I just installed a high flow cat, and my "sweet spot" jumped from around 2500 - 4000 RPM's to 3000 - 4500 RPM's. However, the muffler on it is still wrong; the previous owner had a 3" or 3.5" muffler gumballed onto the pipe. Does the muffler matter? What mods bring the "sweet spot" down, or does it even really matter? Also, I've heard about a 408 stroker. Just to make sure, that's when you overbore a 360 block, and install longer stroke crank (with other misc. parts), right? What are the cons of this? How much would fuel mileage suffer? I happen to have a 360 block lying around. I want a good, solid, all-around strong motor, with emphasis on acceleration and very good torque, but lightweight for off-road, and great fuel mileage. (Quit laughing, Y'all) (OK, enough now, seriously!) Look, the reason I ask all this is I don't have money to soup up one motor, just to yank it out to build another. So... any tips and/or advice would be appreciated. Thanks!!




P.S. I'm still perfecting my prototype truck engine. It develops over 900 HP, 1500 Foot-Pounds of torque, lasts for 600,000 miles, and, best of all, it runs off of mud, grime, and grit!! If I could only figure out how to keep the motor from seizing. Oh, well...

 

the 408 stroker doesn't require boring out. You'd probably want to hone out the cylinders.. and i think boring only gets you like 5ci.

as for your sweet spot.. the high flow cat could of dropped your back pressure enough to make you lose a little low end.. now 100% sure though.

 

what kinda muffler you got on there now?

 

Yeah boring a 360 .030 will give you a 365.

Not sure if you gotta bore and drop in a new crank or just swap the crank

 

Some kind of crummy flowmaster with rust holes trying to form. My main question is: I know all upgrades give you power, but most just give you more top end power. What gives you low-end power?

 

longer stroke

If you can afford the stroker kit...do eeet!

 

do you have tailpipes on it? if not then putting some on might help ya out a little bit

 

This won't get you more power, but lower gears would get the power to the wheels sooner in the RPMs.

 

You can lower the power band by advancing the cam 4 degrees. I think that you can also bolt on some 1.7 rr to improve lower end. Another one you can try is modifing the intake. If you unbolt the intake and look in there are tubes going from one side to the other and sometime a seperating plate down the middle. First get rid of the middle seperating plate then cut those tubes down about 1/2" to 1" for low end or 1" to 2" for highend. Last make the holes for the fuel injectors bigger. Often times the fuel injectors don't sit far enough in and actually create a drip of gas by spraying on the edge of the intake. Another low end producer is Long tube headers.

By the way I know it feels like you lost low end but, I'm would almost bet my truck that if you put it on a dyno in reallity due to the higher flows you have increased HP and exagerated the power curve. What I mean by this is you increased the HP produced throught the range but at lower RPMS it is something like 1 horse while at higher RPMS it's more like 10-12 horse. So there is a bigger differnce between bottom and top end. Which in turn makes it feel like lost low end. IF you have stock manifolds they are "tuned" for midrange horseys. If you install longtube headers they are tuned for low end"