Wierd power drop and vibration ..

[iambiggles]

Odd this - Revs and pulls well up to about 3.5k, then there is a distict increase in noise - like a vibrational noise and a corresponding drop in power - like throttling off, but after about 4.25k starts pulling again!

Stuff thats new - Carb (Hif44), Electronic ingition, electonic fuel pump, alternator, SS exhaust, unleaded head. - Oh and a wolsley diff and halfshafts (3.9 ratio)

Any ideas? I don't remember it doing this previously.

Ta peeps

[Cam]

Probably carb related, possibly ignition related. Make sure the carb piston is moving freely throughout it's travel and not sticking anywhere. Also check you have got enough dashpot oil in and you have the correct needle for your application. Check your mixture setting too.

If you have a spare carb/spare dizzy then a swap over and test will help to identify what's at fault.

[bmcecosse]

What size engine is it ? That's a very big carb - even for a 1275 unless it has other engine mods. Probably just a flat spot caused by the mixture being too weak. What needle is in the carb ?

[iambiggles]

Yup - funilly enough BOTH problems were (sort of) the carb, but I was getting 2 x2 = 5

The vibration noise was the SU air filter that came with the Hif44 - its not too well made by the looks of it and at certain revs vibrates like a bugger!! its around this same rev range that there is indeed a flat spot caused by the wrong needle being used.

Just need to get a BDL to pop in and a decent air filter and jobs a good un.

BM - I've ALWAYS had 1 3/4 cars on this engine - First an HS6 now this HIF44, runs fantastically (with the right needle )

[bmcecosse]

So is it a 1275 ? Keen to know because I have a choice of 1.5 Carb, 1.75 carb and twin 1.5 carbs sitting on the bench waiting for some action on my 1098.

[iambiggles]

So is it a 1275 ? Keen to know because I have a choice of 1.5 Carb, 1.75 carb and twin 1.5 carbs sitting on the bench waiting for some action on my 1098.

Yup - definitley a 1275 (at the moment ;) )

Runs really well - which 1 3/4 have you got? I had the HS6 on before which was great, but hat the oportunity to put the newer HIF44 on which seems to pull a little bit stronger - but its hart to tell as I've changed a few other things too (not least the rear axle ratio).

I recomend it on a 1275, not sure about the 1098 though - probably a bit much for that.

[Cam]

Yes, a HIF38 is better for a 1098 and a HIF44 for a 1275.

[bmcecosse]

That's the plan - the bigger carb is actually destined for a back to back try on my 1275 Mini against the twin 1.5 set.

[wanderinstar]

I have a 1 3/4"" on my 1098. Runs really well. Have w/heated manifold and when I had it on Minisport rolling road he said the power output was equal to a 1098 Midget [55h.p.] Its the later type, the one with the float chamber directly below carb.

[Cam]

The HIF44 will work of course but the characteristics are a bit different and the throttle response and pickup often feels better with the smaller carb.

The HIF stands for: Horizontal type, Integral (or Internal) Float as opposed to the HS which is Horizontal type, side float. Then there's the older H type, but I'll leave you to guess what that stands for!