Lapping valves and CC'ing the L28 head - Home Built Datsun 240z part 29

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[@slasher9883]

Bolt down yer bloody grinder! Or at least use a g-clamp to hold it to the bench. Hard to clean valves with the grinder walking around all over the place. Love your vids BTW.

[@Bansheeboy11]

Get some rivet nuts, i have two grinders and a vise that i need to move frequently so the rivuts are flush with the bench and work wonders

[@_Bram]

Compressionnratio is (cilinder volume + head volume) / head volume. So your compression ration 512,5/53,5= 9,57. Your compression ratio is 1:9,57. Effectively it will be a bit less, because of the head gasket.

[@HomeBuiltByJeff]

You are correct, I forgot to add the head volume.

[@andrewtreloar7389]

Actually its cylinder volume + head volume + head gasket volume divided by head volume

[@stevenbauer7744]

Ideally, you would also add the volume in the cylinder with the piston at TDC, commonly called quench area. It's easier to do with a flat top piston and assuming the top of the piston doesn't stick out beyond the deck of the block. Put the lexan/perspex over the cylider and repeat the same process you did for the combustion chamber.

[@jasonwright9555]

I used Perspex sheet and Syringe method when I CC'd the heads on my 911 rebuild and it worked a treat. ;-)

[@truthseeker8483]

Maybe a good idea to bolt that grinder down before it ends up on your foot....

[@HomeBuiltByJeff]

Haha, you think I would be smarter than that...... Nope ;)

[@ryanmcneill7492]

Hi Jeff , I haven’t read all comments but have you factored in 1 - the volume from the top ring to the piston crown 2- the volume between the piston crown and block deck - 3 - any piston dish or valve clearance cut outs in piston crown ? These , as well as the compressed gasket thickness will all significantly effect your result. Keep up the good work 👍

[@HomeBuiltByJeff]

Yes, that has all been discussed. It is more like 8.57:1, but even that is an estimate. It doesn't really matter too much as that is what it is going to be running with anyway.

[@drunktortila3632]

Nice more l28 build!

[@dariorodriguez7157]

Great Jeff...I follow your videos allways and I learn a lot....thanks for sharing. From Argentina.

[@Ecosse57]

a particularly educational episode from both of you!

[@iainmcglynn833]

Technical but excellent I used to do the valves with my dad on minis He could keep his hands up all day Me not so much 😂

[@mickcoomer9714]

Ideally the valve seat should be radiused to give the minimum contact area and the smoothest gas flow possible. Especially on the inlet side.

[@stevenbauer7744]

Another drill lapping method is to insert the valve into the head and attach a piece of vacuum hose to the valve keeper end of the stem and then the other end of the hose to a fitting on the drill, spinning the valve from the valve train side of the head...

[@lesdmark]

I think you might have something on your lip there mate, Lol. That is the thing I hate about working on anything that involves liquids or goo of any sort. If my hands get anything on them that screams dont touch your face, that is when it will itch or something. Music is still working well, Glad to see everything moving along reasonably smoothly for you.

[@paulladdie1026]

Compression ratio =(swept volume+combustion volume) / combustion volume, I learnt this at college many years ago.

[@paulladdie1026]

en.wikipedia.org/wiki/Compression_ratio

[@paulladdie1026]

I get your compression ratio as 9:57:1 using your figures, kepp up the goow work and videos.

[@paulladdie1026]

sorry typo, 9.57:1

[@HomeBuiltByJeff]

9.57:1 is more what I was hoping for, and I am happy to be corrected.

[@CarsBikesandCoffee]

Great work Jeff!

[@danandyong6653]

Your cc volume may be off if spark plug is wrong, (too deep, or too shallow) try using correct plug for accuracy

[@ovlraglvr]

What done A LOT is take an old valve and cut the stem off. Chuck the stem in a hand drill. Once the good valve is placed in the head run a piece of hose between to two valve stems and run the drill. There is a technique to it though.

[@youanded]

I know this build is over, but a full set of valves is like $110 here in the states. Not sure what that translates to in Aussie land.

[@mrrberger]

Bore, stroke, gasket thickness, tdc recess, valve timing they make a big difference. Valve seat chatter with drill, seat seal width, valve seal width and parabolic paste grinding. Jeff you need some guidance buddy

[@donfinch862]

Was going to comment on the valve lapping, similar to Joe koyshman below, but I remember I have done exactly what you are doing. (even with the drill) So I'll shut up :)

[@onepairofhands]

20 minutes in my mums custard cleans up valves just as well !

[@joekoy7495]

Dear Jeff, lapping the valves is a finishing touch POST the valve JOB, its not a replacement for it.. take the head to your local machine shop and get a 3 ANGLE valve job done., its clearly seen that you got a single angle on the valves. replacing the valves is not necessary but they do need to be remachined.

[@HomeBuiltByJeff]

I agree that is the way to do it properly, but I am just giving this engine a quick freshen up, I am not doing a thorough performance build.

[@joekoy7495]

A proper valve job is not a "performance build" its an essential procedure with the resurrection of any motor. do it now or do it (again) sooner then later guaranteed. Remember: its much cheaper and easier to do it right the 1st time around vs doing it again.

[@plantpoweredhealth9383]

Joe koyshman yep face the valves and recut the seats on the Serdi . Set of k-lines too if the guides are worn.

