newbee questions

[mike332]

Hi all,

Going to be building my first rover v8 engine soon. It's going to be a 3.5, the rules of the formula are that we have to run su's and other than that we are quite controlled.

I'm getting a balancer to do all my own balancing (I'm an engineer by trade, so no worries there ) I'm going to do my own porting as I've done this before on a ford pinto.

I'm looking into the bores and piston ring area at the moment, so I know what to do when the time comes. I want to squeeze every last drop of power I can, so ring sizing is my stumbling block. I've read up on how to do it, but I can't find any sizes or guides for such, to clarify, I mean end gap size. What would be the "standard" recomended gap size, and what would be the optimum for power?

Stumbled accross this forum today, and have been reading loads of very intesting posts and topics, I can see I'm going to be on here a lot over the next few months. I've never rebuilt, never mind tried tuning a v8, so any advice greatly recieved

I will be using the piper 285 ? cam, or at least that's the one I think I was told to use.... I need bags of low down torque, but good acceleration upto around 6,500 rpm from about 1,500rpm, as we leave them in 1 gear all the time, any suggestions?

Cheers

[katanaman]

Ring gap standard is 0.002"- 0.022" so you have loads of scope there lol. I would say you want to be on the tight side for a race engine. Trouble is almost all the rings come pre gaped these days so unless you hunt down so specialist rings (not so easy for a 3.5 these days) your not going to have a choice.

Cam wise I think your pushing it with 6500 rpm on a 285 in fact I think your pushing that with a hydraulic cam period. The 285 is only good for about 6200 and everything else has to be right to get that. I think you would be better off with a mechanical cam if you want to be guaranteed to hit that RPM. Bags of low down torque and highish rpm don't really go together either. You generally get one or the other unless you increase capacity.

In case you don't already know, for those revs your going to have to use ARP studs to keep the bottom end together.

You haven't said what formula your going to run in. If you let us know I am sure someone will could come up with a formula that will suit you.

[mike332]

Cheers for the reply. The formula is V8 Hotstox (Stockcars) racing on both dirt and tarmac ovals all over the U.K.

I was going to fit ARP bolts throughout, I always do when I build a race engine. We aren't allowed to use solid lifters, we have to use hydraulic, that's one of the rules I'm affraid.

The ovals are just under the 1/4 mile overall lap length, running gear is bedford cf mk1/2 zf 4 speed manual, through custom prop to a volvo rear axle. Speed down the straights is around 55mph on shale and 65mph on tarmac, probably down to as little as 20 or 30 round the bends. It's all about getting the power down smooth and fast from the mid point of the corner. Was told to use the 285 by Holly at RPI, obviously I can't ask too many questions there about squeezing power out, I'm sure they would love that seeing as how I'm going to be building my own engine

Do you think it would work if I got an oversize set of rings and sized those up to give a closer gap?

[chodjinn]

You'd be surprised Mike, both RPI and V8 Developments are known for being both very knowledgable and helpful; they certainly have been with my enquiries - and I've currently only bought a few adapters from V8D lol

[katanaman]

oversized rings filled down, no the rings will go oval and not seal properly. Have a look at the spec for the 285 yourself. I cant remember the low figures but its rated to 6200 top but few engines actually manage this on that cam for some reason. They do for a brief second but wont actually run and make power near that. Fair enough with the lifters but maybe you need to set your peak RPM down a bit

[mike332]

oversized rings filled down, no the rings will go oval and not seal properly.

I hadn't considered that probably not a good idea...... I'll keep thinking, I know there was something else I wanted to ask, but I'm buggered if I can remember

[Paul B]

Ring gap standard is 0.002"- 0.022" so you have loads of scope there lol. I would say you want to be on the tight side for a race engine. Trouble is almost all the rings come pre gaped these days so unless you hunt down so specialist rings (not so easy for a 3.5 these days) your not going to have a choice.

Just a thought, but would using rings from the next size overbore and gapping them to suit the stock bore give you all the adjustability you'd need?

[katanaman]

Ring gap standard is 0.002"- 0.022" so you have loads of scope there lol. I would say you want to be on the tight side for a race engine. Trouble is almost all the rings come pre gaped these days so unless you hunt down so specialist rings (not so easy for a 3.5 these days) your not going to have a choice.

Just a thought, but would using rings from the next size overbore and gapping them to suit the stock bore give you all the adjustability you'd need?

already discussed.

There are rings available but what you can get hold of these days for a 3.5 I have no idea they might not fit standard pistons either. Am sure someone else will know what you can get.

[x.l.r.8]

total seal will make rings for a 3.5
also why not use a solid lift cam with hydraulic lifters, it's been done many times before, not good on a road engine apparantly due to ramp, but in practice it's not been a issue.