blowing manifolds

[f@-pots]

Hi guys, just a wee bit of info. I finally got to do a bit of work on the car today , having stripped the manifolds off(and shearing off three bolts) i thought I'd better at least prep them for going back on again and so started to remove the old gasket material. This quickly led to use of various files and my trusty engineers square but the important bit is what I found may very well be the reason for all the blown gaskets. The mating face of the manifold was something akin to the himalayas ! In some places I found less than two millimetres of flat material surrounding the port aperture. Now I appreciate that material can be eroded as a result of a poor gasket but what I found was that the material was never there in the first place!
Judicious use of the afore mentioned files and much checking with the square resulted in me producing flat mating surfaces not only around the aperture(of at least 4mm) but all the way out to the fastener holes. Ah yes that was it , also I noticed that along the whole 'web' there were discrepancies between the level around the port aperture and the fastener holes.This has almost certainly led to leaks forming because as we all know the idea is that the gasket fits between two flat surfaces not one flat one(the head) and one doing a good impersonation of the pennine way!

My advice would be if you are doing a gasket change,take the manifolds off completely and whip them down to your nearest proper engineering firm and ask them to skim them down flat,i reckon it may save a lot of future grief.
Ta Ta...................

[2Munkys]

There's not a lot of land is there. I've always run a good flat file across the manifold mating faces before fitting new gaskets. Can't think how many I've replaced now.

[f@-pots]

Ah ha . the voice of experience.Righto 2munkeys so I haven't stumbled across the answer. How about making gaskets of a material that laughs in the face of exhaust gas temperatures? I got some T'0' condition (soft) 20guage s/s in my shed ,d'yreckon if I fabricated some gaskets out of that they'd last a bit longer? It's gotta be worth a try..... ?

[2Munkys]

Probably still too hard I'd have thought. What about some nice soft copper or commercial aluminium? Maybe they're on the market someplace already. I don't know how much pinch the manifold bolts exert but, you're going to be limited by their maximum torque load figure; you don't want to strip them. Possibly that figure could be increased if you had thread inserts fitted but that's going to a lot of trouble.

I'm sure there must be someone more qualified than myself to add comment; Steve Heath, GreenV8S for instance. Maybe V8D or some of the other RV8 specialists will have looked at this some time.

[spend]

Are you guys intimating that the flange is warping, or that it was down to faulty manufacture. The flanges I have seen looked pretty strong, at a glance.

Dave

[GreenV8S]

On mine there is a decent thickness sealing around each port. The ports in the manifold were a mile out from the ports in the head, but there was plenty of meat around them. (The inside of the standard manifold is also horrible, with a sharp step immediate before the first tight turn, disasterous for gas flow.

The sealing face would originally have been flat but the manifold and head can both be eroded by hot exhaust gases if the engine is run under load for extended periods with a leaky gasket.

[f@-pots]

Absolutely, but the problem I found was not due to erosion as the missing metal was further outside of the port perimiter,imagine the manifold flange was the shape of the tip of a volcano, lots of meat there but only a skinny bit actually doing the work(in places)

[That Daddy]

spend said:

Are you guys intimating that the flange is warping, or that it was down to faulty manufacture. The flanges I have seen looked pretty strong, at a glance.

Dave

Yes Dave,but you thought an RV8 oil filter flowed filtered oil centre to outer

[spend]

That Daddy said:

spend said:

Are you guys intimating that the flange is warping, or that it was down to faulty manufacture. The flanges I have seen looked pretty strong, at a glance.

Dave

Yes Dave,but you thought an RV8 oil filter flowed filtered oil centre to outer

Arr yoo triing too taik ther pee owt orf mee, shirley knot!



Dave

[That Daddy]

Yes

[spend]

That Daddy said:

Yes

From the man who in recent memory has come out with pearls such as:

That Daddy said:

sorry to be a pain,those top and bottom ball joints one is saab one is daihatsu

I think I even answered correctly politely, no suggestion of left & right even


Dave

Not a word about spellink eiver oh & there are plenty more..

[That Daddy]

Trouble is Dave when your in the trade i go straight to the point,i often forget to explain in laymans termsexcept for youalso i am a ladyboy i might add

Edited by That Daddy on Thursday 16th August 10:27

[TVRleigh]

I had the very same problem with mine, no wonder I had so many bills from previous owner for it going in for Exhuast gaskets. there was so much metal missing I had to build it back up with weld. and then grind and file it back to shape. the thread in the head will stripe very easy. so be carefull when tighting them up. im sure once you have flat surfaces, then the standard gaskets should be fine.