Why is my truck slow?

[rlovell383]

Ok guys,
Looking for some advice.
57 Chevy Pickup, TH400, 2500RPM stall, 3.25 gears. Roughly 3600 pounds.

Motor is a 5.3L L33 truck engine with 95k miles.
Edelbrock Performer RPM carb intake with Holley Sniper EFI.
Hooker Cast iron manifolds (they advertise good for 500HP) into 3 inch dual exhaust (Walker Quiet flow mufflers and supposedly they choke it down to like 2 inches inside the muffler...? Didn't realize when I bought them)

With the motor bone stock I ran 14.58 @94MPH. About what I expected.

Swapped a CamMotion 224/228, .604/.580 112* cam. Now it runs 14.1@97. Was hoping to be well into the 13s as they said it should be around 415-420HP at the crank, but it doesn't feel like it.

Motor feels like its struggling to breathe at the top end and not revving like it should. Suspecting the mufflers are choking it? I know the 3.25 gears aren't helping, planning to swap to 4.10 gears this winter and a T56 6 speed when funds allow.


Thoughts?

[andrewb70]

Ok guys,
Looking for some advice.
57 Chevy Pickup, TH400, 2500RPM stall, 3.25 gears. Roughly 3600 pounds.

Motor is a 5.3L L33 truck engine with 95k miles.
Edelbrock Performer RPM carb intake with Holley Sniper EFI.
Hooker Cast iron manifolds (they advertise good for 500HP) into 3 inch dual exhaust (Walker Quiet flow mufflers and supposedly they choke it down to like 2 inches inside the muffler...? Didn't realize when I bought them)

With the motor bone stock I ran 14.58 @94MPH. About what I expected.

Swapped a CamMotion 224/228, .604/.580 112* cam. Now it runs 14.1@97. Was hoping to be well into the 13s as they said it should be around 415-420HP at the crank, but it doesn't feel like it.

Motor feels like its struggling to breathe at the top end and not revving like it should. Suspecting the mufflers are choking it? I know the 3.25 gears aren't helping, planning to swap to 4.10 gears this winter and a T56 6 speed when funds allow.


Thoughts?

It is very likely that your Sniper EFI is not well tuned. Please let me know if I can help you with that. I do remote Holley EFI tuning.

Andrew

[rlovell383]

It is very likely that your Sniper EFI is not well tuned. Please let me know if I can help you with that. I do remote Holley EFI tuning.

Andrew

Thank you. I haven't begun any tuning on the Sniper. That would be nice if I could get some more performance with just tuning it. I actually took a data log on my last run of the day, but haven't had time to download it and analyze. I guess thats my next step.

[andrewb70]

Thank you. I haven't begun any tuning on the Sniper. That would be nice if I could get some more performance with just tuning it. I actually took a data log on my last run of the day, but haven't had time to download it and analyze. I guess thats my next step.

If you changed the cam, I promise your tuning needs to be addressed. How are you controlling timing?

[rlovell383]

If you changed the cam, I promise your tuning needs to be addressed. How are you controlling timing?

With the cam swap I re-ran the wizard and set everything back to square-one. Runs great driving around...
Driven it quite a bit and made 4 passes down the 1/4 mile. Very consistent, but like I said haven't had a chance to check the A/F ratios throughout the pulls with the data log.
I'm using an MSD 6014 for the timing. Tried adjusting the timing from 27 to 31 degrees and it didn't make a bit of difference at the track. I havent confirmed TDC and verified the timing on the damper yet, but with no changes in speed when I adjust I doubt its too far off?

[GoodysGotaCuda]

I'm not an LS guy, but did you change valve springs to match the more aggressive cam? Valve float can feel like it's struggling for air.

I wouldn't expect much better times with 4.10s or a 6spd, honestly. 94mph is your problem...you need high 90s at a minimum to get into 13s, in my opinion.

Verify timing with a timing light,
Check that AFR is in decent shape and that the engine pulls cleanly to where the cam should run.

[rlovell383]

I'm not an LS guy, but did you change valve springs to match the more aggressive cam? Valve float can feel like it's struggling for air.

I wouldn't expect much better times with 4.10s or a 6spd, honestly. 94mph is your problem...you need high 90s at a minimum to get into 13s, in my opinion.

Verify timing with a timing light,
Check that AFR is in decent shape and that the engine pulls cleanly to where the cam should run.

