stevieturbo

Its a bit long winded, I know...

Im having some issues with the LS1 cam I purchased.

I'll give a quick rundown of the engine first.
Basic forged 346, 8.7:1 ported heads, 1.7 YT rockers, stock 01 lifters, 7.35" pushrods, LS6 intake, YSi blower, 73lb injectors etc. LT's

previously I was using a LPE GT2-3 camshaft, which ran fine, but wasnt performing the way I wanted.

My ecu is a non-sequential system, firing injectors in batches, and also firing wasted spark igntion, using 8 coils, as per normal LS1, although not LS1 coils.
Cylinders 1+ 6 fire together, 8+5, 7+4, and 2+3 firing together.

Before this engine, I was running a stock 01 LS1, with the YSi fitted, again with the same ecu, albeit with 57lb injectors.
Both it, and the low compression GT2-3 cammed motor ran perfectly.

OK, my problem.
Ive just fitted a 230/236 112LSA+4 camshaft. ( cam chart says 231.8/237.5 0.596"/0.606" 111.9 LSA SN-E8826 )
All the engine wants to do, is pop and bang out the exhaust. it will not run smoothly at all, and it sounds as if the leads are mixed up, firing the wrong cylinders, which given the 8 coil layout is impossible.

I swapped the cam in situ, removing the GT2-3, fitting the Thunder cam and re-aligning the dots on the duplex rollermaster chain.. preload on the lifters would now be about 10-40thou, as best I can measure, now using 7.35" pushrods.
I did have 7.4" pushrods fitted and the problem was still there. I fitted the 7.35"'s today to reduce the preload, as I though the valves were being held open..
I checked the cam timing, and it would appear to match the cam chart, with inlet achieving full lift around 103 ATDC ( I actually saw closer to 105deg, but its close enough )

Compression pressure is about 175psi on all 8 cylinders during cranking.

I need the car to race next weekend, and I do not want to re-fit my old camshaft.
Although, if I have to, I will....What a PITA.

ive tried ignition timing from 5deg, right up to 50deg, and its still doing it. Fuelling is within the range 11-14:1, varying due to the popping and banging etc. Nearly impossible to get a nice steady setting.

Whats going on ???? I need help.

Thanks, Stevie

CaptUSA

iTrader: (5)

Just guessing here, so don't laugh...

What are the odds of a cam comming off the grinder in a bad way? I've been trouble shooting my entire life, but never on cars, but if I take a good system, and take out a known good part and put a different one in, then the whole system goes to hell..... Well, 99.5% of the time, it's that new part.

Other than the guess, I have nothing to offer but best wishes mate. Good luck!

stevieturbo

Tell me about it....

camshaft is now removed, and it will stay that way for a day or 2, until I can get answers of some sort.

Cam I removed was GT2-3, base circle measuring 1.495"
Thunder cam measures 1.520"

GT2-3 was running perfect with 7.4" pushrods. I initially tried the other cam with these, then thought the problem was too much pre-load. The 7.350 pushrods will more than have made up for the 0.025" larger base circle.

I would be 100% confident preload is not the problem.

The fact I am firing 2 sparks at a time, may be, but I highly doubt it. This is my 4th engine in my car, that has used the exact same setup, although with less aggressive cams I must admit..
When cylinder no 1 is firing, cylinder no6 is nearing the end of the exhaust stroke, with the valve just about to shut. I think it unlikely, anything could be ignited, or would be left in the cylinder to be ignited.

PREDATOR-Z

What springs are you running?

stevieturbo

Whatever dual springs come with FFHP's stage 1 heads. No idea of brand. I specified they needed to be capable of 0.600" lift, as the GT2-3 cam has about 0.580 lift, and was working perfectly, just making crap power.

The springs are in good order, none broken, and have less than 1000 miles on them with the GT2-3. All valve heights are pretty similar. Not identical, but very very close.

It basically wont run now at all.....

I am seriously thinking, the injectors could be a major part of my problem. Fuelling requirements at lower throttles are much reduced due to the cam. Perhaps my injectors simply cannot go low enough, and are overfuelling, with big droplets ( not helped by batch fire injection ), rather than a nice combustable mist.
this fuel lies in the chamber as it cannot ignite, and only ignites on the wasted spark while the exhaust valve is open ??

