Power Loss
Road Master
Joined: Apr 2012
Posts: 979
Likes: 38
From: new orleans,la
engines like the old model T had no over lap -- no real duration --- the valves opened @ 0 and closed @ 0 hence the reason the sounded like they did -- theres more to it than overlap -- cam profile -- base circle - asymmetrical - symmetrical - single pattern -- dual pattern -- constant velocity -- continuous acceleration -- fast ramp cams --- blah blah blah --
like my sons turbo -- 577 lift -- 239 duration -- intake valve opens @ 3 atdc -- not 30 btdc but after -- reason? turbo boost duration and overlap would let the charge go out the exhaust --
F.I. is like 6 btdc where a regular carb is like 30 btdc and closes @ 60 abdc
like my sons turbo -- 577 lift -- 239 duration -- intake valve opens @ 3 atdc -- not 30 btdc but after -- reason? turbo boost duration and overlap would let the charge go out the exhaust --
F.I. is like 6 btdc where a regular carb is like 30 btdc and closes @ 60 abdc
Seasoned HDF Member
Joined: Jun 2012
Posts: 6,157
Likes: 2,564
From: CT/FL
I've had second thoughts about both valves being open at the same time.
I believe there is a point where on the intake or exhaust stroke you have both valves open in a short overlap. If this is true (?) then your observation of both being open at the same time COULD BE normal.
I believe there is a point where on the intake or exhaust stroke you have both valves open in a short overlap. If this is true (?) then your observation of both being open at the same time COULD BE normal.
Seasoned HDF Member
Joined: Nov 2006
Posts: 12,878
Likes: 5,449
From: la la land jerzey
I've had second thoughts about both valves being open at the same time.
I believe there is a point where on the intake or exhaust stroke you have both valves open in a short overlap. If this is true (?) then your observation of both being open at the same time COULD BE normal.
Here's an article about the overlap.
Here's a motor animation.
I believe there is a point where on the intake or exhaust stroke you have both valves open in a short overlap. If this is true (?) then your observation of both being open at the same time COULD BE normal.
Here's an article about the overlap.
Here's a motor animation.
in a hemi motor the TDC lift ( both valves open at the same time - intake closing and exhaust opening it given in thousands on any cam card for checking - example like .203 intake / .187 exhaust the methiod used to check this is a tool that attaches to the head, and with checker springs and 2 dial gages you open to the number < .203 intake / .187 exhaust than the distance between the 2 valves never should be less than .040 with a harley overhead motor ( hemi overhead ) the valves at the angle they are, this is a thing to check when caming the motor as well as valve to piston and that is different to check and how -- hope that helps - jz
Thread Starter
|
Novice
Joined: May 2013
Posts: 15
Likes: 0
From: Minnesota
The problem
Ok first I want to thank everyone who took time to reply to my inquiry, second I want to apologize for abandoning the thread til now.
First, the leak down test was accurate. The head was leaking out both valves. I installed a pair of S&S heads & problem solved.
The reason I choose the S&S heads was simply they were in stock. To have my heads gone through wouldn't of been much cheaper & would of had to wait.
Thank you again to everyone that contributed.
First, the leak down test was accurate. The head was leaking out both valves. I installed a pair of S&S heads & problem solved.
The reason I choose the S&S heads was simply they were in stock. To have my heads gone through wouldn't of been much cheaper & would of had to wait.
Thank you again to everyone that contributed.
Thread
Thread Starter
Forum
Replies
Last Post
fadingfastsd
EVO
17
Nov 16, 2017 02:21 PM
