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Discussion Starter · #1 ·
I built and broke in my 7m last year with an hx35 on 550cc injectors. This year I swapped to ID1000s and an Hx40, finally got the idle dialed in, went out to road test and suddenly lost compression.. Pulled it back to the shop to find that the Intake Technico cam gear dowel pin was ingested into the #1 intake cam cap... I sent the head and my back up head out yesterday to the machine shop. I've heard of BC cam inconsistencies in the journal sizes so I'm not sure what caused it.. The exhaust side seems fine. Very disappointed, but hopefully can be fixed.
The cams were a 272 stage 3 PN BC0322. Anyone else have something like this happen. Trying to stay motivated as this really blows.
I cut no corners and spared no expense on the build. I did the quake mod, the zulu mod, arp and forged everything. I had all assembly done at the machine shop, I only put the head and block together...
We will see what they say...
 

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So, I just put new cam gear dowel pins in my 7M a month ago as part of my rebuild. There is physically no way that can happen as the dowel pin should be trapped in the gear by the subsequent installation of the large, flanged cam bolt that holds the gear on. The bolt covers the dowel pin to trap it.

Are you saying the dowel pin is simply sitting in a hole without being physically secured? There's no way they were dependent upon an *inconsistency' of fit. No way. I'd be very curious, and feel unfair saying this, but suspect the dowel came from somewhere else - accidentally left in there from the build or something. Did you take any pictures of the part before bringing it to the machine shop? If you suddenly lost all compression, then I'll further (and potentially unkindly) suggest you forgot to install the dowel pin, and the cam gear suddenly slid without the dowel pin to restrain it. I'm noting you did not say "Lost compression on #1, but in fact ALL compression (on all cylinders) which would fit that error. Either way, I'm bummed it happened and hope to continue helping you along here.

One comment I'll make is that the dowel pin may have scraped things up a bit but don't accept the shop's diagnosis of "your head is scrap, your cam is scrap" if that's what they say. FIrst show us pictures as we've all seen damage that in real operation barely affected anything vs a shop's position that "everything must be perfect for it to leave our shop" because they're spending customer's money, not their own.
 

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I'm also highly confused.
The dowel pin should have no way to move backwards as it's a blind hole. (Or should be)

If the BC cams did not have a blind hole, they should be paying for a new engine.
Or the engine builder should have caught the issue before it was assembled.
 

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Discussion Starter · #4 ·
I'm also confused... it may have been just cylinder 1 lost compression, I didn't compression test. I went to check tdc and noticed intake came did not move with when it was turning over. I didn't take any pics I wish I would have... it was on the #1 intake cam cap there was smeared metal. On the back side of the cam gear the dowel pin elongated the hole and was smeared around on the back side of the gear. I have no idea what happened. No noise, no tapping, a 14.7-15 afr at idle. Was going about 30 mph in 2nd going to 3rd put it in gear and it basically shut off. Nothing in the oil pan, pistons & cylinders look clean. There is some scouring on the journals of the cam and cap.

I'll keep posted, it seemed to pass the finger nail test on the journals so I'm hoping they can clean them up. It was so unexpected and shocking that I didn't even take pics. I pulled the valve cover, saw that. Cringed and had the head off in an hour and a half. Called the machine shop. I'm trusting they will take care of it I've brought them lots of other work through the shop.

I did of course check flEbay and car-part.com and there are next to no heads available anymore so fingers crossed 1/2 of my heads will be good. Wish me luck...
 

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@Z06gette

Lets get some basics.
1. What did you torque the cam bolts to? I have seen what you describe happen in two cases. One the cam bolt were not torqued down properly. Two. Cam bolts where over torqued past thier plastic region.
2. Was the cam bolt AND washer installed?
3. Dowels pins, were they the originals from the oem cam gears?
 
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Discussion Starter · #6 ·
I did everything per the tsrm, I printed it out and went step by step with a snap on 3/8 torque wrench. The bolt and washers were used for the gears. The ? Is I think they were the original dowels because I didn’t t have new ones with the bc cams.
where can I get replacement ones for take 2?
 

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Discussion Starter · #7 ·
The washer was moving on the gear at failure I could see some witness marks. I’m curious if it over spun from the cam stopping or did it the pin fail and cause the gear to spin? Machine shop should have it there Monday afternoon, they estimated a week turn around time.
I am relieved you guys are on here, not having SM up and running has made this spring much more difficult.
 

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Which snap on-torque wrench? Digital one? Regardles if is digital or click type, When was the torque wrench calibrated?

i am honestly surprised that the BC cams did not come with their own dowels. Might hit up toyota to see if they still have them.
 

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Discussion Starter · #9 ·
I’ll try them. It’s a newer digital one it calibrates every time you use it. Thing is I did them the same and the exhaust is fine.
 

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Oh you snapped a dowel in half?
Dang.
What spring load are you using on the valves?

That's very strange.
 

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I’ll try them. It’s a newer digital one it calibrates every time you use it. Thing is I did them the same and the exhaust is fine.
I use CDI torque wrenches (which is who makes the Snap-on torque wrench). They do a self calibration BUT they still have to be calibrated after X hours/# uses.
 

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Discussion Starter · #15 ·
That I’m not 100% on, it’s my bosses I don’t personally own one. No I didn’t, I’m kicking myself for not. In the moment I was just in shock. Tore it down put it in my trunk of the daily and proceeded with work ( I work at a shop). I was just disgusted honestly.
 

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It seems like the cam may have seized. That would be the only way I see a dowel snapping. Maybe need to look closely at the cam bearing clearances. Those upper cam bearing caps wear especially torwards the rear far from the oil feed and need to be lapped and honed.
 

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You mentioned 272 cams.

What lift?
 

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So, Toyota still has the dowels and they're like $1.69, P/N 90250-05121. My dealer got them in a couple days so you might order them in advance, though your shop may either stock them or have a source.

So the dowel snapped. And in only a small number of miles, too. Even with heavy springs, I can only imagine that would simply accelerate wear on the cam journal caps if the cam gear was secured.

Edit: So, I saw somewhere somebody put new cams and gear on their 7MGTE head and the bolts on the back of the aftermarket cam gears interfered with the head, or a bolt or something back there. It was a straight up manufacturing or design error. The only reason they caught it was they took the gear off for something and saw the witness marks. Tossing that out in case your intake gear was rubbing on something on the back side. Otherwise, it's going to come down to the gear's bolt not being torqued correctly or not holding its torque correctly which would or could be an issue with the gear/cam interface - not your torque procedure. That the other cam's gear install went correctly would have me staring at the machining on the gears, the fit on the cam nose, etc, etc. All it would take is a machining error on the intake gear.

If your shop gives you any business about the cam or head being unserviceable be sure to jump on here with pictures and get advice.
 

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Discussion Starter · #19 ·
Definitely will do, that's really the only thing I can come up with at this point.
Figgie, they're BC 272 I think the valve lift is 08.68mm per BC.
 

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Definitely will do, that's really the only thing I can come up with at this point.
Figgie, they're BC 272 I think the valve lift is 08.68mm per BC.
I saw that, nothing crazy lift wise.
That leads me to think either machining issue on the cam, mechanical issues on the install (for instance, i know that the AEM cam gears require the bolts that hold the back plate be removed as they interfere with the cam gear). It could also be a out of cal torqure wrench but it must be out by a lot so the probability is less than the other two.
 
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