Truck is an 01 1500 Sport with a 5.9 V8. Has shorty headers and a tune on it. I've noticed lately the truck feels VERY bogged down vs when I put the engine together about 10 months ago. WOT takes a REALLY long time compared to before to start climbing speed and never really reaches proper RPM anymore. I've noticed VERY large amounts of oil consumption since I put my synthetic in and some people are telling me its just that synth goes bad faster, but I'm suspecting that plenum already failed because of tune, even though we had a good gasket, sealer and proper bolts. Exhaust/gas smell has become more noticable, MPG did suddenly and randomly drop from like 12 to a 10.5 no matter what I do ever since. Exhaust pipe is also showing a bit of blacking at the tip, indicating a rich mix ( I want to guess because its burning oil leaking through plenum..). Any tips on what it could be and what I should fix. I know I really need to get the aluminum plenum to repair it, but I rather just get a nicer intake, where could I get a good priced one that would perform well across the board? I don't mind losing a little bit of low end torque, as I spend alot of time 1750+ because low RPM just doesn't sound as cool :P

But yeah, any ideas on what the loss of power could be from, and if the plenum could hurt performance (and mpg) that severely? and which intake I could grab to gain performance and eliminate the plenum issue entirely?

 

Check the plenum, as it sounds like the gasket blew up again. Did you shorten the bolts before you put them back in? Not leaving any puddles on the ground?

About the only choices you get for aftermarket manifolds are the Hughes Air Gap, or the M1. The M1 has become EXTREMELY difficult to find..... (they stopped producing them a while back....) Both manifolds move the power band up pretty significantly in the RPM range..... (they are single plane manifolds, after all.....)

 

They should've been shorter bolts as we bought completely new ones to replace it with in a proper kit, and we made sure to torque them to specs in the proper order as well. As far as I can tell I've not leaked oil out onto the ground from anywhere and never have had puddles from anything other than AC drip off after running it awhile. Can the plenum really go bad that fast?

Which of the two manifolds would be a better buy and be more 1750-4k friendly? I don't spend much time at low RPM because of speedlimits/highways in my daily commute, lowest is usually 45 and depending on traffic I may or may not keep it out of overdrive.

 

Anything is possible.... but, you'll have to look and see if that is actually the problem.

I think both manifolds are very similar, with a slight advantage going to the M1, they are priced about the same as well..... (around 600 bucks, unless you get REALLY lucky.....) Hughes is still available, the M1 is hard to find. Keep in mind, you want the M1 for fuel injection, the carb fellers are still out there, but, no provisions for fuel injectors.

 

600 bucks? Wow that's a bit more than what I was expecting from browsing manifolds. I'll check the plenum thread for how to make sure its a blown plenum, and do that in the upcoming month.

What else would you suggest looking at/adjusting when I do a tune up in early '18?

 

Whens the last time the O2 sensors were replaced?

I don't think there is really much to adjust...... TV cable, and that's about it. If the trans is shifting properly, then it's fine.

 

http://www.hughesengines.com/Upload/...ynocompare.pdf

Hughes little graph on their site makes me think that just fixing the plenum on the stock is probably the best idea, as the low torque (except for whatever that is where they started?) is HUGELY lost, and then only starts to get beaten out at like 4.5k+, and even then the horsepower seems to stay within 10-20 even into those ranges. Is there something i'm missing? The graph makes the stock look by far the best of them in anything but passing or racing application, granted it doesn't show anything below 2600 at normal driving RPM.

 

Both 02 sensors are within 3months old, my old ones were throwing codes so I replaced and haven't had issues since.

I adjusted TV cable awhile ago (4 months) so that it would require a bit less throttle to downshift, but it seems to be hanging on in gear much longer than it used to at low throttle than after that adjustment, especially in first gear. It also does shift 'hard' I guess, like there aren't issues shifting into any gears or anything. It's just very abrupt and decisive when it switches, its not a smooth transition like I'm used to in more modern vehicles, like it has RPM built up, and then will suddenly change gears and drop very suddenly, almost like pressure building up then suddenly releasing.

I also noticed lately anytime I give it hard throttle you can hear a very distinct and loud sucking sound, like a rush of air while throttle is down. This used to happen only when cold and only for like 5-15 seconds after initial start and driving, but would go away as it warmed. Sound like anything you've heard of? - I'll try to get a video of this so you can hear what it sounds like, wondering if its possible im mistaking it for another noise (my ear is untrained to engine failure sounds as I've generally kept mine working well :P )

 

The Hughs/Edelbrock air gap is a dual plane and much better for the truck application, had one on my 5.9 before I got my v10 and loved it.

 

How reliable is the plenum fix kit? Will I ever have to worry about it failing again and subsequently repairing (spending money) again?