[6426yy]

+.030 454 Hyperuetectic pop up pistons 9.3:1, Large oval ports 781 mild cleanup, comp cams 4x4 extreme 270, weiand stealth intake with 750 Holley. 1 3/4 full lenght headers.

My truck has true duals with 2 1/4 pipe and Flowmasters; yeah I know they suck, all the more reason to change. Is it going to choke it?

Thanks

[454C10]

I would think so. dual 2-1/2 would be the minimum for a mild/moderate 454.

you are looking at maybe 425hp/550 ftlbs with that setup.

dual 2-1/4's would max out at 400hp if it was made with mandrel bent pipe and not run all the way out the back.

I would use an x-pipe after the transmission and dual dynomax super turbos (20 inch case). Then if it still is too loud, then put on some dynomax bullets on the ends.

I would use 2-1/2 inch with mandrel bent pipe or 3 inch with crushed bent pipe.

I build my own exhaust systems using mandrel bent J-pipes from summit racing. It isn't that hard. got a welder?

I hope you are using an oil additive with your cam. www.zdpplus.com

[GunnerTHB]

I actually don't think 2 1/4 is gonna choke the motor very bad. It may a little bit but think about it. You have 2 1/4in for both halves of the engine.

[Jim Rockford]

2 1/2 is mandatory , even on a mild small block.

[barnym17]

each header tube is 1.75 stuffing the output from 4 of them into a pipe 2.25 ain't gonna get it done. 2.5 minimum 3. better.

[OLNOLAN]

Hey YY, I like real exhaust on my cars, but not too loud. My way of thinking on your setup is a 1.75 primary tube doubled in size quads the flow. So a 3.5 pipe can match the flow of all four header tubes. Yep, thats big pipe. With this size pipe however you get some wall turbulent flow with laminar flow in the middle of the stream. But if you decrease the size of the pipe slightly you increase the velocity and get more laminar flow which sort of creates a suction to help scavenge exhaust gas out. More cubic inches creates a bigger pump, you gotta get it out before you can get more in. Smaller cubic inch engines don't need as big a pipe, in other words 1.75 headers on a 350 ci engine might need a smaller tail pipe to keep the velocity up to help scavenge the smaller pump. Now mind you they have folks around that understand flow and physics way over my head, but this is my way of thinking. Bottom line, your headers are scavenging pretty good cause they are kinda small. 3" pipe into muffler, 2.75" out is about perfect in my book for your 454. Cross over pipes are supposed to boost midrange cause it balances the exhaust pulsations from both sides of the engine and makes both banks of the engine work(pump) more efficiently as in together, I don't really understand the hows on this, just know it works. This is probably a good topic to bring up now and then cause some have exhaust way too small and sometimes way too big. Food for thought. olnolan

[GunnerTHB]

3 inch true duals? Sorry that's way more than a mild 454 will need. I would bump it up to 2 1/2 true duals tho.

[chevy1500z71]

iv always figured on running 1.75x the primary size. in your case thats about 3". im running 2 and 1/4s on my small block and i really want to change my exhaust to 2.5" setup, one thats not 5 miles long either, truck exhaust systems have a tendency to get ridiculously long when you try and run the tips out the back. id prefer dumped under the bed or out in front of the tire.

iv been using zddplus with my motor as well. if youv got a local atv shop around you should try running motorcycle/atv oil, its got tons of zddp, summits new line of high zddp oil is just repackaged spectro motorcycle oil.

[6426yy]

Thank for the replies guys, as far as the ZDDP, yes I'm running that with Rotella oil. The engine was already broke in but I pulled the heads off of it to clean them up, cut for positive seals, set the spring height and install thinner head gaskets. I planned on going 3" with an x pipe and the tips coming out in front of the tires. I don't like the droan when dumped under the bed. I just hope my TH350 will hold up!!

[chevy1500z71]

Originally Posted by 6426yy

Thank for the replies guys, as far as the ZDDP, yes I'm running that with Rotella oil. The engine was already broke in but I pulled the heads off of it to clean them up, cut for positive seals, set the spring height and install thinner head gaskets. I planned on going 3" with an x pipe and the tips coming out in front of the tires. I don't like the droan when dumped under the bed. I just hope my TH350 will hold up!!

im running a 4l60e behind about 525hp and its doin ok...

[bowtieCYRUS]

Originally Posted by 6426yy

+.030 454 Hyperuetectic pop up pistons 9.3:1, Large oval ports 781 mild cleanup, comp cams 4x4 extreme 270, weiand stealth intake with 750 Holley. 1 3/4 full lenght headers.

My truck has true duals with 2 1/4 pipe and Flowmasters; yeah I know they suck, all the more reason to change. Is it going to choke it?

Thanks

I would definitely bump the tubing size up to 2.5" (At minimum from the headers to the mufflers). But, It all depends on the driving you will do with the vehicle. If you plan on getting some rpm out of it I would reccommend going a size larger on the pipe. If you're not on a budget I would reccomend going 3" from the headers to the mufflers then 2.5" for your tailpipes. I know that not everybody is keen to Flowmaster mufflers, but they're not as restrictive as they're made out to be. I ran a 3" SINGLE EXHAUST with a Flowmaster Super 40 on my '94 Z28 and it put down 409rwhp on a dynojet. So, they must flow pretty good.

[Jim Rockford]

Originally Posted by bowtieCYRUS

. I know that not everybody is keen to Flowmaster mufflers, but they're not as restrictive as they're made out to be. I ran a 3" SINGLE EXHAUST with a Flowmaster Super 40 on my '94 Z28 and it put down 409rwhp on a dynojet. So, they must flow pretty good.

flows are junk, imagine how much more you could have made.

[bowtieCYRUS]

Originally Posted by Jim Rockford

flows are junk, imagine how much more you could have made.

I beg to differ. The first time I had the car tuned I had a Dynomax Ultra Flo welded muffler. If I remember correctly it made 411rwhp around 7000rpm and 380ish ft/lbs torque at around 3800rpm. Then I tried the Super 40 and had it tuned again with a new computer in the vehicle and it made 409rwhp at 6800rpm and 390ft/lbs torque at 3400rpm. The car has a 3500 stall in it and runs 12.7's at 120ish mph with a 2.2-2.3sec 60' (no traction). I don't think the 2 or 3 hp in my case was worth the 10+ft/lb loss.

[chevy1500z71]

you guys should read this article, very informative.
http://www.superchevy.com/technical/...xh/index1.html

the whole muffler argument is stupid, flowmasters are fine, as youl read in the article above, you only need 2.2cfm per hp roughly to have near 0 back pressure, a set of flowmaster 40s of adequate size could easily flow enough cfm to support as much hp as you wanted to make. look for some cfm flow rating before you sit and argue what muffler is better.

[bowtieCYRUS]

Originally Posted by chevy1500z71

you guys should read this article, very informative.
http://www.superchevy.com/technical/...xh/index1.html

the whole muffler argument is stupid, flowmasters are fine, as youl read in the article above, you only need 2.2cfm per hp roughly to have near 0 back pressure, a set of flowmaster 40s of adequate size could easily flow enough cfm to support as much hp as you wanted to make. look for some cfm flow rating before you sit and argue what muffler is better.

Thanks for the link. I manage a custom exhaust shop in California, and I've seen about all one person could possibly see regarding exhaust. But, that article brought up some very good topics. As a sidenote, I wasn't trying to argue with anyone. I was essentially trying to say the same thing that the article said, just not nearly as technical. lol. IMO most mufflers in the aftermarket realm will be suitable for most street cars, whether it be Magnaflow, Dynomax, Flowmaster, etc.