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The article featured on this page is from the June 2010 issue of Pontiac Enthusiast Magazine.

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Pierce Race Engines
Lansing, MI 48906
(517) 321-5051

The Quad Shop
(815) 874-4884

Rev Up Motors
(248) 321-3750

Butler Performance
(866) 762-7527

Comp Cams
(800) 999-0853

Harland Sharp
(440) 238-3260

Nitemare Performance
(203) 239-6868

Ram Air Restoration
(800) 421-8455

(662) 796-7373

Stroke Of Genius
We take a ’77 T/A’s 400, stretch it to 436 inches and more than double its original output!
Story and photography by Dan Jensen

Steve Petro, owner of the subject engine, wanted to build a fun ’77 Trans Am SE that would be the calling card for his specialty auto sales business, Rev Up Motors.

Steve wanted to restore his T/A close to factory stock, but take a few liberties to heighten the driving excitement. As far as the engine was concerned, he wanted to keep it looking stock, but make it capable of cranking out double the standard 400’s advertised horsepower of 185 while running on pump gas.

Keeping the engine looking stock limited our changes to the internals only, except for the D-port ram air exhaust manifolds sourced from Ram Air Restoration Enterprises. Internally, there were a lot of options to choose from. Since the engine had to run on pump gas, we would limit the compression to about 9.5:1, using the 6X (#8) head castings with 102.7cc combustion chambers. We ordered custom .045-inch-over Diamond pistons with 8.34cc domes in combination with 6.800-inch Eagle H-beam rods and a 4-inch-stroke cast crank sourced from Butler Performance. With a 4.165-inch bore and 4.00-inch stroke, the cubic inches worked out to 436.

Pierce Race Engines in Lansing, Michigan, handled all of the machine work plus performed the dyno chores on their DTS Dyno.

The heads were left stock except for upping the exhaust valve size from the factory 1.66-inch to the older 1.77-inch valves. A hydraulic roller cam was used so that cam lobe wear wouldn’t be an issue down the road. Steve’s T/A was going to have functioning factory air conditioning, as well as four-wheel power disc brakes, so the engine had to be mild enough to produce sufficient vacuum. A Comp Cams hydraulic roller was selected with 230 degrees duration at .050-inch lift on the intake, and 236 degrees on the exhaust, with .583- and .586-inch valve lift, respectively. The lobe separation angle was 110 degrees with the intake centerline at 106 degrees. We retarded the cam four degrees so the intake lobe was “straight up” at 110. We used matching components from Comp Cams to round out the valve train including roller lifters, pushrods, valve springs, retainers, and locks. We used Harlan Sharp 1.50:1 ratio roller rocker arms, because they offered better clearance to the valve springs and retainers.

We ran into a problem when we tried using the original EGR-style valley tray (sometimes referred to as the pushrod cover) with the “bath tub” in the center. The hydraulic roller lifters would contact the bottom side of the cover as they moved up and down. Fortunately we were using the ’78 and newer intake manifold (casting number 10003395) which has a modified EGR gas routing that doesn’t have the severe casting passages on the underside like the ’73 -77 intakes do. This allowed us to use the early, non-EGR style valley cover that does clear the roller lifters.

Jim McGowan of the Quad Shop in Rockford, Illinois, restored the 17057274 QuadraJet carb with #77 primary jets, #45 primary metering rods, DH secondary metering rods (.0567-inch short tip), and “L” hanger. Note, though, that we used a ’71 Q-jet, number 7041263 on our initial dyno tests.

We drilled and tapped the #2 and #4 main caps to accept the earlier windage tray. We experienced loss of oil pressure when testing other Pontiac engines (other brands too) when they didn’t have a windage tray. Now, all our engines get one. The only other oiling mod was to switch the oil pump’s bottom plate to a Nitemare Performance quarter-inch thick unit. During prior Pontiac dyno tests, we’ve noticed a dip in oil pressure in the middle of a pull. The Melling oil pump bottom plate is not as thick as those that came on the factory 60-psi oil pumps, so we had doubts about it when we saw pressures dip, and then come back. We didn’t experience any pressure dip with Nitemare’s bottom plate.

Ignition chores were handled by a stock HEI distributor with an ACCEL cap, rotor, coil, and wire set up. The mechanical advance curve was all in by 2,600 rpm.

For kicks, we loaded all the engine’s stats into Desktop Dyno to see what the computer’s horsepower and torque predictions would be. The head flow numbers entered were the actual ones we got from Pierce Race Engine’s flow bench. Measured at 28 inches of water, the intakes flowed 211 cfm at .600-inch lift, and the exhausts at 160 cfm. The computer predicted 413 hp at 5,000 rpm, and 511 lbs-ft of torque from 2,500 to 3,500 rpm! Let’s see what happened outside the cyber world.

