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I think that TFS had problems with their earlier heads (the ones that didn't come with bronze guide from the factory), but they've made some changes, including changing to bronze guides that have corrected the problem.

'65 fb restomod
 

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Here is the article I read. I found it at: http://www.totalengineairflow.com/twhistry.html

As always, please remember that this is not my article, I'm just copying it here for your enjoyment. Please, everyone, don't sue me.
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Whenever a new product is developed it must go through many different levels of testing and analysis before it's final debut to the retail market. Quite often, products will make it to consumers before they have had all of the bugs worked out. Many people have owned new cars that would have things go wrong. They would take the car back to the dealership and get the problem fixed. A good example of this would be the 1999 Cobra Mustang having less power than a 1999 Mustang GT. The Cobra should easily have more power than a GT. Somehow the problem slipped out the door and ended up in the hands of consumers. Ford, in response to the masses of upset Cobra purchasers, immediately froze Cobra sales and began working on parts to correct the problem. Although it may have been an inconvenience, there was a solution to the problem and it could be corrected. Some items are so complex that it is extremely difficult to work out all bugs before selling to consumers. It's an inherent risk with developing and releasing new products to the marketplace.

Much like the 1999 Cobra, the Twisted Wedge cylinder heads have gone through levels of upgrade and improvement over the years. The whole history of the TW is very interesting to say the least. The past issue of the TW valvetrain issues are no secret. However, one big aspect of the whole thing that people forget is that the problems have been corrected. You will not find a higher quality or better performing cylinder head on that market right now. It's just that simple. Trick Flow Specialties has gone out of their way to correct, modify and upgrade the TW's so that they will be the top cylinder head on the market. If the TW's are so bad, then why do so many people run them and not have problems? Do people really know the truth behind the TW's? I doubt they do. Every brand of cylinder head on the market has addressed design flaws at some stage in development. It just so happens that the TW's were so popular and powerful, even with the design flaws, that a lot of them were sold before problems were noticed.

I have personal experience with the whole subject and have gotten help from Trick Flow Specialties before I did work for Total Engine Airflow. TFS took my old, bolt-down rocker arm TW's and converted them to stud-mount rocker arms, added bronze guides and sent me guide plates for the pushrods too. Aside from my castings being used, they were brand-new cylinder heads with all new components when I got them back. Please note that they were under the one-year warranty, but I am sure they have a fair policy regarding upgrades. I was extremely pleased with the honest and informative service that they provided me. I never got the impression that they were "sweeping the mess under the carpet" as some people have suggested. They have faced this whole issue appropriately and with the customers in mind.

In order to cure the problems, TFS has redone the valve train geometry on the TW heads. There are a number of reasons as to why the guides failed. None of them mean that the TW is a junk cylinder head. If it was a bad product, it would not be the number one cylinder head in the winner's circle right now for small block Fords. The flow levels that the TW can attain make it a very universal cylinder head for everything from street cruisers to serious race applications. The levels of porting can be tailored to accommodate the demands of each specific engine from a mild 12-second ride to a 9-second brawler. A good example would be the two top Renegade competitors, Chip Haveman and Bob Kurgan. They both run mid-9-second 1/4 mile e.t.'s using Stage III TW cylinder heads.

The Iron Versus Bronze Valve Guide Issue:

The biggest comment I have heard regarding the old TW problems is that cast iron valve guides were the culprit. Using cast iron guides wouldn't have been such a problem except for a few other issues that enhanced wear and longevity. Because the actual location of the rocker arm stud was slightly out of alignment, any type of valve guide would have failed prematurely. Over the years, factory production cylinder heads made by Ford, GM, Chrysler, Honda, etc., have used iron guides in both cast iron and aluminum cylinder heads without problems. It's not uncommon for production vehicles to operate over 100,000 miles without cylinder head maintenance. The iron guides that TFS used to put in the TW's were not the reason the valvetrain failed.

Valvetrain Geometry:

The location of the rocker arm stud in the TW's produced before the spring of 1997 was slightly off from where it is located on current models. Moving the rocker arm stud location was the key factor in attacking the valve guide wear issue. With the correction of the valvetrain geometry in the spring of 1997, TFS kept using the cast iron guides as standard equipment for the TW's until mid-1999.

Pushrods:

Another thing that caused major problems was that TFS used to tell people they could use the stock length pushrods with the TW's on a stock-type short block. A 6.700" pushrod was really the way to go for a stock 5.0 liter application. Now, TFS recommends checking each application with a pushrod length checker to verify precisely which length to use.

Rocker Arms:

With the original design of the TW having the rocker arm stud location slightly off and customers using the wrong length pushrods (i.e., too short), the situation was irritated even more with the use of cheap rocker arms in many cases. I have found that consumers tend to buy the cheapest rocker arms possible after spending all their money on the cylinder heads...bad news. Not only would they buy the cheapest rocker arms possible, but they would purchase the TW's that had the capability of using bolt-down (pedestal-mount) rocker arms... what a mess! Bolt-down rocker arms do not offer the adjustablity and accuracy of stud-mount rocker arms. The only way to know if a rocker arm is going to work for your application is to mock it up and check the sweep across the valve tip and verify other critical measurements. It's a good idea to plan on spending $200 to $300 for rocker arms. The TFS, Crane Gold and Motorsport rocker arm sets are some excellent choices. If you choose to install an off-brand rocker arm and neglect to make sure they meet TFS specifications when installed, you are risking your new cylinder heads. As you can see, a few simple issues irritate each other and the problems begin to magnify.

What has been done to solve the problem?



As of spring of 1997, all TW rocker arm stud locations have been relocated to correct the geometry aspects.

TFS no longer sells bolt-down rocker TW's.

All TW's are now sold with bronze guides.

For use on a stock-type 5.0 liter Mustang engine, a longer (6.700") pushrod length is recommended.

Machined locks are used on all TW's instead of stamped steel.

Instructions reflect that using cheap rocker arms will promote excessive sweep of the roller rocker tip across the valve, thus promoting wear. The instructions recommend PREMIUM rockers, which common sense says to use a $250 rocker with your $1,000+ cylinder heads rather than the $100 cheapo bunk rockers to save money. To further prevent problems, TFS started making their own rocker arms. They realized how much junk was out there in the rocker arm market and wanted to offer good components to their customers and save them some trouble.
So, there you have it! That's the true story behind the well known Twisted Wedge valve guide failure. After all of this redevelopment, the Twisted Wedge has become the most ultimate cylinder head in it's arena. It is the most proven and refined cylinder head ever made for the Small Block Ford to this date. Being in its prime state right now, it can only get better with porting by respectable performance shops like Total Engine Airflow. The winner's circle says all...Trick Flow Specialties and Twisted Wedge are always there.

The Twisted History
by Drew Walz © 2000
This article is used with the permission of the author.









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© 1998-2000 Total Engine Airflow, Inc. All Rights Reserved.


'65 fb restomod
 

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I don' t think the fix was to change the valve geometry, it was to change the rocker geometry to match the unique valve geometry.

I think that, after some work, they have a workable geometry that allows them to use the larger valves without flycuting.

It's a shame that they had a bad start that it tarnished their rep.

Anyway ... I like the AFR heads. But who's to say if they have it right either? They're so new that problems with them could not have surfaced yet. Who's better the devil you know or ...

'65 fb restomod
 
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