Seem to have a few problems.

[Ponyboy Easley]

So i have a 76 datsun 620. Few problems are:

1 Huge clouds of white smoke out of the exhaust

2 Cant seem to figure out where all my coolant is going.

Help?

[datzenmike]

Probably runs like shit too. Your head gasket is most likely blown. Stop driving it.

 

It can be fixed for about $50 or less. Last time I did this it was $23 CDN for a Felpro gasket..... and an afternoon. Before you tear into it find out how to block the timing chain tensioner from falling out. This is important because failure to secure the chain tensioner adds about4 more hours of work to fix.

 

Add $30 to $50 for milling the head flat. This may have caused the gasket to blow, but driving it this way will eventually overheat and warp it for sure.

 

Introduce yourself and tell us your mechanical experience.

[Ponyboy Easley]

Yeah its not the easiest to get going. Okay so first, this is my first datsun and have many plans for it. I live in kentucky and like anything old, muscle or import. If its old, i love it. But i dont love how my datsuns been acting up. My mechanical experience, i know alot do my research but i dont have much hands in experience...so this will be my first gasket replacement....so should i just replace the head gasket or the gasket whole kit? And tentioner, any tips on that? I need as muhc help as i can get. Thanks

[datzenmike]

CHANGE HEAD GASKET ON L SERIES ENGINE

 

Disconnect and remove battery.

Drain coolant at least half way and remove upper rad hose.

 

The intent is to remove the head and both manifolds together. The manifold bolts are very difficult to get at when on the engine. If you have the head planed it's much easier to remove them with the head off. If a stud breaks... again... it's easier to repair with the head off the engine.

Separate exhaust from the down pipe.

remove air filter, unhook throttle cable, any air pump hoses at air pump. (if equipped) vacuum line to brake booster, (tie out of way) PCV hose at intake, idle cut and choke heater wires on back of carb, vacuum line to distributor, top rad hose at head, vacuum line to charcoal canister, unplug spark plug wires at plugs and remove distributor cap so it doesn't get broken. unhook temperature gauge wire at thermostat housing, disconnect fuel line at pump inlet, remove battery ground cable, remove top heater hose from back of head, disconnect the  water  line in front of carb on the intake, remove valve cover, slip socket extension through cam sprocket to lock it and loosen cam sprocket nut... don't remove yet! set engine at TDC... important! GET IT RIGHT! Put transmission in neutral and block wheels also IMPORTANT and drive wooden VEE wedge down between timing chain and chain guides to lock it in place. This will prevent the chain tensioner from falling out... if you don't know, find out or you will be doing twice the work to fix this mistake, mark the timing chain and cam sprocket so you can assemble in same relationship, remove cam sprocket, loosen and remove 10mm Allen head bolts starting with the front two, then the back two and alternating front and back and working toward the middle, keep track of where they go for reassembly, remove the two 10mm bolts at front of head that screw into the timing cover.

This should have the majority of things disconnected so that you can remove the head AND the intake and exhaust manifolds as a unit. Grasp the fuel pump and intake and rock from side to side and the head should easily break loose. Get help and lift the head with manifolds up and off. Avoid turning the carb upside down if possible to prevent stirring up sediment. If worried about this you can remove the carb before hand. Find the two alignment rings or dowels either in the head or block, clean and re-install when ready to assemble. Locate the blown area of the gasket and inspect it.

Tilt head just enough to wire brush or use an angle grinder with wire wheel. Use care, the aluminum is soft. Get it as smooth and clean as possible. If this had blown between cylinders or you had driven it high into the hot range with lots of steam I would say check the head for warps. Thoroughly clean the head bolt threads and wipe with an oily rag. Inspect the blown gasket area, there should be no indication of it on the clean surface.

Fill the middle two cylinders with rags to collect the dirt and wire wheel the block surface. Again, as clean as you possibly can. You can't over clean these two surfaces. Clean out head bolt holes thoroughly IMPORTANT! Inspect the blown gasket area, there should be no indication of it on the clean surface.

Install new gasket on block dowels. Lift head onto block and finger tighten the two rows of head bolts. Make sure that the cam has not been rotated while the head was off. The aligning dowel pin at the front should be at 12 o'clock and the first two lobes set at 10 and 2 o'clock.

Use a torque wrench and begin tightening in the middle and working outwards to front and back like below:

RAD
7...8 P
3...4 L
1...2 U
5...6 G
9..10 S

Use this sequence and tighten to 20 ft lbs. Start at the beginning and in the same sequence torque to 40 ft lbs. Finally in the same sequence torque to a final 60 ft lbs. A few lbs either way is not as important as the sequence that is used.

Match cam sprocket mark to timing chain mark and install onto cam alignment dowel, don't forget fuel pump eccentric. Tighten cam bolt and remove wooden wedge. The rest is more or less the reverse of disassembly. After a dozen full warm ups and cool downs, check the head bolt torque with engine cold. You might want to warm engine and set the valve lash while the valve cover is off too.

I had the gasket blow on my '78 L20B for no reason I could see other than 300,000 km. It blew out water above the #3 spark plug but was also blowing steam out the exhaust. $23 for the gasket and $2 for gear clamps I didn't use. A very good, very cheap and easy fix.

 

Probably best to have a reliable machine shop plane the head so it is smooth and flat.

 

Install gasket dry, never use sealer.

[mcordero8]

Good Luck Ponyboy. Your in good hands with Mike. He know his shit.

[banzai510(hainz)]

https://vimeo.com/19077890

[Ponyboy Easley]

I appreciate all the help guys. Tomorrow I will hopefully take a look and dig into the engine. I went ahead a just got the full gasket set, it wasn't too much more so I just went ahead and got the full set. I will take a few pictures of some other problems. I think a have a decent vacuum leak in a certain spot that looks like it has a rust hole. Ill get a picture of it to see what you guys think. Mike I will get back to you on my gasket progress. Thanks!!

[Kytoaster]

Hey, another Ky native!

Best of luck with the head gasket, looks like you are in good hands! 

 

[banzai510(hainz)]

If power brakes make sure its not draining barake fluid.

I see once a power brake diaphrame broke and the white smoke was from that getting sucked in intake

 

well if coolant is gone then head gasket

[Ponyboy Easley]

Here is a some photos from the datsun and the engine bay. Im concerned about one rust whole of a part i have no idea what it is or called. It'll be photo 1.jpg. Its a vaccum leak and spits out smoke when fired up too long. I am running weber carb which does not seem stock because the trucks running way to lean and idles funny sometimes. Seems like someone just stuck it on and never adjusted it. but that hole is concerning. If you guys see any other concerns from the pics let me know. I can always take more or better ones. I had to take these almost at night so sorry if they are perfect. I should be starting the gasket replacement on sunday. Ill keep in touch. 

 

 https://drive.google.com/folderview?id=0B8vj_66vhMM6OEtXcS01bUs2TFk&usp=sharing

 

^^^link for the engine bay

 

If anyone has a thread on installing a new radio. That would be cool. I already have the radio working but i want to do something pro touring. So i will have a nexus 7 in my dash some way with a head unit hidden in the back of the dash with Bluetooth always on. My problem is i need a higher amp alternator. speakers that are decent and fit, adapters etc. Any suggestions, links or part #s would be great. Ill post more pictures of the progress!