[@sugirosie]

Really have to agree with the other replies Jeff. A little extra money spent and get the seats cut and valves faced then there's no need to keep valves in order and they'll seal properly...no further need to lap. If you've had that head straightened then you're really up against it using lapping paste as the seats can go out of round or not centred to the guides. Also, instead of taping valve stems you can use a piece of old black retic pipe. Changing core plug? Use loctite 601 or similar.

[@adamlemus7585]

Hey you guys in Australia get the same value pack WD40 we have in the states....oh what a small world

[@joeharrison5141]

Bit more progress mate, enjoying this build. Like the change in music again Jeff, must be a nightmare picking creative commons tunes.

[@HomeBuiltByJeff]

Yep, it is the bane of my existence.

[@stangxr93]

yay! audio is fixed :D

[@HomeBuiltByJeff]

Well I am back to using a shotgun mic at least ;)

[@vaunrichards2571]

Jeff ... I'm confused ... episode 29 of the 240Z resto doesn't seem to follow after number 28! 29 starts with a 'previously' segment about the head ... but at no point in the previous 28 episodes have I seen anything like what you describe. Have I missed a meeting?! PS: Loving all your vids .... as you can probably tell ...

[@HomeBuiltByJeff]

I will have a look. There is a high possibility I stuffed it up ;)

[@vaunrichards2571]

Home Built By Jeff Thanks, Jeff.

[@vaunrichards2571]

Home Built By Jeff Sorry, Jeff ... it's a fault at my end, mate. My KZbin jumped a few episodes around 25-27! Sorry to waste your time. 😳🙏🏼

[@robwhite240z]

what carbys and cam will you be using ? compression ratio .total volume of everything by what its compressed into. std cam comp ratio ok 72 deg cam 10:1 + needed. 76 deg cam & triples 11:1 + needed . get your cyl head level and put in fluid volume you need to get the comp ratio you want , measure from fluid to deck with feeler gauge or vernier calipers and shave head to suit . simples

[@HomeBuiltByJeff]

Double checking my calcs and it is actually 9.57:1 which makes more sense.

[@robwhite240z]

what carbys and cam will you be using ?

[@HomeBuiltByJeff]

72 degree with triple OER 45's (or 40's can't remember).

[@robwhite240z]

L-series love big compression . the bigger the compression the bigger the bang

[@ReinierKorth]

How do you know when the lapping is finished?

[@HomeBuiltByJeff]

When you can see the entirety of the valve edge and the seat are shiny and are making a good seal ;)

[@ReinierKorth]

@@HomeBuiltByJeff Great thanks. I have just bought a used N42 head that I want to port and rebuild to replace my N47.

[@andrewtreloar7389]

Jeff, not sure why you didn't just buy new valves and be done with it. Are they NLA? Pay for new valves and a 3-angle valve job and your head will be problem free

[@HomeBuiltByJeff]

If I was going all out I would have for sure, but I didn't want to go that for. Just a quick freshen up is all I am going for.

[@MrJimm1e]

I think I have some spare valves in my shed (I’m in Sydney too) happy to post to your P.O. box if you still need them?

[@HomeBuiltByJeff]

Thanks mate, but I have already got some that are going to do the job nicely from Stewart Wilkins.

[@scanspeak00]

Jeff have you thought about changing the pistons to increase the compression ratio to something like 10:1?

[@HomeBuiltByJeff]

I have actually increased the compression by a bit by shaving the head. I am not looking to go crazy on buying new pistons though.

[@CarsBikesandCoffee]

I did that mod to my P79 head where you shave 2mm (0.08”) off the deck, which will put it at about 10.5:1 in my case. Vid on my channel. Changing to domed pistons won’t change the compression that drastically.

[@HomeBuiltByJeff]

I will have a look. I shaved 1mm off the head, but by the looks of things it didn't raise the compression as much as I hoped.

[@CarsBikesandCoffee]

Home Built By Jeff yeah, mine cc’d around 42.5. Also remember when you shave the deck you have to raise the top (cam towers, valve springs outer and inner) I also switched to 280z valves because they are about 2mm longer than the 280zx. The video explains it all but shoot me a note if you need anything.

[@soranrix]

chevy valves as per the logo on them

[@kitts1234]

Søren Petersen z logo was Nissan not chevy

[@sugirosie]

Not a Z logo either. OP is nearly correct as it's similar chevy logo shape.

[@b3nny90]

Do you know if the maths works with different blocks with different heads?? According to your sums on a 1.5jz the block is 2996cc/6=499.1/41 (cc) gives me a comp ratio of 12.1 given the pistons and headgasket will slightly drop that's fairly high. Be keen to learn a lot more on this.

[@HomeBuiltByJeff]

I believe the calculation is accurate for the total volume of the 'whole' combustion chamber. So mine didn't factor in the thickness of the head gasket, the shape of the pistons and how far they protrude or sit low in the block at TDC. I did find an online calculator for my engine which took this into account and gave me a similar result.

[@mickcoomer9714]

Sorry mate. Your head measurements are meaningless. You need to go back to the block assembly and check that the piston crown to deck face heights are the same. If they’re not you need to equalise them and rebalance the rod/piston assembly. Then you can equalise the chamber volumes.

[@TRUTH4U2NO]

Not 1 married man in the US would ever call his wife by his own first name! Good grief why she is with you is...