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Recent content by Maka10

  1. M

    Penta GX-i Compression results? Help?

    Off the original thread but my question about the compression was answered and confirmed by thanks to makomark. Some may want to research David Vizards experience and reputation on engine mods and Heads. In regards to the last 2 post. A Merc 350 5.7 Mag is not to to run the same boat as fast as...
  2. M

    Penta GX-i Compression results? Help?

    Porting for performance gains is not for everyone. Measure on a flow bench with some experienced knowledge will either make or break. Porting SB Chevy VORTEC heads for real pro results
  3. M

    Penta GX-i Compression results? Help?

    Thanks. Again a experienced Port guy with flow bench can measure lift cfm air from the lowest to highest rpm. I do understand what you are saying about gains being the most in the higher to reline rpm.
  4. M

    Penta GX-i Compression results? Help?

    Yes I agree. Maybe we have some misunderstanding about porting types? A mild casting clean up and Matched Flow Bench measured, port flow CFM improvement will help low rpm, mid and high. A good port job casting and mild clean up for this application should actually improve the mid range with not...
  5. M

    Penta GX-i Compression results? Help?

    Thanks. As far as the porting, and casting clean up, a improved slight flow will help on most any engine, if done correctly. Most of the research, and fuel usage charts I have ever seen, showed the 5.0 to get about 2 - 3 Gal's per hour better than the 5.7 like for like. Keep in mind with...
  6. M

    Penta GX-i Compression results? Help?

    Hi, I put in a great offer on a 2006 Cruiser with Twin Volvo Penta 5.0V8 GX i engines. I had a proper compression test done and attached are the results. I was kind of shocked surprised with 466 hours at the results. I know is well possible but don't see this much from a 2006 engines at all. I...
  7. M

    Penta GSi Compression Head and/or Rings?

    Here are another 2 test done on the Penta Gi 5.7 motor: https://www.marineengine.com/boat-forum/threads/compression-variance-on-volvo-penta-5-7-gic-300-r.479144/ compression test. Here are the numbers. #1 - 180 psi #2 - 190 psi #3 - 165 psi #4 - 190 psi #5 - 180 psi #6 - 180 psi #7 - 180 psi...
  8. M

    Penta GSi Compression Head and/or Rings?

    So the engine I am talking about is 2008 Vortec Volvo Penta Gi 5.7. I got to doing some more research and found this: The Volvo Penta 5.7 GI engine, which is a marine version of the GM Vortec 5.7L V8, typically has a compression ratio of around 9.5:1 with a .0315" (.8mm) gasket and 8.4:1 with...
  9. M

    Penta GSi Compression Head and/or Rings?

    Add to your top list also Exhaust Mani/Riser Gaskets. I have tried to find the Volvo Spec for compression on that Gi motor. Searching around I saw a few 185's as the top number unofficially. But I also saw many say that Volvo never gave a specific number even in the shop manual. I have a new...
  10. M

    Penta GSi Compression Head and/or Rings?

    It was done warmed to operating temp with all plugs removed. Got to thinking about the results? Even if the 8 reading showed some were on the unusual high side? The 2 low ones based on the high grade scale were still lower. Also could be a exhaust or Gasket leak? Getting a Leak down done next.
  11. M

    Penta GSi Compression Head and/or Rings?

    I have had 2 other of these engines. A 5.7 GS and a 7.4. They both use just a very, very small amount of oil, as normal for these. This is about the same and actually far less. Even when the motor has sat for months, on start up there is zero smoke coming out. I asked about the gasket seal...
  12. M

    Penta GSi Compression Head and/or Rings?

    I agree you both, you and him. I think the Guy just has seen so many engines that he feels kinda confident that it's not having signs of combustion chamber pistons, rings, cylinder walls, signs. There are things the engine will show if it was the chamber. Its also normal for a 400 plus hour...
  13. M

    Penta GSi Compression Head and/or Rings?

    Yes I understand that the Volvo engine is a GM and so is the Merc. Yes I also understand there are different options if it's the Valves to correct the Heads if that is actually the problem and the compression numbers are resulting in low compression on 2 cylinders. The Boat is in Fernandina...
  14. M

    Penta GSi Compression Head and/or Rings?

    Thank you for your reply. It's hard for me to just be doubting a experienced Boat tech with 40 years who knows the boat and serviced it for 7 years. Who is also up to date on Volvo Certifications too. I must have respect for them, but then again it's not the end of it because I know that that...
  15. M

    Penta GSi Compression Head and/or Rings?

    Hi, I am new to this forum! I Just had a compression done on a 2008 Penta GSi 5.7 engine. The numbers were 200 - 190 in all the cylinders except 2 on opposite sides. One side was 150, the other was 140. The boat Tech is a very reputable Guy, well known for his 40+ years of experience, honesty...
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