nib1980
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| posted on 17/12/08 at 10:04 AM |
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Head interchangability (engine, not mine)
Hi All.
I'm rebuilding a 1600 xflow, I've had it sligthly overbored to freshen it up (+0.30), and was looking at oing some head work too.
But whilst taking the 1300 I have out, I noticed it looks like the 1300 head has already had some tweaks done, looks like some porting, and bronze
valve guides etc.
I seem to remember someone saying a 1300 head can be used on a 1600 to improve performance?
1) Is this the case?
2) I have a piper 285 cam aswell, if i use the 1300 head will the pistons need machining? (i don't think so)
3) can I put the 1600 head on the 1300 block to sell as a whole engine?
any other advice greatfully recieved
many thanks
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MikeR
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| posted on 17/12/08 at 10:29 AM |
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1300cc pistons can be used on a 1600 as it ups the compression.
The 1300 head has (as standard) smaller valves than the GT head which is what you want (if you're not having hte head modified).
Also, you need to be aware their are two head designs, 711m flat cylinder head and hte 681? (older design) with a bowl cut into the head.
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nib1980
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| posted on 17/12/08 at 10:44 AM |
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quote:
Originally posted by MikeR
1300cc pistons can be used on a 1600 as it ups the compression.
The 1300 head has (as standard) smaller valves than the GT head which is what you want (if you're not having hte head modified).
Also, you need to be aware their are two head designs, 711m flat cylinder head and hte 681? (older design) with a bowl cut into the head.
I've definately got the 711M heads on both, the 1300 is out of a 750MC car, so would it have the GT head on anyway?
how can I identify the GT head?
An will the 1600 work OK on the 1300 block?
som many questions, so little time 
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D Beddows
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| posted on 17/12/08 at 11:56 AM |
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1600 GT heads have 39.2mm diam inlet valves and 33.7mm exhaust - that's the only difference. Every other standard 1300 or 1600 crossflow head
you'll come across will have the same (slightly smaller) valve sizes - and that includes a 1300 GT btw. So, in answer to your question, no
there's no problem putting a standard 1300 head on a 1600 or vis versa because they're actually to all intents and purposes the same.
You can actually find 711 crossflow heads that have had a combustion chamber machined into them to use with flat top pistons but that's a whole
other can of worms 
If it's a head that's been used in a 750MC Locost and it's actualy been ported and/or a GT head then someone's been very
naughty btw....... 
[Edited on 17/12/08 by D Beddows]
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MikeR
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| posted on 17/12/08 at 12:05 PM |
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wish i'd know about the machining of a dish in 711m heads for ultra competitive cars. Got a cheap head on ebay and when i went round to collect
it i assumed it was an early head and walked away. Later realised i'd got a bargain ultra set up head (Valves where huge) 
He sold it again and it went for nearly double what i would have got it for.
[Edited on 17/12/08 by MikeR]
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02GF74
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| posted on 17/12/08 at 12:11 PM |
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quote:
Originally posted by MikeR
wish i'd know about the machining of a dish in 711m heads for ultra competitive cars. Got a cheap head on ebay and when i went round to collect
it i assumed it was an early head and walked away. Later realised i'd got a bargain ultra set up head (Valves where huge)
He sold it again and it went for nearly double what i would have got it for.
I have one of the early heads with the chamber; GT valves but hoooooooge ports - it is the black one in the photo.
also has nice thin head valves.
middle head is ported, bottom is standard - look at the difference in post sizes 
make me an offer I cannot refuse.
 
inlet ports
 
exhaust ports
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