Novice question about pushrod/rocker/valve adjustments
Discussion
Hi,
could someone explain to me in simple terms the setup and adjustments around the rods, rockers and valves in a Grif 500 engine please. What did the standard engine come with, and what was right/wrong/good/bad about that? Why do people want/need adjustable rods and/or rockers? What does it gain for them or fix?
thanx in advance, Pum.
could someone explain to me in simple terms the setup and adjustments around the rods, rockers and valves in a Grif 500 engine please. What did the standard engine come with, and what was right/wrong/good/bad about that? Why do people want/need adjustable rods and/or rockers? What does it gain for them or fix?
thanx in advance, Pum.
Theres very little in the way of adjustment with the standard set-up, just an initial pre-load on the hydraulic tappet which is set with shims under the rocker pedestal.
you can buy adjustable push-rods which have a variable length but I wouldn't recommend them as they're heavy and inherently flexible.
The more expensive rocker gear ( such as roller rockers) have adjusters built into them.
However if your engine is built correctly and you're using the correct oil then the valve gear should never need adjustment.
There are some inherent reliability problems with using the standard valve-gear and the uprated cams and higher revs TVR's tend to see than the SD1 donor. Dislodged rocker pads and broken rocker shafts are not unheard of.
If you want a bulletproof valvetrain then use the sold cast iron rockers (suitablely lightened and polished etc) Cro-moly pushrods, high rev lifters and the machined form solid with end supports for the rocker shaft. This would suit 7500Rpm +
Matt
you can buy adjustable push-rods which have a variable length but I wouldn't recommend them as they're heavy and inherently flexible.
The more expensive rocker gear ( such as roller rockers) have adjusters built into them.
However if your engine is built correctly and you're using the correct oil then the valve gear should never need adjustment.
There are some inherent reliability problems with using the standard valve-gear and the uprated cams and higher revs TVR's tend to see than the SD1 donor. Dislodged rocker pads and broken rocker shafts are not unheard of.
If you want a bulletproof valvetrain then use the sold cast iron rockers (suitablely lightened and polished etc) Cro-moly pushrods, high rev lifters and the machined form solid with end supports for the rocker shaft. This would suit 7500Rpm +
Matt
Edited by 350Matt on Tuesday 29th May 19:17
Thanx for your reply Matt.
So with the standard setup you can only adjust preload a bit. Do adjustable rods or rockers allow adjustment of something else, or just more adjustment of preload? What is preload (in simple terms).
I had adjustable rods in mine, but several split after about 5 years / 8k miles (including trackdays tho'), so I'm not keen on them - when I questioned the durability I was told "yeah, they do that." The idea of fitting them was to allow some kind of adjustment that is needed now the engine is no longer new. They were fitted when my engine needed to be completely rebuilt onto a recon block/crank.
The problem I have now is low compression values on some cylinders. The rings and bores are apparently fine. I'm trying to understand the options for addressing this, as I'm having adjustable rods or rockers recommended to fix the problem. Rockers are more expensive, but sound better, at least in terms of durability.
I'd welcome any more input / advice / explanations.
So with the standard setup you can only adjust preload a bit. Do adjustable rods or rockers allow adjustment of something else, or just more adjustment of preload? What is preload (in simple terms).
I had adjustable rods in mine, but several split after about 5 years / 8k miles (including trackdays tho'), so I'm not keen on them - when I questioned the durability I was told "yeah, they do that." The idea of fitting them was to allow some kind of adjustment that is needed now the engine is no longer new. They were fitted when my engine needed to be completely rebuilt onto a recon block/crank.
The problem I have now is low compression values on some cylinders. The rings and bores are apparently fine. I'm trying to understand the options for addressing this, as I'm having adjustable rods or rockers recommended to fix the problem. Rockers are more expensive, but sound better, at least in terms of durability.
I'd welcome any more input / advice / explanations.
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