"The master cylinder I got had the holes for the lines swapped as compared to the old one. I asked him about this and he said it was normal to have to swap front/rear positions on the lines sometimes. The threads were correct, so no issues there."
So you are saying the front brake line attached to the new master cylinder where the rear brake line attached to the original master cylinder? If so, was this necessity based on the flare fitting size? Thanks.
His factory master (JB6 RPO code?) most likely had the large chamber (front brakes) towards the radiator and the small chamber (rear brakes) towards the windshield. The JB7-spec (1-ton SRW and heavy 3/4-ton) master he appears to be running now has the small chamber towards the radiator and the large one towards the windshield. Both have 1/2" primary ports (front brakes) and 9/16" secondaries (rear brakes), so just some bending the brake lines around some is needed to have them line up with the new ports position when you switch one for the other.
Thanks to everyone for the compliments!
The response from "underdrive" answers your question. The ports that the lines hook to are different threads, so they are not interchangeable. The front line must hook to the front, and the rear must hook to the rear. On the new cylinder these positions were reversed as compared to the old one, and required just a bit of bending to the lines to get them into the new positions. It was not a big deal, but I wanted to mention it so others would be aware if they were considering the swap.
Larry, the cam is stock right now. I put a goodwrench 350 in it, and when installing the distributor I didn't take the time to line it up in the normal orientation that is commonly seen. It runs good and I just wasn't bothered by it. My suburban has the 8.1. I like the power it produces but I don't think I will ever spend the money to upgrade to a big block in the pickup. I would like to get a bit more pulling power out of it with a cam swap or something, but it does a pretty good job as it is so upgrades are not on my short list at this time. Having the SM465 helps a lot with the pulling, so it helps to mitigate the power deficiency.
Any idea how to look up which hydro unit a 98 2500 cummins dodge might have had?
I have sourced one for my 91 burb. This thread is very helpful. Thanks to all for sharing info.
Thanks Larry.
I have a hydro unit from a 98 cummins dodge and would like to install it into my vac boosted 5.7 91 v2500 burb.
So it looks like I need to get a firewall bracket and pushrod for my square body.
I'll just put this here for general information - the mid-'80s 3/4-ton trucks with diesel engines had a 1-1/4" bore master cylinder that has the large chamber on the front and the small one on the rear, however the port thread sizes are switched around to 9/16" primaries (front) and 1/2" secondaries (rear). To make it worse, this being a factory hydroboost application such a master will bolt up to any GM hydroboost unit. Thus, if one is not careful, and simply rearrange their brake lines to match port thread sizes, they will end up with the large chamber and its respective piston feeding the rear brakes, and the small chamber and piston feeding the fronts. Not likely to be any fun whatsoever every time brake pedal is depressed.The ports that the lines hook to are different threads, so they are not interchangeable. The front line must hook to the front, and the rear must hook to the rear. On the new cylinder these positions were reversed as compared to the old one, and required just a bit of bending to the lines to get them into the new positions. It was not a big deal, but I wanted to mention it so others would be aware if they were considering the swap.
I always wondered if that is indeed the case, why are there different listings for the hydroboost units between some 3/4-ton and 1-ton trucks of the same model year. And it's not a matter of different reserve accumulator pressures (IIRC it was 350 psi for the gold ones and 450 psi for the blue ones, not sure what the spring rate is for the silver ones) as they both have the same color accumulators, hydraulic line port threads are all the same as well, so I figured it must be something internal, but what?It will be the same Bosch hydroboost unit in these pictures other than it will have the period correct Dodge truck booster to firewall bracket and rods. The Bosch hydrobooster unit itself really hasn’t really changed at all in the past 30+ years. Some little things changed like thread connections but the unit internals and dimensions haven’t.
I always wondered if that is indeed the case, why are there different listings for the hydroboost units between some 3/4-ton and 1-ton trucks of the same model year. And it's not a matter of different reserve accumulator pressures (IIRC it was 350 psi for the gold ones and 450 psi for the blue ones, not sure what the spring rate is for the silver ones) as they both have the same color accumulators, hydraulic line port threads are all the same as well, so I figured it must be something internal, but what?
There are also differences between power piston diameters internally between models.
Todd Z.
Now I wonder what difference the power pistons make and what vehicle GVWR, etc. drives different piston sizes. The more we learn about these the more we find out there is more to learn. I wonder how much attention to piston diameters paired to the right vehicle spec rebuilders really pay attention to...Hmmm
Subscribed. I want to put this in the Woofwagon.