5 replies to this topic

[Racer_Pete]

Hi everyone, Wanting some opinions or experience from anyone who has had this sort of spec engine using twin HS4 carbs and what needles you have used/started with. In the process of building the engine for my Morris Ital van and wanted a rough idea of what is being used. below is the spec, hopefully be around 110/120bhp Thanks, pete. 1310cc, Block drilled for 11studs
6cc Dished Cast Pistons
Full Race Spec Head 29x37
Kent 296 Camshaft
Alloy/Alloy Duplex
MED 1.3:1 Roller Rockers
Maniflow Stage 2 Full Exhaust System
Aldon Red Dizzy
Crank - Wedged, bladed & crossdrilled
Rods - Lightened & Shot peened
Rotating assembly balanced
Isky Type Lightend Followers
Twin HS4 Carbs
Maniflow Inlet
ITG S/S Filter
ARP Conrod bolts + Head
C/R 12.2:1.

[neal]

You could try AAA's or AAK's for a slightly weaker mid range (3000rpm in 3rd gear using a 3.44 diff at cruise 50mph)

Set your CO at 2.5-2.75% at tickover which I suppose will be around 1200rpm with your cam?

[Earwax]

You didn't specify the use for this motor... track/road  etc.... that cam and the CR stand out to me as track more than road.

 

 

I had a friend build me a similar spec.  Started with 6s and then  CP4 and put an AFsensor in just at the start of the single pipe.  standard adjustment was pretty good , but then tweaked the bridge height a little after looking at AFRs... Did note that on long( 30 second plus) what stints the mixture continued to lean off from high 11s - 12s ( mid twelve was my aim but it could drift into high 13s - so i backed off----- the stock standard profile was so near to ideal for all the rest of the range, i decided i didn't  really do lots of 5km straights- and left it at that  -  i also didn't have the time nor experience to justify a bespoke needle set up

 

My main build differences, cam VP4 ( 290 ish duration), and CR i limited to 11:1 on 97 RON fuel.  I run a 3.7 diff ratio as it is more for twisty fun than motorway work  - i would also recommend the quaiffe diff -  You dont know it is there until you give it some urge - good bit of kit. 

 

I also would look carefully at the rev characteristics of the cam with respect to your FDR..... i think 3.44 might be too tall ( ask cooperman,  he will probably try and convince you to go 286 instead of 296)

 

BUT

 

i had an unfortunate mishap with my historic race motor ( too many revs not enough oil pressure not good for big end bearing), and so swapped this engine in for some sprint rounds.   (  and changed to webber DCOE 45 - we are allowed these in our regs and  it was definitely fasterwith webbers and then swapped up to 1.5 Rockers and was better in the full on environment over 4500 revs.  ) 

 

Notes from my own personal experience:  Some of the difference in lap times from twin HS4s to webber could be fuel float slosh in corners ( i dont run the you beaut racing float bowl mods and every now and then it would not bog coming out of tight corners but certainly stutter  --- i put it down to part fuel and part just dipping below the good torque band)  Times with the webber and 1.5 Rockers were only about 3 seconds a lap slower than the race motor ( 3 km circuit).  This was still on RON 98  not AVgas ---In fact except for maybe uprating the clutch to grey dot and probably changing to stronger gears it could happily plod away towards the back of the pack in some circuit racing,  so maybe 130 -135 hp at the crank and just under 100 at the wheels ( i havent dynoed it so just guesses)

 

Also please note the HS4 s were pretty standard not bellmouth mods or anything whereas my webber has been pimped a little  Also my manifold inlet(s) were the smaller of the two offerings ( 35 VS 38mm  or something like that)

 

 

Secondly - my race motor runs a 12.5 :1 CR on full lead Avgas ( approx RON 105) , and i wouldn't think of trying it on RON 97. so be careful with pinging with that CR

 

I also have a plain old road motor , that i use as a bit of an experiment - much more of a stock standard 1310.   and initally had it running on twin HS4 s with #3 and  then # 6s needles,  but have found better all round tune with a single HS 6

 

So ,  i like hs4s, and think the twins are the best looking set up for the mini and the itg air filter is good and bling at the same time.  I like Hs6 because it works well, it looks a bit lonely , but too be honest , it just seems to work a bit better than the twins in the road car, and it currently sits in my road car. ( i think the HIF44 would probably be better again) For performance , if i spent some time and money and used the experience of the FIA racers, i am sure i could get the SUs to make the most of the motor tune, but my webber set up IS currently faster than either of the SU set ups....... 

 

So  get it built and have a bit of fun trying it out for yourself.  Cheers D

[imack]

Needles used in my previous 1380, 286cam, 1.5:1 rockers,longman gt15 head, 11:1cr, yellow dizzy, twin hs4 on bmc manifold, k&n's and stub stacks, long 3:1 and rc40 were aam, this appeared to run ok but wasn't set up on a rolling road.
Latest set up is:
MED prepared 1380 a+ block
MED tuftrided cross drilled wedged a series crank, lightened a+ rods arp bolts, 7cc dish omegas
Ultra light steel flywheel and back plate
MED clubman 37/31 head 11.5:1 c/r
MED fia15 historic race cam
MED 1.5:1 roller rockers
Maniflow large bore long 3 into 1, single box rc40
Internally modified twin hs4s on large bore maniflow intake, MED ITG filter and stub stacks
Aldon red vacuumless dizzy lumenition electronic ign.
SCCR box, SC 1.09 ratio drops, 3.76fd, quaife atb diff.

Set up on Peter Baldwins rolling road last year he used AAU needles and blue springs.

Attached Files

•  20170729_091803.jpg   65.96K   20 downloads

Edited by imack, 14 November 2017 - 05:58 AM.

[Racer_Pete]

Thanks for the replys, it is a fast road/summer days drive.i had a mini a few years ago and had a sw10 in a 998 then had a 296 in a 1293 with just a HIF44.I thought the sw10 was too tame in a 998. And the 296 was fantastic in the 1293, I dont understand why people moan about cams in traffic. I wish I went for a even hotter cam now like a 310 With the compression ratio Ill be running, differential ratio Ill be running is a 4.3 with a 3J LSD, I also have a 3.6:1 but the 4.3 will definitely make the most of the engine/cam. I will also be changing the box gearset to a GT6 or dolomite 1850 ratios as they are closer a lot closer than the standard Marina ratios. I would have fitted a Weber but wont fit with a 6 maniflow inlet in a marina, and didnt want a swan neck so the twin HS4 are the best of a bad situation. What Sort of power did you get from yours imack?

[imack]

Mine made 138bhp on Peter Baldwins probably optimistic rolling road.
MED's FIA15 cam is based on a 649.