Vanagon EuroVan
Previous messageNext messagePrevious in topicNext in topicPrevious by same authorNext by same authorPrevious page (June 2007, week 4)Back to main VANAGON pageJoin or leave VANAGON (or change settings)ReplyPost a new messageSearchProportional fontNon-proportional font
Date:         Fri, 22 Jun 2007 14:02:15 -0400
Reply-To:     Jim Akiba <syncrolist@BOSTIG.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Jim Akiba <syncrolist@BOSTIG.COM>
Subject:      Re: Timing Chains, Belts, Gears, etc
Comments: To: Benny boy <huotb@VIDEOTRON.CA>
In-Reply-To:  <vanagon%2007062212214398@GERRY.VANAGON.COM>
Content-Type: text/plain; charset="us-ascii"

There is nothing about the inherent design differences in driving the camshafts that will produce more power/torque in and of itself. I don't believe that the flexibility of a timing chain produces more power/torque. It will help dampen power pulses from the crank however, which contributes to longer wearing on valvetrain parts. The valve timing event placement is what will determine the output characteristics of the engine. The primary reason for not using timing gears on OHC engines is because of the distance between the crank and cams. The number of parts and rotating mass are somewhat prohibitive, and belts do have benefits mostly in cost of production and maintenance. The trend toward light chains however is continuing, and as Toyota demonstrated this year, if you can lower the spring rate on the valve springs and not sacrifice sealing or return speeds(they did so iva much lighter valves), you can run a much smaller, lower mass timing chain, which we will start to see more of in the next 5 years. With older pushrods engines, timing gears are much more common. I have a set of timing gears on my 302, but they don't make sense for the majority of OHCs.

As far as "almost all went back to SOHC 4 valves per cylinder" this is true of Honda, but not generally speaking. Also most DOHC 4 valves are simpler than SOHC 4 valve which usually require rockers or oddly shaped lobes to achieve, and the SOHC lacks any ability to alter the power making characteristics without a cam change. Through phasing changes and tuning alone, power adders can be made much more effective on DOHC engines.

" So, now you may have to spend 600$-1000$ for a heas gasket job, a new T-belt, guide and maybe a tensionor after 100k miles of driving your Westy!" Ok, but you also already spent the money to convert it... and you still have an engine with 100k more miles on it. If you had gone with a conversion based off a world engine, you would spend the $600 on another engine with 10k miles on it, swap it in(just install work) and never get into the engine at all, and then everything is low miles all over again, for the same cost as maintaining your older Subaru.. and with far less risk, skill, knowledge, tools, time required. This is one of the additional benefits to owners that vanaru is going to achieve with their new conversion. Maybe you should have waited Benny ha. As far as who drives that much? Our Colorado customer Jason has put just under 30K miles on his westy inside of his first year of owning our conversion. So it can happen very quickly if people are really out there driving.

Jim Akiba

-----Original Message----- From: Benny boy [mailto:huotb@VIDEOTRON.CA] Sent: 2007-06-22 12:13 PM To: vanagon@GERRY.VANAGON.COM Subject: Re: Timing Chains, Belts, Gears, etc

Hi (longish and boring stuff for those who don't like engine stuff)

Gear Driven (cam to crank) gas engine have NO good torque/HP and poor torque curve, i know, i have owned a Honda CB 1000 with that system. That bike had NOTHING before 6000-7000 rpm, i said nothing. It felt like something was wrong, to tight. The funny thing is a broke one gear teath on the crank...

The relation between the cam and crank have big variation in engine power curve and torque. With a belt, that very slight flexibility produce torque. We all know the story about DOHC VS single VS 4 valves per cylinder, many went DOHC with as much as 5 valves per cylinder (Yamaha Genesis), in cars, almost all went back to single (SOHC) 4 valves per cylinder. It was the best simplicity VW power VS fuel consumption. Chain, he he he, anyone here who have owned a Honda CX bike will stay away from timing chain, binder problem. My ZR 600 broke a chain because of a faulty bender, now, get that chain out of there... no easy way, that engine need to go on the surgery table.

Now, let me do my corruptor thing about T-Belt change, that kind of pis**** me off (he he he), i had a few p-mail about that subject, and i find that a bit... sorry to say, stupid. Most modern engine have T-Belt, they all need preventive change at 60k miles. In the case of a Subi, it's a joke, no more dificult than on Honda or Toyota, what the big deal on those???? On your wasser, you may go on 4 head gasket change in that 60k miles, you may even need new heads or a total rebuilt, so tell me, WHAT is the big deal on timming belt? Sorry guys but a timming belt does't break, that's urban legend.

Now, another thing, about Subi head gasket problems... i have did my research way before i choose that path. The early 2.5L DOHC big scary flat four had """some""" problem (even, now we nead to undersand what "some" mean), even "Some" late 2.5L had heads gasket problem, Honda 1.6L and 1.7 also have their share of ealy head gasket problem, now let see how bad this is! Fist of all, most problem found were in general between 60k mile and 100k miles, on top, it is easy to see the problem as occasional overheating occur, so that said, ok, let say you need head gasket job, first there is NO need for new heads, it can be easily done with the engine in the "Van", no rusty bolt, no damage water jacket, no bent push-rod, bottom end O-ring replacement, pushrod seal.

Now, how many of you will reach 60k-110K miles with your westy in the next few years? Also, in general, people have done more than 150k miles before a head gasket job was needed on most Japanese engine, and that is TOTALY normal on most 4cyl engine. So, now you may have to spend 600$-1000$ for a heas gasket job, a new T-belt, guide and maybe a tensionor after 100k miles of driving your Westy! Very far from a total Wasser engine rebuilt or re-seal each 30k-50k miles.

I "would" take a Honda/Subaru belt or head gasket job anytime over a Wasser head job. 1/5 of the price on the Japanese engine and my hands stay way cleaner.

NO one here will ever convince me otherwise. But don't get me wrong, a well maintain Wasser still as in place in the back of our Vanagon, i will give a honorable mention to that engine who worked so hard over the years to get us there, where we wanted to go.

Ben http://www.benplace.com/vw2.htm

On Fri, 22 Jun 2007 06:52:56 -0500, John Rodgers <inua@CHARTER.NET> wrote:

>Just reading the post about "New Engine Conversion" - and I wonder - >besides cost, is there any reason why engines have not had meshed gears >to drive the cams. Piston type aircraft engines all have gear driven >cams. No body wants to try to pull over and park on a cloud when a >timing chain fails. > >Just curious. > >John Rodgers >88 GL Driver


Back to: Top of message | Previous page | Main VANAGON page

Please note - During the past 17 years of operation, several gigabytes of Vanagon mail messages have been archived. Searching the entire collection will take up to five minutes to complete. Please be patient!


Return to the archives @ gerry.vanagon.com


The vanagon mailing list archives are copyright (c) 1994-2011, and may not be reproduced without the express written permission of the list administrators. Posting messages to this mailing list grants a license to the mailing list administrators to reproduce the message in a compilation, either printed or electronic. All compilations will be not-for-profit, with any excess proceeds going to the Vanagon mailing list.

Any profits from list compilations go exclusively towards the management and operation of the Vanagon mailing list and vanagon mailing list web site.