[johnta1]

John Witzke has a W72 pdf that has a lot of info on the W72 from 1977 to 1979.

W72 Technical Information

[BDH79TA]

One thing missing from your comparisons is that there were 2 Pontiac 400 engines offered at the time. The 180 HP had the 6X-8 heads which were around 100 cc head. The 220 HP had the slightly more aggressive cam and the 6X-4 head that advertised closer to 92 cc head. This is where the performance boost came from. Not the type of muffler or cat used. However, the 220 HP did use the dual resonators instead of the transverse muffler because of the need for a little better flow. I haven't searched the in depth info on the difference in the cams between the two engines as it's never been something I've needed or wanted to know. I'd imagine they did use different cams though.

[KSZR]

Originally Posted by Skip Fix

My 78 180 HP and the 2.56s ran high 14s-barely in 3rd.

Can you tell us a little more? Was it stock? Thanks

[steve25]

See if you can track down on line the Sept 2006 issue of High Performance Pontiac magazine.

In it they had most detailed article on the 3 Cams that were used from 77 to 79 in the 400s that one could hope find.

[Skip Fix]

That was stock. Convertor everything. I had Glenn Tinsley's shop (that leased John Clegg/HO's 74 TA) add a228/228 @0.050 Cam Dynamics and it went a little faster but had to add a little pusher electric fuel pump as top of second would run the Q jet out of fuel. Stock Q jet even with an HO Racing rejet kit was lean in the idle circuit , eventually fixed with n SR 73 SD Qjet.

[KSZR]

Very nice!

I have a stock '78 L78 that needs exhaust and one manifold gasket is blown. Was curious what to expect, or what potential it has basically stock once it is up and going.

[steve25]

From the article in HPP that I posted about above here is what the program from an engine Analyzer predicted for power out of the 3 different cams used in the W72 motors.

Unfortunately I believe the L78 motors had less compression so you will fall short of these numbers if your heads have not been milled.

[KSZR]

Originally Posted by steve25

From the article in HPP that I posted about above here is what the program from an engine Analyzer predicted for power out of the 3 different cams used in the W72 motors.

Unfortunately I believe the L78 motors had less compression so you will fall short of these numbers if your heads have not been milled.

Very cool, thanks for finding that!

Sounds like the summit 2800 or something similar would be a nice upgrade as far as aftermarket.

A pypes exhaust system should give a nice power bump, which I need anyway because everything behind the converter is pretty rotten.

[SD455DJ]

Originally Posted by KSZR

Very cool, thanks for finding that!

Sounds like the summit 2800 or something similar would be a nice upgrade as far as aftermarket.

A pypes exhaust system should give a nice power bump, which I need anyway because everything behind the converter is pretty rotten.

Here is the dyno session on a '78 W72 400 with the Summit 2800 cam...

Dan had a good dyno session today with the W72 400. He rebuilt the original numbers matching engine with .040" over Icon forged pistons w/4.5 cc valve reliefs that were .006" out of the hole and with .045" x 4.328" Felpro head gaskets to provide .039" quench depth. The 6X-4 heads were minimally cut for trueness and measured 92.45 cc's average for a final static compression ratio of 8.75 to 1. Dan replaced the cast rods with forged Eagle H-beam rods. New 1-pc valves (2.11/1.66) with CC dual springs were installed. A Summit 2800 cam (204/214/112 @ .422”/.444”) with new 'old' Crane hydraulic lifters along with a new Melling 60 psi oil pump. The one modification was the use of old factory D-port ram air exhaust manifolds with the 2.1" outlets with Pypes 2.5" mandrel headpipes. The original 17058263 Q-jet on the factory cast iron intake with the EGR system and plumbing were reinstalled.

The base runs were made with 42 degrees total timing in by 3000 rpm, 45 primary rods/74 jets/CH secondary rods on an I hanger. The 3rd (and best) base pull made a corrected 360.3 hp @ 5000 rpm/456.1 lb-ft torque @ 3600 rpm (351.2 hp/444.5 lb-ft uncorrected). The correction factor was a low 1.026 as the weather conditions were very good...low humidity, high barometer, and very cool temperatures (65 in dyno cell). After rejetting the carb to 40 primary metering rods/72 jets/DA secondary rods on an 'I' hanger (same total timing at 42 degrees), employing the 'big' dyno room dumps for the headpipes, and installing the air cleaner base, the max hp jumped to 371.4 hp @ 5000 rpm/459.2 lb-ft @ 3600 rpm (362.0 hp/447.6 lb-ft uncorrected) on the final pull (#14). The highest torque reading was on pull #13 at 460.3 lbft.

Dennis

[mrmark1957]

Originally Posted by jerry455

I bought a 20,000 mile, used W72 Gold 1978 T/A in the spring of 1982. I removed the cat, richened the carb, quickened the ignition curve and opened the scoop. It made a world of difference. I was beating a lot of my friends "faster cars". They were surprised that my T/A ran that well. It ran really strong. Most people used to laugh at the T/As, calling them the disco cars. I stopped a lot of those comments when I beat their cars.

I did the exact same mods to my wife's gold '79 400 4 speed car. The car ran 16.1 at 86 mph all stock. Felt WAY faster with the mods but my BIL wrecked the car before I could run it at the dragstrip again

[Skip Fix]

I have the 2801 in a low CR 400 and idles smooth.

[KSZR]

Originally Posted by mrmark1957

I did the exact same mods to my wife's gold '79 400 4 speed car. The car ran 16.1 at 86 mph all stock. Felt WAY faster with the mods but my BIL wrecked the car before I could run it at the dragstrip again

Damn brother in law, they can't be trusted. That sucks.

[mrmark1957]

He spun out on a damp road and put it backwards through a fence and the rear of the car stopped against a tree. He compressed the back of the car so much that the trunk lid was crumpled up and he had to climb out the window because the doors wouldn't open. Wife took the insurance money and bought a Mitsubishi Eclipse 5 speed. That was a sad day.