Thanks for responding,

Yes I did upgrade the valve springs to match the cam. I did a full freshening of the engine when I did the cam swap, oil pump, timing chain, gaskets, new roller rockers, pushrods, etc...

Its running 97 MPH with the new cam. 2.2 second 60 foot times.

[68Formula]

Tuning is likely part of it. But those exhaust manifolds are holding it back. You need long tube headers. Also more gear and a higher stall with that combination.

When you swapped the camshaft, did you verify the new pushrod length?

[rlovell383]

Tuning is likely part of it. But those exhaust manifolds are holding it back. You need long tube headers. Also more gear and a higher stall with that combination.

When you swapped the camshaft, did you verify the new pushrod length?

I do agree I feel like its a combination of things. I do want to upgrade the exhaust from front to back at some point and see what that does. Although I'm more suspect of the mufflers than the manifolds, based on richard holdeners results with stock LS manifolds on youtube. I will have to make my own headers I think, to fit the truck.

Yes I have about .090 preload on the LS7 lifters which should be about perfect.

Thanks for the ideas.

[68Formula]

Contact Speed Engineering, they may be able to help you out. Their mid-length swap headers might even be the ticket. There's usually not much difference between mid-length and long tube headers (but a big difference from shorties). Make sure you have an H-pipe or X-pipe. And for mufflers go with Borlas (ProXS version if you want quiet).

[rlovell383]

Contact Speed Engineering, they may be able to help you out. Their mid-length swap headers might even be the ticket. There's usually not much difference between mid-length and long tube headers (but a big difference from shorties). Make sure you have an H-pipe or X-pipe. And for mufflers go with Borlas (ProXS version if you want quiet).

Thanks, I will check those out... They look pretty affordable too.
No H-pipe or X-pipe at the moment. I definitely think there is power to be found in the exhaust. I hope anyway.

[andrewb70]

Thanks, I will check those out... They look pretty affordable too.
No H-pipe or X-pipe at the moment. I definitely think there is power to be found in the exhaust. I hope anyway.

On my Cougar I also use the Hooker cast manifolds. I had a X-pipe and 19" case Borla ProXS mufflers installed and I am very pleased with the sound. It is much quieter than my older setup, which was no X-pipe and Holley V304 mufflers.

Andrew

[protour_chevelle]

As an FYI... The last holley efi that a friend tuned on a cam only 6.0 picked up 50rwhp and 60 ft lbs from the "Self learning" tune.

Andrew above Im sure can get you straightened out.

[68Formula]

On my Cougar I also use the Hooker cast manifolds. I had a X-pipe and 19" case Borla ProXS mufflers installed and I am very pleased with the sound. It is much quieter than my older setup, which was no X-pipe and Holley V304 mufflers.

Andrew

Andrew, do you have a sound clip?

[andrewb70]

Andrew, do you have a sound clip?

I have some on my IG account. Look up Projectgattago

[rlovell383]

On my Cougar I also use the Hooker cast manifolds. I had a X-pipe and 19" case Borla ProXS mufflers installed and I am very pleased with the sound. It is much quieter than my older setup, which was no X-pipe and Holley V304 mufflers.

Andrew

So... I finally had time to download the data log. Its holding around 12.5 A/F through pretty much the whole run with not too much variation. You want to take a look and see what you think?

[andrewb70]

So... I finally had time to download the data log. Its holding around 12.5 A/F through pretty much the whole run with not too much variation. You want to take a look and see what you think?

I'd be happy to take a look. Send me a PM and I'll give you my email address

[rlovell383]

I'd be happy to take a look. Send me a PM and I'll give you my email address

PM sent

[Lonnies Performance]

I see a few things... you do not have much gear & I'm guessing you have a decent sized rear tire, further killing the gearing.

You added a larger cam that favors higher RPM power that you may not be able to take advantage of.

Also LS engines respond well to being leaner. 12.8-13.0 is common & should pick up some more power.

[andrewb70]

I see a few things... you do not have much gear & I'm guessing you have a decent sized rear tire, further killing the gearing.

You added a larger cam that favors higher RPM power that you may not be able to take advantage of.

Also LS engines respond well to being leaner. 12.8-13.0 is common & should pick up some more power.

Why I normally would agree with the assertion about running leaner, the fact that his system is throttle body injection negates that point. He still has all the inherent issues of fuel distribution inside the manifold, so a slightly richer mixture is not unreasonable.
I had a look at his tune and there are no red flags or low hanging fruit. It's dialed in fairly well.
Andrew