| Author |
Message |
    
John Graham (John)
| | Posted on Thursday, July 18, 2002 - 09:30 pm: | 
|
Well, dealer confirmed what I had suspected, exhaust value in #2 stuck open. I'm going to pull the valve cover to be 100% certain over the weekend.
So I've read all the bench wrenching discussions, but now I need some thoughts from someone who has installed a set of replacement heads.
and information from anyone who has purchased replacement heads and/or had heads machined by a local performance shop (i.e with new guides installed, etc.).
Any help online or offline would be great. I've been around bmw, porsche, etc. but the v8 is new ground for me and though I am confident I can easily swap the heads, I would like to get some first hand experience and insight into tricks/etc.
Thanks,
John
'97 Disco 66500 miles - dealer comment today when I picked it up 'most people don't get that many miles on them prior to the valves sticking' |
MarkM
| | Posted on Friday, July 19, 2002 - 08:36 am: |
|
Don't have any experience, except with chevy heads a couple of decades ago.
I may be in line for new heads mysewlf for the same problem.
I was looking here. Seems like a good buy from across the pond.
Thanks,
-Mark
http://www.rpiv8.com/offers.htm#heads-new |
Paul T. Schram (Paulschram)
| | Posted on Friday, July 19, 2002 - 10:20 am: |
|
Once you get the heads off of them, they're all small block Chevys! Or, in this case, small block Buicks.
Chances are that you will not be able to see much from pulling the valve covers as the amount of opening of the valve necessary to degrade performance is very little. The only time I have ever been able to determine which valve was causing problems (yes, I know you know which one it is) was when the valve spring and assorted valve train components were strewn about beneath the valve cover. I wouldn't even bother with looking for the problem, unless I was going to continue and remove the rest of the top end of the engine.
If you must confirm the dealer's diagnosis, run a compression test instead. Chances are the affected cylinder will have no compression. A leak down test will show little to no retention of pressure.
As Ho would say "Just go for it". Warm up those wrenches and get into it. |
Dee
| | Posted on Friday, July 19, 2002 - 02:39 pm: |
|
Paul is the torque for the new composite head gasket much lower than the old style? |
Paul T. Schram (Paulschram)
| | Posted on Friday, July 19, 2002 - 04:04 pm: |
|
Dee:
I'm not sure and I'm not all that sure of their fix for a supposed failure. With 147K on my truck with original head gaskets and the full complement of head bolts, I wonder if they really needed the "Fix". For that matter, my '95 runs real well with a distributor and the stock valves! As for the torque, I seem to remember having read that the only difference was in the torquing sequence. Again, I'm recalling this from a faded memory, I believe that if you follow the original torque sequence you might run into problems because of where the bolts were left out-again, this is from memory. If it weren't for my boss, I'd have my reference books here and if it weren't for the damned contractors, I'd have a shop and could quit the day job!
Now, if I can just get this damned Defender to run right, I'll be happy! So will its owner!
Finally, I got a new batch of aluminum sheet stock. What was the exact diameter of that cross tube? |
Dee
| | Posted on Friday, July 19, 2002 - 07:22 pm: |
|
Paul,
I have the heads off and ready to reinstall but something tells me the new gasket has less Lb torque, I switched to the composites on the intake and head..
Email me when you have time
Dee |
John Graham (John)
| | Posted on Saturday, July 20, 2002 - 12:29 am: |
|
Please post the torque spec's if you could. I am not certain I am following the thread correctly. What is this new gasket ? Do you have a pre 1994 rover ? My understanding is that rover switched to the #2479 head casting in 1994. This is the same head on both 4.0 and 4.6 rover v8's. This also included a switch from metal to composite gaskets and a smaller 29cc chamber volume (to adjust for the thicker gasket). Additionally, the use of 10 head bolts instead of 14 (if switching the older style to composite gaskets, your to insert the lower 4 bolts, but only torque then to roughly 20 lbs. Tighten the other 10 as per install manual. So the torque settings for anything after 1993 -> should be the same (10 bolt).
Thanks for the help so far, I have calls into the local speed shops to inquire about machine work and installation of new guides, just trying to understand all of my options (also looking into RPIv8 for possible replacement heads).
John '97 NAS disco |
Norm
| | Posted on Saturday, July 20, 2002 - 01:12 am: |
|
Invest in the official Rover V8 OVERHAUL manual (as opposed to the SERVICE manual) and a new set of head bolts. There are differences in the gaskets, head bolts, etc. between the various motors that the parts suppliers always seem to get wrong. Check the factory overhaul manual to be sure the first time.
