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L Series Head & Gasket Replacement - Shop Checklist

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It's time to replace a failed head gasket on my 510. I'm trying to do this on my own for the first time. Pumpkn210 (RIP, Dave) did this job for me about 10 years ago while I hung out. I dont want to ruin the engine, so I'm creating like a step-by-step shop checklist for myself and other learners. I found info from h2theizzo YouTube, @banzai510(hainz) is that you? as well as from @Skib's rundown, and a couple manuals. Many of you can do this in the dark, so I appreciate help from your experience, thanks everyone! If you see any corrections / additions, comment below.


Also, a couple questions:

- how do you turn the engine to TDC? Just turn the crank pulley in neutral? 

- what gaskets should be replaced other than head gasket? 

- head bolt torque specs: I've seen both 40 and 60ft/lbs. Any thoughts? 


L Series Head & Gasket Replacement - Shop Checklist


Drain the fluids

  • Drain coolant
  • Drain engine oil


Remove auxiliary parts

  • Remove exhaust manifold
  • Disconnect hoses
  • Remove distributor 
  • Verify distributor slot at 11:28 position for TDC


Time engine to top dead center, compression stroke

  • Take valve cover off
  • Turn crank pulley to approaching TDC 
  • Verify mark on crank
  • Verify timed head (intake at 10 o’clock, exhaust at 2 o’clock positions)
  • Verify v-notch on cam sprocket aligned with dash on cam plate


Loosen cam and crank bolts

  • Put screwdriver through cam plate (is this a good method?)
  • Loosen cam bolt (19mm) 
  • Loosen crank bolt (is this only for full-engine breakdown?)
  • Make sure nothing got moved out of TDC 


Remove cam sprocket

  • Mark sprocket and chain link with paint pen to help with reassembly 
  • Insert timing chain tensioner tool and make sure it is well seated
  • Take off cam bolt (19mm)
  • Remove the cam sprocket 
  • Check the cam gears for wear. If gear is worn, replace with OEM Japan parts


Remove front cover bolts

  • Remove top (2) 10mm bolts from front cover 
  • Below steps are for full-engine breakdown only:
  • Also remove remaining 10mm bottom cover bolts
  • Take out oil pump and oil pump drive. Keep in a clean place
  • Take off crank pulley. Keep in a clean place. 
  • Take off cover, but keep bolts in cover so they go back in their same holes
  • Tap cover with something soft on both sides to loosen


Remove engine head

  • Clean oil out of Allen head bolts where debris can collect
  • Loosen head bolts with Allen socket (10mm)
  • Loosen and remove from inside to outside
  • Soak head bolts in carburetor cleaner to clean
  • Verify cam dowel is in 12 o’clock position to verify TDC timing
  • Put a breaker bar in an exhaust port and gently lift to separate head
  • Do not left head fall off! 
  • Check head gasket, head, and block where failure occurred for defects


Remove old gasket & clean surfaces

  • Clean gasket surfaces thoroughly. Check with fingers for any traces of adhesive, old gasket, etc
  • Prep the block face and head face by removing all oil residue. A spray can of ether (starting fluid) works well, and some lint-free cloths / old t-shirts
  • Chase the head bolt thread holes. Remove all water, grime, grease etc that is in the bolt holes. You can use a thread tap. Use a small vacuum hose to blow gunk out of the holes if needed


Install front cover gasket (if doing full-engine breakdown)

  • Use blue RTV to hold gasket
  • May have some complications with oil pan


Install new head gasket 

  • Seal / hold head gasket using Permatex Copper-coat (optional)
  • Place new gasket on block


Install head

  • Place head on new gasket, aligning with block dowel pins
  • Ensure head sits flat 
  • Install head bolts with washers (10mm Allen)
  • Follow cylinder head bolt tightening sequence 
  • Use a quality torque wrench
  • Torque in long, even stroke in increments of 20ft/lbs
  • Finish at 40ft/lbs torque (check on this, someone else said 60)
  • Make sure the cam dowel is at 12 o’clock position for TDC
  • Make sure #1 piston is up to ensure TDC 
  • Install the two front cover top bolts (10mm - torque spec?)


