Build the head up complete & torqued correctly minus the lifter shims, then measure the cam to lifter gap for each valve (as they WILL be different); that simple.
Build the head up complete & torqued correctly minus the lifter shims, then measure the cam to lifter gap for each valve (as they WILL be different); that simple.
We will be setting the final gaps by full assembly, we're only using the valve clamp to get the shims as close as possible.Originally Posted by BRoadGhost
We have a standard head with standard valves that we are going to try with the cams and buckets to see if we can get a decent inlet and exhaust valve clearance, this should tell us that the cams and buckets are correct, the cams are brand new after all and the buckets, cam face to "dick" measure exactly what QED have on the shelf so they appear correct aswell.
Our line of thinking currently is that the valve seats have not been cut correctly for the +1 inlet valves meaning the valve isn't sitting into the head as far as it should. Obviously we can't cut 80' (or 2mm in new money) out of the seat so we are thinking what options we have.
I guess at the end of the day the fact we're running a 230' shim doesn't actually matter providing we have all the correct spring bind clearances, valve to piston clearances and full valve lift from the cam profile.
As Darren has said something just didn't look right, QED assure me that they supply 230' shims on other engines the hold parts for so it's not as if no-ones ever heard of shims that big. Piper stock a 6mm shim to fit a 7mm valve stem so....... it's not unheard of.
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Last edited by steveboyslim; 04-12-15 at 07:53 AM.
Steve,
We're still in the investigation stage. Comparing the head I have with the standard head we have in stock.
If it appears that we have standard valve seats then we're well aware that we can't cut +1's into them (as stated above) and would require new seats and by extension the throats would need to be machined also, possibly something that we would require someone with extensive experience to do (with reference to the throat work), valve seats we can change but removing material from the throats is sometimes best left to guys that have experience with the specific head. (Namely yourself)
I appreciate all your input, whilst it's sometimes easier to just send the head to you straight away, we don't learn by doing that, it's a voyage of discovery after all!!!
So, just got off the phone to Darren, my head does indeed have standard valve seats on the inlet. A standard valve works with my head and gives and expected valve clearance.
Now for the solution!!
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Last edited by steveboyslim; 04-12-15 at 07:53 AM.
Thanks Steve,
The stems have been changed for what I assume to be colisbro ones, the guys will have checked them already and we know they are new just not the make.
Jay and Darren are proceeding with changing the valve seats for some +1mm items as it appears that the inlets a simply standard sized with a new seat cut but nowhere near right enough for the +1 valves.
The exhaust valves, which are +1 also, seem to have simply had new seats cut deep into the standard size seats. We can't believe this would be the ideal solution and would also explain why the shims for the exhaust were down at 70' cos they're cut too far into the seat.
The long and short is, new seats all round.
Another really interesting point that has come about today, the port bored Coscast head that we're using has got smaller throats directly above the valve than the standard GM head, this makes no sense to us?!? Indeed when Jay called QED to ask if they knew anything about the Coscast head having smaller throats they knew nothing at all about, very strange.
Steve, is part of the port boring process to narrow the throats? surely this would only be achieved by welding material into the throats and there's no evidence of this so we can't figure it out!! Have you ever come across a Coscast head that has narrower throats than the GM one?!?
The end result we've decided on is to fit the +1 size seats and open the throats and blend into the new seats. This is without doubt the best solution.
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Last edited by steveboyslim; 04-12-15 at 07:54 AM.
Thanks again Steve, I'll pass that info on, the only issue we can see is that the exhaust needs a shim at 70' to get the correct clearance, which seems quite small, would you be ok with this!?
As for shims we'll get the seats fitted and see what the shims we have are saying, I've spent nearly £300 on shims at this point so I'd like to see if the ones we have will work first!!
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