NITROUS OXIDE ( nos / n2o ) advice forum

I've had a few issues with the last build. So I've done it all over again now.
That's unfortunate.

I think I've pretty much maxxed out what I can do with a rover V8 on a tight budget.
The bottom end is complete custom and should be good for 700hp assuming the block does not split.
It has big billet main caps and chevy 5700 rods. Its been X bolted as well.
Obviously your budget wasn't as tight as mine (lol), as all I could afford was a set of recon rods and ARP bolts & studs and yet mine still held together OK on close to a THEORETICAL 950 hp (200 motor and 3 stages of 250 nitrous), so I can't see you having any problems with this new lump.

The heads have been maxxed out with the biggest valves I can shove in there and they are ported to match.
It has a mech crower cam with solid lifters and a full Kenne Bell roller rocker set up on top.
Apart from the cam mine was 'almost' stock, although I did HOG out the exhaust ports.

I've fitted custom Omega pistons and dropped the CR down to 7.5:1 so I can run max boost and nitrous.
I also had Omega pistons but they were the stock replacements they offer for the 3.5 V8.

I've already run a stock 4.6 Rover V8 to 10.2 seconds with boost + WoN. But when I upped the nitrous I bent the stock rods and wrecked the engine. Not surprising really as this was 12psi of boost and a 250 shot fixed hit. No wonder the stock rover rods decided to give in eh?
Either that proves how much more aggressive blower power is compared to nitrous or your motor was suffering detonation, as I never had any problems with recon rods and none of my customers (who were using the same specs and adding as much nitrous), did either.

But now she has Chevy I beam rods which I have been told will be good for 700hp.

This is the LAST ROVER V8 for the MGB for my 9 second attempt in my 2600lb full steel bodied door slammer car.

I'll have it all back together in the next few days and then back in the car for shakedowns on the 1st June.
Hope that all goes well.

I'm now hoping that my old FRED controller will do the biz for me. Or should I be looking to upgrade to a new controller that can monitor my AFR for closer control?
That would be wise, considering your past experiences.

I have 2 wide band sensors fitted on the V8 with 2 gauges and a data logging system as well. This is a Zeitronix system. Can this be integrated with a WoN controller to adjust pulsing of fuel and nitrous to keep me safe?
Almost certainly, as we've not had any issues connecting to any other brand.

Here are some pics of the last Rover V8 engine that I'm going to use in the MGB.

Custom billet bottom end with ARP and chevy rods:
The only thing I would have done after going that far with the bottom end, is to have made/fitted a full girdle plate but as my dead stock bottom end handled more power than you plan to make, all you need to do is AVOID DETONATION and/or AVOID RAISING 'PEAK' COMBUSTION PRESSURES and just rely on increase MEAN pressures.

It was the Chevy Pistons Trev. They were supposed to be forged,
It's easy enough to tell a forged piston from a cast one but I'd need to see more of pics of them.

but they distorted around the valve cutouts with only 6psi of boost and no nitrous. There were no signs of degradation or melting. They just seemed to go soft under mild load. I've taken Rover cast pistons past this much power on nitrous only.
They may not have suffered in the normal way from signs of a lot of heat but there's plenty of signs that EXCESSIVE heat was the cause!!!!
I can say with a great degree of certainty that either the bore was too tight or the ring gaps weren't big enough, as the piston crowns have been DRAGGED UPWARDS and there's ONLY 2 ways that can happen;
1) The excess heat caused the rings to butt up and they locked in the top of the bores, so that when the piston tried to move down again, the rings tried to lift the crown off.
2) The excess heat expanded the crown more than there was adequate clearance for and in the process the crown momentarily seized at the top of the bore and as the rest of the piston tried to move down it lifted the crown before breaking the seizure.

It could even have been both at the same time and you can actually see the seizure areas quite clearly, to prove number 2 certainly happened.

They distorted and hit the heads and scuffed the bores. On left hand side there may be a hint of melting but I was running 12 degree's of retard for 6psi of boost with AFR showing mid 11's. The sharp edges on the valve cutouts on top of the piston are pristine with no signs of metling.
Excess heat caused by blowers causes different damage to heat caused by nitrous, so it's easy to be mislead when you've not had much experience of blower related damage.

Maybe the rod failure was just bad luck.
NO that would be as a result of the piston/s seizing/locking up in the bore/s and suggested that the seizures occurred just before TDC and then continued through to after TDC, subjecting the rod/s to immense force breaking the seizures.

The old engine did have 180,000 miles on it. And it was only 1 rod. All the others were fine.
That indicates that the one damaged piston/rod was running hotter than the others, causing the piston/ring to expand more than the others.

I'm only going to run the blower to about 75% so as not to stress it too much, and then use nitrous to top it off for my final power adder.
You'd have more success with nitrous alone as it doesn't heat the air charge like a blower does but at least adding nitrous to the mix with the blower will certainly help.
I can say with 100% CERTAINTY that the rod failure was NOT due to excess power and was ENTIRELY DUE to the piston seizure.

