tuned 1098 sluggish

Post by **racer** » Sun Apr 11, 2004 9:55 pm

Hi to everyone ,I'm new to this forum . I have tuned 1098 /piper 255 cam/metro mani./big bore /lumenition /12g295 head unleaded ,running on 5*optimax fuel. /11/2"su . I have used standard 1098 pistons . BUT the whole setup seems to "hold back"-like the points were playing up type of feeling. I have lumenition . Anyone got any suggestions?

Post by **les** » Sun Apr 11, 2004 10:01 pm

Welcome. Check your ignition timing, it may need advancing. Don't forget to enter your location!

Post by **racer** » Sun Apr 11, 2004 10:09 pm

Thanx for that les . Should I hgave got the head skimmed -I've read other posts recommending this ,but they dont say by how much? Also should I invest in a vernier timing wheel to time the cam in ? ,or a needle change ?

Post by **les** » Sun Apr 11, 2004 10:47 pm

I don't think you need go as far as a vernier, just set the timing statically, it will vary depending on your state of tune. This is ignition timing, not valve timing. A needle change may be needed, but again you will have to experiment. Somewhere on this board there is an SU needle guide web site.
The head will need skimming as the chamber volume is too large compared to the minor head, but I can't tell you offhand how much to skim it.

Post by **Robins** » Mon Apr 12, 2004 11:58 am

Hi Racer
I have a very similer setup to yours in my traveller but minus the sporty cam. And have the same problem, it feels like the power is there (or should be) but won't let me use it, holding back.
Just out of interest what needle are you using? I'm going to get it setup on a rolling road when I can find someone in my area that does that, no luck yet though.
I did wonder if the problem is the Luminition moduel thing? You can't set the timming statically with one of these either, can you?
What is the timming ment to be using a stroboscopic timming light? the book only says for static.
cheers, Daniel

Post by **57traveller** » Mon Apr 12, 2004 12:24 pm

BMC Workshop Manual advises stroboscopic timing is set to 6 deg. BTDC at 600 rev/min. Doesn't say anything about vacuum advance pipe on or off though.

Post by **racer** » Mon Apr 12, 2004 5:15 pm

Hi ,As Les says the head prob. needs skimming . I cant actually find out by how much though! I know about the brass plug controlling max depth ,but not what is acceptable to skim. I c/c'd the chambers but was told the wrong method ,so the figure I had was'nt worth calculating the skimming from. i'VE JUST CHANGED THE DIST. COVER &CLEANED THE PLUGS (NOT SURE IF THEY ARE RIGHT TYPE FOR SET UP,it seems marginally better ,although has always had a mis-firewhen driving steadily @about 2000 rpm in top . I've just booked a rolling road for weds. ,so will let you know what the guy reckons . Part of my lack of power on take off is prob trying to pull a 3.9 diff .All a bit puzzling to me ,hence the posting on this forum!

Post by **racer** » Mon Apr 12, 2004 5:23 pm

Something I forgot ! I had all the mods I mentioned and the prob. was the same ,then I fitted the cam ,thinking this may "free it all up" ,but all it did was allow the engine to rev better ,and as I said the prob. persists . I was told the cam may need timing ,so I will prob. do that next ?

Post by **les** » Mon Apr 12, 2004 9:51 pm

Well I can't see the cam needing timing, as far as I'm aware you line up the dots on the sprockets and that's it, just choose your cam carefully. There is a sprocket available with a vernier adjustment facility, but that is getting pretty advanced and I would think you would need to spend some time on a test bed fiddling with it.
the volume of a standard 295 head is 28.3cc. standard 202 head 26.1cc according to the spec.

Post by **Cam** » Tue Apr 13, 2004 12:31 am

The cam on my 1380 (Kent 276) is timed in the conventional way (dot to dot on the sprockets - as Les said). Don't mess with the cam timing unless you know what you are doing as you can knacker your engine! If it's timed at 0 degrees (neither advanced or retarded) then it should be fine. If the engine is not pulling with a 255 (quite torquey) then I would look elsewhere for the problem. In my experience it is usually carb related.

Just out of interest, have you tried running on standard points just to eliminate the Luminition? I don't know if you can statically time the engine with the Luminition, you can with the Aldon Ignitor though!

