Discussion
I know they will increase lift the same as a "high lift" cam. They won't change the timing or overlap. Do they put undue loadings on the valve train in the same way that a very high lift cam would (increasing the rate of lift). Are they a good easy fit alternative to a cam change if the engine is in a car.
There's plenty of folk out there with them fitted, what's your experiences?
Tony H
There's plenty of folk out there with them fitted, what's your experiences?
Tony H
The 1.5:1 roller-tip variety are really good and actually reduce the side loading on the valve stems/guides and hence valve guide wear.
You need to change the head gasket when you fit the new rockers as you have to remove half of the head bolts, but otherwise it's very straightforward EXCEPT that you must very carefully check that with the 1.5 rockers the valve springs don't 'coil-bind. To do this open each valve to fully open (i.e. spring fully compressed) in turn and with feeler gauges measure the minimum gap between coils. If the gap is less than 0.020" have a care. The Kent VS2 spring will normally give clearance with most high-lift cams and standard head configurations. On one engine I built with 1.5's the coil clearance at fully open was only 0.005", so I changed the springs to VS2's get clearance.
Do this check with the old gasket still on, then fit the new gasket once the checks are completed.
Remember to set a bit more cold clearance than with standard rockers - usually about 0.016".
You'll find the valve train is a lot less noisy with roller-tips.
I hope this helps,
Peter
You need to change the head gasket when you fit the new rockers as you have to remove half of the head bolts, but otherwise it's very straightforward EXCEPT that you must very carefully check that with the 1.5 rockers the valve springs don't 'coil-bind. To do this open each valve to fully open (i.e. spring fully compressed) in turn and with feeler gauges measure the minimum gap between coils. If the gap is less than 0.020" have a care. The Kent VS2 spring will normally give clearance with most high-lift cams and standard head configurations. On one engine I built with 1.5's the coil clearance at fully open was only 0.005", so I changed the springs to VS2's get clearance.
Do this check with the old gasket still on, then fit the new gasket once the checks are completed.
Remember to set a bit more cold clearance than with standard rockers - usually about 0.016".
You'll find the valve train is a lot less noisy with roller-tips.
I hope this helps,
Peter
I'll second Coops. I've got full roller rockers on mine, only because roller tip only weren't available at the time....... But I had non-descript twin springs, as per the Cooper S pack, and they went coil-bound on full lift with a Kent MD276. The non-descript springs were changed out to Issky springs and I've had no problems since.
As discussed in a previous thread there may be a change to the rocker clearances with this setup.
Edited to say : Doh, just read Coops closing line, and he already says about increased clearances.......
>> Edited by phil hill on Monday 24th May 16:51
As discussed in a previous thread there may be a change to the rocker clearances with this setup.
Edited to say : Doh, just read Coops closing line, and he already says about increased clearances.......
>> Edited by phil hill on Monday 24th May 16:51
Peter, I got my Isky's from my local engine builder in Lincoln, Mike Barratt. His (new and improved) web site is www.mberaceengines.co.uk or phone on 01522 545189.
phil hill said:
Peter, I got my Isky's from my local engine builder in Lincoln, Mike Barratt. His (new and improved) web site is www.mberaceengines.co.uk or phone on 01522 545189.
Thanks, Phil.
Do you live near Lincoln?
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