The V8 Owners Forum -

Here is a short armature video of my fist heat yesterday, if you listen carefully to my car as it goes past you can here the crackling/misfire on full revs, and i notice it more towards the end of the race when the engine is hot. its a bad video but you get the gist of what i do and whats going on.. some of the cars look rough but there's some big money inn there engines as you will here, . I also noticed the car ran rougher as the day went on. http://www.youtube.com/user/littleyello ... nMroCUSZ0M i am in the black sd1 ,i have to start at the back of the grid because of my red top grading.

Hi
it strikes me that what might help alot here would be attempting to reduce valve train mass and a conversion to mechanical cam and lifters maybe add 10 degrees to exhaust duration whilst you are at it and increase the LSA to about 112 to 114 degrees. It would allow the engine to over rev more freely, probably give a little more power below peak torque. This coupled with a change in gear ratio may make the car quite a bit faster. How many gears do you actually use in a race, is it just 1st and second? Certainly, from what I understand from US short track oval racing generally a 2 speed box is used with no clutch, no torque converter and simply a powerglide that you jam into low ratio when you want to start moving, reverse pattern box, they race from a rolling start. Now it may not be the same overhere but you seem to be geared a little low in second to be reving it that hard at the end of the straight and to be running perminently in second is robbing you of power that a straight through gear and a lower final drive would gain you.
Best regards
Mike

Get some higher profile tyres for the rear - instant change in gearing

Ian

fist of all i only use 1st gear to start off then the car stays in second for the entire race, I have already changed the profile of the tyres one this year , i went from 195 50 15s to 205 55 15s and its hasn't made much difference, the next step would be 60 profile and they dont think they make toyo proxies in 60s, Plus it would also make me slower accelerating out of the bends. The best thing to do is eliminate this valve bounce or what ever it is, my engine is a twin plenum engine and it has different rockers than normal vittesse, They are hydraulic but the were made as adjustable but the nuts are welded in place , Something to do with the engine speck had to be the same on the road cars as the ones they use in touring cars , On close inspection today i noticed that one of the rockers was dry and no oil pumped out of the little hole in the top, All the rest are fine on both banks, Could this be my problem

Hi
The change of tyres would have only changed ratio by an effective 5% so Im not suprised you did not notice much differance.
It sounds like getting the final drive/ tyre combination with the right cam/torque curve is critical to getting your car working properly.
As I said above I would go mechanical cam, (or a real steel turbo cam and anti pump lifters). Get some replacment non welded volvo rockers and suitable valve springs. I would invest in a set of lightweight stainless valves from someone like Manley (probably through real steel) and get some lightweight titanium valve caps. I would keep the head mods basic, stage 1 type stuff and keep the ports small but above all get the valve train mass down, possably even go for a rev kit for the engine (extra springs in the valve train above the tappets holding them into the lifter bores).
Not sure what you are allowed to do to the engine for your class regs but I really would consider the change of gearbox and back axel ratio, it could save alot of weight, especially if you are doing rolling starts.
Best regards
Mike

Looking at the picture of the valve gear you have a steel retainer on the left of the picture and a sintered one next to it, the flat top means it is steel, the curvy chamfer means its sintered. If I were you I would first try a set of rhoads lifters, your description sounds like lifter pump up to me, valve float would be more of a buzzing sort of sound and much less misfiring. If you have the steel ones, then change them all, dropped valves are expensive!! Presumably it has a Group A cam which is stock lift but more duration, a real steel blower cam with rhoads lifters and dual springs will really wake it up.

Alan

What ecu are you running?
If it is a 4cux Lucas system I was told by a dyno house they have a built in rev limiter at 6750 rpm. At this point it knocks out spark

You may be at the limit of the ecu

Ian

That is i flat steel retainer . I had to replace four exhaust valve top because they split, so i replaced them with early sd1 tuned steel ones, I am going to changing them all but i thought i would try it fist after replacing the 4 split ones. If i can just make it to the end of this season with this engine i can build another over the winter. I just need too keep this one together for 4 more meetings. I am currently 3rd in the points championship and after this weekend i have closed the gap slightly. The majority of the formula are ford powered cars, RS 3.1s or highly tuned 2.9 v6s , and there's a 5.0 liter mustang powered sierra. I have a lower budget than some of the other guys am not a rich man . I am running a 390 four barrel not injection...

Hi
no reason you can't make a very fast car using the rover engine as a base, and do it on a low budget. I think what you are after is a wide powerband and flexability rather than peak power numbers and the rover is ideal for that. For your rebuild next year keep it simple, stage 1 or maybe stage 2 heads (bigger inlet valves basic porting, just clean up the ports do't open them up too much).
If you can find a 4.2 crank then fit that to the 3.5 block, but you will need to sort out pistons and rods that will give you good CR, it will give you usefull bottom end power out the corners whilst still letting the engine rev (larger capaity rovers really suffer from the heads being too restrictive and the power band narrows as a result) the RS blower cam and the Volvo lifters should make a motor with really good pick up and cleam reving with anti pump up lifters, or go for a mechanical cam of a similar spec.
I would consider the change of gearbox and rear axel to let you run in a straight through gear, it will liberate about 15 bhp over what you have, as I said earlier, if you do rolling starts you can save a heap of weight aswell by making the change and doing away with the clutch, you would need a different back axel, but one of the Sherpa vans has a rear ratio around 5.5:1 and with straight through gearing in the gearbox you would be around 5600-5800 revs at the end of the straight where now you are at (guessing) around 6250 to 6400 and valve floating on your current set up.
Best regards
Mike