As noted before, we started our tests with a known carburetor – a 1971 400-stick model, number 7041263. These are supposed to flow as well as, or better than the original 800 cfm unit that we would install later on. The ’71 carb had #75 primary jets, #46 primary metering rods, “BU” (.0547-inch short tip) secondary metering rods, and an “N” hanger. Timing was set at 37 degrees as the engine warmed up on 93-unleaded fuel. Mandrel-bent 2-inch down pipes were bolted to the Ram Air Restorations exhaust manifolds. Attached to the down pipes were 2-inch straight pipe leading to the exhaust cell. To more closely replicate the engine in the car, we ran the engine’s water pump, fuel pump, fan belt, and the alternator (to act as an idler). All systems were go!

We set our rpm test range conservatively at 3,200 to 5,200 rpm for our first pull. Jimmy Nordhof, our dyno operator, hit wide open throttle and the 436 came to life! Experience tells us that it can take a half-dozen pulls to seat the rings with power gaining on each successive run. This first pull gave us 380.8 hp at 5,200 rpm – our upper rpm limit – indicating that the engine power was still climbing when the pull was over! Torque was 425.3 lbs-ft at 4,200 rpm – a higher rpm than expected.

Brake specific fuel consumption (BSFC), which we use to tell us if the carb is lean, rich, or right on, was .42 – too lean. (BSFC is a measurement of fuel consumed per hp output.) Generally speaking, low compression engines seem to like BSFC’s in the .50 range or maybe a little higher, while high compression engines like to be in the lower .40 range. Another way to look at this is that the higher the compression, the more efficient the engine, thus needing less fuel to produce a unit of power.

We immediately changed the secondary metering rods from the BU’s with .0547-inch short tips to AX’s with .0397-inch long tips. Horsepower and torque jumped to 405.9 at 5,200 and 458.6 lbs-ft at 4,100 respectively! BSFC’s came in at a reasonable .49.

It was obvious that our lower and upper rpm limits were too low at 3,200 and 5,200, so we upped them to 3,700 and 5,700 and made a few more pulls. By now, the rings were seating well and our best numbers in baseline trim were up to 417.4 hp at 5,500, and 468.8 lbs-ft at 4,000 and 4,100. From here on out, we would also keep track of average hp and torque between 3,700 and 5,500 rpm. Averages on this pull were 386.0 hp and 443.4 lbs-ft. BSFC’s were now at a safe .51.

Since the engine responded well to more fuel, we thought we’d feed it a little more by changing out the “N” hanger to a “G”. Power went up, but minimally, so we believe that the carburetor jetting was close to optimal. So what did we get? Peak horsepower dropped back to 415.6 at 5,300, but average power went up to 387.4! Both peak and average torque increased to 471.0 at 4,000 and 445.0 respectively. BSFC’s were still good at .50. Since we still had to run and fine tune the actual carburetor that was going to be on the engine when installed in the car, we didn’t waste any more time changing our test carb.

An easy change to make was simply advancing the timing from 37 to 41 degrees. The engine liked it up top more than at any other part of the power curve, rewarding us with 6.5 more peak horsepower, or 422.1 hp at 5,500. However, the average horsepower only increased one-half hp to 387.9. This is what usually happens when we advance an engine’s timing, we gain peak power at the expense of peak torque. That’s precisely what happened here: peak torque dropped slightly to 468.1 at 4100. However average torque hung right in there at 445.3.

If the engine liked 41 degrees, would it like 44? Yes, it did … kind of. We were fighting the law of diminishing returns: Instead of peak horsepower going up in whole numbers, we managed only 8/10ths, peaking now at 422.9 at 5,500. The real story was the average horsepower, which fell slightly to 387.4. Peak torque dropped back further to 465.9 lbs-ft at 4,100 and average torque suffered too, now settling in at 444.5, telling us 44 degrees was too much for this engine.

We set the timing back to 41 degrees, and to confirm that it was the right move we made another pull. The engine responded better than it did before at this setting, probably because the engine was more broken in. (Regardless, we’ll always take higher power numbers, no matter how it’s achieved!) At 41 degrees, horsepower was now 425.0 at 5,400, while the average hit 390.2! Torque hit 471.1 lbs-ft at 4,100, with the average at 447.8. These numbers were our highest so far! BSFC’s were at .50 as before. Beautiful!

