HS2's or HS4's

[Darren Groves]

More planning for my winter engine rebuild.....

 

As my current engine has a fast road cam and bucket lids for valves, after taking advice from the Rolling Road guy I ended up switching from HS2's to HS4's. Made a small difference, but mainly just cost me a few mpg.....

 

The new engine will be my old 1296cc block sleeved to be standard bore, Spit MK3 25/65 65/25 camshaft and a Spit MK4 head, so the larger inlet valves and with a CR of 9.0:1 or slightly higher if it needs a skim.

 

So my question is do I stick with the HS4's or go back to HS2's?

 

I sold my old HS2's, so the cheaper option would be to keep the HS4's, but not that that's a reason to keep them.

[Pete Lewis]

I guess if you have got them then thats the plan,, providing you can get a needle and spring to suit the spec then its not a bad move.

 

you dont want to over carb and engine , but   4s should perform OK 

 

PETE

[Steve P]

Personally i would go back to HS2`s,i have a similar spec FH 1300 engine in my 13/60.I have HS4`s on it and it is over carbed with little gain in performance.

 

I am building a 1500 currently so i will use the HS4`s for that.

Steve

[AndyTV8]

You don't mention the exhaust system being used..... If you are running a decent extractor exhaust & sports system then your 1296 will benefit from correctly setup HS4's.

 

If the head has had some decent work on it (not just CR) then that will help to.

 

........ Andy

[Darren Groves]

You don't mention the exhaust system being used..... If you are running a decent extractor exhaust & sports system then your 1296 will benefit from correctly setup HS4's.

If the head has had some decent work on it (not just CR) then that will help to.

........ Andy

I have a Bell extractor manifold and Vitesse semi-sport system.

[AndyTV8]

I have a Bell extractor manifold and Vitesse semi-sport system.

In that case, personally, I wouldn't go back to the H2's

....... Andy

[Bob Horner]

Just to add to this topic many years later......  I've recently converted my standard Mk3 engine to run on Hs4s (using 1500 manifold and air box) and converted to cable throttle.  At the same time I fitted a phoenix extractor and richer needles.  Its absolutely transformed the engine - really flies.  Massive improvement in performance (not checked fuel consumption yet though!).  All pretty simple to do bar getting the accelerator linkage in the right place.  I did see an article from back in the day where someone tested a similar set up done as a factory kit and they were impressed.   It previously ran on Hs2s (which were rebuilt so improvement not to do with worn carbs being replaced) but using a standard exhaust manifold.  All pretty reversible bar the cable throttle as had to cut the original pedal to get it out.  However, a mk4 inlet manifold could be used if swapping back to Hs2s.

Bob