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- - '78 W72 400 Dyno Results (https://forums.maxperformanceinc.com/forums/showthread.php?t=855368)

'78 W72 400 Dyno Results

We thought we'd share this in the Street Forums. Dan had a good dyno session last week with the W72 400. He rebuilt the original numbers matching engine with .040" over Icon forged pistons w/4.5 cc valve reliefs that are .005" out of the hole and with .045" x 4.328" Felpro head gaskets to provide .040" quench depth. The 6X-4 heads were minimally cut for trueness and measured 92.45 cc's average for an final static compression ration 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. He had a Summit 2800 cam (204/214/112 @ .422"/.444" is pretty close to the original W72 cam specs) on hand, so was utilized, along with new 'old' Crane hydraulic lifters along with a new Melling 60 psi oil pump. The one modification/upgrade was the use of 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 (and all) pulls 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 lbft torque @ 3600 rpm (351.2 hp/444.5 lbft uncorrected). The correction factor was a low 1.026 as the weather conditions were very good...low humidity, high barometer, and 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 lbft @ 3600 rpm (362.0 hp/447.6 lbft uncorrected) on the final pull (#14). The highest torque reading was on pull #13 at 460.3 lbft.

This engine surprised us by exceeding our first 350 hp/450 lbft prediction. Pretty good for a smog motor!

Dennis

That’s very nice!
Surprising numbers seeing as it was not even 9 to 1 compression and it was driving its own water pump in the test!

To make that level of power it would seem that intake flow wise the motor was using 180 cfm out of the about 208 average cfm that those heads flow.

I would be interested in what muffler might have done to those numbers in regards to that 8.75 comp!
Congrats and thanks for posting it!

Nice build, thanks for sharing

Nice build! About what I have in the 81 except a Peformer intake and a 73 Qjet.

Big WP pulley!

Nice numbers! Just goes to show how well a basically stock engine with the right combo of parts can run.

I'm curious why you used 42 degrees timing and didn't change or experiment with it? That seems high...?

..good results but seems for me a but high for such a tame cam ....

Dennis,
Thanks for sharing some more information.

Dennis posted this in the race section.

Quote:

Originally Posted by SD455DJ (Post 6302415)

Don, Jonny, & Stan - We found that there was no quick way to check a cam's legality without taking extreme measures, time, and effort for a race where there is nothing at stake, except maybe bragging rights. Having fun and learning about your musclecar are the most important 'rules' of the race. We've had cars that didn't run really fast that had bigger "illegal" cams by the rules and cars that downright flew that had smaller than advertised factory spec cams, so we began to realize, as did the racers eventually learn, that the factory got it right in the first place which translated very well for our type of race with street tires. Now we do check compression ratio (1.5 max over advertised), displacement, convertors, and tire rubber (no 'treated' street tires or tread depth into the wear bars) on any new car that runs much quicker that we feel they should, such as a '74 Laguna low compression LS4 454 running low 13's at 105 mph, red flags go up, and we're going to look that car over. If we find 'issues' he is allowed to race still, but has to make corrections to the car if he brings it back next year because we will check it again.

Jonny, I built a '70 XV code 330 hp 400 4-bbl (small valve 10.0 compression) for my Tempest that made 380 hp/450 lbft torque through exhaust logs (2" outlets!) with a Summit 2801 cam. It has a very mild idle and made 20" at 1200 rpm, so running an 068 cam is not an issue. The et difference between the 067 and 068 cams in a good engine may be .2 seconds at the most. We are not going to get excited about that at the race...except if you were running low 12's , then well give your car the 'once-over'. If you had at least 10.0 static compression, I bet the 2802 cam would manage 18" vacuum at 1200 rpm.

Yes, you can run any cam that can meet the vacuum rule and race. As Mark Weymouth said in the quote Stan had in a previous reply, we found in dyno-ing several RAIV engines of identical parameters, with exception of the cam, that the factory 041 cam (and faithful clones) made the most power on the dyno and at the track. The factory engineers (Mac McKeller) knew what they were doing.

Dennis

This graph shows the HP curve for each.

Stan

Interesting..I've always thought those engines were underated..many enthusiasts get hung up on the low net hp ratings. Also combined with the lazy gearing most came with from the factory. I've always found on those low compression engines cranking the timing up in that 40 degree total or higher range works well.
My son's car with a worn out stock 400 with 342 gears mild convertor full weight ac car dips into the 13's easily.

Really impressive numbers for that small cam and low compression

Quote:

Originally Posted by OCMDGTO (Post 6303887)

Really impressive numbers for that small cam and low compression

I think the test DA was really good as well...I'd like to know more details on the cam install??

Quote:

Originally Posted by ta man (Post 6303892)

I think the test DA was really good as well...I'd like to know more details on the cam install??

The cam was degreed to verify specs and installed "dot to dot" (straight up) and that put it a 108 degrees, or 4 degrees advanced.

Dennis

Quote:

Originally Posted by Stan Weiss (Post 6303869)

Dennis,
Thanks for sharing some more information.

Dennis posted this in the race section.

This graph shows the HP curve for each.

Stan

Thanks Stan for sharing the graphs for the W72 and the XV 400's. It isn't unusual to get 425 hp/475 lbft from a 11.0 to 1 D-port 400 with an 068 cam in Pure Stock Race trim.

Dennis

Quote:

Originally Posted by Will (Post 6303846)

Will, Dan dyno'd another '79 W72 400 back in 2012 that was just a re-ring and new bearings with a custom ground cam (202/219/[email protected]"/.450") with only 8.1 to 1 static compression that made the most power at 42*(lost hp/tq at 40 and 44 degrees), so he just used that as a starting point and left it there for all the pulls.

Dennis

Quote:

Originally Posted by OCMDGTO (Post 6303887)

Really impressive numbers for that small cam and low compression

Thanks OCMDGTO! This W72 is a good and careful rebuild (not blueprinted like an NHRA stock class racer) with good quality forged pistons and rods, careful finish hone on the cylinders for moly rings. There is no head or manifold porting, let alone any port matching, smoothing, casting flash removal at all. It's a low compression pure stock type build with the benefit of factory RA exhaust manifolds and Pypes 2.5" mandrel headpipes. The exhaust system is a distinct improvement over stock by 10 hp/lbft. If the engine was built with the max allowed compression (8.1 + 1.5 = ) of 9.6 to 1, it would make in the 380 hp/470 lbft range, the cam being the limiting factor.

Dennis

Thanks Steve25, PAUL K, Skip Fix, and dragracerx2813 for the compliments!

Dennis

Quote:

Originally Posted by ponchorob (Post 6303853)

..good results but seems for me a but high for such a tame cam ....

ponchorob, It comes from years and years (30+ now) of building, tuning and running lots of Pontiacs at the Pure Stock Drags.

Dennis

That would make a great daily driver,thanks for sharing

Hmmm. And 400`s don`t make torque.:rolleyes::)

Figure the NHRA stockers with a 78 motor are running mid 11s!.

The Summit cam in the 400 in the 81 degreed right on "dot to dot". I built the 81 car out of someone else's stalled 301T to 455 SE TA and extra parts I had collected from the 78 (HO oil pan) for the kids to drive to high school. So I did not want it to have too much HP! Son never got used to a car with a carb and a choke in the cold! Put a Shaker hood and extra Shaker scoop on it this summer.