Stock Stroke 340 Build with NC Engine Builder

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gzig5

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I hope you’ll all stay with me on this because I can get a little verbose. Hopefully it will make for some interesting reading and some discussion at the end. I want to put out a build thread on the stock stroke 340 I’m having done by @NC Engine Builder. According to Shawn it is a relatively mild build, and I’m sure that it is compared to some of the stuff he gets to work on, but for me it will be the stoutest motor I’ve had. I’m a lifelong Mopar guy. My first car in 1983 was a 72 Barracuda 318/904, then a 77 Aspen RT with 318/A833OD and moon roof. We had several Dusters, Chargers, Cordobas, Satellites, and Sport Furys over the years. This motor will be going into my 73 Cuda that I hope to do a lot of road course racing in and drive on the street regularly. Might do some drag racing but the chassis is being setup to handle and stop. I hang out at FEBO as well, but this story is about the motor and there is usually more traffic on FABO. Car was an automatic but I’m converting to an A833 four-speed. Rear-end will be a B-body 8 ¾ with spring relocation shackles for tire clearance, sporting a 3.55 SureGrip. May need to go 3.91 or steeper but that is going to be getting into overdrive territory, which I hope to hold off on for a while.

So the story of this car is a long ordeal over many years so far but I’ll try to cut to the chase and stick to the motor. Motor/trans was non-numbers matching and didn’t run when I got it. It’s a 71 340 standard bore block and 2.02” J-heads. It was road hard and put up wet by previous owners, and was a bit of a half-assed assembly job as it turned out. I redid the ignition wiring and a full tune-up and oil change which including dumping about a quart of fuel out of the oil, so the 4160 carb was rebuilt and I got it running. Ran OK, but definitely not great. Started driving and making improvements over the next 18 months and then found out that it was unsafe to drive due to improper repair that was hidden. Engine had to come out to fix the chassis so I took the opportunity to disassemble it in order to understand what was in it. Turns out it had 10:1 pistons, standard 340 cam, and -.010” forged crank (later realized that it was a 318 crank because the journals were not drilled. Probably was way out of balance with 340 pistons). As I took the number seven piston out, the compression ring fell in two pieces. It was cracked and let go when it could expand. I was going to just re-ring and drive it for a while but I realized that it had about .005” taper in the bores. Mike from B3 suggested that a rigid hone might take some of that taper out and still allow use of the stock pistons. Turns out the shop I asked to do that work just ran a ball hone though and did a sketchy job on the hot tank, not getting all the plugs and junk out. A real cluster.
 
Fast forward to this fall and I decided I needed the engine ready for when the bodywork is hopefully done this summer. I had picked up a spare 340 block but the main caps didn’t match so needs line bored. I was thinking I would rebuild the original 340 mostly stock and play with it for a while, and have the extra block line bored and prepped for a stroker kit when the funds would allow the kit and appropriate heads. After the trouble with the first shop, I couldn’t find anyone nearby that would/could line bore and hone with a torque plate for a Mopar. I’ve been impressed with the work that NC Engine Builder had discussed over the years so I decided to contact him and see what we could do. We had a phone conversation around Thanksgiving and I would be able to drop off the week before Christmas as we have family we visit regularly in Florida. We came to an agreement on my expectations and his responsibility and the task was set. The detour to Concord, NC from Milwaukee only added about an hour to the first leg of the trip. As I gathered all the crap I’d collected for the build, which I had every intention of doing myself, I realized my current budget wasn’t going to allow the second block to go along. I filled half the bed on my Ram truck with the engine and all the extra and duplicate parts I had, just in case something was needed and I wouldn’t have to ship it. Included were the 71 block, lightly used ProMaxx 171 heads, original pistons/rods, set of NOS +.030” L2316 forged pistons on stock rods, original crank which I realized was a 318, spare 340 forged crank I picked up, used custom Comp SFT cam I picked up on FABO, new Comp SFT lifters, PRW 1.6 rockers I had gone through and measured for B3 shim kit on the ProMaxx heads, Mopar M1 intake, Eddy RPM AirGap intake, SpeedMaster head studs and damper, new water pump, Kevco 7 qt pan, Hooker 1 ¾” headers, some gaskets and other crap. Trip was uneventful and met with Shawn on Sunday morning and unloaded most of the stuff I had brought. Discussed the build and away we went to Florida. I had decided to let Shawn do the full monty, machine and assembly rather than assemble it myself. I need to focus on the other stuff and I felt confident that he would do a good job.