---Norm |
Don
| | Posted on Saturday, July 20, 2002 - 10:44 am: |
|
land rover uses the new composit head gasket from 94 on,they all use the same gasket.there is a torque sequence but it is basically start in the middle and work your way out.the head bolts are stretch bolts,you need to tighten them down to 15lbs,then turn 45 degrees,then anthor 45 degrees for a total of 90 degrees.the best way is to mark the top of the head bolt with paint after your 15lbs of torque, and after your degree settings are done all paint marks will be facing down.hope this helps...........Don |
John Graham (John)
| | Posted on Saturday, July 20, 2002 - 10:56 am: |
|
Don, yes, this helps alot. I have the sequence. The paint trick sounds good. Thanks, john |
Milan
| | Posted on Saturday, July 20, 2002 - 11:12 am: |
|
up to down is 180 degrees |
Jake Hartley (Jake)
| | Posted on Saturday, July 20, 2002 - 12:09 pm: |
|
As to the original question: DON"T BUY NEW HEADS!!!! The problem can be fixed by a valve job conducted by any competent machine shop. It doesn't even have to be a performance shop 'cause the Rover V-8 is not a performance engine. I don't know what a set of heads costs, but it is going to be a lot less expensive to fix what you have. The problem is execess carbon, not the head itself. New head bolts are cheap insurance, although many folks don't even do that. |
Paul T. Schram (Paulschram)
| | Posted on Saturday, July 20, 2002 - 12:14 pm: |
|
I believe that due to the stretch method of torquing, the use of new head bolts is indicated to insure consistent torquing. Given the high rates of expansion due to thermal influences on an aluminum block/head engine, the replacement of head bolts is a very good idea.
As for Torque specs, the Rover manuals list torque specs for different diameters of fasteners in the back of most sections. |
John Graham (John)
| | Posted on Saturday, July 20, 2002 - 04:06 pm: |
|
Agreed, new head bolts are now on my list. I am exploring the local machine shop valve job route, and have a call into a few differenet local machine shops. This brings up a good question, I realize that carbon is the issue, but exactly where does it normally collect causeing the valve to stick ? Is the carbon collecting on the edges of the valve (between the seat) ? or is the issue carbon build up on the base of the valve stem ?
Ok, well I degress a little.
So far some great information, use new head bolts, mark the top of the bolt to assist in getting proper torque, the shop manual has sequence and torque values. Use a local shop to rebuild existing heads should be most economical solution.
I'll let you know what I find on the last topic.
Also, though I agree the rover v8 is not a performance motor, if I end up going with a local shop to rebuild, I see no reason not to put out a few more dollars to have the ports matched to the gaskets, and have the intake & exhaust ports matched as well. I figure this can only help. |
John Graham (John)
| | Posted on Sunday, July 28, 2002 - 11:23 pm: |
|
So here's the latest news. I have spoken to a local machine shop, looks to be less than $300 to rebuild both heads, and an additional $150 (or so) for the gaskets, and head bolts. I'll be pulling the heads this week, and plan to have things back together by the next week. One last piece of information I found through a friend. A new valve was used to replace the '95-96 valves. This new valve has a grove cut into the stem to clean 'carbon' from the stem where it meets the guide. The machine shop I spoke with was already familiar with this change by Rover, and recommended that we pull the heads apart prior to ordering new exhaust valves. I'll post an end to this story once my disco is back in service, and summarize what I've learned. |
Paul T. Schram (Paulschram)
| | Posted on Monday, July 29, 2002 - 09:32 am: |
|
John:
Buy a tap that matches the head bolts and chase those threads. Head bolts in particular benefit from this process as one will find all manner of gunk in these bolt holes as some of them are exposed to coolant, some oil and in some cases, exhaust gases. Your torque wrench will thank you. Do the same on the head itself also.
As an aside, I try to chase every threaded hole I encounter (now if that doesn't sound bad!). I rarely pull a thread and given the sometimes delicate nature of these engines and blocks, it's real cheap insurance.
When you are ready to put the heads back on, pay attention to what the bolts will be exposed to and choose your lubricant/sealer/locking material accordingly. In most cases,this would be one of the few places I'd suggest a drop of light oil, rather than anti-seize.
Also, when you get your new heads back from the shop, put the plugs in and set the head up so that the combustion chamber is facing up. Carefully fill the combustion chamber with gasoline and check to make sure that your valves are sealing. Sometimes, they will come back and not necessarily seal all that well and a quick lapping will work wonders for initial start-up. You might tell the shop you intend to do this and can they check it for you... |
|
Closed: New threads not accepted on this page