Mainly because the blower is not very controllable. Once I've spooled up about 20 feet off the line the blower is all or nothing. But if I keep the boost down a bit I know I can control the extra power very smoothly even with old FRED
Another overriding reason for nitrous..... UNRIVALLED CONTROL.

I only need ONE power ramp. Thats for 1st gear only as I'm at WOT straight off the line and I dont need to back off for gear shifts with the auto box and ratchet shifter. Although my ign retard control is fixed so I have no ability to alter that during a run.
That's far from being desirable, that's for sure.

The engine is at peak torque rpm very quickly off the line which is where I shift gears. The down side I've experienced with the low revving Rover has been after the 1/8th mile marker where I'm in top gear (normally running around 6 seconds to 107mph) and then slowly moving above my peak torque rpm where the engine then starts to just soften off. I'm wondering if at this higher rpm I should be adding timing back in?? 6 seconds to 107 and then the slow haul to 131mph in another 4-5 seconds.. It seems like a lifetime from inside the car??
There's a whole bunch of potential reasons for that but I wouldn't start playing with timing as my number one option, as that could cost you another engine.

I'm so close to a 9 second ticket that I can almost taste it
I knew how that felt for a good while. Remember I was THE FIRST to run a 9s 1/4 in a Street legal Rover THREE POINT FIVE LITRE engined car, although I was never officially credited with it, just as was never officially credited with being quicker than Steve Green and many other accolades I should have had, just because I didn't go around kissing certain people's asses.

But this 0.3 of a second is not that easy to find, especially on my old stock 4.6 with nowt more that Omega's and a better cam.
You would have run a 9 LONG AGO 'IF' you'd stuck with the nitrous ONLY and acted on my advice, just as MANY other people have achieved their dreams and goals by doing so.
Switching to a blower MAKES NO SENSE as it SOAKS UP POWER to drive it, whereas nitrous is FREE POWER.
If you'd spent ALL that money that you spent on the blower on building a motor to MY SPEC and had ME fit and set up the nitrous system for you, 9s would have been A BREEZE.
The ONLY good thing about a blower, is the noise it makes but the noise doesn't make the car run any quicker.

I've got my 60 foots down into the 1.45 second area so I'm not sure I can improve much more than that with the stock back end and suspension. So I'm thinking I need the engine to run a little bit stronger after the 1/8th mile marker for just 2-3 seconds. Thats why this engine was put together. I'm hoping I can pull hard off the line and stay in my 1.4 60 foot times, but then have the engine run harder for another few seconds. I really hope this works because I'm past the point of financial return now with the Rover V8. If this set up runs a 9.99 I'll be happy and then I'll pull it out and sell it so I can put the money towards a Chevy engine for next year.
It's VERY UNLIKELY that improvements in the second half of the 1/8 will give you a 0.3 secs gain from where you are now. You'll need AT LEAST a 0.1 gain in the 60ft followed by ADDITIONAL 0.1 gain in the 330 ft to even have a chance of making a further 0.1 gain from there on.
The ONLY car combo that might pick up 0.3 in the last eighth ONLY would be a turbo combo.
Your best hope is to get SOME nitrous in EARLY and keep it flowing strongly through to the 1/8, so you get the 0.1 sec improvements in all sectors.

Come and watch my Swedish Pro Mod customer next weekend at the Pod and with a bit of luck he'll produce some impressive times and show a few people what a CORRECTLY DESIGNED & FITTED WON nitrous system can do, despite being on a TOTALLY UNSUITABLE engine.

Agreed, the top ring is far too thick, plus the crown is far too thin.

So now you have 2 opinions indicating that excessive ring expansion (or put another way ring gaps too small) and or bore clearances too tight and the cause of the problem.

I've now got Omega pistons fitted again. I've gone for 30% bigger bore to piston clearance. Ring gaps are supposed to be 22 thou. I've gapped them to 35 thou on the top rings which is my normal 50% ish bigger gap that I've always done. And I've gone 30% bigger on the second ring gaps.

This was the formula I was using on the old engine before the rod let go on the old Omega's

I guess I made a real rookie mistake when I bought this engine. I was told that it made 350hp with a 150 shot of gas on the dyno. It had only made a few passes on the 1/4 mile in a TR7 when it ran low 12's. But this was on a manual gearbox. I know my auto box and ratchet shifter will give me 0.5 of a second on the 1/4 mile with slicks and good traction. So I was thinking high 11's on half the nitrous I had been running would see me back in the 10's with no problems. I was told that the CR was about the normal 9.3:1 but when I pulled the engine I measured and found it to be about 12.5:1 CR.

Shit happens eh?

Time to look forward rather than back methinks...

I wanted the blower because I've always wanted one. I already know I can run 10.2 on the blower at 70% output with a 150 shot of nitrous chucked in under the carb and into the blower.

I just made a mistake and wrecked the last engine. So I think I'm close to being back where I was last year. But this time I have much stronger rods, a solid bottom end, max ported heads and valves, and my trusty Omega pistons fitted with a much lower CR which is about 7.5:1 now