Over the next couple weeks, Shawn got into the pile of stuff and started on the block. I started looking into sourcing a solid roller cam that would be appropriate for my intended use and complimentary to the head flow. I sent out five RFQs looking for something with a solid low-mid range and about .600-.625” lift so we could use the valves I have but change springs. I had decided to get a little more aggressive with the 340 build than originally intended and not spending on the second block freed some funds for the roller, supposedly.
 
He confirmed that there was at least .005”-.006” of taper in the bores but they should clean up at .020 over which I was happy with as that should leave some extra meat for the future. The taper is probably what caused the ring to break. Because I want it to rev he suggested a modern piston and ring package. The cost is reasonable and for my intended purpose, less reciprocating weight would provide a little free HP and rev like crazy. He has a set of Icon .020 flat top pistons and Scat rods readily available. They will allow us to get to the 10.5:1 - 11:1 compression range I want to be in. I had intended to tube the lifter galley but he wasn’t too high on that course of action and suggested bushing the lifters, which provide several benefits. Since I have plans for future builds with bigger heads and cam, it made sense to spend the extra for the bushing work, which already paid dividends which we’ll see later. The difference in weight on the new pistons/rods was an impressive 355gr per hole.

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In very short order, the lifter bushings were installed and the bores were over bored and torque plate honed to fit the new Icon pistons. The decks had previously been dressed and were well within what he considers acceptable and the pistons end up one or two thousandths in the hole. Correcting the decks to zero-zero would require a non-standard head gasket thickness and isn’t worth the trouble.

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Next we were on to balancing the rotating assembly. Tech tip for the inexperienced… I had drug along my flywheel and clutch assembly as I’ve read of people using them while balancing the crank. I was told to take them home because those parts can change over the life of the motor and you don’t want the balance to be dependent on something like that. A flywheel can be balanced separately if needed.

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Then it goes into the block. Notice the Swiss cheesed counterweights as a result of the lighter rotating assembly. I think there was only one hole in each originally. I think he said 186 grams came off one end and 160 something the other.

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The heads I brought are a lightly used pair of standard port ProMaxx 171 that I picked up off the FABO classifieds from someone that went to TF heads. Shawn started playing with the heads early on so we would know what to tell the cam grinder an get an idea of how far we could go. He flowed an intake port and got 246 @.550 which is about 5 cfm less than advertised by PM. He said he would clean them up to see what they would do, but try not to go crazy. Some quick chamber work and knocking a few barnacles off in the port resulted in 268@.550. No tubing, or other significant work. Commented that he SSR was pretty nice and valve job not bad. He went back later and spent a little more time on the chamber area mainly and the result is as follows on the intake side.

Lift inchIntake advertisedbefore Port workAfter Port work
.1007177.4
.200133138
.300191197
.400236242
.500251264
.550246274
.600254278
 
So on the same bench with a very reasonable amount of work, the flow was improved 28 cfm at the .550 lift mark. I think that is a great result and should suit my current needs very well. They really shine at the higher lift. He can comment on any techniques but there was nothing fancy.

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Heads were cut to 57cc to give us 10.7:1 static with a .039 Fel-Pro head gasket.