I did only run it briefly with the old cam, and 73lbs, just to ensure they were working. Maybe for 20 miles or so. Then once I was happy things were ok, I swapped the cam.

I'll try swapping the old 57lb's back in, although I still want to try and sort a cams sensor for 8 seperate sparks too. Cant do much more until I get info on Monday as to what my ecu needs as far as cam sensor goes.

PREDATOR-Z

I believe your powerloss is due to springs. You have .600 springs with a .606 cam and BOOSTED.
I think you springs are incapable of closing your valves properly under boost. You prolly already had that problem with the LPE GT-3 cam under boost, it just intensified with the bigger cam.

stevieturbo

The engine has never received boost with the 230/236.. Its not a power loss

It will barely even run, let alone drive.

Demon SS

iTrader: (3)

the springs are not an issue, or should not be. while I don't remember Steve's exact head setup as far as the springs go, we have used Comp 918's, Crane LS1 Duals and mostly Patriot Gold Series LS1 springs. All of these will handle a .606 lift easily.

Steve, I will give your problem some thought and also have Brad read this thread and see what we can do to help resolve this issue.

stevieturbo

The springs are duals, and I would be 100% certain they are not the problem. At full lift they are nowhere near close to binding..
I am totally happy with the heads you supplied me Scott.

It may be a tuning related issue, not helped by how my ecu is running the engine, combined with the relatively large 73lbs fired in group fire mode.
The injectors are fired in 4 pairs, in no real order.
At idle with the small cam, and 57'bs, my IJPW's were down to about 1.3ms ( 50psi base FP )
With the 73lbs, although I only ran it briefly, this dropped the numbers to around 1.15ms, at 43psi base FP to get a good idle.

When it first ran with the cam, the numbers to get it to run, were below 1ms, and eve then it has fouled the plugs badly.

Im going to refit the cam and 57lbs again now and see what happens.

Trying to adapt a cam trigger for sequential sparks and injection is going to be a lot more difficult than I originally thought.

Any help or advice is appreciated Scott.

stevieturbo

Would ya believe that swapping back to the 57lb's has sorted it.

Damn 73lbs must be far too big for my ecu to control. No doubt partly due to its group fire injection...

Oh well....initial impressions are it still lacks midrange power, but still need more work tuning it..

Slowhawk

iTrader: (12)

I was just going to say the tuning is causing it.

That bigger Cam will make alot less midrange than the old Cam.

stevieturbo

So what cam will give me the best of both worlds ??

I took it on good advise that a more radical cam would give improvements in most areas.

Both cams Ive tried so far, GT2-3 and 230/236 on this engine, feel worse in most areas than the totally stock engine did with the blower.
The GT2-3/low compression+13psi was faster, it just didnt feel as good all round as the stock engine+9psi, again, lacking the instant mid-range. Top end even with the stock engine, still felt pretty good.

CaptUSA

iTrader: (5)

I don't remember who it was, but one of the sponsors makes a blower specific cam. The FI section should be able to answer your question in a heartbeat.

Glad to hear you fixed your main problem though. Good job.

stevieturbo

Cam is a strange thing though. What some people say works for them, just doesnt for others.

The stock engine felt great when I first got it running. Then when I added the blower, with only 9psi at 6k, it was awesome everywhere. Basically from idle to 6k. Instant power everywhere.

I'm just dissappointed the new engine doesnt have that same responsiveness, albeit with more power everywhere. The lower compression may dampen things a bit, but I would have thought ported heads, and some more boost, and of course a suitable cam, would have more than made up for that.
The GT2-3 was good, esp top end, but just lacked a bit down low, but ultimately it was faster than the stock engine. But I am using more boost too. So its no big achievement to be faster.

So far the 230/236 lacks everywhere. I'll try working more with it later, but I just feel its not what I want.
I know mild cams usually work, which is why I was happing using the GT2-3 initially.

Pro Stock John

iTrader: (34)

1) Glad you fixed the car.

