Exhaust Question

[Hugh Mongus]

I had flow master 40s installed on my truck shortly after buying it. It had a good sound up until I swapped the cam and heads. Now at WOT it pops like glass packs and sounds like crap. Could something I changed cause this change in sound? It runs good and it sounds ok cruising, but when I get into it I hate the sound.

[piecesparts]

Just a thought, it sounds to me, that you may have a valve floating under WOT and the popping is coming from that.

[Hugh Mongus]

How would I check that?

Edit:

I was reading up on valve float on the web. It sounds like valve float causes a dramatic loss of power higher in the RPM band. I am not experiencing any power loss.

The engine runs great, it just sounds like crap. (When I say crap, I mean it doesn't sound the way I like it to sound) The engine doesn't miss, starts easy, idles and runs smooth, runs great, awesome throttle response since the upgrades. The tone of the exhaust has changed.

[WIDESIDE72]

Your new cam probably has more overlap (when the intake and exhaust valves are both open). Did you install a "bigger" cam?

[Hugh Mongus]

Yes, I installed the Lunati 60102.

I called a local mechanic today. He told me the engine is probably breathing better with the vortec heads and larger cam which will alter the sound of the engine. Would you guys agree?

[T3AMCH3VY]

Really hard to diagnose from the description... When you say pop under acceleration I think misfire.

[Norcal72]

After porting my heads, the exhaust sound changed dramatically. If you changed heads and cam it will sound diffrent. I noticed it as soon as I fired it up the first time. Sounded rasper and louder at idle and full throttle. I think it sounded much better after. Your probably making enough noise now the super 40s can finally come alive. Just kidding.

[Fitz]

That's flowmasters. They are made to make a stock truck sound like it's not stock. When you hook them to something more robust than stock you get...what you got. A loud irritating exhaust that doesn't sound all that great.

[Hugh Mongus]

I am probably going to buy some Borla mufflers. I hate hitting the gas right now the sound makes me cringe.

Thanks for all the input.

[joey8383]

Are they true duals? If so, do you have an H-Pipe or X-Pipe?

[Hugh Mongus]

They are true duals. No cross pipe. Would a cross pipe make a difference in the sound?

[GASoline71]

Could be a lean condition. Bigger cam needs more fuel, and probably a little more advance in the ignition.

Gary

[Hugh Mongus]

Originally Posted by GASoline71

Could be a lean condition. Bigger cam needs more fuel, and probably a little more advance in the ignition.

Gary

I ordered a Holley Street Avenger for it that will be here tomorrow. I am currently using a Eddy 1405 which I am tired of messing with. I have a feeling the mixture is in fact a little lean.

[junksaver]

I know flow masters are popular, but I never cared for them on any vehicle that didn't have catalytic converters on it. If you change mufflers, look into the dynamax ultraflo mufflers. I think it's one of the best mufflers made. Good flow, but not too loud.

[Hugh Mongus]

To give you all an idea of what I'm looking for, the video below is a Borla video. Around the 2:05 mark of the video they talk about Borla Touring Exhaust. That is the sound I'm looking for. My truck sounded similar to that prior to the upgrades.

https://www.youtube.com/watch?v=fISsmDRSXgY

https://www.youtube.com/watch?v=X1uHhUixiAs

[Lattimer]

Originally Posted by Hugh Mongus

To give you all an idea of what I'm looking for, the video below is a Borla video. Around the 2:05 mark of the video they talk about Borla Touring Exhaust. That is the sound I'm looking for. My truck sounded similar to that prior to the upgrades.

https://www.youtube.com/watch?v=fISsmDRSXgY

https://www.youtube.com/watch?v=X1uHhUixiAs

Listened to the video. You really won't get that kind of sound from an engine with an aggressive cam. On a stock, modern engine, you get that, but with the hot cam you get a more staccato sound.

I've never been a fan of Flowmaster sound. The open chamber design just doesn't sound "good" to me.

Any turbo style muffler will sound closer to what you want, but they are all a little different. Borla is nice stuff, but pricey.

[Hugh Mongus]

Originally Posted by Lattimer

Listened to the video. You really won't get that kind of sound from an engine with an aggressive cam. On a stock, modern engine, you get that, but with the hot cam you get a more staccato sound.

I've never been a fan of Flowmaster sound. The open chamber design just doesn't sound "good" to me.

Any turbo style muffler will sound closer to what you want, but they are all a little different. Borla is nice stuff, but pricey.

I agree. To me buying mufflers is like eating a box of chocolates. you never know what you're going to get until you buy and install them. If the H pipe doesn't fix it I am going to buy different mufflers.

[RichardJ]

>>T3AMCH3VY
Really hard to diagnose from the description... When you say pop under acceleration I think misfire. <<


I am thinking the same thing. You didn't say what ignition and I wonder about plug gap.
You changed heads and possibly increased C.R. ?? You may need to close plug gap.

[Hugh Mongus]

Well, the clown that did the head swap for me cracked the porcelain on the #1 plug which caused an arc from the plug to the block . When I pulled that plug out it was gapped at .055, so I gapped the new plug the same and reinstalled it. The ignition is a new Accel dizzy with a high output coil.


It's definitely not a misfire. It runs fine. Think more 12" glass packs under heavy acceleration. The raspy popping you here with glass packs is what I'm getting from my flow masters. I hate that sound.

[Lattimer]

Originally Posted by Hugh Mongus

Well, the clown that did the head swap for me cracked the porcelain on the #1 plug which caused an arc from the plug to the block . When I pulled that plug out it was gapped at .055, so I gapped the new plug the same and reinstalled it. The ignition is a new Accel dizzy with a high output coil.


It's definitely not a misfire. It runs fine. Think more 12" glass packs under heavy acceleration. The raspy popping you here with glass packs is what I'm getting from my flow masters. I hate that sound.

.055 is too much. With an HEI I believe .045 is recommended, it would be less if you still had points.

Probably has nothing to do with your sound though

[joey8383]

If you're sure it's not mechanical and just scavenging sounds from exhaust, throw and H pipe or X pipe on it.

[Hugh Mongus]

Originally Posted by joey8383

If you're sure it's not mechanical and just scavenging sounds from exhaust, throw and H pipe or X pipe on it.

I actually just got off the phone with flowmaster. The tech said the bump in compression is throwing the sound off. He said an H pipe would fix the sound problem. I called the exhaust shop that installed my exhaust and they are going to install an H pipe for me tomorrow for $30. Hoping that really fixes it.

[Hugh Mongus]

Thanks for all the input and suggestions everyone. Hopefully tomorrow everything will be ok. If not I will be back.

[Fitz]

Originally Posted by Hugh Mongus

Thanks for all the input and suggestions everyone. Hopefully tomorrow everything will be ok. If not I will be back.

Here's a link to a video with sound for my truck at full throttle and just normal driving. Mufflers are straight through magnaflow 14 in with no X or H pipe. The motor is a big block with 254 degrees intake and 262 degrees exhaust with 0.632 lift on both. Not a stock cam but not a really hairy beast either, but the mufflers sound good!

http://s851.photobucket.com/user/BWF...tml?sort=3&o=1

at idle outside it sounds like this:

http://s851.photobucket.com/user/BWF...tml?sort=3&o=0

Much mo bettah than blowmasters!

[Mike C]

Balance pipe makes a huge difference with flowmasters. My buddies big block Chevelle sounded like crap without it while my Camaro sounded sweet with pretty much the same setup except the balance pipe.

I hope that cleans yours up.