Looking for DYNO results on a stock 1969 L78

[WILMASBOYL78]

I'm sure you have the read the old article.."The 13 second grocery getter"....this was a 69 L78 TH400 Nova in as delivered trim as I recall, ran high 13's. Not sure why you would want info with no smog, blueprinted, tuned, but no headers..?? why do all that and run it thru exhaust manifolds..?? anyway, I seem to recall an article about a Bill Thomas blueprint of the original 1965 L78...and it really produced 425hp...I know of a number of 1970 L78 motors that have made similar power on the dyno...but they all used headers. The horsepower on these motors was under rated...but, probably accurate in stock trim. They need to breath...performance tuning and headers are a must to reach full potentional.

wilma

[Chevy454]

LOL...you know, these engines *will* actually run, and better yet, they'll even *perform* using the bone stock exhaust manifolds. I regularly see guys post dyno numbers of engines with headers comparable to numbers I've seen for engines with exhaust manifolds, same builds, etc, and all that tells me is the headers are just a band-aid for something else...

We built an L72 for Pure Stock years ago...we rebuilt it to "as delivered" specs, as I wanted to see exactly what a factory L72 would/could do. So, that meant crappy TRW pistons (28cc dome where it's supposed to be 34cc), uncut heads (110+cc chamber where it's supposed to be 105.9cc), didn't deck the block (pistons were all over the place, probably averaged .014"+ down in the hole), original rods/crank/etc, factory blueprint cam...all of this sloppiness got us barely 10:1 compression. Ran it through the stock exhaust manifolds, and it would pull between 425hp and 430hp on the engine dyno, so around 1hp per cubic inch...this engine carried our stock Camaro to mid-12s @ 108+ at a 3750lb race weight, on F70-15 tires. Now, my blueprinted L72 I did the following season, same intake/exhaust manifolds, same carb/ignition, same factory blueprint cam, etc, just a blueprinted long block, soundly put 50+ hp on the first L72...through exhaust manifolds.

So, as delivered, with a simple going over of the jets/timing I'd say you're looking at 1hp/cu-in, or somewhere around 395hp-400hp...blueprinted, 450hp+ pretty easily (I know of a couple L78s that have done this).

[WILMASBOYL78]

So, are you saying there won't be an increase in HP with headers..?? even on a well tuned or blue printed motor...

[Salvatore]

Rob, are those exhaust manifolds you guys run flowed and worked on some? I heard that rumor somewhere that they were even a little lighter than originals. Thanks!

[Chevy454]

[ QUOTE ]
Rob, are those exhaust manifolds you guys run flowed and worked on some? I heard that rumor somewhere that they were even a little lighter than originals. Thanks!

[/ QUOTE ]
Uh, no...that would be the F.A.S.T. (Factory Appearing Stock Tire) class. Our manifolds in Pure Stock must be untouched...we can run a stock reproduction, but they have to be exact copies...and if the repro's are lighter it's news to me...mine are originals, though.

[ QUOTE ]
Rob, what kind of jetting and advance curve did you run in that factory sloppy stock 427 to make the 425 hp. I know that just getting those two in the ball park made a difference that you could actually feel. 20-25 hp? A friend still has his '69 L78 4 speed Chevy Nova. He told me that he went a best of 12.8s with headers, slicks and tuning. He said he was beating on it pretty hard to get there too. How about some real world experiences here.

[/ QUOTE ]
Without looking at my notes, I'm gonna guess I had the timing all in by 2500 or so, with total ~37 degrees...jetting was close on the primaries at 73-ish (stock 72/76, iirc) and secondaries 78 I believe? Probably woulda been a *tad* better with my current carb (blocked rear power valve, different jet setup, fresh rebuild from Eric).

[Salvatore]

Got it! I thought you ran that F A S T class. Thanks.

[Chevy454]

[ QUOTE ]
Got it! I thought you ran that F A S T class. Thanks.

[/ QUOTE ]
They actually have a Factory Stock (Pure Stock) class at most of the F.A.S.T. events, that uses the same rules as our Pure Stock class, and normally the Pure Stock guys do the tech, so it's pretty much the same faces & rules...but it is definitely confusing!

As for the big hitter F.A.S.T. class itself (Stock Appearing), my plan is to give it a go with my Y-Chevelle...

[Groucho]

Good thread BTW.

[Keith Tedford]

Rob, what kind of jetting and advance curve did you run in that factory sloppy stock 427 to make the 425 hp. I know that just getting those two in the ball park made a difference that you could actually feel. 20-25 hp? A friend still has his '69 L78 4 speed Chevy Nova. He told me that he went a best of 12.8s with headers, slicks and tuning. He said he was beating on it pretty hard to get there too. How about some real world experiences here.

[LS6 RAT]

Rob,

I had a '69 Camaro SS convertible L-78 that I had Bob Harris at Camaro Specialties completely restore. I had him send the engine to his engine shop for a complete stock re-build, still at standard bore, this engine complete with A.I.R. system on an engine dyno put down 389 hp in stock configuration.