Gambi80

I don't get 30lbs of boost w/my 427.

1,000 cubic inches...? That gets me a bit excited. Time for a 1,000 inch motor in a truck, truck fund piggy bank.

I've stood beside a couple 99/00 Macks at idle and they sounded pretty rough too...was always told that's just how it is. They ran like a bat outta hell but sounded like hell at idle.

I thought the advertised HP on Mack trucks was what its rated at the wheels....E7-427=427 at the wheel and so on....?

I've got a '97 CH with air ride and it's ok off-road but won't hold a candle to my dad's 88 R-model with camelback springs. Both trucks are used on the farm also, so there's a lot of in and out of fields in less than marginal conditions. The absolute worst off-road is the Kenworth 8-bag air ride, hands down.

Hard to imagine people new to driving those trucks could become confused...lol I think I will stick to kickin it old school. The only buttons I want to have to hit are either the cruise or to change the radio station...not to recharge the DPF PDQ before I'm SOL and the truck is DOA at my local Mack dealer.

Yea I have the same problem. I put 8 brand new drives on mine, albiet the next to cheapest ones, but they shimmy. The crappy mis-matched ones that I took off ran smooth as can be. $2400 for square tires.

Thanks for the info. What led me to wonder is that my dad's truck, an '88 R-model w/a 350 has a jake on it (one setting only) and it makes about 7-8 lbs boost at a high rpm. I figured my engine, bigger displacement and bigger power should make more than that. I was planning on having the rack run sometime in the near future. I don't know if I'd want to tackle that myself or not. I suppose I could have the jake looked at at the same time. From the way it sounds it's not too big of a deal to have it rebuilt.

That's some good news then as I was expecting buku bucks for parts. Is it very labor intensive or just pop off the rocker covers and pick apart some parts? I'm a big fan of the jake brake too. Makes for a much nicer to handle and drive truck, not having to use the brake pedal near as much.

I know this is an old topic, but I had the same problem with the coolant system being pressurized. It started with a hole in the radiator, replaced it. Hole in the coolant tank, replaced that. Still had the same problem. Finally gave up and took it somewhere to get looked at and the guy said it could be one of two things. The worst being the head gasket bad or...the air compressor going bad. A test where some doo-dad is stuck into the recovery tank and if the compressed air contains carbon it turns the liquid a different color showed nothing. They then bypassed the coolant lines from the compressor and determined that's what the problem was. After they got it off, they took the compressor apart and found that the head gasket was shot and allowed compressed air into the coolant. Since then I haven't had a bit of trouble and have never had to add coolant. I've sent in a couple random oil samples and they've both come back excellent. Just something else to consider anyway since I didn't see it mentioned and is relatively cheaper than tearing the engine half apart.

So someone mentioned rebuilding the jake brake, what all is involved with that and maybe ballpark the cost...?

I'd post one but evidently my picture was over the max of 2mb...anyone know how to reduce pictures? Think I got it... not exactly looking its best, but its the thought that counts.

I was joking about the flex pipe. I was just saying how I didn't expect the replacement parts to cost so much. I intend to do it right, couple extra bucks for peace of mind. Just curious what people with way more experience than me had to say.

Would it be a BFD if I took it out? A decent portion of the exhaust needs to be replaced anyway. It has duals and the 90* elbow where it splits is cracked, among other things. I about crapped my pants when I went to the parts counter at my local dealer and priced parts...$800+ for just the elbow and 4' or so of pipe (the shiny one of course!) to the passenger side muffler! I think I'm going to get creative with flex pipe and an exhaust catalog.

Well...keep in mind I'm no mechanic. I'd make a good parts changer but no doctor. If the 'stealth brake' is what I think it is, my truck has one. A doo-dad about a foot back from the turbo with what looks to be a shock absorber hooked to it. If that's all it has for engine braking then I guess I have to deal with it..? Or is that in addition to a regular jake brake? I suppose I should make sure of what I have before firing questions.

I have a 1997 CH 613 w/a 427 with approx. 600k mi. What is the max boost supposed to be at full throttle? Also, how much boost should the engine brake build...if any at all? Full throttle boost varies between 22 and almost 30, different everytime I floor it at the same RPM. I really have no complaints on the power, MPG varies a lot...between 5 and 8...mainly due to the work I do with it. I suspect the engine brake isn't working correctly, for whatever reason. It doesn't sound like it should or build any boost and there is little feel to it when I turn it on. It sounds like its hitting on all 6, but very weakly(?). Any ideas..? Or is this all I get? I want it to work 100% because I mainly do construction work-dump trailer with it, so there's a lot of stop and go. I've had this truck for almost a year...bought used (have had a couple suprises already!) Any replies would be appreciated.

Yea, just joined from north central IL. Bought a '97 CH w/427 and an 18sp earlier this year...well, last year (already!). For the most part, grew up around Mack trucks and learned to drive in one...now I jumped in head first and bought my own. As always with anything pre-owned...its a work in progress. So I hope that I can come away from this site with some much needed and helpful advice. Thanks in advance!