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How to add crankcase ventilation to your H&F block.

Hey KS Fam, I get asked this question all the time: "How do I add extra crankcase ventilation to my H&F series engine?" In this post I'll tackle that question and hopefully help out!

You all know where I stand on H&F series engines; as far as I'm concerned they're the best four cylinder engines ever made if you wanna make BIG power. They can't be broken; they're literally fucking unbreakable, and they make great power with bolt ons or a 72mm turbo but I won't go off on that tangent.... So first of all, it's not a B-series and that means that you can't just buy threaded plugs with -10an fittings and thread them in. The two open, threaded holes in the back of the H-series engine (pictured) lead to coolant so don't try and use them for crankcase vents!  

The best place to add a crankcase vent is right where the balance shafts *used to go. If you're reading this then you've already removed your balance shafts using our Balance Shaft Eliminator Kit, and so the best place to add a crankcase vent is to the right of the oil filter, on the hump that used to house the rear balance shaft. I like to drill a hole for a -12AN fitting right there and just weld it on. The reason I suggest using this location is because it's pretty well shrouded from oil sling off the crank which means it will keep your catch can from filling up with oil. Welding it is best but if you can't weld it, you can tap the block because there's plenty of meat there (it's about 1/4" thick). 

Then just run a line from this fitting to your catch can and you're done. Easy. Don't lose any sleep over drilling the block. There's an incredible amount of strength to the block (the block pictured lives it's life above 40+PSI of boost and 11,000 RPM) and trust me, adding extra crankcase vents is a very good thing. 

*How much crankcase ventilation do you need? This question's easy. The more the merrier. For reference, we use (2) -10an fittings on the valve cover, (1) -12an fitting on the block (pictured) and a -10an drainback to the oil pan to support mid 8-second cars with 1,200 WHP. 

**How much oil is OK to get in my catch can during a pass? During a pass where you're on the limiter a lot, it's not uncommon to completely fill a normal size catch can so don't freak out! You'll notice that if you're not riding the limiter, you won't fill the catch can as quickly. If you're trying to use the catch can as an indicator of engine health, what you should be looking for is trends: pay attention to how much your catch can is filling up each time you go to the track and be mindful if it's filling up faster. 

I hope that helps! -Reid Lunde,



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Posted by lodopolla on December 10, 2020

Where is the best place to drill into an H series that doesn’t have the balance shafts removed?

Posted by Mike on April 01, 2020

Why send dirty oil back into the pan? Or does it not matter in this specific application since you’re on race gas anyway?

Posted by Austin Larsen on January 13, 2018

This is an awesome thread… never even thought about adding a 3rd line for the catchcan, I have 2 -10 and fittings from my valve cover. next build will get one of these also just because.

Posted by Tyler Poore on August 14, 2016

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