• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

TR2/3/3A Vacuum Leak at Intake Manifold

Share this page

mgedit

mgedit

Jedi Knight
Country flag
Offline
Think I have sorted out why I could not get my 56 TR3 to idle. Identified leak at intake manifold using propane. When I took manifolds off, the new gasket was clearly "compressed" at the exhaust manifold, but not at the intake. All bolts seemed snug and gaskets were new. Suspect that studs that hold the two manifolds together may have been limiting movement of intake manifold and not allowing it to seal properly. Anyone experienced this before? Are those studs essential or can I do without them? As a side note, I was surprised that the new gaskets delaminated and will need replacing. The car has not run for more than 20 minutes or so as I've fiddled with carbs, but the gaskets are toast. Is there a recommended suplier or brand of gasket that might be more durable, or is delamination just par for the course? Cheers, Mike
 
Hey Mike,

When I initially tried to start mine some time ago now, I could not even get it to fire as the intake was not seated properly. Fixed that problem and it started right up. Glad you found your issue. Did you resolve your brake issues?

Cheers
Tush
 
Unless one of the manifolds has been machined, I don't see how the interconnection would be a problem. What I have seen happen is that the intake hangs up on the two pins, and doesn't seat well on the bottom. That said, I don't think not having the two manifolds connected would be any problem, people running headers don't have that connection.
 
Darrell_Walker said:
... That said, I don't think not having the two manifolds connected would be any problem, people running headers don't have that connection.
Click to expand...

Just as a cautionary bit of information, if you do decide to put headers on like I did. Do not forget to remove the two studs on the bottom of the intake manifold. I left them in, and one of the studs bottomed out on one of the header tubes (put a small dent in it), and wouldn't allow the intake to seat properly. It looked fine, but caused a massive vacuum leak.

IMG_0583C.JPG
 
I'd suggest doing a test fit without the gaskets. That should make it quite obvious where the problem is. I've seen intakes where someone didn't get it lined up quite right with the pins, which then turned up a burr inside the hole that kept it from seating all the way.

The delamination says to me that you also had an exhaust leak, which sort of suggests that the studs between the manifolds aren't the problem. Another fairly easy check is to lay a flat edge across the ports and look for any place it doesn't touch the manifold flange. The flanges sometimes warp. When I have a head off for rebuilding, I like to also remove all the studs (and the pins), so I can check the head surface for flatness. It's common (in my experience) to find high spots around the stud holes.

I've run for many years without the connection between the two manifolds, which doesn't seem to have caused any mechanical problems. I could be mistaken, but my belief is that the factory did that to conduct some heat into the intake manifold, to help prevent fuel from puddling inside the manifold in cold weather (and when the engine is cold). Many American cars of the period also had a "hot spot" between the two manifolds for the same reason, although most of them actually had a thermostatic control to reduce heat once the engine was warm (aka heat riser valve). I've never had the TR3 carbs ice up, but I have occasionally had a stumble that I think might have been caused by liquid fuel laying in the intake.

But you live a lot farther north than I do, so it may be more of an issue for you.
 
Thanks all for the good suggestions. Think brakes are sorted for now Tush, but still looking for options to fit the stainless hoses. Trying to track down some extra banjo bolts for front connections that I can have modified. Randall, I don't think there was an exhaust leak as the gaskets were "indented" evenly around the exhaust manifold and seemed to be well sealed. No indentation around intake so could well be the pins. Definitely further north but that just means driving season is shorter, don't think icing should be an issue. Cheers, Mike
 
Back
Top