NITROUS OXIDE ( nos / n2o ) advice forum

I'm looking to change my stock camshaft. I know Trev will be glad to hear this

The engine is a Rover 4.6 running a holley 600dp and a harcourt single plane unheated inlet manifold.

I have recently retarded the cam timing by 4 degree's to see if this would move the power a bit further up the rev range. It seemed to work?? When I ran some nasp test passes it left the line like a bus and took ages to get into some decent power. I let it run until I felt it was pulling best and shifted to 2nd gear. I let it run again and crossed the line in 2nd gear at around 6200 rpm at 102 mph.
On gas this would be my 1/8th mile speed. This was 13.9 seconds. I tried a shot of gas and she left the line ok but started to wobble a bit at 5000rpm in 3rd at the 1/8th marker so I shut the gas down and ran half pedal to the line. This was 120mph in 12.7 seconds.

I can rev the engine at a standstill and she's fine nasp. But when it has some load in the burnout she has this feeling of running on 7 cylinders at 5000 rpm. But when I go WoT nasp on the track she runs smooth??

I'm doing some more testing in 2 weeks to see if I can figure this one out.

So!
Back to the original query. The 218 cam I have seems a bit tame. I have been offered a free 248 cam to try out. But thats all I've been told. Its a 248 race cam for a Rover V8. Does anyone know the difference??

Perry

The 248 race cam is probably going to need solid lifters ,stronger springs and machine work to the spring seats to accommodate the extra lift. Also valve- piston clearance will need checking, its a big step up from from a stock ish cam but would rev, if you can get the spec card, it should have there recommendations on installation .


Austin

X 2 but if you're going that route you should go the whole hog and fit a 256 (that's what I had in the Escort at the end if I remember correctly and it was MENTAL ON GAS ), because the bigger the cam the bigger the hole in the torque curve but the longer you have for nitrous to fill that hole and my God does it do that!!!!

That all sounds good chaps!!
I already have the heads machined for the double valve spring setup I use to a max of 1/2" lift all round. So just a set of solid lifters eh?? I have mol;y adjustable rods so thats not a problem.

I'm happy to fit a 256 cam Trev. I just need to know what it does re lift and performance etc... Cams are a black art for me so I rely on folks in the know to help me. I can see this elusive 0.7 of a second to get me a 9 is gonna be another years work

I'm happy to be patient. I already have the quickest Rover powered 1/4 mile MGB in the World. I would just like to rubber stamp that 10.6 with a flat 10 or any 9 to make sure nobody can take that away from me

I've been trawling the MGB world and the last record for a Rover V8 + nitrous MGB was a 12.2 I think. This was with a 3500 RV8. That was a late 90's car with a full chassis etc. Mine is a stock bodied door slammer with full interior (minus the passenger seat) and still running all the original steering and cart spring suspension + WON nitrous

So I could just stop here. I've done what I set out to do. My Factory MGB V8 still runs a Rover V8 with nitrous. But the RV8 is now a 4600.

To try and get some response I have posted my record claim on some US MG websites to see if I can get someone to call me on it

Although I'm not happy with a 10.6 I will gladly use it, and the world record status to try and get some sponsors on board.

Well!! You gotta try aint ya??

I'm now with Brett on a record claim for a car still running a factory engine + WON. There are a few MGB's out there in the world running exotic Supra turbos and big block engines that will no doubt be just as quick or quicker on the 1/4 mile. But I'm still using a UK Rover V8.....The car came from the factory in 1975 with a Rover V8. And it still has a Rover V8 fitted.. It may be a shallow victory. But I'm still claiming it as nobody seems to want to make records with Rover power anymore..

Perry

I'm not an expert on cams but if my memory serves me right the last 2 numbers of most cams represent the lift, so the 248 has 48 thou lift, while the 256 has 56 thou lift.

Fitting bigger cams generally raises the operating rpm range and the point at which peak power is achieved, at the expense of low to mid range rpm torque.

I guess the 48 means 0.48" lift then. So I should be good to go I reckon.

Pel ,which ever cam you go with check your valve guide height .if they have not been machined down the retainers will strike the top of the guide and jump out and the valve will drop . The grind # usually refers to the inlet duration at a certain lift.

Austin

Oooops that shouldn't have been 'thou' and should have been as you've deduced 0.48" & 0.56".

What a silly arse I can be sometimes.

Are these the Cams ------- from Real Steel catalog

we should do a "drag strip widows section" you lot are never out the garage or the bank

I'm just glad I said beforehand that I was NOT a camshaft expert.

I thought 1/2" was a bit big as I typed it.