Post by **racer** » Tue Apr 13, 2004 11:42 am

I have'nt tried removing the lumenition yet ,but it was something I thought of . I'm a bit reluctant to do anything until the rolling road session . The guy who is doing it ,apparently is a bit of an a-series whizz,so he should (hopefully )be able to diagnose the prob. Regarding the cam timing ,I've been told that some cams are ground out of sync. with the original,and COULD be a few degrees out ,therefore needing timing in .As far as fuel probs. go ,I had a needle change (can't remember type) and it did improve things a bit .

Post by **Kevin** » Tue Apr 13, 2004 12:47 pm

I would also get a copy of David Vizards book if you are in to tuning the `A` series engine as it has loads of information.

Post by **Cam** » Tue Apr 13, 2004 1:07 pm

I think piper and kent cams are OK and not offset (kent definately are OK). + or - a few degrees is not THAT critial anyway (unless you are trying to squeeze that few extra BHP out!).

Like you say, best let the rolling road chap have a mess with it. Let us know how you get on.

I would also get a copy of David Vizards book if you are in to tuning the `A` series engine as it has loads of information.

Absolutely! It's a must if you are messing about with the A-series.

Post by **turbominor** » Tue Apr 13, 2004 5:01 pm

i am sure that the cumbustion chambers on the 12g295 are larger than the standard head, and you will have dished pistions.

Most people have to skim 60thou of the 12g295 to get a half decent compression ratio

Have you checked that the compression is something sensible?

Post by **racer** » Tue Apr 13, 2004 6:35 pm

I haven't checked the compression .According to Info I have seen else where on the forum ,the head should be 2.75" BEFORE any skimming ,I was wondering whether this was correct ,cos mine is 2 5/8",&I'm sure it hasn't been skimmed in a previous ownership. I swapped the lumenition to points as Cam suggested ,but no difference at all . 'Phoned Lumenition today ,they suggested several probs. eg good earth to base plate,disc to module clearance etc -checked all those -all ok . My coil was supplied by Bull Motif as being OK for lumenition ,but it isnt a bonafide lumenition coil (theyre expensive!) so could be the wrong ohms coil. Carburation &head skim are about the only things left!

Post by **winger300** » Tue Apr 13, 2004 7:54 pm

Does the engine rev smoothly whilst accelerating? Im having a bit of trouble setting the mixture on my HIF38 properly at the moment and when its cold it seems to backfire and spit a lot.

Post by **les** » Tue Apr 13, 2004 10:06 pm

2.75 is the standard head thickness on a 1275 head, and would expect the same for all. If you need to know for sure I can measure a 295 tomorrow.

Post by **racer** » Thu Apr 15, 2004 8:23 am

The rolling road showed upseveral small faults some significant ,some not .My misfire @2000 rpm was due to a slightly worn choke spindle on the hs4.the lumenition actually expired whilst on the r/road!!!Put points back on -all fine! A fine crack in the rotor arm causing earth leak to spindle -swapped over -all ok .petrol pump (recently new) not pumping to max pressure ,but ok for my road use . needle/carb setting didnt need attention -spot on -I got something right! Eng.generally isnt performing as per a large chambered head that needed skimming,so he deduced from my 2 5/8"head that it must have been worked previously.Saw 90mph on rollers ,58/60 bhp. Went home a happy (but skint!)man.!!

Post by **rayofleamington** » Thu Apr 15, 2004 8:55 am

racer,
I almost suggested rotor arm when you mentioned missfire! There must be loads of faulty rotor arms out there as this is a common problem.
60 bhp sounds nice for a 1098 - glad to hear you have made some improvements. Did it seem to drive a lot better?

Post by **racer** » Thu Apr 15, 2004 9:50 am

I'm not out of the woods yet !(low oil press.)But it was good to drive ,amazing the things the guy looked for -the tiniest details which we sometimes pass off as "ok".Still got a missfire due to carb spindle -wheres the best place to get a new hs4? For the first time ,as i pulled out of a side road ,the o/side rear wheel let loose -felt like a real boy racer ! The very first thing he looked at was throttle travel-I ended up cutting the carpet from under the accel.pedal to give more travel!