The V8 Owners Forum -

My engine is being rebuilt at the moment.
Its a TVR derived 4.6 rover V8 and is being rebuilt with custom spec ceramic coated forged pistons and will run a CR of 8:1.
The big valve heads are getting ported, chambers matched, bronze guides.
For next year i am fitiing a bespoke nitrous friendly cam and will rely on gas to give me the power i need for my part time drag racing fix.

I wish to go forced induction at a later date but have a lot to learn and am wondering what my options and performance figures i can look forward to wether sucked or blowed.

The car will remain fully road legal and will be used as a weekend car as well as drag racing and track days.

So any ideas please guys?

8:1 is low, I'd have thought 9:1 would be much more suitable? Is it just for drag or track too? If wishing to go forced- I think a centrifugal would give excellent potential, you can fit it in the engine bay much easier than a roots or screw blower, unless you get a big turbo on the front of your foreward facing TVR headers, and an anti lag system!!!

My engine builder wanted to go as low as 7:1.
I intend to ultimately add 300 bhp of nitrous on what should be nearly 300 NA.
I thought as far as forced induction goes then the lower the CR allows for more boost pressure and therefore more power?
I need a degree of moderation as i said the car will have a lot of relatively normal use as well as some track action and plenty 1/4 mile racing.

Low CR will allow more gas etc- but when on the road and not armed I can't help thinking you would wish for some more compression!

topcatproduction wrote:Low CR will allow more gas etc- but when on the road and not armed I can't help thinking you would wish for some more compression!

The priority power wise is the drag racing.
I have been told that 8:1 wont be too noticable a NA difference as the engine is being built with close squish and should run efficiently.
As long as it gets over 25 mpg and gets me reliably to the shows, meetings and drag strips and can pass all the repmobiles then i will be happy.
I will have a second 'road' nitrous kit with a 'small' 100 shot just in case

Hi
With 8:1 CR you can probably run 18 to 24 PSI without detonation due to CR, your issues will be getting the exhaust out and the charge in, what heads have you? With this boost you probably want ported merlins or wildcats or you will just heat up the inlet charge and it will detonate. On that basis and a 300 BHP base engine you will be looking at 700 to 800 bhp, with ported standard heads you will have a big detonation problem. Holding the bottom end together will be an issue, add nitrous and it will be a big problem.
I don't think you will get 25 MPG
Best regards
Mike

I run 10 psi boost on a 9:1 cr block ( Supercharged 3.5 V8 in a Ford Capri mk1) and I get 17 MPG on longgggg road trips ( Holland to the UK via France and viceversa).
I do reach 25MPG without the supercharger attached.

7-800bhp from a Rover Mike??

I get 14mpg on a good run, down to 9mpg on short fun outings...

Hi Tom,
700-800 on a rover with the right heads yes, like any engine if you can get the mixture in and ignite it without detonation it is possable. A NA rover with wild cat heads can be made to generate about 450 to 500 bhp if you can get it to hold together while you rev the nuts off it. Trouble is getting it to hold together. If you don't use the right heads and try and use 22 psi, it will get so much heat into the inlet charge it will go bang anyway, that is unless you are Big Al and run the thing on methanol.
Best regards
Mike

7:1 CR is old old old old skool.

Unless you're aiming for say 30-40psi boost, dont even consider such a low CR.

For most sensible builds low-mid 8's will cover most options

Realistically though with normal RV8 parts, I wouldnt expect to get much over 500bhp for most builds, without getting into really fancy parts.

7-800 bhp

The 25 mpg is before adding forced but i know of TVRs running blowers at modest boost to give over 400 bhp and claim better mileage than 300bhp NA.

I would be happy (at first) to boost for 450-500 on my engine. All ARPd with ringed head gaskets so i hope it would be reliable enough.
My heads are big valve TVR with 43 and 37mm valves and have been ported by Pete Burgess and fitted with bronze guides.

"My heads are big valve TVR with 43 and 37mm valves and have been ported by Pete Burgess and fitted with bronze guides."
In that case I would up the compression to about 8.5-9:1 and keep the boost below 16psi, should still see you to 500 BHP if you use an efficient (read big) intercooler, which will be more than enough to rattle your main caps!
As Stevie says the CR's you are quoting are distinctly mid '80s thinking.
Best regards
Mike

kiwicar wrote: In that case I would up the compression to about 8.5-9:1 and keep the boost below 16psi, should still see you to 500 BHP if you use an efficient (read big) intercooler, which will be more than enough to rattle your main caps!
As Stevie says the CR's you are quoting are distinctly mid '80s thinking.
Best regards
Mike

The build is too far on now for major changes.
The compression ratio will be 8:1 and cant be increased with a change of head gasket due to the squish being minimised. I suppose the only option would be to weld material into the combustion chambers but i am happy to experiment with the engine as is. The initial intent was to have a reliable engine that can sufficiently get my 1060kg TVR to meetings and cruises and the odd track day but can soak up a 300 bhp hit of nitrous at the drag strip to run into the 10's.
I still think this is all possible.
This thread was started to see if i could make my engine work at a later date with a supercharger or turbos, not to make big differences to the work i am currently having done.

All good food for thought however, please keep it coming

Hi
I would go with what you have, 300 bhp of nitrous may be tricky to get to go down the ports, but 275 should go, for later developments with forced induction you should have a development platform where you will not have an issue with high CR causing detonation, this should leave you to develope the rest of the package with one less thing to worry about. It might be worth thinking of nitrous and forced induction on this spec, if you intercool then aim nitrous jets straight down the ports you may find the cooling effect and the ram effect of the nitrous would enable you to get a very large amount of charge into the chamber, you would then just have to hold the bottom end together .
Best regards
Mike

So what gearbox, clutch and diff are you using???

Tom.