Should the head gasket block/cover waterways?

[dcallaghan2011]

Looks like I might have to take you up on one of those heads as mine has been written off Unless anyone knows if a 410 head will fit as I have an old 410 engine (condition unknown)?

[ScottieJ]

The 970cc head will fit, the heads themselves are pretty much identicle, but there are 2 types, there's an extra section on the front of some heads and not others, think its to do with cam? Dunno why? i haven't really looked to closely at them for comparrison. Ill have a look tomorrow, I would compare the two you have as well. You should be able to use it though i would imagine. The 970 head also has slightly bigger valves so would give a bit more power.

[dcallaghan2011]

Ok cheers for that, I'll strip the head off tomorrow and have a look, if it does appear the same would I use an lj80 head gasket?

[Edweird]

I think the head gaskets are the same. If I remember correctly the difference between an F8 and F10 is the stroke.

[ScottieJ]

I think the head gaskets are the same. If I remember correctly the difference between an F8 and F10 is the stroke.

Both the bore and stroke are different dude
F8a is 62x66
F10a is 65x72
I doubt it'll really matter what headgasket you use? There's only a few mm in it, I would possibly go with the f10 headgasket just because its probably easier to get unless you already have an f8 headgasket then just use that.

[dan_2k_uk]

Surely go with the f10 gasket if its slightly larger as the metallic reinforced ring around the top of the cylinder will be correctly aligned and compressed rather than possibly compressing into the space around the valves on the larger head. Sure it will all be clear once you look.

Dan

[dcallaghan2011]

Ok guys thanks for your help, I have stripped the 410 head off the engine and it is practically the same, I have ordered an F10 engine head set from my local motor factors at a price of £30 including vat, that will be in Monday, I may give the head to the engineering shop to have a look over, so if all goes well I'll be able to have a run next weekend I'll put some pics of the two heads up later.

[juncopartner]

Scotties right there are two types of head the earlier one has a seperate housing at the front of the head that unbolts off the head and holds an oil seal, wheras the later ones have a head cast in one piece. If you swap these around you will need to change the rear timing cover as well as the later one has a deeper pressing to fill up the space created by not having the extra housing. I should have plenty of the different type of covers, I kept them for this reason.

I've always used the F10 gaskets whenever I've had different engine/cylinder head combinations and never experienced any problems. Usually F8 heads to F10 blocks though. As I said before I don't use F8 blocks. You really should just just throw it away!!!!

[ScottieJ]

I've been reading another thread about this on LJ10.

Apparently the valves on all f8a and f10a heads are the same, however the cam duration is longer on the f10a. You might need to be careful with this as f8s are already and interference engine, so if the valves are opening even more with the longer cam duration you'll have to make sure you are very careful when assembling the engine and timing it.

I haven't had a chance yet but this week I'm going to pull apart all the engines that I have and compare all the heads that I already have lying around with the ones on the engines to see what all the differences are.

[juncopartner]

That might explain why the F10 has indents in the pistons and the F8 doesn't. Mind you I'm sure I fitted an F10 head to an F8 block many years ago without any problem, but can't remember for sure, it was over 20 years ago!!! It may have been another F8 head though!!! Best thing to do is to turn engine over by hand very gently, but thats always a good idea on any engine rebuild. 10 years of building Lambretta engines taught me that, people build them with different stroke cranks and shave bits off the piston, pack the barrells up and shave the barrells down as well, so when you fit the heads everything locks up!!!! Then you have to strip the whole thing down to work out what conrod/stroke they've used. It a bit easier with an LJ.