Re: Carb upgrade for stock-ish qt50 as first mod.

Bill Mazzacane /
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Assuming a 10:1 compression ratio = 150 psi. (the only compression related data was for a corrected CR of 6.0:1).

Also assuming that the 1.5 mm plate is sandwiched between 2 base gaskets, the actual increased height is closer to 2mm.

Recalculating the CR, it drops from 10:1 to a lower 7.17 CR and a new compression of 107psi. That is a loss of 43psi for using the plate.

A rule of thumb: engine requires ~100 psi to run. Obviously the engine with the plate & gaskets still runs, but a loss of ~43psi demonstrates the need for the cylinder to be decked ~2mm just to maintain stock compression.

At least raising the exhaust port to a 21' to 23' BDT can be easily accomplished.

Bill M.

On larger engines an increase .001" of deck height = a loss of 1psi. In this example .002" = 1psi.

This single post is part of a larger thread. Start from the top or view this post in context.
Subject Written By Posted
  Carb upgrade for stock-ish qt50 as first mod.Topic by: Rob LaFreniere Rob LaFreniere 04/10/19 04:14PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Jack Rutherford Jack Rutherford 04/10/19 08:16PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Rob LaFreniere Rob LaFreniere 04/11/19 11:49AM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Bill Mazzacane Bill Mazzacane 04/11/19 07:06PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Bill Mazzacane Bill Mazzacane 04/13/19 04:38AM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Jack Rutherford Jack Rutherford 04/13/19 10:03PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Jack Rutherford Jack Rutherford 04/11/19 07:16PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Bill Mazzacane Bill Mazzacane 04/11/19 08:54PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Jack Rutherford Jack Rutherford 04/11/19 07:26PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Jack Rutherford Jack Rutherford 04/11/19 11:53PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Jack Rutherford Jack Rutherford 04/12/19 12:06AM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Rob LaFreniere Rob LaFreniere 04/12/19 09:33AM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Bill Mazzacane Bill Mazzacane 04/12/19 07:24PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Jack Rutherford Jack Rutherford 04/12/19 10:50PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Rand Jacobson Rand Jacobson 04/13/19 07:02PM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Bill Mazzacane Bill Mazzacane 04/14/19 04:37AM
  Re: Carb upgrade for stock-ish qt50 as first mod.Re: Jack Rutherford Jack Rutherford 04/15/19 07:26PM

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