Cummins 300 question

85COE · Feb 17, 2020

AModelCat said: ↑

Since when is 120k a superload?
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According to the DOT person in the permit dept, when I called.

Dino soar said: ↑

There should be a tag somewhere on both rear axles. Sometimes it is on the differential sometimes it is on the housing.

You have to look very closely because if there is a lot of dirt and grease on the rears they blend in.

I use a rag with thinner to wipe the tag to be able to see it better.
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Thanks, I'll check when I get home Friday.

Brettj3876 · Feb 18, 2020

379_largecar said: ↑

I had a formula 300 big cam in an 85 freightliner (back when freightliner was respectable and not plastic!) first thing I always do to a big cam is swap the button to a 5, drill the ball and crank that pressure waay up, get the spring to crank 2300 rpms install a pyro and run the lines to both front head and rear head. Swap out the steel fuel lines for high psi hydraulic lines (I had a problem splitting the steel). I thought it was doggy hauling 100,000 of sand. Ran it it for several years and only blew one head gasket on the number three head. Shoot about 5 hours and I had the thing tore down and put back together in my driveway. I then bought a Pete with a 525 red top and man did I wish I had my 300 back!
Had to have a geek turn that n14 way up to even get close to the old shaker!!
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If you would of lowered the compression you wouldn't of blown the head gasket and prob close to burning the pistons. @OLDSKOOLERnWV will tell ya what to do op.

bzinger · Feb 18, 2020

ODR said: ↑

Be careful of cranking the fuel pressure up on a big cam. Everything has limits. Larger injectors to handle the extra flow without flattening out your cam would be a good thing when upping the the power. Lower compression pistons and changing the timing may also be needed. Also clutch, trans and rear ends might not be able to handle extra power
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Lol...1st truck I bought was an 85 9670 , formula 300 freshly overhauled.
Would do about 64 mph until one day somewhere in texas while running with an A@H driver out of Footeville wisc he said hit this rest area I'll make her run .
About an hour later it hauled arse and would smoke up a trailer quik .
I heeded his advice to watch the temp but still went thru some injector cups and a head gasket or 2 .

OLDSKOOLERnWV · Feb 18, 2020

85COE said: ↑

Not sure what all info you would need to answer this, but I'm looking at doing some super loads from MI to OH, 165 miles 1-way loaded. According to a dealer, it's considered a "medium-duty" engine. 808,xxx miles, 9 speed.

Permits in Ohio would allow me to be up to 120,000lbs on the roads. Tractor weighs in @17,500lbs, trailer will be around 15k-20k or so (extra axles).

Just wondering if my engine could handle it on a daily basis. 165 loaded miles max 1-way.
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Just curious, what’s your CPL number? It will be on this tag....

MACK E-6 · Feb 18, 2020

Brettj3876 said: ↑

If you would of lowered the compression you wouldn't of blown the head gasket and prob close to burning the pistons. @OLDSKOOLERnWV will tell ya what to do op.
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Once upon I time I drove just the truck he could’ve used., an 85 R model with a 350, 10 speed with deep reduction, and a 44K drive tandem. Pulling trailer mounted grinders with it would work you. Like someone else said earlier you had to watch the pyro, but it got the job done.

379_largecar · Feb 19, 2020

Brettj3876 said: ↑

If you would of lowered the compression you wouldn't of blown the head gasket and prob close to burning the pistons. @OLDSKOOLERnWV will tell ya what to do op.
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No I’d say it’s because it had more than 1.5 on the ticker... I’ve done it to A lot of big cams... not saying it’s right but it’s always worked for me

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