Now, it was time to install the engine’s correct carburetor – the 800-cfm number 17057274, just as Jim McGowan had restored it. All we can say is that Jim did a great job! The numbers speak for themselves with horsepower peaking at 427.2 at 5,600 and average horsepower maintaining 389.2. Torque didn’t change too much: the peak fell slightly to 468.1 at 4,000, as did the average to 446.5 lbs-ft. These numbers may not seem impressive at first – until you consider that the BSFC’s were indicating a rich condition: we were up to .53 for the pull.

To lean the carburetor slightly, we decided to just change the rear hanger from the “L” to a “P”. Our guess was right on the money: our BSFC dropped back down to .51. We were rewarded with the numbers going in the right direction again – upward! Peak power was now at 433.1 at 5,600, the average at a new high of 391.8. Peak torque rebounded to 470.4 at 4,100, but the average jumped big time to 449.4 lbs-ft.

Satisfied with the carburetion and timing, it was time to open up the exhaust by replacing the 2-inch pipe extensions off the down pipes with 6-inch header pipes. This gave the engine an authoritative sound, like it had open headers. Hopefully the better sound would net better numbers. And, boy, did it! Peak horsepower jumped – no, leaped – to 439.4 at 5,600! Average horsepower jumped even more, by 7.1, to 398.9. Torque was equally as impressive with the peak now at 476.7 lbs-ft at 4,000, 4,100 and 4,200. Average torque climbed to 457.5. Surprisingly, the freer breathing exhaust pipes didn’t affect the BSFC, which remained at a safe .51. A quick look at the spark plugs and checking the exhaust gas temperatures (1,200 degrees) confirmed things were OK.

For our last test, we installed a factory air cleaner base that had been modified by removing the sides. The idea here was to aid air flow into the carburetor in hopes of making more power. (What else?) We’ve seen the air cleaner base both help and hurt an engine’s output. If it helps, maybe we’d get similar results in the car with its air cleaner installed. Fortunately on this carburetor, the air cleaner helped tremendously. We experienced the best numbers across the board. Horsepower peaked at 446.5 at 5,600, and average power eclipsed 400, reaching 403.8. Peak torque climbed to 481.8 at 4200, while the average settled in at 463.0. It’s amazing how much the air cleaner base affected the engine’s dynamics because the BSFC dropped to .48, suggesting this carburetor appreciates a cleaner air flow path in. In hindsight, we should have enriched the carburetor a little to bring the BSFC back to around .50. There’s a good chance that the 436 would have hit 450 hp and maybe 485 lbs-ft of torque.

Regardless, Steve’s goals were achieved: the engine made more than double the standard 400’s horsepower on pump gas. Heck, it even made more than double the optional W-72 400’s power. Yeah, we could have gone for even more power, but we did pretty well, when you consider the only deviations from stock were the stroker crank, roller cam valve train, and exhaust valve/manifold upgrades. Steve can open his TA’s hood and show everyone what looks like a stock 400, yet it can lay waste to his steamroller tires at will.

Steve Petro’s 436-inch “400” produced more than double the horsepower and torque on the Pierce Race Engine’s DTS Dyno than it originally did when Pontiac screwed it together in ’77 for Steve’s Trans Am.


1 The original 400 had served Steve well and was in good shape internally when torn-down, but he wanted to boost power while freshening it up, to make the car a bit more enjoyable to drive. His goal was simple: double the engine’s 185 horsepower rating from the factory on pump gas.

2 Here’s the block after cleaning and standard prep work, all handled by Pierce Race Engines. Note the two-bolt mains. The block was deburred, the cylinders were opened up to 4.165-inch, the mains were align-honed, the decks were milled to true them up, and new cam bearings were installed along with fresh core plugs.

3 The four-inch stroke cast steel crank came from Butler Performance and was responsible for a good part of the engine’s displacement bump and monster torque.

4 The #2 & #4 main caps were drilled and tapped to secure a factory-style windage tray, then the caps were secured to the block with ARP main studs.

5 While a forged crank and four-bolt caps would have added some upper rpm durability, Steve didn’t plan to run the engine at sustained high rpm, so the cast crank and two bolt caps were deemed more than sufficient.

6 Custom .045-inch over Diamond forged pistons with 8.34cc domes would yield about 9.5:1 compression with the 4-inch crank and 6.8-inch H-beam rods from Eagle. The ring gaps were checked and filed to fit, as needed, then their gaps were indexed to minimize blow-by.

7 The new piston and rod assemblies filled up the block quickly and would bump compression to about 9.5:1 with the 6x heads’ 102.7cc chambers.

8 You can’t tell true compression without cc’ing the cylinder volume with the piston at TDC, and that’s what’s going on here.

