Engine Modification Help: Automotive Technician Q&A

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Discussion Overview

The discussion revolves around the effects of modifying engine oil flow in a 1982 KZ1000 "J" engine following performance modifications, specifically concerning the impact of oversized studs on oil delivery to the camshaft bearings. Participants explore the geometry of oil passages and the implications of altering hole sizes in the cylinder head and block.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Alex raises questions about the geometry of oil flow, specifically regarding the impact of replacing 8mm studs with 9.4mm studs on oil delivery to the camshaft bearings.
  • Some participants express concern that modifying the oil system could lead to engine damage, emphasizing that engineers designed the oil flow for optimal performance and cooling.
  • One participant suggests that increasing the cylinder head's hole size to 11.8mm could restore oil flow to its original state, but notes this would equalize the size with the block holes, potentially altering flow characteristics.
  • Another participant questions whether eliminating the step-down from block to head ID could lead to overcompensation in oil flow, raising concerns about maintaining proper oil distribution between the top and bottom ends of the engine.
  • Mathematical calculations are presented to compare cross-sectional areas for oil flow under different configurations, indicating how modifications could affect oil delivery percentages relative to the original design.
  • Some participants seek clarification on whether equalizing the block and head IDs is beneficial or detrimental to oil flow dynamics.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best approach to modifying the oil passages. There are competing views on whether enlarging the head hole to match the block hole size is advisable, and concerns remain about the implications of such modifications on oil flow and engine integrity.

Contextual Notes

Participants express uncertainty about the effects of turbulence and flow characteristics resulting from the modifications. There are limitations in knowledge regarding the structural integrity of the engine components and the potential consequences of altering oil flow dynamics.

  • #31
Pressure might actually increase in that hole. Pressure doesn't matter as much as flow rate in cases like this.

Heads get hot. Heads with insufficient oil get even hotter, due to possible insufficient lubrication as well as decreased cooling rate (heat getting transferred into the oil).

The increase in head temperature can increase risk of warping heads. The higher peak temps can also weaken fastener joints such as valve cover gasketed joint, exhaust, and head gasket. Higher peak temps will also expose the small amount of oil in the heads to higher temperatures. That means the oil will degrade faster. The light ends of the oil molecules burn off more quickly, which will leave you with a lot of sludge. That sludge will further worsen the root cause of the problem.

Keep an eye on the engine's oil level. Also be sure to do a leakdown test. Compression tests are good, but leakdown will tell you a lot more. Compression tests won't change much until the engine is very worn out.
 

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