7 replies to this topic

[postve]

Hey folks

I was thinking tonight I want to experiment and remove one is the head gaskets from my cylinder head so I would end up with just decompression plate and one BK450. When I fit the SC I did the calculations and found I had 8.0down from original 9.5 - this was fine as per specs. Using classic mini DIY I got 7.86! What I am trying to figure out is how much increase in compression would result and whether or not my engine would go “nuclear” ? Curious if anyone has tried this before or has some input - thx for all who respond - expecting increase in performance if this works!

Edited by postve, 18 July 2023 - 02:46 AM.

[timmy850]

You’ll need a head gasket on each side of the decompression plate otherwise it won’t seal

[postve]

Yep and doing some calculations Tim and I find I am only getting 7.38 compression - using mini DIY compression calculator - does this make sense based on VMAX decompression plate

Chamber size - 25.5
Piston deck - 0.10
Bk450 -3.44
Crankshaft - 81.28
Piston size - 71.10 (.20 over bore) - 1293
Vmax decom/extra head gasket 12.4

I only get 8.21 compression and I have always wondered if I was down on this but will leave well enough alone . Just fishing for thought and thx

Note all calculations other than VMAX numbers were painstakingly done by me with help from Keith Calver

Edited by postve, 18 July 2023 - 04:06 AM.

[timmy850]

Yes adding a thick decomp plate and an extra gasket will give you a much lower compression ratio..

If you want to run higher compression with boost you need a very well tuned mapped ignition system and good quality high octane fuel

[postve]

Thx again Tim!

[IronmanG]

Yes adding a thick decomp plate and an extra gasket will give you a much lower compression ratio..

If you want to run higher compression with boost you need a very well tuned mapped ignition system and good quality high octane fuel

Seeing as the ERA ran at 7psi at 9.7 (ish?) With injection that should be really easy to get to these days?

[timmy850]

Low compression/boost/timing is the safe zone for a bolt on kit like the vmax.

The higher you push any three of those, the more time/money/engineering will go into making it work safely. It can definitely be done

[postve]

Sound advice and was just curious as to thoughts and agree more tinkering, more costs and substantial once ya start pushing the envelope