Install cam sprocket and timing chain 

  • Install timing chain sprocket, align with paint marks (when trying to put the sprocket back on, it might seen hard to get it up on the dowel and center part of the cam. If so, move the cam left or right to get slack in one side to help raise the sprocket up)
  • Install cam sprocket bolt (19mm, torque spec?)
  • Remove timing chain tensioner tool


Install remaining parts

  • Install valve cover (torque spec?)
  • Install exhaust manifold
  • Verify distributor at 11:28 position for TDC
  • Install distributor
  • Connect hoses


Refill fluids

  • Refill the cooling system 
  • Refill the engine oil 





H2theizzo YouTube L series head replacement

Is this you banzai510 (Hainz)?


(From Skib's Quick Head Swap Write-Up)

…some manuals from the shelf


Parts to be ordered & replaced

Head gasket

Thermostat gasket?

Other gaskets?


Special tools and Supplies needed

10mm Allen socket

19mm socket

Torque wrench

Timing chain tensioner tool

Gaskets (head, etc)

Permatex Copper-coat


Engine Oil

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Wow, I do not remember writing that post. 


Felpro makes a whole head gasket set with everything you'll need.

Part number HS21178PT3


The old full size timing tensioner tool was Powerbuilt/Alltrade 648831, 


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I pull the exhaust to the side

put to TDC mark chain on the dimple.Break the cam bolt loose then put back to TDC

  Use chain wedge, pull all the bolts


If you want to leave the front cover ON you need the chain wedge. to hold it up and make sure the tensioner dont pop out,  Fotr this You dont even need to drain the oil. just drain the water and leave everything in place.  You pop the tensioner out then  your taking front cover off oil pump ect...everything off. THE SHORTER ONE IS NOT THE CORRECT ONE ITS FOR A NAPZ MOTOR648831timmingchaintool.jpg.eb218e20c22e223395d19ee4bd040903.jpg


Edited by banzai510(hainz)
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Disconnect the battery!!!!!!!! Unbolt the ground strap from the head behind the fuel pump.


Take valve cover off. Loosen the cam sprocket and the crankshaft bolt*. Turn engine with 27mm socket and bar at the pulley and line the timing mark up with the zero on the timing scale. Look at #1 cylinder. If both valves are closed you are at TDC on the compression stroke. If not, turn engine ONE turn and line up marks... NOW you are at TDC compression stroke. 


*Do first before setting TDC accurately. Have in 4th gear with brake on. Save doing it twice. Then place in neutral so engine is easy to turn to TDC


You don't need to drain oil unless changing it!!!


You can remove the manifolds but if careful and have help lift the head off with manifolds attached. Less chance of stripping a stud or the new manifold gasket not sealing. Disconnect at the exhaust down pipe. I've done this by myself before. Keep level, do not place face down unless you have 2x4 blocks to set it on. If carburetor left on tilt up just enough to clean surface, ot take carburetor off now, it's easier than on the engine. 


Disconnect the top radiator hose and the heater hose from the head. Disconnect the coolant hose from the intake in front of the carburetor as well as the by pas from the thermostat housing. Optional: take the radiator out. Makes getting at the crankshaft bolt easier.


You don't have to remove the distributor but take the cap and wires off so they don't get broken.


There's no way to tell by looking if chain/sprockets are worn. There is a way to check and adjust for stretch and wear. More on this later.


Timing cover does not need to come off to change head gasket only if you fuck up and drop the chain tensioner.


Remove fuel line to fuel pump. If there is a return line disconnect it here also.

Disconnect the temperature sender on the thermostat housing.

Disconnect the throttle cable

Unplug the auto choke heater wire and the idle cut solenoid. (if equipped)

Disconnect the vacuum hose to the brake booster. (if equipped)

Disconnect the vacuum advance hose to distributor.


Remove head bolts and save the washers!!! They prevent the steel bolts from chewing into the soft aluminum.


Don't forget the two 10mm bolts on each side of the head at the front that bolt it to the timing cover.


The head is aligned to the block on two dowels that look like 1/2" copper pipe. They fit into over size holes around two of the head bolts. They may stay in the block or the head so look for them and don't lose them.


Clean head and block. Use a straight edge to check head for any warp. 0.004" feeler gauge is the limit. Factory says this but probably get away with 0.006". Head gasket will crush and seal easily.


Head bolts are reusable if undamaged and clean. Wipe with oily rag. Use a torque wrench. L16/18 are 40 ft lbs. L20B are 60 ft. lbs final torque.


Head gasket goes on DRY. This isn't the '50s so re-torquing the head gasket is not needed.



(probably forgot something small)








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