ned
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| posted on 7/4/05 at 09:34 AM |
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pinto engine prob
thought i'd post this up as there must be loads of people out there with experience of tuned pnito's.
basically we had some problems with a freshly built 2ltr pinto at the weekend. it is to sports 2000/ff2000 spec ie standard bottom end, vernier
pulley, dry sump, capri carb and some minor head work.
The main problem we had was that both in practise and the race one of the (different each time) rockers decided to jump off the rocker post, making
the engine only run on 3 cylinders. After it happened the first time in practise the clearances were checked with feeler gauge and all the rocker
posts/rockers were checked for tightness etc. The engine is being run to about 7200rpm.
Does anyone have any ideas on why this happened?
The other problem we had was that the engine was losing oil. There was no obvious leek ie no holes/leaky hoses etc. I don't have too much info
on how it is plumbed (it is as said running a dry sump system), but it appeared to be losing oil from near the top of the engine as it had oil down
both sides of the block etc. We wondered whether this could be related to teh rocker coming off issue ie some odd pressure due to the way the system
was plumbed causing oil to leak out of the rocker cover (gasket looked ok though) and at the same time causing a rocker to jump off. I know in the
practise it was an exhaust rocker, not sure about the one that went in the race. In the practise it managed about 4 laps of brands gp and in the race
about 10-12mins (maybe 7-8 laps) of brands gp.
Any ideas pinto people?
cheers,
Ned.
[Edited on 7/4/05 by ned]
beware, I've got yellow skin
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mookaloid
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| posted on 7/4/05 at 10:31 AM |
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I think I read somewhere about rocker geometry being very important and if it is too far out it can result in the rockers jumping off.
Vizard or Hammil I think goes into this. Also I have a link somewhere to more info which I will post when I find it.
Oil can leak from the rocker cover area for a couple of reasons.
1. Breathing (or lack of it)
2. If a high capacity oil pump has been fitted and the spray bar has been modified with bigger holes then the rocker cover can fill with oil and
overflow if the return passages have not been opened up also!
HTH
Mark
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mookaloid
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| posted on 7/4/05 at 10:36 AM |
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Link to Puma Racing
http://www.pumaracing.co.uk/pinto.htm
Good info on valve geometry
Cheers
Mark
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NS Dev
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| posted on 7/4/05 at 10:45 AM |
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stretched keeper spring? Daft but maybe worth checking?
No ideas on the oil front though, should be under vacuum so must be a lot of oil!
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ned
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| posted on 7/4/05 at 10:48 AM |
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we recon in the race it had lost 1/2 to 2/3rds of engine oil..
It was only really noticable on the track at the left hander at the end of brabham (behind pit garges) straight where the track goes from the indy to
gp circuit as the oil was getting onto the exhaust and creating a lot of smoke!
Ned.
[Edited on 7/4/05 by ned]
beware, I've got yellow skin
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mookaloid
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| posted on 7/4/05 at 11:18 AM |
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Sounds like the oil return from the rocker cover to the sump is not emptying the rocker fast enough and it is just spilling out of the top!
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ned
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| posted on 7/4/05 at 12:00 PM |
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pics:
 
Rescued attachment pinto1.jpg
beware, I've got yellow skin
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ned
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| posted on 7/4/05 at 12:00 PM |
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again..
 
Rescued attachment pinto2.jpg
beware, I've got yellow skin
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mookaloid
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| posted on 7/4/05 at 12:03 PM |
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Sorry I'm not sure I am being clear
the oil from the spray bar returns to the sump down drain holes in the cylinder head. these holes are not big enough to accomodate the extra oil flow
if a high capacity oil pump is used (or if the engine is used at very high revs I guess).
The net result is that the rocker cover fills with oil and eventually overflows.
This would result in very high oil consumption because:
1. oil will leak out on to the exhaust etc
2. if there is a breather pipe from the rocker cover to the inlet manifold, oil will be sucked in the engine and burnt.
I don't think that the oil consumption/leaking thing is connected with the rockers jumping off.
Cheers
Mark
ps very nice looking car BTW
pps just noticed - my 500th post
[Edited on 7/4/05 by mookaloid]
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ned
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| posted on 7/4/05 at 12:08 PM |
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thanks and congrats mark 
Ned.
beware, I've got yellow skin
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andyharding
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| posted on 7/4/05 at 12:25 PM |
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Drool 
What gearbox is that?
Are you a Mac user or a retard?
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ned
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| posted on 7/4/05 at 12:35 PM |
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hewland mk9
beware, I've got yellow skin
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macspeedy
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| posted on 7/4/05 at 03:11 PM |
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just my pennys worth, the head has one hole to return the oil to the sump the head is slightly sloped towards this which is the back of the engine so
an adverse angle may cause excessive oil to be in the rocer area, we have a small oil leak from the front crank oil seal this can sometimes be caused
by the seal being in a slightly different place than before and this new place isn't a good seal due to corrosion also seals do take sometime to
bed in, hope this of help
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jacko
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| posted on 7/4/05 at 05:45 PM |
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Ned just a thought at 7200rpm it could be valve bounce letting the rockers come of and i think mark is right about oil over flow Jacko
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flak monkey
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| posted on 7/4/05 at 06:02 PM |
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In the Des Hamill book theres a fair bit about rocker geometry, and i seem to remember its quite critical in pintos. Remember most group 1 valve stems
are about 2mm longer than standard valves. ( i am assuming the engines highly tuned). This will screw up rocker geometry and could lead to major
problems and premature wear of various bits.
If the engine is being revved to 7000rpm+ double valve springs should be used IIRC, with a significantly higher 'over the nose' pressure
than standard springs, to prevent valve bounce. Which could possibly lead to the rockers jumping off.
David
Sera
http://www.motosera.com
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DrEagle
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| posted on 7/4/05 at 07:36 PM |
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Our Van Diemen FF2000 was rocke nightmare if you missed a gear they would jump off or break.
Make sure you have forhged ones not cheep cast ones and yeah its all in the set up.
Never be afraid to try something new!
Remember that a lone amateur built the Ark with no budget,
where as a large group of professionals spent millions building the Titanic!
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ned
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| posted on 11/4/05 at 09:38 AM |
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pretty sure all the valve gear/train is standard as per the engine regs.
I had a look at the oil plumbing, basically he has blockup the drain in the head to stop oil dripping onto no.4 crank end and oil splash reducing
power (every little helps) and has tapped into the back of the head right next to the normal drain location with a hose going down to the dry sump
pan, right next to the scavenge, so therory is scavenge should help suck oil out of head a little.
We are agreed that it's excess oil/pressure coming from the rocker cover, which I don't think has a breather.
I asked him about the spray bars and he says they are currently standard, but recons they might be producing to much oil which is affecting the high
amount of oil/pressure in the rocker.
He is talking about welding up the spray bars and drilling them to half size to reduce the amount of oil buildup in the head. the engine only
typically runs for 20mins at a time and recons that the standard spray bars are for a car that will last 100,000 miles, so he isn't bothered if
the cam wears/needs replcaing after a season of racing..
cheers all,
Ned.
beware, I've got yellow skin
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