Anemic brakes in '91 with LS3 engine swap (1 Viewer)

[callmeDW]

As stated, super soft braking power - I'm the new owner of a '91 FJ80 the PO dropped in a 5.3L LS3 engine among many other upgrades.

But the brakes totally suck - local Toyota mechanics (great reputation in Wilkesboro, NC) -- we had evidence the LSPV valve was bad, replaced that - bled the system and ensured we were finally getting fluid to all 4 corners. But the master cylinder indicated it was bad - so they replaced the master then the booster. Bottom line, we're sitting with a little better braking power but still pretty anemic.

Suspicious of the vacuum setup off the LS engine - does anyone have some specs we could measure against to chase if we're getting too much / not enough vacuum pull? The master and booster are OEM spec to the FJ80. Next would be swapping out front calipers. Just trying to gather some info to pass along to the shop - any help / experience is greatly appreciated!

 

[NeverFinis]

Does the LS motor have a cam? Is the engine lopey?

I have a L96, completely stock, and it produces enough vacuum for the booster. Google search shows spec is 18-21 inHg.

Relevant Thread: Need opinion on brake issues Land Cruiser 80 LS swap, second posting. - https://forum.ih8mud.com/threads/need-opinion-on-brake-issues-land-cruiser-80-ls-swap-second-posting.1342461/

 

[White Stripe]

Did you bleed and adjust the lspv to the proper caliper pressure?

 

[ppc]

Have you checked all of the rubber brake lines. One or more of the rubber lines could be breaking down and ballooning reducing pressure and also feel spongy.

 

[robnicko]

really nice looking 80 !!

Have the rotors & calipers been upgraded to the later FZJ80 type or still 1991 fj80 spec?
theres a big difference in braking power with the later equipment predominantly the rotor diameter / size

 

[cruisermatt]

Have you measured the actual stopping distances from various speeds and can you post them?

 

[callmeDW]

Wow - everyone always says how awesome the IH8Mud forum is... but my first posting, it's overwhelming!

Short version of where things are now - replaced the LSPV valve, redid the brake lines connecting (due to damage in the swap from rust issues); everything properly bled and flushed. New master cylinder and booster installed and dialed in to the best of the mechanic's abilities. Compared to 'before' the stopping power is MUCH better - but still not optimal according to the mechanics. They plan to order / replace the front rotors - I believe OEM spec, not the FZJ80 version.

Once I know, I'll update - and I'll try to post some stopping distance metrics. The speedo is off a variable amount because of the larger tire size (35") and lift - which I just pace based on traffic and feel. But apparently you guys want scientific accuracy and methods

 

[cruisermatt]

My question of measuring stopping distance was a bit tounge in cheek, but was meant to highlight that your question was a bit subjective

With that being said, I would recommend the 93-97 rotors/calipers (use OEM Toyota) which will be a bolt-on to your vehicle. You have the large rims to accomodate them. If your front brakes are new, and your master cylinder, booster, and hoses are all new OEM Toyota parts, assembled and bled properly, your brakes should work well with your 35" tires.

How was your intake manifold adapted to your brake booster? I sell a nice inexpensive kit for that which is super clean and requires no adapter fittings or multiple hoses.