View Full Version : Wedge TR8 Cam Lobes

05-26-2011, 10:15 PM
I have heard that the cam lobes of the TR8 frequently wear prematurely. I will be looling at a TR8 for purchase and would like to know how to detect if the lobes worn. Would worn lobes result in an engine miss? Is it necessary to take a compression test?


05-27-2011, 06:33 AM
The cam lobes wear because it is a flat tappet camshaft. Modern oils are not formulated for the high forces exerted by the cam lobe pushing on the lifters. Modern cars use roller set ups. The crucial additive in the older oils is ZDDP. Oil manufacturers have greatly reduced the amount of ZDDP in their oils because it has been found that the additive leads to premature failure of catalytic converters. A compression test won't show you the effects of a worn cam lobe unless the lobe is really really bad. The engine doesn't spin fast enough in a compression test limit the amount of air getting into and out of the cylinders. The only way to test for worn lobes is to remove the valve covers and check how much the rocker arms move as the lobe for that particular valve comes around. If you are thinking about buying a TR8, plan on changing the cam anyway. Too bad you are 3000 miles away. I just finished restoring a nice TR8 for the wife. Now that it's done, she's decided she would rather have another TVR. I sold the last TVR she used without checking with her, and she was a little miffed. While I'm looking for another TVR, I'm toying with the idea of selling the 8. Problem is the 8 came out so well, I'd like to keep it for a while. They are great cars when properly sorted out. Good luck with the search.

Mickey Richaud
05-27-2011, 06:38 AM
Todd -

If you do end up selling, let me know. There's a guy in Nashville looking for one.


And no, Don, I'm not the guy... :smirk:

05-27-2011, 07:29 AM
Can you remove the rocker assembly all together and use some sort of measuring device to check cam dimensions?

I ask because I would love to see just how worn my camshaft is. It is the original one and has many, many miles on it. Car runs and idles perfectly so I hate to just tear it apart becuase they are "supposed" to be bad.

05-27-2011, 10:29 AM
You can use a dial indicator to measure how much the valves depress or open. Stock rocker ratio is stated to be 1.6, but actual is more like 1.58. Most cams for the Buick/Rover have a stated lift based on a 1.6 ratio. To get actual lobe dimension, divide the valve lift by 1.6. Preload on lifters and lifter squish will affect the numbers you get, but the readings you get will be sufficient to tell if there is a problem lobe or two. Once they start to wear thru the hardened outer layer of metal on the cam, they wear down rather quickly. You could remove the rockers and pushrods to get readings directly from the tops of the lifters, but that would be difficult and risky. There is always a chance one of the pushrods could fall into the valley of the engine. I had that happen recently and was lucky enough to pull it out with a magnet. If you are going to swap out the intake anyway, you can just look down into the cam and check it visually once the valley pan gasket is removed before going to all of the trouble removing the front cover.

05-27-2011, 10:33 AM
Just for my future reference, can the cam be changed with the engine in the car?

05-27-2011, 10:35 AM
I did mine last year Darrell,not to hard

05-27-2011, 11:15 AM
Yes. You need to drop the radiator and fans, remove the intake, valve covers, engine balancer, front cover and everything bolted to the front cover except the water pump. To put back together you will need a new valley pan gasket and rubber end seals(about$50), oil pump gasket, change of anti freeze and engine oil, new front cover seal(about $10), and probably new valve cover gaskets. You'll probably end up changing the t-stat and hoses since your in there, maybe even do the pan gasket since you probably tore the front of it removing the timing cover. You will need to pack the oil pump with petroleum jelly to prime the pump for initial start up, and you will need a cam break in lube like ZDDPlus. You should change the oil again after break in. Warning- it's hard to just change the cam without wanting to upgrade all kinds of other stuff. Could be leading you down a long dark expensive path. Mods on a TR8 are like drugs. Once you do one, you end up wanting more and more. Next thing you know, you have a car with thousands of dollars in mods, but a much faster fun to drive car.

05-27-2011, 11:40 AM
Warning- it's hard to just change the cam without wanting to upgrade all kinds of other stuff. Could be leading you down a long dark expensive path.

Yes, that is something I'm very familiar with. I really had to control myself on the current projects on the TR8, and focus on the goal of a daily driver. For example, I pulled the diff cover off to change the rear end oil. Since it was off, I cleaned it up and repainted it. But it looked bad with a nice clean cover on the dirty axle, and it was about all I could do to not pull the rear end all the way out and clean and paint (hey, I had all the suspension apart, so really the only think holding it was the drive shaft). Of course, that probably would have led to rebuilding the rear end "just because".

05-27-2011, 11:53 AM
Darrell, that would have led to a 8.8 Ford

05-27-2011, 12:02 PM
Darrell, that would have led to a 8.8 Ford

No doubt! And the rear disc brakes, changing the bolt circle on the front hubs to match, another new set of wheels......

05-27-2011, 12:05 PM
Here's what you need for the rear disks with your rear.

05-27-2011, 12:26 PM
Here's what you need for the rear disks with your rear.

You are going to get me into (more) trouble :smile:

05-27-2011, 12:29 PM
My guy ,about 2 miles from, who does AL. fabrication has it saved to his computer so he can whip you up a set

05-27-2011, 02:34 PM
Don, that's sweet. I might need a set "just because". What calipers and rotors are you planning on using? Ebrake? Every time I get another TR8, I say "I'm just gonna fix this up a little". It always ends up being a complete resto. Being able to do just about anything with cars is a double edged sword. On one hand it's nice to be able to fabricate, paint, tune etc. because you don't have to pay someone else to do it. On the other hand you find yourself completely stripping to bare metal and painting cars that really aren't that bad to begin with.

05-27-2011, 02:46 PM
Using the Ford stuff Michael's info said.
SHO calipers and Tempo disk, I believe

05-27-2011, 08:11 PM
The calipers are Ford SHO (1989-ish) due to the smaller diameter rotor that is from a 4 bolt tempo (1986-ish) it has the right radius pads.You can ger cross drilled, slotted and vented rotors for about $100.00 a set. I just got a ford 8.8 rear narrowed for a TR8 and it turns out to have the same caliper as the Fods SHO but the pad radius is for the larger disc brake. The rear is from a 1986 Mustang SVO with a 4 bolt lug pattern.Only thing you need to do is drill the tempo rotor for the TR8 lug nut/bolt pattern. The calipers are cheap too!

05-27-2011, 08:15 PM
Mike , I think you can get larger disk for that SHO

05-27-2011, 08:52 PM
Im sure you can go up on the sizes.

05-27-2011, 09:43 PM
Re read your post .You where talking about pad sizes