422 dyno fail

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About 18 years ago I reconditioned and bowl ported a set of J heads(240cfm) that went on a basic street/strip 416.
250/259-106 SFT cam, RPM A/G, HP750, 1-3/4 x 3 headers.
Made just over 500ft/lbs, and just under 500hp(like 498).
 
Just a 1” carb spacer and a new/different distributor added about 30 hp and 30lbs tq.

What info can you get off that ?
 
I think there could be a valvetrain control issue in the upper rpms of the OP’s build.
The bsfc numbers really tank up top, as the hp numbers start falling off pretty fast.
That in itself isn’t unusual, but the fuel flow is also stagnant for most of the top end of the sheet.
If there were an air flow sensor being used, I think you’d see the air flow was also stagnant...... or dropping off.
 
The motor in the butterscotch Duster has heads that flow a little less than the OP’s heads, and the engine is 5 cubes bigger.
That engine makes peak hp at 5700....... but at 6600 is only down 12hp.
 
What do you mean by a valve train control issue? Like valves not opening or closing correctly? Or an air flow problem?
 
autoxcuda said:
Just a 1” carb spacer and a new/different distributor added about 30 hp and 30lbs tq.

What info can you get off that ?
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I’d have had to see how that progression unfolded to have a feel for how that went down.
Sometimes the right spacer can really wake a combo up.
 
PRH said:
About 18 years ago I reconditioned and bowl ported a set of J heads(240cfm) that went on a basic street/strip 416.
250/259-106 SFT cam, RPM A/G, HP750, 1-3/4 x 3 headers.
Made just over 500ft/lbs, and just under 500hp(like 498).
Click to expand...


Just curious. What did it run and at what weight.
 
Jim Ward said:
What do you mean by a valve train control issue? Like valves not opening or closing correctly? Or an air flow problem?
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In the simplest of terms.... “valve float”.
But in realty, with HR cams..... it’s usually actually lifter collapse from aeriated oil and/or insufficient lifter refill/check valve control problems.
 
PRH said:
In the simplest of terms.... “valve float”.
But in realty, with HR cams..... it’s usually actually lifter collapse from aeriated oil and/or insufficient lifter refill/check valve control problems.
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Spring surge? Seen this on some HR engine where the engine is pulling and has a couple off key/sound drop and pickup in upper ranges.
 
Jim Ward said:
I get all of that but that low of HP?? I think it should be darn close to 500lb ft. I asked the shop about porting the intake and they didn’t recommend it which also seemed odd to me. I know Edelbrock isn’t known for Optimim HP but again I think it should of at least made 1hp per cube…
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Honestly I'd like to see the rest of the flow numbers on the heads. 255 at .600, I would see 255 by .500 normally, at least , or its not really ported...its bowl blended with a good vj.
What if...
Now what if you dont have a stroker...
Think about that.
 
Spring surge?
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Possible...... but at the rpm this motor is running, I’d say not that likely.

Whereas, 5500-6000 is the rpm range where the hyd system in the lifters often gives up.

However, without being able to see what’s happening with the air flow through the motor......it’s just speculation.
There may not actually be any valvetrain control issues with this combo.

I’m just seeing the power quickly dropping off, the bsfc numbers climbing pretty high, and the fuel flow in stasis........ and theorizing what might contribute to that.
 
It doesn’t just fall off a cliff at 5400 where it makes peak hp which is what valve train instability will look like. It’s airflow limited.
 
I don’t think there’s a valvetrain problem at 5400........ but I think it’s getting unhappy at about 6k.

So, no....... if that’s happening, it’s not affecting the peak output at 5400.

The motor in the Duster, which should be more air flow restricted with the stock intake, air filter, and exhaust manifolds, along with heads that don’t quite flow 255cfm..... makes peak power at 5700........ has only lost 12hp at 6600.

This motor loses about 50hp from 6000 to 6400.
 
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TT5.9mag said:
It doesn’t just fall off a cliff at 5400 where it makes peak hp which is what valve train instability will look like. It’s airflow limited.
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I’m hoping the air gap intake will help with this. I should know tomorrow. I will keep everyone posted.

thanks again to everyone who has chimed in with actual input and not comments of why build a stroker? I knew I would get some of those kind of unhelpful comments by posting this thread.
 
has the dyno guy got some bigger headers he can try? 1 5/8" seems small to me for this size motor. would you put that size header on a big block, even a 383? no, and this is big block cubic inches. air has to get 'out' too, not just in. when you're constipated, you can't eat any more. same thing, lol.
 
Jim Ward said:
I’m hoping the air gap intake will help with this. I should know tomorrow. I will keep everyone posted.

thanks again to everyone who has chimed in with actual input and not comments of why build a stroker? I knew I would get some of those kind of unhelpful comments by posting this thread.
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Sorry if my post offended you and I hope you enjoy your build. It just kinda gets old everytime someone asks about building an engine the crowd jumps in and says “you gotta build a stroker”. Sorry, good luck, and have fun.
 
If it hasn’t been done yet, a timing sweep should be done before going much further.
They want what they want, but the best SBM I’ve tested made the most at 33*.
Don’t “assume” 36* is best.

Also, maybe some fresh gas.

Is there any A/F monitoring happening on this dyno?

Just as an observation...... not any criticism........
This is one of those situations I refer to as “start low/end low”.
The TQ output is way below where it should be, and drops off pretty fast...... and as a result the HP just never comes around.
 
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pittsburghracer said:
Sorry if my post offended you and I hope you enjoy your build. It just kinda gets old everytime someone asks about building an engine the crowd jumps in and says “you gotta build a stroker”. Sorry, good luck, and have fun.
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It didn’t offend me it just isn’t helpful to my situation but I expected it.
 
Fun with numbers!!!
The OP’s combo:
422ci, heads flow 255, cam is a HR, 240@.050 with .570 lift.
422/8 = 52.75
255/52.75 = 4.83cfm/ci

A mild street 505 we had here:
505/8 = 63.125
Prepped/blended rpm heads flowed 285
285/63.125 = 4.51cfm/ci
This motor was 9.7cr, and had a smallish HFT cam(232/237-112, .483/.483)
The manifold was an old original Torker and the carb was an old school Holley 850vs, and it was tested with 1-7/8 x 3 headers.

If the OP’s combo is struggling to make 1hp/ci with 4.83cfm/ci...... how hard is it with 4.51cfm/ci?
 
PRH said:
I guess since iron heads can’t make any power on a stroker...... then if you combine them with the stock intake, TQ, air filter, and exhaust manifolds....... a combo like that doesn’t have a chance.

View attachment 1715932436

View attachment 1715932437
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Everything is ported.....even if illegal, most guys run aftermarket blocks, stroker cranks and have big cubic inches......way more to what the picture shows as to why those guys generate the numbers they do.
 
PRH said:
I don’t think there’s a valvetrain problem at 5400........ but I think it’s getting unhappy at about 6k.

So, no....... if that’s happening, it’s not affecting the peak output at 5400.

The motor in the Duster, which should be more air flow restricted with the stock intake, air filter, and exhaust manifolds, along with heads that don’t quite flow 255cfm..... makes peak power at 5700........ has only lost 12hp at 6600.

This motor loses about 50hp from 6000 to 6400.
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Boy you really enjoy trying to make people believe that most of the butterscotch Duster is bone stock........shame more people don't have a better insight to that class of racing so they could call out B.S.
 
Headers aren't holding it back... Those headers have been on 530hp 6300rpm strokers
 
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