All other dimensions being equal, the distance would be less if the rail is raised. Right?

Tom

 

Right, my measurement is 1 1/4 on the second measurement.

 

I looked at this carefully and determined that the measured result depends partly on some details in the measurement procedure. So, I decided to document the exact procedure that I am using.

First I pulled out an unrestored original 1967 '462 head that I know has never been altered or had the valves re-done (the engine had never been apart when I personally disassembled it). I thought that a prior valve job might have altered the seat heights on the swap-meet head that I reported on earlier. Here is the procedure I used with the known-stock 1967 head:

1) I re-installed two original exhaust valves that I had removed from that same '462 head. These measure 4.91" long and were installed at opposite ends of the head.

2) Using an ordinary carpenter's level as a straight edge, I set the level across the two exhaust valve tips so that the level spanned the length of the head. The 1" width of the level's edge was centered on the valve tips, and rested squarely on the valve tips.

3) Then I taped a metal ruler on the side of the level to show the height of the valve tips above the valve cover rail at that particular location.


As the photo below shows, the measured distance is just over 1.5". Note that this particular position places the steel ruler exactly parallel to the valve stems, and measures the valve cover rail height at a point that is 1/2" forward of the centerline of the row of valve stems. The corner of the valve cover rail that the ruler is touching is on the exhaust manifold side.

It turns out that the valve cover rail is not the same height all the way around when measured with respect to the flats of the valve tips. The measured height is approximately 1.5" on the rail that runs parallel to the exhaust ports, but it's only 1.1" on the rail that runs parallel to the intake ports.

Mark, if you can check the TF heads using the exact procedure that I did, hopefully we will find that the TF heads have at least as much valve cover rail height as the stock heads.

BTW, at some point (possibly even tomorrow) I will check the heads that are installed on my 383. These are Dart heads that were modified by Brzezinski Racing to look like '462 heads.

One of the machining operations was to reduce Dart's raised valve cover rail height to (presumably) the same height as the '462 heads. Even so, I managed to fit full roller rockers under the stock valve covers on these Dart heads because the only interference point was with the stud and Polylock. Some careful shortening of the studs and Polylocks solved the problem.

 

 

Here’s a link to an article on the TF DHC heads. In it TF states that they raised the rails 3/8”.

http://www.enginelabs.com/engine-tec...ds-trick-flow/

 

Joe, my measurement is 1 1/4”. I’ll post a picture when the cloud wakes up.

I noticed the comment in the article about the a/c bracket. I rushed down to the car and there is plenty of room. I don’t see an issue here. Whew!

 

Good article, but the author needs to bone-up Gen I heads. The 461X first showed up on both 1961 283 CID FI engines rated at 275 HP with the base engine hydraulic cam and 315 HP with the Duntov cam. That's how they got the name "fuel injection heads", however, for '62 utilization spread to the 300 and 340 HP carbureted engines in addition to the lone FI engine with Duntov cam rated at 360 HP.

The 461X heads are essentially cast iron versions of the ill-fated 1960 aluminum head.

This utilization continued for '63, but the equivalent '64 engines had the new 461 head, which had more material around the valve seats to support the 2.02/1.60" valve sizes.

The 462 replaced the 461 for '66, and it eliminated the narrow quench zone on the spark plug side of the chamber, which increased nominal chamber volume about 2 cc to about 66 cc with the big valves compared to the 461's 64 cc with big valves. 461 and later heads could be processed for both valve size sets.

291/292 followed for '68, and I believe these were the first with accessory holes on the ends. The 186/187 followed for '69 and were last used in '70, including the LT-1. For '71 all heads got larger combustion chambers for lower compression to support the management directive that all '71s be able to use 91 RON (today's 87 PON) unleaded fuel.

I believe the 492s were strictly OTC replacements for previous big port castings and were never used in production.

AFAIK 461 and up big port heads have the same port cores, nominally in the range of 160-165cc compared to the 461X that were about 172 cc.

These Trick Flow heads that "appear" to be OE double humps are a great idea for a road engine that doesn't need a radial cam to make high specific power output, and you want to maintain original appearance to casual inspection They flow about the same as massaged OE big port heads and save 40 pounds. I bet they will be big sellers, and I'm surprised that it took so long for the industry to produce an aluminum head that looks like an OE big port cast iron head.

