Upgrading VX engine

[mikemeade]

I have a std VX set up for class A 750mc (producing, I assume, about 180 bhp) with 45's and a 4-1 stainless steel manifold feeding a 2.25 id carbon silencer. I am looking to try and find an optimum trade off between increasing the power, but at a reasonable cost. Given that cost is an issue, 230-240 is probably the most that I could hope to afford. Presumably the possible steps could include: Higher compression ratio. Different cams, but std followers std springs and std pistons. Vernier pulleys and re-time cams. High lift cams with pocketed pistons, solid lifters and new valve springs. Porting the head. The primary use of the car will continue to be on the track. What order should I change things in to improve power and what would each step gain me?

 

All advice would be much appreciated.

[Alex Wong1697456877]

The main companies who can help are Swindon, QED and SBD.

 

Each has their fans.

 

Arnie Webb is pro Swindon and rather anti SBD and QED.

I'm very happy with my 241BHP QED engine

SBD have made some stunning engines too. I think Graham Ford's 280BHP engine is an SBD one.

 

To get 240BHP using QED, my engine has the following spec

 

Arrows Steel rods (bought direct from Arrows)

QED supplied :

Omega flat top pistons

Bigger valves (+1mm inlet and outlet) on standard stems

Extensive porting and head shaved a bit

Q450 cams

double valve springs

hydraulic lifters modified to be solid

 

SBD supplied an EN08 steel lightweight flywheel.

 

To use this, you need a 7.25 inch clutch - I used a QuaterMaster twinplate from Demon Tweeks.

 

All this was fully balanced by Coventry Balancing

 

My car is also throttle body injected

For this, you'd need a new fuel tank with injection pump, injection fuel hose, throttle bodies, injectors, 3D ECU and pressure regulator.

 

To fuel inject your car, budget about 2000GBP. More if you're paying someone else to do it. - John Noble is a good person to get to do this conversion.

 

To modify the engine to about 240BHP, budget at least 3000GBP and that's if you do some of the work yourself.

 

To dyno the engine, budget about 400GBP

 

To get a genuine 240BHP on carbs is probably difficult.

 

Edited by - Alex Wong on 9 Jan 2002 22:26:43

[Alex Wong1697456877]

The jury is out on what throttle bodies to use.

 

Mine are DCOE style 45mm ones. Dave walker of CCC reckons the Caterham manifold is rather good and his tests showed the most mid range torque from this setup and good peak BHP figures.

 

Those who prefer tapered bodies will no doubt chip in soon, and to be fair, they generally have more powerful engines than me.

 

After trying both back to back, mine is very similar to a JPE engine but with a wider power band.

 

Edited by - Alex Wong on 9 Jan 2002 22:23:24

[Alex Wong1697456877]

For me, step one would be Cams and verniers, solid lifters, deeper pocketed pistons and injection.

 

Doing any of these on their own would only incur more expense in remapping the engine or upgrading cams later.

 

 

 

Edited by - Alex Wong on 9 Jan 2002 22:30:37

[EFA]

You won't get over 230bhp without raising the max rpm over 7800. To do this you need steel rods to dramatically reduce the risk of major engine failure.

 

Best option without steel internals is to go for injection and some cams that will work with the std pistons such as Swindon 235 cams. Convert the lifters to solid using inserts -you do not need true solid lifters in an engine which does not rev over 8500rpm.

 

I have some std pistons which have been machined for these cams which you can have for a £50 donation to NTL.

 

Alex, Dave Walker will tell you the Caterham manifold is good because he dislikes VX's that are beyond K series maximum reliable (i.e. non liner wobbling) power output. Swindon will verify the Caterham manifold used with the DCOE injection on the JPE costs that engine at least 15bhp!

 

 

 

 

 

 

 

Fat Arn

The NOW PROVEN R500 Eaterid=red>

See the Lotus Seven Club 4 Counties Area Website hereid=green>

 

[Peter Carmichael]

Alex,

 

It struck me while reading the CCC recommendations for your car that DW had missed a trick. You were suggesting a change of throttle bodies and he was saying that there was no point. Your manifold arrangement does however mean there is a sharp corner in the inlet tract. If you sorted this out (with taper TBs or the like), I am certain you would see an improvement. You would however need a new bonnet with a different bonnet hole.

[Alex Wong1697456877]

Peter,

 

I asked him about this and he is adamant that from his tests on the QED dyno, the Caterham manifold does as well as tapered straight but with alot more mid range torque. Something to do with resonance that I didn't really understand.

 

I can't help but think that you're right though and I have considered Arnie's setup and Swindon's very expensive but very sexy setup.

 

Alex

[Alex Wong1697456877]

Arnie,

 

I get 240 BHP at about 7500rpm.

[EFA]

Carbs Alex, Carbs..... 230's the limit. On Inj and very peaky cams (a la JPE) you can just get 250 at 8250.......

 

Fat Arn

The NOW PROVEN R500 Eaterid=red>

See the Lotus Seven Club 4 Counties Area Website hereid=green>

 

[Tazio]

Or even a little bit more......

 

L7 FUN

NotSoLightVx - but with 262.5Bhp!

[Paul Ranson]

To do this you need steel rods to dramatically reduce the risk of major engine failure.

 

I went past some stand at Autosport (possibly QED) and they were offering steel cranks at about a 1000 and rods at 600. If you're going inside the engine and over 200BHP then go the whole way, IMO.

 

Paul

[EFA]

WITHOUT PREJUDICE

 

Bet they sell cheap reticular tin bearings to go with them.

 

 

Nothing like a repeat business strategy.....

 

 

 

 

 

 

 

 

Fat Arn

The NOW PROVEN R500 Eaterid=red>

See the Lotus Seven Club 4 Counties Area Website hereid=green>