aren't shrewd enough to comprehend the difference and (quite laughably) think they're watching the cars as they ran when new.

Here are two ACTUAL engine dyno tests of PRODUCTION LINE ZL1s. Each of the two owners is highly respected in the ZL1 community. Bill Porterfield owns the Grumpy Jenkins racer as well as the one on the first link.

376 SAE NET HP for Bill Porterfield's ZL1: http://www.camaros.org/copo.shtml

420 Gross HP (with the stock exhaust manifolds and no engine accessories at all) for Pete Simpson's, which was professionally rebuilt not long before this test was performed: http://members.cox.net/harddrivin1le/ZL1DYNOTEST.JPG

Both engines made more power when optimally tuned, stripped of all engine accessories and air cleaner and fitted with open long tube headers, but so will most other engines.

Urban legend would have us believe that ZL1's made "575 HP." Perhaps an early development Can Am ZL1 racing engine fitted with unknown parts did make that on a GM engine dyno. The production line engines that were sold to the public (all 71 of them) made nothing close to that figure in their "as installed" condition. The two tests I just posted prove that.

The ZL1 was the king of the 427 Chevy engines. The L88 was a close 2nd and output fell off rapidly from there (L71, L89, L72, etc).

The old cylinder heads were JUNK by modern standards. They had very unfavorable valve angles and horribly inefficient combustion chambers. The cams had good specs, but they also had lazy lobe profiles. Reciprocating masses were heavy (no titanium rods then). ACTUAL (vs. "advertised") compression for the ZL1 was 10.8.1. Pete Simpson cc'd his virgin stock chambers and did the math, so he knows that to be fact. The only way to get 12:1 out of a ZL1 is to mill the heads and deck the block to its NHRA tech bulletin specs.

[Old Sage]

You don't have any real experience with these engines do you ...?

[zilch1]

You don't have any real experience with these engines do you ...?

Pal, you have NO IDEA who you are talking to.

E-mail Dan Jensen and ask him what modifications are allowed in the "pure stock drags."

He'll tell you that the engines can be fully blueprinted to their NHRA tech specs (including decked blocks and milled heads), overbored up to .070" and fitted with "improved stock" cams. He will also tell you that modern exhaust systems consisting of mandrel bent, 2.5" tubing and low restriction mufflers are permitted as well as forged aftermarket cranks, rods and pistons and various other mods.

The faster "stock" cars running in that series are little more than purpose built spec cars. Dan's own T-37 is a good example of that.

Many of the old engines can be MODIFIED to make respectable levels of power. But in production-line stock form, 375 SAE NET HP was about it for the "muscle car" engines and only the rarest and most expensive of them (L88, ZL1 and the later street hemis) could do it.

Most of the other stuff was pure junk that had difficulty putting 200 HP down to the wheels on a chassis dyno.

L-88 - production line stock circa 1969 and fitted with 9" wide slicks: - 13.56 @ 111 MPH

http://members.cox.net/harddrivin1le/HOTRODL88.jpeg

2004 Z06 Corvette - production line stock circa 2004 - 11.97 @ 118.8 MPH - on 92 octane unleaded with full power options, ABS, AC, a nice stereo and 19 city/28 highway MPG:

http://www.gmhightechperformance.com...vette_feature/

And the new Z06 is even faster.

That's called PROGRESS. More than 40 years have passed since the big block Chevy was first introduced. Computer modeling techniques have yielded advances in engine design (particularly in the heads and chambers) that were unthinkable back then.

[Old Sage]

I don't feel like I'm your pal, but ok.

Well Mr Expert err Mr Google, then off the top of your head you should know this ...
tell me the origin of the 6.135 connecting rod



Sorry, I had to remove the hints, I almost gave you the answer.