My new stock stroke 400 build

[gtxrt]

to compare carbs you would need a 750 cfm edelbrock to be equal to the 650 cfm Holley carb. they rate the carbs differently.

 

[1KoolBee]

Compression and head flow would be on my to do list. Deck the block and mill the heads.Every little bit helps. Head porting for the win.
Sounds like a good plan.I look forward to your results.

Or offset grind rod journals .010-.020 to push pistons up further in the bore, raise compression, and pick up 2.5-5 cubes.

 

[PRHeads]

It made 420 lb/ft of torque at 3900 with over 400 lb/ ft from 3000 to 4300. Horsepower was a little disappointing with only 340 at 4800 rpm. I guess I needed more cam, but I did say low end torque was the goal.

My “rough guesstimate” rule of thumb from back in the day when a build like this was the norm.
Before there were tons of aftermarket head options or very many good piston options for certain combos.

You need enough duration to allow the TQ curve to extend into the upper rpm’s……..and aim for peak hp to occur after 5300rpm.

For me, the number I used to target 1hp/ci was [email protected].

Yes, that comes with driveability compromises……..but you need to be into that duration range with those old school builds if you’re shooting for 1hp/ci.
With better heads(more porting) and/or higher CR you might be able to tweak that down a little bit if driveability was a big concern.

I think you made the right call with the cam.
Cam it for how the car will be used, and stop worrying about the numbers on the sheet.

 

[qkcuda]

Yes, I had previously built a 400 with a 222/234 cam and managed a little over 1 HP per cubic inch . I am satisfied with this build, but the drag racer in me always wants more power. Here are the Holley and Street Demon dyno sheets for what they are worth.

 

[gtxrt]

Yes, I had previously built a 400 with a 222/234 cam and managed a little over 1 HP per cubic inch . I am satisfied with this build, but the drag racer in me always wants more power. Here are the Holley and Street Demon dyno sheets for what they are worth.

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if your comparing this build to your last build they need to have been on the same Dyno.

 

[BSB67]

Can't compare, Chrysler did not put headers on the 383.

Word is that Chrysler did use headers and zero accessories for rating their engines. Don't know that to be true, but sure would explain the 383s performance relative to its rated hp.

Mopar Performance has published the 68-70 383s as having like 285 hp.

 

[qkcuda]

if your comparing this build to your last build they need to have been on the same Dyno.

Actually they were.

 

[gtxrt]

Word is that Chrysler did use headers and zero accessories for rating their engines. Don't know that to be true, but sure would explain the 383s performance relative to its rated hp.

Mopar Performance has published the 68-70 383s as having like 285 hp.

you could be right can't find anywhere that they used headers or not.

 

[qkcuda]

For those who were looking for a comparison between the AFB and the SD I am attaching the AFB dyno sheet. You can see the A/F ratios were very close between the two carbs, so I think it is a fair comparison.

 

[Orig69]

You got lots of torque here.

I'm guessing the SD carb was running a little bit lean.

 

[qkcuda]

The Street Demon was initially lean, but with a jet change and then a metering rod change it was fine, which is the dyno sheet I posted.

 

[qkcuda]

Here is a build Jim La Roy posted on A bodies a while ago. It was one of my references when putting together this package. You will see I made a bit more torque and he made a bit more horsepower. The higher compression (8.5 versus 7.5) and the dual plane intake versus the single plane probably accounts for the torque difference. The single plane intake and larger carb probably accounts for the horsepower difference.

 

[PRHeads]

The engine used 30+ cfm more air with SD carb vs the AFB.
That’s where the extra power with the SD is coming from.

It also produced the best bsfc numbers of all 3 carbs.

With the Holley the airflow was up another 10-ish cfm from the SD……and it made the most power despite having the worst bsfc.

 

[qkcuda]

What do you think about the final A/F ratio on the SD? Am I close? I have to remember that the dyno test was with open headers, and in the car it will be running through manifolds and full exhaust.

 

[PRHeads]

It’s certainty safe enough to start out with it like that.
I wouldn’t be shocked if you found it was a little rich at part throttle cruise.
It’s showing rich at the lower rpm, but that’s at wot…….. so you’ll have check some plugs after some highway miles(or install an A/F ratio gauge).

Also, Depending on how long after the load was applied the “pull” was started, can impact what the A/F ratio looks like near the beginning.
In general, the longer you hold it before pushing the go button…….the richer it will look at the start of the pull.
This is when using a SF dyno, and relying on the air and fuel flow turbines for determining A/F calculations…….which it appears is happening on those sheets.

 

[qkcuda]

Yes thanks, it is an older SF 901, and it was using the turbines not oxygen sensors. I will be putting the carb back on my 361 tomorrow to head to a car cruise on Sunday. I had the carb pretty well dialed in for the street before. I plan on leaving in the larger primary and secondary jets and swapping to the leanest rods, and see how it runs.

 

[qkcuda]

I said I was going to run the car with the 361 to get a baseline, so I did yesterday at St. Thomas Dragway. Not impressive, 17.4 at 81. It had a bog off the line and the trans was shifting early, so I probably could have shaved a tenth with more experimenting, but why bother?

 

[Pedalpusher]

I said I was going to run the car with the 361 to get a baseline, so I did yesterday at St. Thomas Dragway. Not impressive, 17.4 at 81. It had a bog off the line and the trans was shifting early, so I probably could have shaved a tenth with more experimenting, but why bother?

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Have enjoyed your thread, to me you have accomplished what you indented to do. The pass down the strip came full circle & I bet you had a grin ear to ear. Enjoy the ride…….
Ron

 

[BSB67]

I said I was going to run the car with the 361 to get a baseline, so I did yesterday at St. Thomas Dragway. Not impressive, 17.4 at 81. It had a bog off the line and the trans was shifting early, so I probably could have shaved a tenth with more experimenting, but why bother?

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Nice that you got out. Car looks good. Like it’s stance. Thanks for sharing.

 

[qkcuda]

Have enjoyed your thread, to me you have accomplished what you indented to do. The pass down the strip came full circle & I bet you had a grin ear to ear. Enjoy the ride…….
Ron

To be clear, that run was with the original engine. I just wanted to be able to gauge the improvement. The new engine and transmission probably won't be installed until the fall, since cruising season has started.