Duke

 

This is great news. The extra 3/8" will make it much easier to fit roller rockers under the stock valve covers. It's likely that with the extra 3/8", roller rockers could be made to fit with no modifications to off-the-shelf studs and off-the-shelf Polylocks.

For my project on the modified Dart heads, I started with the shortest stud I could find (can't recall the length) and the shortest Polylock I could find, which I think was .875" from Crower. I had to trim both of these a little bit to get them to fit under the stock valve covers with no allowance for gasket thickness.

The challenge here is that the parameter that controls how short the stud can be is the pushrod length, which must be selected before the stud length can be optimized for clearance.

 

Hi Mark:

I realized that I have been thinking about this backward. If the measurement on the TF head is smaller than the corresponding measurement on a stock '462 head, that means the rocker rail on the TF head is higher than the '462, which yields more clearance on the TF heads for roller rockers.

So, if my measurement on a '462 is 1.5" and your measurement is 1.25" using the same measurement procedure on the TF heads, that means the TF heads have 0.25" more clearance for roller rockers under stock valve covers.

 

Glad you're going with Howard's rather than Comp Cams.

I placed a hydraulic roller (Comp Cams), into a BBC complete with their roller lifters.

The engine did sit for about 1.5 years prior to starting it.

The motor started right up and sounded great......except for the constant ticking from one of the lifters.

Took off the valve covers and re-adjusted the lifter. Again, nothing but constant clatter out of one lifter, and possibly two.

Called Comp Cams and they wouldn't warranty as it sat for 1.5 years. They said that I probably collapsed the spring.

Went down each rocker and found one that wouldn't hold strong, and would allow it to collapse just by pushing it down.

They sold me one set of lifters. Tore the top end off, and replaced that lifter.

Put it back together, and then another lifter making noise.

Went ahead and replaced the entire set, and so far they are doing well.

Then a few weeks after my event, another friend called and said he had experienced the very same thing with the Comp Roller Lifters.

But he had not assembled the engine and let it sit. He experienced a failure as soon as he built the motor.

Of course we looked all over the net and found that many individuals are not having good luck with Comp Roller Lifter.

Anyway, I don't want to hijack your thread, but very glad to see you're going with Howards!

Pat

 

Pat, I got a tip from Gearhead Joe and after spending several hours on the net it appears to be a problem with the CC lifters. I am told by Howard’s that their lifters are not made my the same company as CC. Thanks for the heads up as I am sure others can use the tip.

 

Agree, that’s good news.

 

Marc.
There are also different thickness VC gaskets. From about .060 to over .300. A 3/8" raised rail and 1/4" gaskets may be all you need.

Tom

 

I agree that we should not hijack this thread and get sidetracked on the subject of valve train noise with Comp Cams hydraulic roller cams.

That being said, I am also having this problem with my recent 383 build. I have been planning to start a separate thread on the topic, but I'm holding off because I'm still in conversation with Comp Cams about how to resolve it, and I don't want to poison those discussions with a bunch of negative comments on CF.

The problem appears to be quite complex. It appears that some people have this noise while others don't. Some people say that changing to a different brand of lifters solved the problem, while others say that the problem is with the lobe profiles and not the lifters. Other variables include the lifter pre-load, the oil viscosity, and the oil pressure.

I still have a few things to try before I start a separate thread on this topic, but if someone else wants to start a thread I will be interested to see the feedback.

 

Same here!!!

 

 

I knew I was going to get the heads but it took a while before I decided on the cam change. I ordered the cam today and the lifters are back ordered. I am told the lifters should be coming in within 2 weeks. I am hoping it will be done for April.

We were out there in late October. We had a great time.

 

Agree 100% I was one of the old "die hard" and did the ZDDP thing, adjusted valve spring pressure, ran lifters with orifice etc etc. After my 1st roller, a ZZ4 in a modified 383 I was amazed at the crisp throttle response and good manners with lots of low end torque. The extra money spent is worth every penny, not to mention peace of mine and not have to always be checking the oil filter for metal! Will never look back.

 

Anything new with this?

 

Pat and Mark,

I've been using custom grind hydraulic roller cams from Chris Straub (Straub Technologies) for the past 7 years (3 hyd roller cams) and am very pleased with the product as well as the customer service. Chris recommends Morel lifters. They are a little pricey but the quality is excellent. I would suggest that anyone who is considering a camshaft change at least contact Chris to discuss what your needs are and what he can do for you. Just my 2 cents worth.

Rex