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Oversized Head gasket sizes availible?


molten

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Hello
Does anyone know what range of head gaskets are availible for 1500 spit?
By this I mean are there oversized gaskets, IE: if the deck was machined flush to the recessed bores, is there a gasket availible to restore the distance of removed material?
Or gaskets for specific applications/modifications?

Sounds daft but I have reason for asking (if you have seen my other resto thread, you will know why)

Thanks for any help

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If the block is decked enough to remove all of the recesses you can use the gasket for non-recessed blocks.  Alternatively the recesses can be recut.

However, with this much material removed you'll likely have an issue with the pistons sticking up above the block face whereas before they would have been slightly below.  Flush with deck is ok (even desireable) but more than a very small amount (sorry no numbers off hand) can result in contact between piston and head.  I suppose a small skim of the pistons to bring them back flush might be ok.

Compression ratio will also have been increased but possibly not excessively - needs measuring and calculating.

Nick

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Hi Molten ,

Are you using 2.5 pistons ? as this is one reason for skimming the block .
You need to use a early 1500 head gasket they didn't have the recesses, you can't use a pre '70 1300 ( small journal crank ) head gasket as the head studs have different positions.



If you must use 2 gaskets you need to use a steel plate between the two , this was used a lot in the early turbo days for lowering the CR .

BUT i still wouldn't recommend it !


Gordon

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Nick_Jones wrote:
If the block is decked enough to remove all of the recesses you can use the gasket for non-recessed blocks.  Alternatively the recesses can be recut.

However, with this much material removed you'll likely have an issue with the pistons sticking up above the block face whereas before they would have been slightly below.  Flush with deck is ok (even desireable) but more than a very small amount (sorry no numbers off hand) can result in contact between piston and head.  I suppose a small skim of the pistons to bring them back flush might be ok.

Compression ratio will also have been increased but possibly not excessively - needs measuring and calculating.

Nick


Hi Nick

I took my block & head over to a guy who rebuilds kent 1600 engines for formula ford race teams.
He too mentioned that a flush deck is desirable and felt that if an appropriate thicknes gasket was availible, the deep combustion chamber (on 1500 head) could likely (TBC) be able to cope with max valve lift even if the piston sits proud at TDC. However he rang me today to tell me that an oversized gasket (thickness) was not availible. However I want to fit a large journal mk3 cam and maybe this might be asking too much for the combustion chamber to cope with valve lift.
How does the non-recessed gasket differ from recessed?
If recess was recut then the crowns would probably need machining to suit and standard gasket could be used.
How do you think compression would be affected with the option above?

Thanks
scott

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That_Man wrote:
Scott, do you Know how much has been removed for the top of the block ?

Valve to piston contact is very rarely a problem as the piston is not at TDC at full lift

I think piston to head contact is going to be your problem !

Gordon




Hi Gordon
I need to drop of the push-rods off tomorrow so he can bolt the head down to determine the clearances, so dont know how much material can be removed yet. I could have done this myself but this lad as more accurate gear so can be more precise. When he lets me know I can post on forum. If piston crowns are also machined then contact between piston & head will be avoided. Just not sure how much we are talking yet and dont want to severely weaken crowns.
cheers
Scott

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That_Man wrote:
Scott, it may be possible to machine a counter bore into the head rather than machine to top of the piston .


Hi Gordon

I had the same thought after writing my previous post. I will get chance to chat with him tomorrow on this. If necessary, it would seem like best option - looking at around £200 for the work but at least it will keep the original 'seasoned' engine and should be better than a new one??

Cheers

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2597 wrote:
However I want to fit a large journal mk3 cam and maybe this might be asking too much for the combustion chamber to cope with valve lift.

The Mk3 cam has the same or slightly less lift than the 1500 cam, I've got the figures somewhere...

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One of the original US GT6 engines I dismanted had a thin metal sandwich plate cut like a head gasket next to the head gasket between the head & block.  It was obviously from the factory to lower the compression to meet US emissions regulations.  Why that one did not have a fatter head, I do not know.  Maybe some supply problem at the time at the factory.

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That_Man wrote:
You need to use a early 1500 head gasket they didn't have the recesses, you can't use a pre '70 1300 ( small journal crank ) head gasket as the head studs have different positions.
Are you thinking perhaps of the 1147, which has the 11-stud head? AFAIK, all 1300s and 1500s have the same spacing of the ten studs.

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Quote:
Are you thinking perhaps of the 1147, which has the 11-stud head? AFAIK, all 1300s and 1500s have the same spacing of the ten studs


HI Hearld948, When they went to having the recesses in the top of the block ( although it may have been before that ?) they moved the front stud on the spark plus side backward 3/16" , i assume this was to stop silly people putting the head gasket on upside down !
13/1500 head gaskets before that were symmetrical so could be used either way up .

Gordon

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That_Man wrote:


HI Hearld948, When they went to having the recesses in the top of the block ( although it may have been before that ?) they moved the front stud on the spark plus side backward 3/16" , i assume this was to stop silly people putting the head gasket on upside down !
13/1500 head gaskets before that were symmetrical so could be used either way up .

Gordon


This can't be right... otherwise how do you fit 1300 heads onto 1500 blocks and vice-versa, as many do (including me). I've got both on the bench in the garage at the moment, so I'll have a look at lunchtime to make sure I'm not going mad.

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Skimming the block is usually beneficial as it effectively raises the compression ratio.  This gives you more power but has problems on very poor fuel / 75 octane and less. The recess ( in the block ) can be removed with a .025 to .030" skim.  The depth of a compressed gasket is about .037" ( varies between makes )    So even if the pistons run .020 to .025" above the deck ( from about .008" below ) that still leaves a clearance of  .015" before touching the head.  At TDC the piston is within the bore of the gasket ( its top ring way below in the block bore ) and engines like this will be perfectly reliable.  If the 1500 has a squish area opposite the plug  - there are even more advantages -  faster combustion and definitely no unburnt fuel in that space between piston and head that is now practically eliminated.

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sparky_spit wrote:


This can't be right... otherwise how do you fit 1300 heads onto 1500 blocks and vice-versa, as many do (including me). I've got both on the bench in the garage at the moment, so I'll have a look at lunchtime to make sure I'm not going mad.


Hi Gordon - just checked a 13/60 GE head and block, and the head off my 1500 FM engine with recessed bores, and the stud spacings are exactly the same. It must be the earlier 1147 heads you are thinking of? Or do the 1300FWD engines differ to 13/60, Spit Mk3 and early Spit Mk4 engines in this respect?

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Hi Herald948,

that's very interesting, seem i've made an assumption based on bad info, a while back i skimmed up a head for a lad i did my apprenticeship with, he said it came off a 1500 dolly and wanted to put it on his "Mk3 Spitfire" so i worked out the cr difference and skimmed accordingly. i saw him a few months later and asked if the head was ok, he said it didn't fit the block as one of the studs was wrong ! maybe he had a 1147cc engine or it was a earlier car? he said he'd sold the car with the original head, maybe he was to embarrassed to admit his mistake, I'm not !

I have to admit the early 1300 engines are the only one i know really well, i've race tuned a few, yes they will do 9000 :) but expect them to wear quickly :(

Gordon
(suitably embarrassed )

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