Date: Sat, 27 Oct 2001 21:32:59 -0400
Reply-To: Robert Donalds <bostneng@FCL-US.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Robert Donalds <bostneng@FCL-US.NET>
Subject: Re: 1.25 or 1.4 rocker arms?
Content-Type: multipart/alternative;
Joel Sell wrote
. I have checked the archives on these questions, and have read conflicting answers.
1) I've read that the 1.4 rocker arms are good to use, but I've also read
that the "ramps are too steep" and can cause valve damage.
Which statement is true?
Joel
I think that both statements are true. You need to a stronger spring to keep the valve from free falling back onto the valve seat because of the increased valve speed the ratio rockers offer. I have seen the guides close around the valve due to the retainer striking the guide when ratio rocker are used on bug engines
Bob
2)It appears that Type 1 rocker arms are the way to go, but do I need to
buy just the rocker arms, or the whole shaft and assembly? Will the T1
rocker arms just slide on my waterboxer rocker shafts? I'm also planning on
getting the swivel foot adjusters.
The type 1 rockers would be needed to use the 8mm swivel foot adjusters and the shaft size is the same
my dyno testing of ratio rockers on stock bug engines showed that the engine gained 6 hp with stock springs above 3000 rpm and lost 1/2 of that when the heavy duty springs where added. The vanagon engine does not need top end horse power it needs low end and mid range increases the higher air flow at lower lifts provides that.
I posted this back in june you can see what the extra lift will give you in air flow then compare that to the heads with the bigger valves.
I have been building a 2.1 engine for my own 85 camper and along with the usual upgrades of the reground OEM cam with more duration, a little more piston skirt clearance and some major head work. I decided to try a set of 3mm larger valves and larger harder valve seats. After all the work to get larger valves and seats into a pair of AMC heads and doing the high flow valve job I sent the heads out to have them flow tested on a flow bench. The flow bench measures cubic feet of air moving threw each port at a given valve lift. Some of you might recall that I had some flow testing done when I started doing high flow valve jobs on stock heads with varying degrees of porting work.
Flow bench test results
1 stock AMC head intake port
2 ported and polished AMC head stock valve intake port
3 Boston Bobs big valve AMC head minor porting now in Bobs camper
CFM.
-------------------------------------------------------------------
Lift NO.1intake NO.2 intake NO.3 intake
.050 24.8 33.0 34.8
.100 47.1 52.2 57.3
.200 89.6 91.4 108.4
.250 115.4 116.7 132.8
.300 125.3 128.5 145.8
.350 137.6 145.3 171.4
.400 144.9 158.8 181.3 this is above stock lift
.450 147.8 174.1 186.0
.500 154.6 179.0 190.6
Bob Donalds
http://www.bostonengine.com
as always all right reserved
[text/html]
