The performance of an engine is dependent on a number of systems, where each individual system works in sync to influence the final result. The valve train is one of those systems and correct rocker geometry is critical, as it makes a significant difference to engine power and durability.
Valve movement is affected by the location of the rocker. Locating the rocker correctly can be achieved by moving mounting points, combining different length pushrods and valve stems, or changing rockers. But what is the correct rocker position?
The tip of the rocker should operate around the centreline of the valve stem when the rocker opens the valve. Incorrect contact between the rocker and the end of the valve stem can cause side loading on the valve, erratic valve movements, loss of valve lift and rocker binding. All of these problems can lead to loss of performance or valve train failures.
Fig 1: The contact patch on the valve tip should be between 1.5mm and 2.0mm. The patch slightly off valve centre is preferable to a wide contact in the centre of the valve.
A process can be performed to check this roller/valve tip relationship. To view the process for solid lifters, click here. To view the process for hydraulic lifters, click here. (see the bottom of this page)
|If the tip of the roller contacts the stem towards the outside of the head, the pushrod is too long. Or if the contact is toward the intake side of the head, the pushrod is too short.|
The pushrod is too long. The patch is wide and shifted to the exhaust side of the valve tip.
The pushrod is too short. The patch is wide and shifted to the intake side of the valve tip.
The pushrod is the correct length. Notice that the patch is narrow and central on the valve tip.
|Hydraulic lifters have a small hole in the lifter body, which is supplied oil under a consistent pressure via an oil channel. The lifter is free to fill with oil while the valve is closed. As the cam enters the lift phase, the check valve inside the lifter shuts. As oil does not compress, full cam lift will now be transfered to the pushrod.|
The diagram below shows the internal structure of a hydraulic lifter. A preload is applied to the lifter so that the plunger is positioned away from the circlip.
To determine the correct rocker geometry when hydraulic lifters are being used, a slightly different method needs to be employed, than setting up with solid lifters. As there will be no oil pressure to fill the lifter with oil, the lifter has no oil to compress, so the adjustment in the pushrod is taken up by the lifter. Therefore, there will be an incorrect result. Click here for the process which can determine the correct pushrod length required when using hydraulic lifters.
Contact us for more information on this topic.
|Click here for the pdf version of the process which can determine correct pushrod length when using solid lifters.||Click here for the pdf version of the process which can determine correct pushrod length when using hydraulic lifters.|
SHANNON'S INSURANCE POWER PALOOZA
Frequently Asked Questions
How do I know if my engine needs reconditioning?
Tell-tale signs that your engine requires attention are that it has lost performance or efficiency, it blows excessive smoke or it has developed an unusual noise. However, a vehicle needn't have these symptoms to benefit from a reconditoned engine. A complete and comprehensive recondition of your engine will increase power, fuel efficiency and extend the life of your vehicle.
Do you remove and refit engines?
Galloway Engines is a precision workshop which deals in machining and reconditioning engines. This ensures we are specialists in our field and only a quality job of the highest standard will be delivered. We can arrange engine removal and fitment or contact your regular vehicle servicing centre for this service.
Can I supply my own parts?
Yes. You are quite welcome to supply your own new parts should you have a preference for a particular brand name. However, our parts prices are very competitive and our high standards ensure that only quality parts are fitted to any job. We have liaisons with many Australian and international companies allowing us to have access to world-wide sourcing of parts.
Do you offer a warranty?
Any reputable product will come with a warranty as proof of its quality. Galloway Engines are no exception. We offer a full warranty on all of our work. Contact us for more information on the terms and conditions of our warranty.
Why should I use Galloway Engines?
Galloway Engines supply a quality engine which is completely reconditioned to comply with original manufacturers specifications and are in accordance with Australian Standards AS4182 for petrol engines and AS4427 for diesel engines. Our up-to-date equipment produces quality precision work and our team of specialised technicians are dedicated to detail. This ensures you are getting the best job possible.
Can you recondition any engine?
Yes. Whether it be a Caterpillar engine from a giant earthmoving machine or a small three cylinder Suzuki engine, we have the equipment to be able to meet your needs. Contact us to see how we can meet your requirements.
Do you offer engines which suit LPG?
As LPG has different properties to unleaded fuel, an engine can experience problems when converted to LPG. We can offer options which can enhance the performance and reliability of an LPG engine. Galloway Engine Reconditioning also stock a range of exchange heads which are modified to run on LPG.
Do you have EFTPOS?
We have full EFTPOS facilities available and are able to accept payment via Credit or Debit Card.
Address:Galloway Engine Reconditioning,
25 Baker St,
Pinjarra WA 6208
Phone / Fax:08 9531 1366
08 9531 2321