big vave head on a Kent

[eric]

Hello

 

I think more and more to rebuild my engine

I have an unleaded stage 2 Burton head ( 39.5mm inlet valve, 34 mm exhaust valve)

I am tempted to try a stage 3 ( 40.7mm inlet valve, 34 mm exhaust valve)

 

The future engine would be AX 1628 cc with accralite forged piston, compression ratio about 10.5 / 11 , std con rods, std crankshaft, 5.3 kg Flyweel, 234 camshaft, single vernier pulley, ARP con rods bolts, Aldon distributor with ignitor, high pressure + high capacity oil pump, mecanical fuel pump ... all fully balanced

 

The car will be used mainly on the road, 1 or 2 trackdays a year

Any advice on the head or in general welcome

 

 

Many thanks

 

 

eric

[jonboylaw]

Maybe Roger King will be along soon to give his valued input.

One thing I would check is the valve to cylinder wall spacing as the cylinder bore maybe a bit tight with the big valves. Are you considering increasing the capacity at the same time ?

 

 

 

Jonathan

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My Flickr Gallery

 

92 Supersprint, Ford LSD LA, RK AX Crossflow. Stealth model (Matt Black and Ali), rebuild completed.

 

[DaveMorris]

I'm no expert - but I think that with what you are proposing you would end up with a head that was bigger/better than the cam that you are mating it to.

Also, as per Jonathons comments - unless you took the bore size out slightly you might have problems with the valve clearance to the bore wall.

 

Roger will definitely know, and can pass a much better, fully informed comment,

 

Dave

 

[eric]

No I would just rebore for the need, I want to keep the max of material possible.

But I don't know what I would find inside.

 

I like the lighter piston possible and also the security in case of need of next rebore.

 

eric

[Roger King]

Dave Morris makes a good point in saying that you might end up with a head that is better in a way that the cam can't make full use of. Far better to retain the current valve size and have the porting optimised to make the best of the existing valve size.

 

If you really do want to spend some extra money it would be far better to fit a 3D mapped ignition. The difference this makes to part throttle driving and economy is huge (if the map is set up properly). The best description I was ever given was "it makes my engine feel as if it's half a litre bigger - same power at the top end, but massive increases in the mid range, particulary on part throttle."

[jonboylaw]

Megajolt :)

 

There are a number of us on here that are running MJs so getting a suitable base map will be easy. As Roger says, it really smooths out the power delivery, plus the cranking is much easier as you can pull the advance back and save your starter motor.

 

 

 

Jonathan

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My Flickr Gallery

 

92 Supersprint, Ford LSD LA, RK AX Crossflow. Stealth model (Matt Black and Ali), rebuild completed.

 

[eric]

Ok I will stay with the stage 2 head ! Gasflowing a Burton stage 2 head , I think this was already done by Burton, however it is impossible to do here as an after market service.

 

 

3D mapped ignition is not for me too as there is nobody here to set up and also what I like with the Kent engine : there is no map, no electronics (except the ignitor), no fuel injection, no need for an electrical fuel pump .... simplicity is what I like

 

 

Many thanks for all your advices

 

 

 

eric

[jonboylaw]

Eric,

The X-Flow is really easy to set up with the 3D MJ, any rolling road tuner can do it as you just plug it into a laptop and set the advance. It does not have to be spot on either to be a big improvement on the Dizzy set up, plus the spark you get with a coil pack is much better than your current set up. Loads of Xflow maps available to get you started and you should find one to meet the spec of your engine.

 

When I went MJ, I made most of the brackets and did the loom myself, it was not difficult. Triggerwheels do a complete kit for the X-flow but you can source cheaper if you want to.

Blat mail me if you want more info on this.

 

It really makes a HUGE difference to drivability and makes the engine feel a lot stronger in the mid range with much better pick-up, with out the on-off feel you get with a tuned X-Flow on Dizzy.

 

 

 

Jonathan

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My Flickr Gallery

 

92 Supersprint, Ford LSD LA, RK AX Crossflow. Stealth model (Matt Black and Ali), rebuild completed.

 

[eric]

Thank you jonathan

 

It will be interesting later ( the best solution is to come i, England with the car)

 

 

 

eric

[eric]

in fact the stage 2 head from is not big valves but a 1600 std valves

the big valves is the stage 3

[bstark]

Just wanted to second Jon's comments re: the Megajolt.

 

I'm still running the safe map that 7 Indulgence installed having fitted the Trigger Wheels kit, and the improvement in performance and driveability is HUGE . (and that's on an engine that was previously nicely set up on a rolling road with the dizzy / Aldon).

 

Really looking forward to seeing how it goes after a rolling road session.

 

Bob Stark

Supersprinter

[eric]

I understand that the megajolt is a true improvement, but difficult to set here as no professional to do it.

 

eric

[puremalt]

Also an MJ will give about 25% better economy - I saw 30 + mpg in France this summer 😬

 

And on the track day at Castle Combe the jag XKr behind me couldn't out drag me from 3rd gear corners as the pick up was instant-another 😬

 

Is there an auto electronics place near you, it's worthwhile honestly.

 

Windscreens... They're for poofs

[jonboylaw]

Eric,

If you are competant with a soldering iron then you can fit the MJ easily, lots of help on here if needed and there are a few threads you can search for.

 

Buy the MJ from Autosportlabs.com and download the SW from there as well. They have a step by step guide to installing.

 

For tuniging, then a normal rolling road chap should be able to do it as you just wire up a laptop with the SW and then play with the advance at different revs and loads to get it spot on. A map from a similar spec engine should be available if you ask around and will be pretty much spot on for your 1st try and just need a bit of tweaking to dial it in.

 

 

 

Jonathan

=========================

My Flickr Gallery

 

92 Supersprint, Ford LSD LA, RK AX Crossflow. Stealth model (Matt Black and Ali), rebuild completed.

 

[eric]

Here there is a rolling road (one or two max) but they cost a fortune and I don't want my car touch by someone who doesn't know. It is an upgrade, my 7 works well except a small problem of fumes in the catch tank, I don't want it stopped by someone without experience. This upgrade could be easily transformed in a downgrade

 

If I was in England, I will rebuild my engine as it have some 120 000 miles on the clock. But I will only renew my head and try an METAL 5 oil treatment as it is impossible to get off the engine from the car without hassle. However the engine have a good oil pressure and except the fumes when I accelerate hard, works well

 

Repair a Seven here is like to go in England without speaking English, it is possible but all is more complicated .

 

eric