52 replies to this topic

[Minigman]

I'm in the process of building a pre a+ 1098 engine for my mk1 and want to retain the original look as much as possible including the HS2 carb. I've seen the ADO16 1100 has a single 1.25" and made 48bhp. How much more can the HS2 give before running out of air flow?

[Swift_General]

Very little more I would suggest. Looking at the Vizzard book the carb is already struggling at that figure and the engine woild no doubt benefit from a bigger carb.

[slidehammer]

According to David Vizard's book low to mid 50 bhp

[Retroman]

If the HS2 is modified internally to Vizard spec you can probably get 60 bhp out of it, and the outside will look standard. I am doing one for a mildly modified 848 '72 van same idea....do you plan on a standard tune or a head & cam etc?

[carbon]

The Austin A60 was fitted with the 1622 'B-Series' and a single HS2 carb. Factory claimed output was 61bhp

 

Using the 'Vizard' internal carb mods you can get the HS2 to flow more, but in my experience the more you modify them the trickier they are to set up at part throttle settings.

 

For a 'fast road' tuned 1098 a single HS4 carb should give you the airflow you need, and also be pretty straightforward to set up.

[Minigman]

I'm at the point where I can go either std low compression pistons with the std 202 head or go for flat top pistons and 12g295. I have all the bits in the garage. I guess up to the point where the carb 'runs out' it would make good use of the improved performance. I'm not looking for a fast car particularly, just a safer more usable car. Seems silly not to build an improved engine if starting from scratch. My only other thought was go for some period twin H1s but they're rare.

[carbon]

For a fast road 1098 would suggest either single HS4 or twin HS2s. Leave the twin H1s for the guys building early 850's, they are rare and won't be as easy to set up correctly. Also with the HS4 or twin HS2s there are a number of 'factory' settings you can use as starting point.

 

If you have a 12G295 head in original unskimmed condition that would work well together with flat top pistons in a fast road 1098, and when combined with something like the Piper 270 cam should give decent output.

[Minigman]

Mine is an early 1960 850, hence why I don't want twin HS2s. I'll try modifying a single HS2 Vizard style and see what I get. Will go with flat top pistons then deck the block and skim the 12g295. Hopefully will achieve a decent CR. Be interesting to see what I can manage torque wise.

[CityEPete]

SU have started making fuel injection throttle bodies in SU look a like castings!

[carbon]

Mine is an early 1960 850, hence why I don't want twin HS2s. I'll try modifying a single HS2 Vizard style and see what I get. Will go with flat top pistons then deck the block and skim the 12g295. Hopefully will achieve a decent CR. Be interesting to see what I can manage torque wise.

That's a good reason to stick with a single HS2. If you can stretch to mid/late 60's tuning accessories I would suggest trying to get one of the early Oselli Torquemaster alloy inlet manifolds with the two vertical studs for HS2/H4 fitting.

 

With the 12G295 on a 1098 using flat top pistons you shouldn't need to skim the head much, if at all. Depends on cam and fuel you're planning to use.

[Minigman]

Used the 295 on flat top 998 pistons before and only managed 9.5:1 as I didn't deck the block. I'm pretty sure the head had 80 thou removed. I guess the 295 head should be used with D top pistons. I will deck the block with is 1098 build, plus an overbore will help too with unswept volume. I have now been reliably informed that I will get a good 55hp through the HS2 by someone who built an almost identical engine last year. I will let you know how I get on in the next month or so. Thanks for the input.

[blacktulip]

Interesting read, I've often wondered this when building my 1046 last year. I went to a hif38 in the end. Although I don't need to worry about it anymore as I have sold it.

[carbon]

Used the 295 on flat top 998 pistons before and only managed 9.5:1 as I didn't deck the block. I'm pretty sure the head had 80 thou removed. I guess the 295 head should be used with D top pistons. I will deck the block with is 1098 build, plus an overbore will help too with unswept volume. I have now been reliably informed that I will get a good 55hp through the HS2 by someone who built an almost identical engine last year. I will let you know how I get on in the next month or so. Thanks for the input.

55bhp should be enough to keep up with the traffic, just make sure the brakes are also in good order. If you're keeping drums then twin leading shoe will be highly desirable, along with a pair of minifins up front.

[Minigman]

Yes have some 18 spline drive shafts and twin shoe brake / hubs at the ready. Will keep the original 19 spline and single shoes in archive.

[jabos7]

Pardon the follow-up----

 

I'm running a 998, changing to the flat top pistons as well.  Without going too far, will I achieve a decent bump in performance on a

stock head, or is it worthwhile to pursue a 1100 head - and is it a bolt-up and go?

 

Also I'm changing to an HS4 - please help me understand why I see the side-pod/tank on those having 2 and/or 1 fuel connection?

Is 2 ports for pass-through when running a double-carb?