20valve head

[Isimmo]

Until recently I'd have agreed with you, but having had a 'gasket' comparing session with Pete Berry at White Cottage Quattros, I was amazed to find there are quite a few differences between a WR/KE type head against and MB/MC head and then with an ABY/KV type... I've lumped them together like that because the gasket bore of a KV is bigger than an ABY, which suggests an ABY gets 2226cc from a smaller bore and longer crank throw against a KV which suggests a wider bore and shorter crank throw. Suffice to say, there are differences with the galleries between the block and the head over the development of the 5cyl engine and one big one is the front water gallery. The easiest way is to order the gaskets for a KV and the chosen head, and align them on the kitchen table... Suffice to say, I'd put a £1 on the KV gasket cylinder bore being bigger. However, there's no reason ultimately, why you couldn't get a gasket machined out to match, at the end of the day....

[BW2309]

Originally Posted by sam

theres a few threads on www.motorgeek.com about ghetto 20vs which is a 7a head on n/a 10v bottom end which gives low compression, therefor ideal for turbo'ing. get searching on there i'm sure you'll fnd something

Thanks!!!!!

[Puglife]

Originally Posted by BW2309

Is that also true of the difference between the turbo'd 10 and 20v heads??? I'll be gutted if they're different?
So is the whole block defferent then? Seems a big engineering excersice to change the block AND head when they went 20v? I know the 20v turbo heads have different external water outlets for the water manifold and turbo cooling but that's easy to get around. It's the internal jackets I'm now worried about!!!!

10v and 20v blocks have a few differences... you have to remember the engineering of an engine at manufacturer level doesnt constitute just moving a few galleries. With twin valve heads such as 20v you have to rework the chambers, this then means reworking the water flow through the head and also oil feeds and galleries. Its a complex process designing them. I can try get some drawings made up of the galleries on a 20v block and those of a 10v and overlap them to show the differences.

7a engines come about readily (i've bought 3 so far one fully rebuilt and they all totalled under £500).... pistons are expensive for turboing, conrods are £250-300, crank is fine, water manifold from turbo engines can be fitted with about £150 of machining to allow the additional watercooling holes. £200 engine + £1200parts = £1400 for an engine that you could essentially with manifold and turbo run 400bhp on....

[pimpdriver]

buy mine and do this:

http://www.geocities.com/jeg1976/conversion_home.html

[Gaz]

Originally Posted by pimpdriver

buy mine and do this:

http://www.geocities.com/jeg1976/conversion_home.html

Jesus! lol

[20vcqdriver]

The bore is slightly larger on a 7A 82.5mm compared to 81mm for the KV but the main issue is the pistons. The 7A pistons are as shown and completely different to the KV which has a small bowl. The 7A normally runs a 10.3:1 compression ratio so you will have a KV with 20v head and low compression and possibility of valves hitting the piston. Cheaper to get a whole 7A with larger capacity which it needs to compensate for the loss of torque at low revs.

[Gaz]

Originally Posted by 20vcqdriver

The bore is slightly larger on a 7A 82.5mm compared to 81mm for the KV but the main issue is the pistons. The 7A pistons are as shown and completely different to the KV which has a small bowl. The 7A normally runs a 10.3:1 compression ratio so you will have a KV with 20v head and low compression and possibility of valves hitting the piston. Cheaper to get a whole 7A with larger capacity which it needs to compensate for the loss of torque at low revs.

what if i wanted to put a 20valve 7A head on my 2.5?

or could i just take a complete 7 A engine and fit my crank and pistons? and have some head work done to the 7A ? would that be any easier?

[Isimmo]

David (20vcqdriver) has had the 't'shirt and full hospitality pack for modifying KV's, fitting 20v 7A's and ultimately winding up with a 3B... I'd guess if David says it's not worth hassle, it's not worth the hassle...

[20vcqdriver]

Originally Posted by Gaz

what if i wanted to put a 20valve 7A head on my 2.5?

or could i just take a complete 7 A engine and fit my crank and pistons? and have some head work done to the 7A ? would that be any easier?

What stroke is the 2.5? If it is a 92.8mm as I think it is you can use the crank and conrods in the 7A block and just get hold of some pistons normally used in the 2.0 16V 4 cylinder (same bore). Might be close with the throw of the crank but nothing that cannot be fixed. With that combo you can get 220bhp with a schrick cam and almost 200lb/ft torque. Head flows brilliantly as standard so not worth polishing and porting for the sake of 10bhp (unless you're after every last HP). Was going to do this myself until I was talked round to the 20Vt....

[ferris360]

Right then so easyest and best thing for me to buy is eather a 2.2t 10v or a 2.3 20v n/a so whos got what