Fitting HR-style HG requires very simple mod, it could be done with a rotary tool.

I'm going with ARP head studs (non L19 ones). These aren't TTY, right?

 

you want the strongest studs you can buy, if L19's are available, you would be foolish not to get them. TTY are bolts, not studs, so if you are buying ARP head studs, no they are not.


sealing the heads properly is one of the biggest concerns building these motors. the cooling mods you are discussing are not as important

 

Thanks. I had VQ35DE '03 that was prone to overheating and overfilling coolant overfill reservoir if you were driving WOT for few minutes and going over 120 mph (surely the issue was in cooling/HG sealing when the engine's hot).

 

Pathfinder mod diverts coolant flow to aid with block cooling, so more coolant cools the block and less goes to the head.

HR mod requires shaving down diverting walls in the block because the coolant flow is changed: it goes to the block and then enters the head right near exhaust valves (the hottest part of the head). Doing that also increases coolant flow going to the block and cooling cylinders.

I'm not sure doing both mods is a good idea: when secondary thermostat opens less coolant goes to the head. Not sure how big the chagne in the flow though.

 

i am getting the pathfinder mod done and i have the HR mod done so ill let you guys now if its better or worse. If room i wonder if a valve on the line that allows it to be flow to thepathfinder t-stat or not flow is a good idea. would the pressure blow the pipe if its not allowed to flow through into the T-stat?

 

I've done both mods, two years of abusing, no problem.

You should really get L19 bolts if your HP goal is more than 500WHP. ARP 2000 head bolts doesn't have enough clamping force, that's a well known and proven fact.

 

Thanks! Did you do anything else to your cooling system? How much HP are you pushing? Is your car SC or turbocharged?
L19 head studs are already on my shopping list. Going with ARP L19 head studs & ARP main studs.

 

Blocking that pipe is absolutely safe. The pressure there is about the same as in radiator.

 

Having fully built motor and Boosted Performance mid mount turbo kit with PT 6266 turbo. 600+ whp. 34 row oil cooler, stock coolant radiator and fans.