Pulled both heads tonight... Yeow! Removed retainer and spring on #8 cylinder intake valve and does it ever wobble. Trick Flow gave me an RMA# today, so off they came tonight. I'll ship FedEx and hope I get them back in time for Knott's.
Oh, great! That's what's on a 351W on my 1/2 a fastback (was a '65 FB someone chopped so I had a M II front suspension stuff on it - project car #2). By the time I get it to run TF is going to tell me TS. Oh well, when that happens I'll dump the heads and get something more reliable...
It would be interesting to hear from the rest of the group who have TFS heads on this subject...
I think it has to do with the rotated polyangle valving arrangement they've come up with to get their airflow numbers....
Most aftermarket heads use bronze or bronze sleeve valve guides which have an excellent service record in the rebuilding insdustry...I did have some difficulties early on with valve guides I made myself because they were of the wrong alloy and had poor wear characteristics against hard chromed valve stems....I would only get one season or so out of them before replacement.
Do those TFS heads by any chance use a 1.7 rocker? If so, that may also be contributing....it magnifies any error in the machining angle of the rocker stud or bolt boss and threading...doing stuff like this, when departing from the OEM design, can be tricky even if all the numbers sound right...
As much as I think the TFS heads are cool (and, in 1995, when they were a new design, I felt the same way), I'll continue to recommend the more pedestrian heads like the Edelbrocks I have on the race car because of their proven design and reliability. You should get at least the OEM lifespan out of a set of aftermarket heads if they're to be considered for street use....
I had considered getting TFS heads for the race car at some point but will have to do more research on their maintenance requirements under racing conditions before justifying the cost vs performance improvements...
I hope everything works out ok for you....keep us posted..
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.
I'd be curious to know what they did use on the early heads for valve guides....
When I bought my Edelbrocks in '95, TFS (I think Summit owns a chunk of them) had just come out with the Twisted Wedge heads and they were backordered....I coulda sworn from the catalog description that they had stellite seats, bronze guides, screw-in studs and guide plates from the factory on the bare heads.....
Those catalogs are long-gone so I have no way of verifying that...
I've been doing machine work for a long time now and the only viable alternative I've seen to either stock cast iron guides or solid bronze guides has been a bronze sleeve guide (thin wall) which installs within the stock cast guide or existing bronze guide with a special ream and installation tool...
If there's some new technology out there that someone knows about in this area, I'd love to hear about it....
FWIW, my ca. '95 Performer RPM's came with solid bronze guides...exemplary service received...
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.
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.
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.
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.
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.
As I surmised, the root cause of the TFS problems was their departure from OEM valvetrain geometry...
Although this article, if entirely accurate, would contradict my assertion about the original TFS heads having bronze guides, I wonder why they, in contradiction to every established norm for the performance industry at the time, would install iron guides in an aluminum performance head...
There are a number of issues with this marriage and I am nonplussed as to why they didn't sort them through in pre-production.....
Thanks for setting the record straight on this products history.....
I think the iron guides are a bandaid fix to valve angle problem. I love the flow numbers of the TW, thats
why I bought AFR heads. Same flow numbers with a conventional valve setup. Great low and mid lift numbers as well.
I bought my TFS heads from Total Engine Airflow. Their story jived with my machinist's regarding rocker arm geometry, without him even knowing about them, so my fears were put to rest. We're waitng until the heads are on the motor to see what length pushrods we need. I bought the heads from Total and I got a good deal. The standard assembled heads, 7/16 stud upgrade and a set of TFS roller rockers for $1300 including shipping. I'm happy. Just a few more weeks, then vrooom. . .
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