As the OE restoration of my 71 340 Cuda convertible progresses nicely, it was time to finish up on the engine rebuild via 8 pulls on my builders dyno here in NJ this past week. They have 50 years of experience in the business at the highest level.


After a thoroughly discussed and careful selection of components, and expert machine work for the matching number block, only polishing the original crank (NOT A STROKER), and utilizing the original heads as well of course, the results, after some carb jetting and timing adjustments, were VERY satisfactory!


Eagle rods, Manley stainless valves (2.02 / 1.60), a special Comp cam grind (hydraulic roller), and Comp Cams adjustable rockers were the primary changes from OEM. Pistons are original Chrysler .020 over factory cast pistons that I have had for over 30 years. I sent the intake manifold to Extrude Hone in CA for mild internal cleanup and enhancement of .025 per surface, which is the minimum. Not cheap, but a nice finish. Compression ratio is 9.57 for pump premium fuel. BP is the most consistent currently. Driven oil.


Max. HP: 407.2 at 5900 Max. TORQUE: 399.8 AT 4400 Both carbs were within 2 HP. The car will have a 3.91 axle, and I will add a slight more loose torque converter from Turbo Action.


This was not a cheap deal, but like most things in life, you get what you pay for!


Bill Rolik

Nice build. Thermoquad for the win.

So take off 20% for the factory manifolds? Maybe not, but they will hurt a little bit...

Obviously, there will be some loss with factory manifolds, but it is typically nowhere near 20% on any engine.

The only way to know the exact number of course is to do the swap. I had my exhaust manifolds coated at Jet Hot (cast iron finish, and they look awesome). My NOS front head pipes, which may be one of the few sets on the planet, just came back from ceramic coat, so we would have to LENGTHEN THE DYNO ROOM by 8 feet in order to facilitate that, and of course that is not going to happen! LOL!

BR

nice to see you used a T-Quad !
i like them as well ! how much jet and metering rod tuning did you do ?

OEM concours restorations of course mandate the Thermoquad to be used, and they are good units for throttle response and driveability anyway. Ceralli had offered a suggestion to just build a stroker, which is a popular upgrade, but I declined. The overall compression ratio was matched with being able to use BP premium fuel. Per NHRA specs for Stock and Super Stock for a 71 340, if you run maximum deck height of .045 above the block deck, matched with a .036 compressed gasket thickness, and a minimum chamber volume of 63.3 cc, your static compression is right at about 12 to 1 (And that does not include using "tuliped" valve reliefs in the pistons, as opposed to flat cut valve reliefs. Then the ratio is a bit higher). I wanted no part of using VP or Sunoco race fuel for street driving. Otherwise detonation would occur.


Much thought and research went into the cam profile for my desired results. There will be showtime, but I will drive this car periodically as well. At least in my case, as far the tuning on both carbs, it was minimal, but did show much more sensitivity than I had anticipated to jet size. Metering rods were stock. Timing was pretty sensitive as well. Of course, there will probably be some minor carb adjustments when it finally goes in the car with the factory exhaust and air cleaner installed.


Bill Rolik

Will you extrude hone the exhaust manifolds? I’m guessing you’ll have a high 12’s/ low 13’s car on the Polyglas.

I did not do the exhaust manifolds. Cost prohibitive (900.00 not including shipping both ways) versus the potential results. That is only .025 material removed per surface, so .050 total width. More removal, more $$$. It is more important to fill the cylinders. Can't do anything else about factory manifolds and a full exhaust system when OE spec. And I have no time, desire, or extra $$$ to develop the BS27 Cuda as a F.A.S.T. CAR. I am full bore on my new Super Stock car now.


I may run the car when finished, but that was not the focus here.This is an OEM GOLD type resto with a carefully crafted and user friendly, strong engine combo underneath.


But I can tell you this: Before my original 71 340 Duster became my Super Stock car in 1974, I would DRIVE to Island Dragway and run that. Headers, manual shift valve body, and a 4.89 gear (yes, correct. I drove it on the street like that. With L78-15 Cadillac Goodyear Polyglas tires.) I would run 13.0-13.10 at 102 all day on hard as a rock, borrowed and well used 7" Cheater slicks. With 7 pounds of air. Scary at times. 100% untouched engine. The only other addition was a Carter electric fuel pump. I had a quick disconnect exhaust system with flex pipe and Cherry Bomb mufflers for the street. Those were the days!


With the significant power difference in this engine, hard to say on ET and speed for the somewhat heavier Cuda BS27, (but well into the 12's for sure, perhaps 12.40 or so), because it would pretty much obliterate the Polyglas tires. I would have to go with a borrowed pair of short 28" X 9" Hoosiers or M/T real drag tires for legitimate consistency.


BR

Yes, TQ!

Are the cam specs a secret? I'm always interested to see what cam specs make good power while keeping good drivability.

Nice. Are you posting your build on here?

Body and paint is quite a ways off. Serious $$$ there! I am in the midst of component restoration, and most are done. All powder coating done. All plating done, except bumpers (1500.00 or so for that for sure). Broken/pitted fastener replacement (all correct head markings of course) was over 2000.00. Fasteners are a world all by themselves! Differentials (3.91 and 3.55) and transmission can be assembled most anytime, all three with 100% NOS Mopar components. Torque converter from Turbo Action anytime. Still need to order the seat covers, convertible top and curtain, and dash pad, all of which have LONG lead times. Otherwise about 99% of all NOS parts (60 some odd tote bins worth), correct date coded where applicable (even my original dated motor mounts), and the very small handful of reproduction parts are on hand. I have 8 NOS F70-14 whitewall tires (Tire code T86), 16 NOS wheels, and 16 NOS W11 code "flying saucer" wheel covers (original to the car). Even enough for all of my Polyglas snow tires as well. LOL! FYI: This whole deal of acquiring and refinishing parts involves over 30 years, including traveling the country years ago to literally hundreds of dealerships. The volume of parts I have acquired are pretty much not out there at any price today, so I am just fortunate I started when I did. Body and paint source to be determined.


And all of this is going on side by side with my new Super Stock car, which after numerous upgrades is expected to be ready some time next year.


I do sleep now and then! LOL!


Bill Rolik

Okay, Bill. All the best!

I like it that you upped the power SIGNIFICANTLY even though this will be a concourse restoration. I never understood restoring a car and having the budget to have professional results- but then rebuilding the engine to exact OEM output. So many power improvements can be had without changing the external appearance of the engine or disrupting drivability. In the 1990s I read one reason so many concourse big block cars at car shows ran mid high 15s when the owner FINALLY ran the 1/4 mile. A big factor was that the engine was rebuilt with typical 8.0:1 compression replacement pistons as the owner was not interested in best power possible. Shame.

Those headers look familiar ! nice motor !

Yes, Bill


I am sure they look familiar! LOL!


Bill Rolik

I bought them just to dyno my motor there as I didn't want to put the 8 sensors in my new headers .. turns out those headers didn't fit my W2 bolt pattern anyway

Bill, Great build. You are going all out on this one. Nice talking with about it today,. Thanks for all the info.
Bob