347 EFI Low Power

w_jake17 · Jul 8, 2022

Hello everyone, I bought a built 347 stroker from an engine builder not too long ago and after getting it in and getting a Dyno tune I was upset with the power it made. I dynod 325 whp and 365 torque. The torque seems pretty good but being that I have and AOD that only puts me at 380-400 engine horsepower.

The combo that it has in it is, Heads: Liberty heads 180cc intake and 60cc combustion, Cam: Elgin cam, I believe it's 550 lift and 280 duration, Intake: Edelbrock Performer RPM (not RPM II), MAF ProM 75mm and TB 70mm, 36# injectors.

I feel that I should be more in the 420-450hp range to the motor. I'm thinking that the throttle body might be the limiting factor here but cant imagine gaining 20 hp from that, also on the Dyno sheet, my power Flatliners right at 5500 but this cam should pull to 6500. My tuner thinks it's air related.

Can anyone help or give input?

w_jake17 · Jul 8, 2022

Hey everybody,

I recently bought a 347 stroker from a local engine builder and had it dyno tuned. I was disappointed with the numbers and feel that I am missing something, It made about 325 whp and 365 torque. The torque seems on par but the HP seems low, given that I have an AOD that puts me at 380-400 HP.

Specs
Liberty Heads; 180cc / 60cc
Elgin Cam: 550 lift / 280 duration (Need to confirm when I get home, numbers are close though)
Edelbrock Performer RPM Intake (Not RPM II)
Pro M 75mm MAF and 70mm Throttle Body
36# Injectors

I feel that with this combo I should make 420-450 HP, I think the TB I have is probably too small but I cannot imagine gaining 20HP from 5mm bigger. My tuner seems to think it is also air related. Also, my valve train is pretty loud and chattery.

Could someone give their input, thanks.

TOOLOW91 · Jul 8, 2022

Two posts an hour apart ? Lol

We need the actual cam specs , what kind of compression ?

What fuel - I’m guessing pump gas

What was total timing ?

What converter is in it ? ( this is a big one )

Dyno is only a tool not law . What the car mph in 1/4 mile would be a indicator of what type of power it’s making

Noobz347 · Jul 8, 2022

Dyno type, etc...

General karthief · Jul 8, 2022

The dyno operator should have been able to give you some guidence on what it needs based on some info the dyno should provide, airfow, temps, timing, even header tube size and length can effect hp, torque area.
a quick search found 347s making between 350 and 425 hp.
many variables will effect hp/tq numbers and (more importantly) where at in the rpm range.
Too many unknowns to really say do this or that to make bigger nnumbers.

w_jake17 · Jul 8, 2022

TOOLOW91 said:
Two posts an hour apart ? Lol

We need the actual cam specs , what kind of compression ?

What fuel - I’m guessing pump gas

What was total timing ?

What converter is in it ? ( this is a big one )

Dyno is only a tool not law . What the car mph in 1/4 mile would be a indicator of what type of power it’s making

My bad, Im new here, didnt say the other posted haha.

They told me 10.5:1 compression

Cam: Elgin E1836P
Intake Valve Lift: .542"
Exhaust Valve Lift: .563"
Advertised Intake Duration: 286
Advertised Exhaust Duration: 289
Intake Duration @ .050": 224
Exhaust Duration @ .050": 232
Lobe Separation: 112

93 Octane

I'm not sure on timing as I had someone time it, he just told me to put it at 10 when I brought it and he added timing through the tune

So, the converter is supposed to be a 2500 stall but the car only stalls at 1700-1800, second time this has happened with a converter for me

w_jake17 · Jul 8, 2022

w_jake17 said:
My bad, Im new here, didnt say the other posted haha.

They told me 10.5:1 compression

Cam: Elgin E1836P
Intake Valve Lift: .542"
Exhaust Valve Lift: .563"
Advertised Intake Duration: 286
Advertised Exhaust Duration: 289
Intake Duration @ .050": 224
Exhaust Duration @ .050": 232
Lobe Separation: 112

93 Octane

I'm not sure on timing as I had someone time it, he just told me to put it at 10 when I brought it and he added timing through the tune

So, the converter is supposed to be a 2500 stall but the car only stalls at 1700-1800, second time this has happened with a converter for me

And now that I am looking I dont think this cam goes to 6500 so maybe that why? But would I gain from a bigger TB because my intake pipe is only 3 inches.

General karthief · Jul 8, 2022

Just a driver or drag car?
Was proper procedures done when setting timing?

General karthief · Jul 8, 2022

w_jake17 said:
And now that I am looking I dont think this cam goes to 6500 so maybe that why? But would I gain from a bigger TB because my intake pipe is only 3 inches.

car weight, rear gear, and a bunch of things go into building a combination rather than just picking a number to shoot for.

w_jake17 · Jul 8, 2022

General karthief said:
The dyno operator should have been able to give you some guidence on what it needs based on some info the dyno should provide, airfow, temps, timing, even header tube size and length can effect hp, torque area.
a quick search found 347s making between 350 and 425 hp.
many variables will effect hp/tq numbers and (more importantly) where at in the rpm range.
Too many unknowns to really say do this or that to make bigger nnumbers.

He just said that

General karthief said:
Just a driver or drag car?
Was proper procedures done when setting timing?

It's just a weekend driver but I do go to the strip sometimes. It was set properly when I brought it there to base timing.