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We went round and round on the solid roller cam and it’s an involved story, but in the end, there were going to be delivery issues due to the availability of cores and the relatively small lift of what I needed exacerbated that because most cores available would cut through the hardened layer to get down to my lift numbers. Howard’s, Bullet, and Scheider all came in fairly close to each other and in rising order of aggressiveness. I probably would have gone with the Bullet offering. But as we talked and Shawn got to playing with the heads, he felt that the SFT that I brought would handle the job. It would also save close to $2000 in parts for the cam, good roller lifters, and melonized oil pump drive. I can spend that money elsewhere or put it away for future improvement. God knows I’m not done spending on this car! Here is a summary of the offerings and then the custom Comp grind that I picked up used. It’s about a step smaller than the smallest roller

HowardsBullet Racing662-893-5670Schneider619-297-0227
Solid rollerSolid Roller
INT. DUR
277​
Core
311619​
Duration Advertised288 / 296
EXH. DUR
285​
Duration AdvertisedDuration @.050"254 / 262
CAM LIFT INT/Ex
0.390/.390​
Duration @.050"249 / 255Lobe Lift.394 / .397
Valve lift @ 1.5
.585"/.585"​
Lobe Lift
0.375​
Lift ratio 1.5.591 / 596
Valve lift @ 1.6
.624"/.624"​
Lift ratio 1.5
0.563​
Lift ratio 1.6.625 / .635
INT/EXH DUR @ .050
245 / 253​
Lift ratio 1.6
0.600​
Split108°
​
Split
108​
LOBE SEPARATION
108.0​
Install CL
104​
ADVANCE
4.0​
LobesHR305/375
HR311/375


Comp SFT we used

Duration Advertised @.020272 / 276
Duration @.050"242 / 247
Lobe Lift.360" / .366"
Lift ratio 1.5.540" / .549"
Lift ratio 1.6.576" / .585"
Lobe seperation109
Install CL105
Valve Timing @ .050OpenClose
Intake16 BTDC46 ABDC
Exhaust56 BBDC10 ATDC
 
Now the fun with the heads really started. The PRW rockers are pretty nice pieces but they fit horribly on these heads and need to move up and away from the valves to avoid the springs, which in this case were only 1.470” diameter. Maybe this isn’t a standard size or the pockets were shrunk to fit them but Shawn was having trouble finding something to fit. After some looking around he found some new ones on his shelves somewhere that would fit the bill. He seems to have a lot of “stuff” on hand.

We were discussing several options for fixing the geometry including having him do the shims, B3 do the shims, topping the saddles and doing blocks like a W2 head, who was going to cut the shafts, etc. I was in talks with Mike at B3 a couple years ago and took all the measurements, but hadn’t pulled the trigger because I didn’t know what cam I’d be running back then. In the end B3’s schedule couldn’t get us in the timeframe I needed in order to pick up the engine on my next trip in March. We decided that it didn’t make sense to have Shawn do the shims or shafts, when I have the capability at home with my mill and lathe, but just hadn’t got it done before. The quick and dirty solution was to put on a set of 273 style rockers from Crane which he had and were already clearance. That gets us going. I will have some time before the motor is in the car and will arrange for the shims with B3 to finish the job, and I also have a set of 273 rockers as backup. This is significant though because we now have .026” less lift on the intake valve with the 1.5 ratio rocker.

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A couple of the cam grinders suggested that I use the DP AirGap intake instead of the Mopar M1 single plane I had planned on. Shawn suggested the AG would help with the low and mid range torque for getting out of the corners at lower engine speeds. I knew this was a possibility and is why both were on hand. Shawn did me a solid and threw the intake into his vapor blasting tank to clean the corrosion off of it. I had a battery blow its top off while charging and spray battery acid all over the engine bay and my garage. That caused a bunch of issues with the surface finish (and a soiled pair of shorts as I was in the car) because I couldn’t get it cleaned off immediately. Now it looks like new. Because the heads were surfaced to get compression, the intake didn’t fit properly. The intake faces of the heads could be adjusted to compensate but Shawn’s stance was to cut on the cheaper part. I’m good with that and if I need to use the intake on another set of heads, doubling the gasket should take care of it.

