LCAM-01XA
Full Access Member
pressure hoses - very important!
If you are running a GM booster with Ford pump-to-hydro pressure hose, you may wanna consider converting your pump to Saginaw with 16mm fitting and your pump-to-hydro to any '80-up GM pressure hose that will work for you based on shape and length. Reason for this - recent investigation on my part revealed that the GM hydroboost has 18mm inlet and 16mm outlet ports, Ford hoses are made to work with 7/16" SAE inlet and 3/8" SAE outlet, and SAE threads run smaller than the metric ones. The difference is not too large and as proven on my own truck for several years and countless moron-avoidance stops Ford SAE hoses can and will seal to GM metric ports, but IMHO this is only due to the fact that both setups use the same line size and shape on the o-ring end.
To elaborate some more, it is the actual thread engagement between the line nut and the hydroboost body on the booster inlet port that has me concerned: the 7/16 SAE thread on the line nut translates to OD of 17.44mm (actual measurement), while the metric line nut GM used has OD of 18mm - that's a difference of 0.28mm per side, on a thread that under full engagement only has depth of 0.8mm IMHO it's a big reduction. Now let's look at the actual force that thread has to handle - assuming a dead-headed 3/8" line subjected to 1500psi pressure the force trying to pull the nut out of the booster is about 165lbs. Is 165lbs a lot for a threaded connection running on only about 65% or less of its rated capacity - I honestly don't know, but considering what happens should that threaded connection fail I'd much rather err on the side of caution.
The situation with the outlet port is much better - the 3/8" SAE thread on the Ford hose measures at 15.86mm, metric GM line nut is 16mm, those make for difference of 0.12mm per side on a thread with full depth of 0.8mm, so only 15% decrease in thread engagement there. The two threads are actually so dang close that I personally cannot feel any difference in the way the SAE line nut threads into the metric booster port as compared to threading the correct metric line nut into the same port. With the larger inlet port, if one pays attention they can feel that the 7/16" SAE line nut threads into the 18mm port a bit too easy and loose (and so no, I obviously wasn't paying enough attention when I put the thing together the first time around).
So there you have it - just another proof why it's very important to do your own research and take measurements for yourself if possible, instead of blindly relying on information from some random yahoo on the internets (me) and hope they actually knew what they were doing... In case you're wondering what I did to fix all this, I installed a Saginaw pump with the metric fitting, switched my booster to a newer GM unit (not necessary as it still has the same 18mm inlet and 16mm outlet ports, but I wanted the newer ABS-friendly design), and connected the two with a proper GM hose that matches both the metric pump fitting and the metric hydroboost inlet port. Based on my experience so far I feel the threaded connection at the booster outlet port is perfectly fine and safe as is, so I kept the Ford hose between the hydroboost and the steering box and just gave it a new o-ring as a good measure.
If you are running a GM booster with Ford pump-to-hydro pressure hose, you may wanna consider converting your pump to Saginaw with 16mm fitting and your pump-to-hydro to any '80-up GM pressure hose that will work for you based on shape and length. Reason for this - recent investigation on my part revealed that the GM hydroboost has 18mm inlet and 16mm outlet ports, Ford hoses are made to work with 7/16" SAE inlet and 3/8" SAE outlet, and SAE threads run smaller than the metric ones. The difference is not too large and as proven on my own truck for several years and countless moron-avoidance stops Ford SAE hoses can and will seal to GM metric ports, but IMHO this is only due to the fact that both setups use the same line size and shape on the o-ring end.
To elaborate some more, it is the actual thread engagement between the line nut and the hydroboost body on the booster inlet port that has me concerned: the 7/16 SAE thread on the line nut translates to OD of 17.44mm (actual measurement), while the metric line nut GM used has OD of 18mm - that's a difference of 0.28mm per side, on a thread that under full engagement only has depth of 0.8mm IMHO it's a big reduction. Now let's look at the actual force that thread has to handle - assuming a dead-headed 3/8" line subjected to 1500psi pressure the force trying to pull the nut out of the booster is about 165lbs. Is 165lbs a lot for a threaded connection running on only about 65% or less of its rated capacity - I honestly don't know, but considering what happens should that threaded connection fail I'd much rather err on the side of caution.
The situation with the outlet port is much better - the 3/8" SAE thread on the Ford hose measures at 15.86mm, metric GM line nut is 16mm, those make for difference of 0.12mm per side on a thread with full depth of 0.8mm, so only 15% decrease in thread engagement there. The two threads are actually so dang close that I personally cannot feel any difference in the way the SAE line nut threads into the metric booster port as compared to threading the correct metric line nut into the same port. With the larger inlet port, if one pays attention they can feel that the 7/16" SAE line nut threads into the 18mm port a bit too easy and loose (and so no, I obviously wasn't paying enough attention when I put the thing together the first time around).
So there you have it - just another proof why it's very important to do your own research and take measurements for yourself if possible, instead of blindly relying on information from some random yahoo on the internets (me) and hope they actually knew what they were doing... In case you're wondering what I did to fix all this, I installed a Saginaw pump with the metric fitting, switched my booster to a newer GM unit (not necessary as it still has the same 18mm inlet and 16mm outlet ports, but I wanted the newer ABS-friendly design), and connected the two with a proper GM hose that matches both the metric pump fitting and the metric hydroboost inlet port. Based on my experience so far I feel the threaded connection at the booster outlet port is perfectly fine and safe as is, so I kept the Ford hose between the hydroboost and the steering box and just gave it a new o-ring as a good measure.