All he told me was that he thinks it should make more then it does and that he thinks its airflow restricting it. I have shorty header 1 5/8 to 2.5" exhaust. I would like longtubes but its hard to find them for AOD cars. Also the car does not rev snappy and hangs when coming back down, I heard that I need to get a motorcraft IAC valve.

w_jake17 · Jul 8, 2022

General karthief said:
car weight, rear gear, and a bunch of things go into building a combination rather than just picking a number to shoot for.

Its got 3.73 in it. I know that its not just about numbers but I feel like something is off

General karthief · Jul 8, 2022

First question to ask is what is the car going to be used for the most.

w_jake17 · Jul 8, 2022

General karthief said:
First question to ask is what is the car going to be used for the most.

Now that it is not my daily, I would say mainly just to go to shows and stuff and couple times a year to a 1/8mile strip

General karthief · Jul 8, 2022

Ok, research time: look up where the intake manifold works in the rpm range, where the cam works in the rpm range and flows, look at your header tube size and compare all that stuff to the head flow numbers.
Figure the engine will spend most of it's time running 1500 to say, 4500 rpms on the street, what does the dyno sheet read between those numbers.

Bullitt347 · Jul 8, 2022

Shorty headers?
What mufflers?
Still have catalytic converters?

w_jake17 · Jul 8, 2022

General karthief said:
Ok, research time: look up where the intake manifold works in the rpm range, where the cam works in the rpm range and flows, look at your header tube size and compare all that stuff to the head flow numbers.
Figure the engine will spend most of it's time running 1500 to say, 4500 rpms on the street, what does the dyno sheet read between those numbers.

cam: 2200-5500rpm
intake: 1500-6500rpm

head flow (.550 lift): intake ~235cfm exhaust ~180 cfm (estimated from other similar heads)

i can't really find anything for the headers.

I included some pulls he made while he was tuning it

w_jake17 · Jul 8, 2022

Bullitt347 said:
Shorty headers?
What mufflers?
Still have catalytic converters?

Yes shorty headers 1 5/8"
Mufflers are cherry bomb vortex (glass pack)
No cats or any smog related stuff

rednotch · Jul 8, 2022

What's the dyno curve look like up top without smoothing? I'd say its about average for box stock parts threw an aod, pretty much 302 parts on a 347....... Liberty heads are the China dart clones everyone sells now, decent budget head but port work helps a lot if your going after hp na in my opinion . Exhaust ports ain't that great as cast. Same casting as the afr enforcer but much cheaper valve train if bought asembled from liberty. Springs maybe to light for the cam in most cases but the dyno should show that. The elgin 1836p is pretty much the first gen Tfs stage 2 grind old part number was TFS-51402001

Sounds like most "crate" 347s advertised these days in the 420 hp range when dynoed with a carb, electric water pump and uncapped exhaust. Most box stock efi 5.0 intakes are done by 5500 range on a 302 including the first gen rpm. Had the same heads on a old 347 ported with decent springs,an old voodoo cam wiith similar specs but a better exhaust and induction. never dynoed it but probably in the 450 crank range on motor based on it ran at the track.

w_jake17 · Jul 8, 2022

rednotch said:
What's the dyno curve look like up top without smoothing? I'd say its about average for box stock parts threw an aod, pretty much 302 parts on a 347....... Liberty heads are the China dart clones everyone sells now, decent budget head but port work helps a lot if your going after hp na in my opinion . Exhaust ports ain't that great as cast. Same casting as the afr enforcer but much cheaper valve train if bought asembled from liberty. Springs maybe to light for the cam in most cases but the dyno should show that. The elgin 1836p is pretty much the first gen Tfs stage 2 grind old part number was TFS-51402001

Sounds like most "crate" 347s advertised these days in the 420 hp range when dynoed with a carb, electric water pump and uncapped exhaust. Most box stock efi 5.0 intakes are done by 5500 range on a 302 including the first gen rpm. Had the same heads on a old 347 ported with decent springs,an old voodoo cam wiith similar specs but a better exhaust and induction. never dynoed it but probably in the 450 crank range on motor based on it ran at the track.

Ok, so let's say I wanted to squeeze more power. I would need to port my heads and probably intake to match? I really do want to get 1 3/4 headers just kinda hard to find right now. If I got better springs is it possible that I could put 1.7 rockers to get more lift? Would it be beneficial if I went to a 75mm TB from 70 and upped the pipe size to 3.5" in the short term?

w_jake17 · Jul 8, 2022

rednotch said:
What's the dyno curve look like up top without smoothing? I'd say its about average for box stock parts threw an aod, pretty much 302 parts on a 347....... Liberty heads are the China dart clones everyone sells now, decent budget head but port work helps a lot if your going after hp na in my opinion . Exhaust ports ain't that great as cast. Same casting as the afr enforcer but much cheaper valve train if bought asembled from liberty. Springs maybe to light for the cam in most cases but the dyno should show that. The elgin 1836p is pretty much the first gen Tfs stage 2 grind old part number was TFS-51402001

Sounds like most "crate" 347s advertised these days in the 420 hp range when dynoed with a carb, electric water pump and uncapped exhaust. Most box stock efi 5.0 intakes are done by 5500 range on a 302 including the first gen rpm. Had the same heads on a old 347 ported with decent springs,an old voodoo cam wiith similar specs but a better exhaust and induction. never dynoed it but probably in the 450 crank range on motor based on it ran at the track.

Also just curious, what would show in the curve if the springs are too light. It's possible he bought them unassembled and installed his own springs

347 EFI Low Power

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