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I would have loved to have been there for the pulls but not to be. I guess the session had several challenges with the equipment but the engines ran well. We didn’t get all the data we had hoped for but I’m solidly happy with the results. The 750 dyno carb was leaking and had to be changed for Shawn’s shop 950 Holley, out of the box with no tuning. Even with all that, the motor made 439.4 ft-lbs @ 4300rpm and 457.8 hp @ 6300rpm. The oil pressure is superb, as it should be with good bearing tolerances and the bushed lifters. The HP hadn’t peaked quite yet and may have had a couple more with a couple hundred more rpm but he didn’t see a need to push it. I have not idea what the timing was or if it was played with and maybe he can comment on the runs.

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Edit to add chart for better visuallization.
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I am confident that with a little bit of carb and ignition tuning the current combo would be over 475. The addition of the 1.6 rocker could add another 10-15 hp? The heads are working pretty well in that area of lift that I’m missing from .540-.576 and should be getting the valve open a little faster. All good fodder for discussion.
I’ll be heading to Florida and picking up the motor on the way back at the end of March. Communication with Shawn throughout the process was very good. We typically were exchanging texts on one subject or other or updates two to three times a week or more. That is important on something like this. Nothing was done without an opportunity for input and there was always reasonable advice when I asked for it. I’ll use Shawn without hesitation for my next build, even if I have to ship the parts. He has an excellent, full service shop and can do it all with excellent turn around. This build took less than two months front to back and includes time lost waiting for parts.
 
Hope you enjoyed the show. Shawn should be able to fill in any details I wasn't privy to. Most of this was harvested from the text thread we've been running for the last couple months, so I am sure there are some gaps.
 
This is the car after I got it running.
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And as it is currently

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A ways to go.

And that's enough E-body content.
 
Very nice build and good numbers that will only improve with your rockers.

I also have nothing but high praise for Shawn and will continue to use him for all my machine shop needs. IMO he is a gold mine of knowledge and resources.
 
Shawn is excellent to work with.
That’s a heck of a lot of work needed for that Cúda.
I’m in for a similar amount myself.
 
gzig5 said:
I would have loved to have been there for the pulls but not to be. I guess the session had several challenges with the equipment but the engines ran well. We didn’t get all the data we had hoped for but I’m solidly happy with the results. The 750 dyno carb was leaking and had to be changed for Shawn’s shop 950 Holley, out of the box with no tuning. Even with all that, the motor made 439.4 ft-lbs @ 4300rpm and 457.8 hp @ 6300rpm. The oil pressure is superb, as it should be with good bearing tolerances and the bushed lifters. The HP hadn’t peaked quite yet and may have had a couple more with a couple hundred more rpm but he didn’t see a need to push it. I have not idea what the timing was or if it was played with and maybe he can comment on the runs.

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Nothing better than reading a good write up on a Sunday morning with a cup of coffee-well done, very enjoyable. Sounds like good 'ole dyno issues, which is not surprising. It looks like a DTS docking cart with an older SF 901 absorber/console with Depac data acquisition a real mix of three separate systems-I could be wrong. Testing two different engines on the same day especially with a flat tappet cam requiring break in and likely a spring change is a nerve wracking and long day for the builder and dyno operator. I'm sure @NC Engine Builder had his game face on and checking off all the boxes. @gzig5 That is pretty stout torque for a little 340 and a super wide 2000 rpm spread between peak TQ/HP engine should be a rocket. With a solid flat tappet it would have been nice to see a pull to at least 6500rpm, maybe 6700rpm but there is likely a reason and it was probably a lack of time. I would love a good write up on how the lifter bushing process was accomplished. Thanks @gzig5 ! J.Rob
 
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