48.5BHP from TVR - and SU needle experiments

So, you have ported your exhaust manifold, siamised the inlet's branches according to one method or the other, fitted an atomiser gauze, checked your Disi components and timing, checked the gaps on your plugs.

Your engine is thoroughly 'on song', but ... maybe it can give a bit more?

As mentioned elsewhere, when Reliant employed TVR to try and get a few more BHP out of the engine,

A sharper cam was fitted [Kent P06]

The head was 'swept' around the valve seats

Progressively through the tests the following variations were tried at each stage

1mm was removed from the head face, to raise the cr to 10.5:1 [ie a head from an HT-E engine]

The manifolds were cleaned and ported [A 4 > 1 manifold was tried but gave no improvement]

Different needles were tried: the 'richer' ABQ needle loved by enthusiasts, and the even 'wetter' [by as much again] AAE

Conclusions were as follows:

By far, raising the cr made the biggest difference.

A good second is to increase the valve clearance to 15thou - to start with, 8thou exhaust and 10thou inlet were used. The 'book' 6 thou risks valve damage but is acceptable because customers like a quiet engine, it runs OK, and valve damage is lucrative for the dealer

Needle choice - for all after the first 2 tests the AAE needle was left in place. The benefit is not clear - it is very far adrift from any of Reliant's standard needles. But, remember needle renewal is a regular service item - every 20 - 30k miles, so, why not try? Any new needle will be better than the old worn one. [Don't replace the jet, they are very much harder and intended to last a lifetime whereas the needle is soft and sacrificial.]

What's that? How much BHP did they manage? 48.5BHP at 6,500 revs. [which is about the safe limit for sustained work as on a fire pump]. It's pretty certain the Kent cam was too expensive, so they probably settled for around 45 on the standard cam with 15thou tappets on a high cr head, ported and swept.