Holbay Engine

[Hubbell]

My understanding after a bit of Wikipedia research. 4 variants of the 1725cc rootes set up

1. Iron cylinder head and inlet manifold with singular zenith carb
2. Alloy head and inlet with single webber
3. Alloy head and inlet with twin webbers
4. Alloy head with twin webbers and holbay bottom end

What did Holbay do to the engine to get over 100bhp?

 

[Panky]

They lied

Founder of the Non-Facebook Club

 

[Panky]

I think that should read.
Single Stromberg
Twin Strombergs
Single Webber
Twin Webbers with Holbay head and cam.

Founder of the Non-Facebook Club

 

[commeracer]

Holbay engineering 'breathed on it' in the same way Cosworth did with the Sierra, and in doing so changed just about every part. Most of the power comes from the better breathing head and cam with more lift/duration.

"You,re only supposed to blow the bloody SLIDING doors off"
Founder of the 6 speed club

 

[Hubbell]

They didn't lie I just couldn't be bothered to check my facts via Wikipedia! Do twin carbs use a lot more fuel to produce just a little more power? Was it the standard alloy head Holbay used and then ported it? How much power increase would I gain if I did that or would it be a pointless exercise without the holbay cam?

 

[commeracer]

Twin carbs is alot of cost and hassle for very little gain, mostly because the inlet manifolds are too poorly designed to take full advantage of the better breathing [xx(]
Holbay head is completely different.
There is room for improvement on any head, with some careful port work up to 10-15% more power. You don't have to change the cam, but the benefits are greater.
(And i do head porting)

"You,re only supposed to blow the bloody SLIDING doors off"
Founder of the 6 speed club

 

[Hubbell]

I'll bear that in mind. If I've got some spare cash this winter a bit of porting might be a proposition along with a Lexus box.