View Full Version : Early 1.2 cylinder head info required.
A few folks i've spoken to recently seem to think that the eary 1.2 ohc novas (a, b and c reg plus antibes?) had a cylinder head with enlarged valves in. These were the largest diameter of any vauxhall small block apparently, with cathederal ports.
So does anyone know;
A, if this is actually true?
B, what models they were actually fitted to?
C the part no. of the head in question?
the reason for this is a friend is building some sort of hot/stock rod, and is limited to 1400cc and can only use "production" parts to build his engine. the block will be a 14se block, with hopefully this head on, standard inlet with twinchoke carb.
Ps, anyone know what the mk1 astra carb was, and if it's better than the 2e3?
:thumb:
I did read one tech data book that claimed the 12NV (carb engine) had 2bhp less but 2lbft more then the other 1.2's.... and that it was an opel higher torque lump... how true this is i do not know.
Hmm, yaeh thats the engine code i've been told, do you know what the standard 12nv valve diameter is stu? I have a couple of old 1.2's, one from an a plate and one from a b plate, to compare valve sizes too. Iirc someone has posted over on mig about this, but i can't seem to locate it in any of my searches.
If we can't find one of these mysterious heads, whats the next best head to fit?
never took my 12NV appart..... it was in a 1.2 (funny that) flair 1991 (mk2 body)
next best head is the normal 1.2, then 1.4/1.6mpi heads (but the latter have no single carb inlets available)
I've just pulled a 12nv out of a J-reg flair...
No idea on the valve size tho.
are T40 vauxhall production parts? (sport) if so, 14se head. If not any 1.2 head.
BTW how do 'they' know if your using standard or larger valves?
So In theory the 1200 head is better as standard? You'll get the smae result with flow work on any of the se heads though?
I did read one tech data book that claimed the 12NV (carb engine) had 2bhp less but 2lbft more then the other 1.2's.... and that it was an opel higher torque lump... how true this is i do not know. 12NV was just a 1200 carb engine that used a SPi block afaik.
Standard carb head, same valve sizes as all other nova carb heads(33mm inlets, 29mm exhausts)
John-I'd use a 1300 carb head, a mk1 Astra 1300S twin choke inlet manifold(it flows much better than the std 1.3 sr inlet), and a weber 32/34 dtml(or 40s if there permitted)
OR if your allowed to mod head ports, use a sri head with the ports opened up to cathedral shape.
Mk1 astra 1300 engine used a twin choke GM Varajet carb.
Dave-H-The SRi/gte/gsi(c14/16se) head is the best one in terms of flow, it has larger valves than the rest of the nova heads.
Using the 1200 head on the 1400 block should give you a useful lift in compression too.
No, he has to use std carbs so weber's are out. I've just flogged a varajet but still have the inlet. They are good for 115 HP if rebuilt and modified accordingly. The price of the inlet has gone up to ?90 as they are also used in autograss.
Also if you are a front runner it is quite likely they will take the head off to measure the valves etc!
What would you class as a standard carb tho?
Will they know exactly what carb it should have fitted? Seeing as nova's never came with varajets?
greg1.4
05-07-07, 12:41 PM
i have just fitted a 1200 carb'd head onto my 1300 SR block and there seems to be alot more compression... i have the 1300 SR inlet manifold and twin choke carb.
on my other nova i have a 1400 block, 1300 head (whick works well with the 1400 block) and twin 40's..
Greg
I'd say a std carb in this case would be one that came on a vauxhall. It all depends which class you race in and what the rules stipulate.
the MK1 astra was rated at 75 hp compared to 69 on a nova for what is the same engine (just different indution system)
hendrix
05-07-07, 01:32 PM
I have a varijet carb, inlet and a mild nova sport ENEM cam forsale.
PM me if interested!
Also have an early 1.2 cylinder head, 55k miles from new
Take it the 14 and 16SE heads are exactly the same then? Or is the valve area deeper/shallower?
Also, does the 1.4 head fit the 1.6 block I.e bore size?
Cheers for the replys peeps. Ok here's the deal,
he's going to run a c14se bottom end, over a 14nz etc.
he can run any head as long as it's a standard production item, ie has a vauxhall part no. it must not be gas flowed or altered in any way
he can run any production carb, intended for 1.3/1.4, but not an aftermarket one. ie 32/34
He can run any performance cam, but must retain standard lifters and valve springs.
Ad/stu, build me a spec!
if the varajet/mk1 astra manifold is better than the 2e3, then i think we'll go for that.
:thumb:
The varajet inlet is better than than the 1.3 sr one, so yeah i'd go with that. It will cost tho, the inlets alone go for quite a bit. The astra carb choke ports are wider than a 1.3 nova iirc too.
Id go for:
14se block
1300 head
Ast2/bp300 cam(on std hydraulics)
Mk1 astra 1300S Inlet manifold and Carb
This is the inlet you want:
http://img.photobucket.com/albums/v86/Nova-crew/mk11.jpg
I had opened that one out, as i ran it on Spi.They flow well even as std tho.
Cheers for that ad, so you reckon there'd be no more gains using a 1.2 head over a 1.3 head?
keep em peeled for a mk1 astra manifold and carb for me!
I had a mk1 inlet a while back, but i sold it garyc,lol
There would be gains with a 1.2 carb head as it would raise compression, but i haven't a clue how high it might go. It might run fine.
Or you might have to run it on higher ron petrol all the time.
He'll probably skim the block and head, to up the compression as much as possible. Are they allowed to run additives?
I'd also check out the short circuit magazine forum as someone on there will tell you who will sort out a varajet if you get one as they are real specialist. I'd rebuild the carb with a service kit too.
If you need a 1300 head drop me a line I have got a couple going cheap as they have studs sheared on the exhaust side.
the early MK1 astra heads are different too, I'd try and lay my hands on one of them.
Gary
Many moons ago I did work out the compression ratio's from different combo's and posted them. It is simple maths.
He'll probably skim the block and head, to up the compression as much as possible. Are they allowed to run additives?
I'd also check out the short circuit magazine forum as someone on there will tell you who will sort out a varajet if you get one as they are real specialist. I'd rebuild the carb with a service kit too.
If you need a 1300 head drop me a line I have got a couple going cheap as they have studs sheared on the exhaust side.
the early MK1 astra heads are different too, I'd try and lay my hands on one of them.
Gary
cheers for that chap, you know the part no of that early head?
He's hopefully going to be competeing next year, he just wants to be up to speed with his engine specs before the season start!
Cheers mc, not too bothered about cr's at this stage, just need a reliable, quick motor,if it runs, then he'll use it!
Sorry I dont know the part numbers. You will need to look for a head from the 1st couple of years of manufacture. They are date stamped.
Also I dont honestly know if they are actually any better than the nova one. They dont flow any more apparently. You'd probable be better find a std 1300 head that is a "good" casting rather than looking for a MK1 astra as they are quite rare now. best to try and track down 6 or so heads and pick the best.
The 1300 astra had a higher compression ratio too. That coupled with the better inlet gave it 4/5hp more than a nova 1300.
i have also noticed that the ports in the 1300mk1 astra head are a slightly different shape to the keen eye (inside the head as the gas travels to the valves).
If it is any interest, i have 2 varijet carbs complete with the inlet manifolds, but only 1 has a throttle linkage, but no cables, if anyone is interested???
pm me prices please chap!
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