9 Here, you can see the Comp Cams hydraulic roller cam inside the deburred block. A hydraulic roller was chosen to minimize lobe wear. A double-row timing chain and gears linked the cam to the crank.

10 Here, the cam is being degreed to ensure it was ground as indicated on the cam card.

11 Piston-to-valve clearance was checked with lightweight valvesprings. Note the Harland Sharp full-roller aluminum rockers.

12 Oiling system mods were few: a new Melling high-volume pump was equipped with a Nitemare Performance pump cover plate to eliminate pressure fluctuations, and a windage tray was installed – also to minimize pressure changes.

13 Here’s a close look at the difference between the stock oil pump cover plate (left) and the extra-thick Nitemare Performance cover plate, installed. The standard cover will literally flex and bend, allowing the gears to move and therefore pressures to change.

14 The engine really started to come together when the rebuilt 6X heads went back on, with new valve springs, retainers, locks and valves. The stock oil pan, timing cover and water pump were used to retain the stock appearance and save a few bucks.

15 Wearing a fresh coat of GM Blue and sporting its full valvetrain, including the Harland Sharp rockers and custom-length pushrods, the engine was just about ready for testing.

16 Fully dressed out with Ram Air Restoration Enterprises tubular exhaust manifolds and other goodies, the engine was ready to go on the test stand for break-in and inspections.

17 With a test carb installed for break-in, the engine was nestled into a break-in stand constructed from a modified F-body (or X-body) subframe. Breaking it in on a test stand allows you to check for any leaks or problems and correct them before spending big bucks on dyno time.

18 Here, Dan Jensen is performing one of the numerous metering rod and hanger changes in the never-ending quest for optimal power on the DTS Dyno at Pierce Race Engines.

19 Yup … that’s Dan again … with another metering rod and hanger change. Dan’s one of the best in the business at tuning Rochester Quadrajets for max power.

20 Dan tweaked timing several times, too, as high as 44 degrees, which proved to be too much. The engine made max power with 41 degrees total.

21 Here, Dan prepped the engine’s original carb to replace the test carb. The original was restored by Jim McGowan at The Quad Shop and jetting was just about perfect – Dan tweaked it with a hanger change.

22 What’s it take to fine-tune a Q-jet on the dyno? For Dan, it comes down to patience, experience and a boat load of hangers, metering rods, jets and miscellaneous “spare” parts.

23 Testing the engine with it’s original carb and an air cleaner base yielded a power leap to our best pull of 446.5 hp with 481.8 lbs-ft of torque. BSFCs had actually dropped a little, so changing that hanger again may have yielded better than 450 hp, but our crew was satisfied with the engine’s performance, as it had more than met the goal.

24 Here, Dan Jensen (left) and Steve Petro (right) sport big grins after a hard day’s work in the dyno cell at Pierce Race Engines.

All Revved Up

Growing up in suburban Detroit where almost every dad on the block worked for the “Big Three,” it was not hard to fall in love with cars. It seemed like every garage had a new car in it at the time. My passion with cars grew while playing with my Hot Wheels and grew more and more every day as I got older. I would ride my bike up to the store to see if they had the latest issue of Hot Rod and Car Craft magazines.

On my 12th birthday, my parents took me to see Smokey and the Bandit. When Burt Reynolds drove the Bandit Trans Am out of the back of the semi trailer ... I was hooked for life! It was a life-defining moment for me, even at 12 years old.

I followed my dad’s footsteps and went into the automotive industry. After working 20 years in Engineering and Design for GM, it was time to take my hobby of muscle cars to the next level and start Rev Up Motors.

I have had the privilege of owning some real nice cars along the way. With owning hundreds of Trans Ams, I have noticed a common theme with many of my customers. They loved the second-generation Trans Ams, but one thing was lacking ... POWER! Especially for the later models. After having several real fast cars, I wanted a 1977 Special Edition Trans Am that looked stock to the untrained eye ... but wasn’t.

I located the car I always wanted and started to just do a repaint on it. Then it snowballed into a complete rotisserie nut and bolt restoration. After talking to Dan Jensen, I told him I wanted my car to be scary fast but to appear stock in the engine bay. A few other requirements were to have over double the horsepower of a stock engine and run on pump gas. We could have achieved this goal easier by starting with a 455 engine, but I wanted to start with a 400 block and heads and see if it could be achieved.

The engine build exceeded my expectations in every way. It definitely kills the tires and pulls very hard throughout every gear, without any loss of power. This particular car was delivered to the dealer on my birthday, the day I saw Smokey and the Bandit. Coincidence? Fate? It’s just the right one, the worthy one. — Steve Petro

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