So the whole number represents JUST the I/L lobe lift in thou (I hope I've got it right this time), so I was reasonably close in my first statement, just shouldn't have excluded the first number.

I had the valve guides skimmed down to accept a 1/2" lift. But I will check again when the heads are off. I use soft check springs so I can measure the total movement from closed to the cap hitting the guide. Then I know where my danger point is. I think I use 100 thou as my safety gap between guide and cap. (I'll have to check my old notes)

The cam I have at the mo is a real steel blower cam. But It doesnt seem much different to the standard one to be honest. The 248 cam might be a real steel one. I'll have to ask. It is is i may have to trim the guides down some more.

Pel , you may not notice the difference by eye but if you degree it up it will show up the longer duration and greater lobe separation , just one thourght have you got a high enough stall converter ?

I meant it doesnt feel much different on track. My converter stalls at 3000rpm. Now I have retarded my existing cam the power is further up the rev range. I'll look into a 4000 rpm converter after the Euro finals at the Pod. My friend is testing this upgrade in her Camaro.

It's more usual for those numbers to relate to the cam duration in degrees. It's usually measured at 0.05" of lift to the same on the closing side. So bigger numbers mean the valves are open longer. Lift is another thing to consider as is the overlap (LSA). It'd be well worth getting some decent cam advice from someone who knows that kind of V8 unless you want to play camshaft roulette.

For my TVR with basically the same engine i had advice from Rob at V8D.
Kent are grinding me a mechanical cam with the inlet from a 238 and the exhaust from the 256 to give 285 deg inlet and 310 exhaust with 112 lsa to keep overlap low. Its nearly £300 for the cam alone and then i need compatable double springs, solid lifters and adjustable pushrods.
I am going to run a low compression of 8:1 with ceramic coated forged pistons so should be able to add plenty of the good stuff.
I may even add a turbo or 2 at a later date.

"I may even add a turbo or 2 at a later date."

Oi Dell boy!!
Stop nicking my ideas

Cams are just black magic for me. As you say. I need to go to an expert and ask advice.
I'll be out next Sunday doing nasp runs to see if I can get the best from the latest cam timing settings. Then I can add gas if its ok.

Perry

I'd stay away from turbo's on Rover V8's especially in tight engine bays if I were you, as I've NEVER seen a satisfactory installation. Nic Mann is the only person I know of who ran good numbers with a turbo Rover but I never got to see how well it was fitted but as it was a purpose built car from the ground up, I'd expect him to have made plenty of space fo the turbo to be fitted correctly.

There are a few twin turbo projects on the go at the moment and all in Chimaera's and Griffith's.
There is a lot of room in front of the engine where the manifolds run forward.
I will be keeping an eye on these and looking for any problems.
Another alternative which is very popular and proven is SC powers supercharger kits.
I know 1 with over 450bhp and has no problems in everyday running.

I will be happy to run as is with the gas for at least next year.

Why fit them in the engine bay??
I can just cut holes in the bonnet and have them outside for extra cooling

Yes the TVR has a great deal more engine bay than most cars of its size, so it would certainly be easier than on other similar sized cars.

instead of turbo's (still think they are some sort of evil wizardry!) i was considering an eaton m90 on my rover v8 Perry, mounted in the vee, but with a single sidedraught carb mounted on the back so its sucking through the carb, or a 90 degree adapter with a downdraught IDA or similar, i estimated a dcoe 45 should give enough for my 3.5 capacity, but id need to use 2 plates to mount it to a spread bore manifold such as ahuffaker, one mounted to the manifold with countersunk screws, one mounted to the blower and sandwich together

better solution than turbo's as you arent ever off boost, you can increse boost with a pulley swap, ad you can still use a plate system to inject the nitrous which should also help cool the intake charge and hopefully increase its density at higher boost

just a thought ive been playing with, especially as eatons are for peanuts from the states!

Evil Wizadry The black art is the blowers - turbos are fit and forget! You cant get blowers from the scrapper easy but there are LOADS of good turbos................

And turbos a shot of N2O

aslong as you dont go stamping your foot at tickover

Listen, i had a skyline GTR i know all about the turbo and its drain on society!

problem with turbos is to get the good power you up the boost, then the cars slower point to point cause if you change gear and drop off boost you are into the world of lag. then theres the heat they put into the intake charge, increased det, the hopeless off boost performance etc etc they are just wrong W R O N G!!

too much brains, not enough engineering!!

seriously though, they are ok at low boost levels and when they are new/stock/in good nick, but so expensive to fix when they go wrong, and the breakers wernt full of N1 skylines!

never mind though, tried them, didnt like them!