2) Regarding 'less midrange' and it 'feels slow' well... Those are generalizations. Do you drag race or road race the car? What has it run before? I would not expect the car to make more power from 1000-2500 rpms but it should be stronger where I would spend most of my time... like between 5000-7000 rpms.

3) I'm running a 236/246//114 and make way more power than most of the small cam guys do at like 4500-5500 rpms. I consider that to be midrange. You might to start looking at folk's dynosheets and look at how peaky they are. If someone makes like 700rwhp peak but the hp line looks steep, so the car did not make much at like 5000 rpms, well... that means your average usable hp won't be as strong as say a car that makes strong HP all the way across. Think about it. When you shift the car, you want to shift the car at peak hp or a bit past peak... But what will your combo drop down to on shifts? If it drops to 5000, well, what power do you make at 5000, 500rwhp or 650rwhp? Some veteran racers strongly advocate having the power band be as straight across as possible. Some will generalize and just shoot for 2000 rpms of usable power where the average hp is not far off from the peak hp. A car that makes 750rwhp peak, but with an average hp of 700rwhp for 2000 rpms might be faster than a car that made 800rwhp but the curve was very peaky.

Worst come to worse, start dynoing the car or put some laptimes on it, or some 1/4 mph runs on it.

I went 136mph with a slipping belt, seeing 14psi, with a tune for 18psi.

Recently I've gone 144.6mph, saw 18psi on the dyno, with a tune for 21.5 psi. Might have hit 19-21 psi at the track but was not able to datalog that day.

My feeling is that your combo should work pretty good and perhaps peak at like 6500. That is not the cam I would have run but it should still work well.

stevieturbo

Unfortunately, there are no drag strips in Northern Ireland. Nor do I have easy access to a Dyno. Both these things dont help matters. Basically this country sucks.

I consider midrange to be around 2500-5000, although Im perfectly happy to rev to 7k if needed. Top end is 5k +

I do drag race, and apart from normal road use, its the only sport I use it for. I do have to travel to England to do it though, which is like a 350 mile trip each way + ferry across to mainland UK, so it doesnt happen often.

So far best with stock engine + YSi I only got 1 and only run ( stock clutch slipped after that ) which was 12.2 @122 using 225/50x16 Kuhmo Ecsta tyres, 2.1 sec 60ft. I'm sure I could have broke into the 11's if clutch hadnt packed in on 2nd attempt

Only comparison I have with new engine + GT2-3/13psi is using a GPS based performance meter on the road, but with 245/45x16 Bridgestone road tyres. Road surface isnt great, and traction as always isnt great
1/4 was 12.36 @ 127. With like a low 8s 95mph 1/8th.
60fts are like 2.1 sec.

I still havent tried the new cam with this device yet, but will do later tonight if it stays dry. I will be heading to a proper timed event in England this weekend, which is why the panic to get it ready.
I also have a pair of Nitto 555R's to try this weekend too.

Pro Stock John

iTrader: (34)

I'd run bigger diameter dual exhaust.

I run 1.875 into 2.000 step headers into 3" dual exhaust. I was told by the blower experts to run 3" dual exhaust.

stevieturbo

I will upgrade to 3" at some point, but when I put it together, I just re-used my old rear 2.5" sections.
Headers are difficult, as I had to modify the RHS header quite a bit to fit past my steering.
I cut a pair of mac headers along with the paceasetter tubes and used the bends to make 2 new front tubes for it.

The Kooks 1 7/8" look as if they too would be close, but I will have to modify them too. If I can buy a selection of bends in that size, and stainless, I'd do that too at a later date.

Had a brief test again last night. Ive gained some improvements, although also added water inejction and bumped up the timing.
Still crap 60fts around 2.2s, but 8.0s @ 100mph 1/8th, and finally broke into 11.95 @ 130mph ( crossing still in 4th gear at approx 6000rpm )
Still on road tyres. Weight of vehicle with me on board is about 3700lbs.

ASP are to get me shorter belts, when they arrive, I have a smaller pulley I can try.
The cam doesnt feel so bad now, but Im sure there is still room for improvement.