1st and goal

Well I dyno'd my mystery motor in my 73 Z/28 last night.

It's a numbers matching block so it is a 350 but I have no idea of the compression, what cam it is, etc.....the only things I can tell are the obvious stuff, it's got 1.6 Summit Roller rockers, Weiand dual plane intake, Holley 750 vac secondary carb, HEI, headers, flex-a-lite fan. I put my 4L60E into it and the rear end has 4:11's

I dyno'd on a Mustang dyno (which generally read lower than a dynojet)
On 34* timing it made 217 RWHP / 226 RWTQ and with a 100 shot it made 283 RWHP / 317 RWTQ (also w/ 34* as I have no retard box).

Then we did a couple simulated 1/4 mile pulls and it ran 13.6 @ 100 on three different runs (naturally aspirated). I have not run the car yet at the track so I can't say how close it is but another customer has run within a tenth of what is car actually runs. There is a link to the simulated 1/4 mile run of the guy I was speaking about at www.maximumperformance.biz, it's about halfway down the main page and the car left @ 5500 off the trans-brake

My dyno pulls are at:
http://www.tta89.net/cars/marc/73z/73zdyno.jpg
http://www.tta89.net/cars/marc/73z/100shotdynopull.jpg

www.maximumperformance.biz is located in Portsmouth Rhode Island and if anyone in the area needs dynoing or any performance related work I highly recommend this shop. They also specialize in transmissions and they rebuilt my 4L60E for me back when I had it in my 94 Z/28 that made 654 RWHP.

Marc

FiefSS

Not bad for a 73, I'd bet with different heads you would be making alot more power if they are the stockers. Any pictures of the car??

1st and goal

Oh forgot about the heads, its got some dinky world heads on it......

Some pics of the car are located in this folder, I don't have any with the front spoiler I put on the car (makes it look much better )
http://www.tta89.net/cars/marc/73z

Marc
P.S. Pay no attention to the wheels as they will be gone in about a week. I'm going to put some Torque Thrust D's on it

xpndbl3

swap to a double pumper 750 and pick up .3 i'd imagine. also get an electric fan to free up another 10 hp or so. good luck

DarthIROC

He doesnt list a stall convertor in his mods, so he should stick with vacum secondaries.

If its a numbers matching block that would lead me to believe (and the dyno supoprts my theory) that its a stock set-up all together. I can tell you now that your heads are holding you back alot. After 1970, and majorly in the year `73 HP dropped massively in nearly all production muscle cars because of emmisions standards. Your heads are most likely 76cc chambered dogs, which is gonna put your compression pretty far down there. Not to mention your cam is gonna be pretty weak too coming fromthose years.

twozs

72 z 28 255 hp; 73 z 28 245 hp, seem to me only 10 hp but two totaly diffrent motors

DarthIROC

Ok but look at drops from the LT1 cars in 69 or 70, and then again in 73 with the same displacement. 73 was the cutoff year that all american power went downhill. Look at drops in big block power. 73 wasnt necessarily the biggest drop for every car, it was just the year that everything went down.

Pretty much the only ride that kept its ***** in 73-74 was the 455 SD Trans AMs

roadblock

The compression reduction came in the '71 model year for Chevrolet. The resulting horsepower loss was minimal but that coincided with the ratings rules change which lowered the numbers to more reflect reality. The next performance reduction came in '73, that was the intake and cam profile. While the '72 Z/28 had 9:1 so did the '73. '73 marked the demise of the solid lifter LT-1 and introduced the L82 as its replacement. Interestingly, the L82 shares the same engine internals as the LT-1 such as steel crank, pink coded rods, forged pistons, 4 bolt mains etc. The L82 camshaft was the old 350 horsepower 350 from the '69 Vette lineup. The end of all good components for the Z28 came at the end of '74 model year. The Z28 was reintroduced in '77, it was a gearing, suspension and graphics package. That car was better than the standard version but lacked the Zap of the old Z.

1st and goal

The cam sounds fairly healthy and has no vaccuum at idle.

I have a Vigilante Torque converter in there, it was a 3600 stall converter when it was behind my old blown LT1 in my 94 Z/28 that made 654 RWHP but is alot tighter with this motor.

I did a compression test and leakdown test on the motor over last winter and everything checked out OK but it's been going through some oil lately and it's not leaking it.

I just hope to make it through the season on this block and then I'll throw a crate motor in there and save the original block.