Cracks in BT Hi Riser HeadsMay 17 2017 at 5:47 PM
|bart (Login RATPOISON511)|
I have a set of BT Hi Riser heads which have developed cracks from where the head top rear head bolt bushings go into the bolt holes into coolant passages. We have welded plugs in the rear passageways in the heads to stop the cracking and H2o leaks. It appears that other cracks are starting to appear in the front top bolt holes, although they don't appear to be headed to H2o passages.I would suggest that anyone using these heads look closely at the aforementioned areas. Hope this helps someone.
Do they look something like this?
|May 17 2017, 6:00 PM |
Re: Do they look something like this?
|May 17 2017, 7:25 PM |
Not as bad, but we had one that was dumping water into the oil pan which we thought wqas being caused by the sheet metal intake manifold.
any idea on the cause?
|May 17 2017, 10:24 PM |
Is that maybe caused by the rockers trying to pull up the top of the head?
I saw on a blown Cleveland where cylinder pressure tried to push down the tops of the head bolt bosses on the exhaust side and the fix was a steel strap across the tops of the exhaust ports.
Re: any idea on the cause?
|May 18 2017, 5:49 AM |
I have seen that before. It is the design of the rocker system in combination with spring pressure. The head is not strong enough for how the valvetrain bolts on. High spring pressure and big ports will eventually cause this. They really need a better way of anchoring the rockers.
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BT casting failures
|May 18 2017, 7:35 AM |
In my experiences, Jay's assessment is absolutely correct. A solution already exists in the T&D inventory but it includes milling off the "as cast" T&D rocker mounts from BT and following T&D's method of mounting their "competition" FE rocker system on a Ford or other OEM-style, pedestal-mount rocker designed head. The revised method includes a 0.600 thick, secondary solid steel bar that bridges the intake port roof castings and ties all the upper head bolts together while also providing the mounting points for the previously included T&D adapter bar/plate for mounting the rockers. Obviously, this method removes all the valve spring opening load from the cylinder head casting and transfers it to the head bolts. While the HR head presents a worst case scenario for this problem I believe it exists, to some degree, in all the BT heads employing their supplied T&D mounting bosses. This is not a new phenomenon for the HR head design and was seen in many lower-end engine failures beginning in 63/64 for those who have been racing them that long. In defense of BT quality, when these designs were conceived, likely, NO one imagined they would be running with 400# seat and 1100# open pressures. If your application is less aggressive that simply means you can run more cycles before failure but no guarantee that it won't fail.
Is this something only seen with the BT HR ....
|May 18 2017, 7:22 AM |
and not yet seen with a BT MR head, and I perhaps only with roller cam spring pressures?
I have seen this a few times so far
|May 18 2017, 8:29 AM |
Once on Jim's heads and once on a set of my own, and once on a medium riser set. All the ones I have seen are on pretty serious solid roller applications, although I have never gone to that 400lb spring level on anything here - probably 100 lighter than that at the most.
When I saw it on mine I assumed it was because I had radically milled the intake face when I made other changes. I think its a twofold issue - the head bolt insert area give the crack a "place to start", and the rocker load gives it a "reason to happen".
I have not done it - but suspect that we could fabricate a mounting plate that would go to the root of the rocker boss holes and leave the rest of the head unmodified.
Re: I have seen this a few times so far
|May 18 2017, 9:43 PM |
Pretty sure those heads are on one of your shelves?
Can I please send them back?
Every time I see Marcella he makes fun of me for having them - something about building a Pontiac.
old castings are a little weak there, new one are beefed up a bunch
|May 18 2017, 10:42 AM |
I have seen and measured the differences between the two castings side by side. They beefed up around the end head bolt holes from top to bottom, water jacket is smaller in that area, also all along the top where the rocker stand bolts to, there is more meat and there is also a "bridge" or gusset of aluminum that goes from the rocker pad at the end of the head over to the front and back valve cover rail, past the end head bolts. There is more material in between "rocker pads" where the other head bolt holes go, bridging across there, basically running continuous across the entire head even past the end head bolts, versus having 4 separate pads between head bolts, big difference. The new castings weigh 2 1/2 pounds more than the old castings. I have pictures of the two side by side but can't post them at the moment.
Also those particular heads (I took those pictures, but not to post on the web...) are the old castings that had issues, they were also angle milled over .100 and that took meat away from the already weak corner head bolt area, because they angle milled the intake face as well as the deck. Those heads also had 420/1140# springs and .850'ish lift, ran 8400 RPM for years... were the older castings and were replaced by the newest revised BT HR castings run 3 years ago. The new heads (same port program) and new intake made 168 more HP than before, 1087HP versus 919.
|This message has been edited by XR7 on May 18, 2017 11:01 AM|
|May 19 2017, 4:20 PM |
You state that new BT heads make a heck of a lot HP over the old ones. How can they if they have the same port configuration as the old heads? I believe the billet cant valve heads put a lot more HP than the in line wedge heads. Reply. Thanks
Wasn't the heads as much as the
|May 19 2017, 6:24 PM |
carb and intake upgrade as far as I know.
|This message has been edited by Posi-67 on May 19, 2017 7:44 PM|
What is THAT going in?
|May 19 2017, 6:38 PM |
I see a front sump pan, so maybe a certain Cougar?
|May 19 2017, 6:55 PM |
That was Jim's engine on the dyno, not mine. I just changed the whole top end, and a timing belt, that was all.
It was a lot of little things...
|May 19 2017, 6:53 PM |
not only the heads, but they were 28 CFM better than before at some lifts, just better everywhere. It was the same CNC port program, newest HR head casting, different valve job, and I rubbed on them some more, had 30+ hours into the manifold adapter and intake. Changed a lot of valve train stuff. I'll keep the other things to myself, unlike some guys.
The billet heads do make more power, should have been a lot more... but so far hasn't showed it. Jim's HR made 1087@8200 and the only N/A billet head engine that has been dynoed made 1112@7700 built by Kuntz. That engine was a 528, Jim's was a 496 so... if you do the math 1112 / 526 is 2.11 HP per CI, 1087 / 496 is 2.19 HP per CI. The billet head "should" have made way more power... in my opinion, but with only one example (the only billet head FE engine built) did not.
|This message has been edited by XR7 on May 19, 2017 7:04 PM|
Re: It was a lot of little things...
|May 20 2017, 9:11 PM |
That is enough power to have won races in Pro Stock in the early 80's. Something nobody tried with an FE in the 500" era. Pretty impressive.
Old News Tom...
|May 21 2017, 10:12 PM |
Since I posted the pictures and Dyno results last fall. I wasn't there nor had anything to do with the result but am pretty good on passing along info.