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Author: Subject: Big V8
ADD

posted on 21/7/05 at 02:12 PM Reply With Quote
Big V8

How much of an issue is it going to be on the handling if I drop a ford 302 or rover 4.6 V8 into my 7?
I get mixed messages some say the handling will be horrendous others say that it wont make a huge difference if I set things up right.
The other issue is traction, with all the torque am I just going to make alot of smoke and not go anywhere?

Adam

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carnut

posted on 21/7/05 at 02:33 PM Reply With Quote
If your going to go v8 put a rover in. Rover V8 weighs similar to a pinto so wouldnt upset handling to much. I'd stay clear of the yank v8's unless oyur going to drag it.

Carnut

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NS Dev

posted on 21/7/05 at 02:47 PM Reply With Quote
As above, the weight of the rover isn't really a big problem (ok, the car will be no lightweight but it won't handle "badly"

Traction, on the other hand, may be more of a problem!!

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donut

posted on 21/7/05 at 03:41 PM Reply With Quote
Make sure you can fit the gearbox in the tunnel!!





Andy

When I die, I want to go peacefully like my Grandfather did, in his sleep -- not screaming, like the passengers in his car.
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mackie

posted on 21/7/05 at 04:35 PM Reply With Quote
Is this for an existing chassis or a new build?

A Rover V8 will be a very tight fit in a std chassis and the LT77 (not sure about the T5) gearbox will certainly not fit in the standard tranny tunnel. Most RV8 builders on here have gone 4 inches wider I believe.

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ADD

posted on 21/7/05 at 05:01 PM Reply With Quote
Its a new build thats already underway. Making the tranny tunnel bigger wouldnt be a prob but making the whole chassis wider would be a pain in the nuts.
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Guinness

posted on 21/7/05 at 05:20 PM Reply With Quote
I was at a mates birthday once when the local Sevens turned up. After a while they all started up and one by one sped off down his road. The R300 Caterham, the Crossflow Caterham and a VX powered Westie all shot off down the road. The big V8 Dax just sat there spinning its rears and weaving from side to side.

HTH.

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quadra

posted on 21/7/05 at 07:41 PM Reply With Quote
I would say go with what ever floats your boat and don't listen to stories about a mate of a mate etc. Wheel spin is easy in any seven, its how you drive it not what engine it has in it. A standard rover will put out no more power than a tuned VX 16v although it may have more torque lower down. In my experience the V8 makes a for a very relaxed cruisers and has the soundtrack to match. I have no idea if it would fit in a locost but its worth a try just to be a bit different.

Mike

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bimbleuk

posted on 22/7/05 at 10:57 AM Reply With Quote
RAW just built a supercharged rover V8 engined Striker for a customer. Bloody awful and nobody wants to drive it. the Striker being relatively small even for a 7 just hasn't got the room for one.

In the right chassis though built with the V8 in mind then they can work well. The Razor V8 springs to mind in the 750 kitcar championship.

[Edited on 22/7/05 by bimbleuk]

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NS Dev

posted on 22/7/05 at 12:54 PM Reply With Quote
The fact is that you need an engine with a power/torque curve which approximately matches the ability of the wheels to put that torque on the road.

Having loads of torque at low revs is of no practical advantage in a seven because the laws of physics (and therefore the traction that can be obtained) mean that the maximum torque that can be transmitted to the road via the driven wheels is very low.

As wheel rpm increases, you can transmit progressively more power (same TORQUE!) through the driven wheels.

What you really need is an engine with a very wide power/torque band and a very big rev range.....................but then that's what we are all trying to achieve!!

As was pointed out, all the reasonably powerful engines can spin the wheels of a 7 with relative ease, the difference is that most of them have bigger rev ranges and their torque tends to fall from the bottom of the power band to the top, hence whilst accellerating, the likelihood of breaking traction decreases with speed through each gear.

Here the v8 becomes a problem as it's rev range (for the cheaper end of the market!) is limited, and in each gear the torque tends to build to a peak and then fall off again (remember that for any engine, the power and torque curves (in bhp and ftlb) cross at 5250 rpm, how does that compare to peak rpm, if it's near the limiter then all your driving will be on the increasing part of the torque curve!!)

The next problem is that with that limited rev range, the time until the next gear is short, and then the problem is repeated all over again!!!

Now contrast that to a revvy 4 cyl or 6 cyl engine (I know this is not scientifically correct, but I am referring to commonly available engines, not the "ideal world"!) where (for my Vauxhall XE for example) the working rev range is basically 5000rpm to 7500rpm. Torque peaks at around 5000rpm (as it does for most roughly square bore-stroke 4 cyl engines) and then falls all the way to 7500rpm, but the power peaks at 6500rpm ish. This means that if you can get away from a standing start fairly cleanly, traction should increase through the rev range, whereas with the v8 it will actually decrease.

Horses for courses though..............v8's sound awesome!!!!!!!!!

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NS Dev

posted on 22/7/05 at 12:56 PM Reply With Quote
Should add, if you can extend the rev range of the v8 to 7000-8000 rpm (like the 8000rpm 6.3 chevy in the Ultima Demo car!) then you regain the advantage!!
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