No power below 2.6k RPM

[iani]

I got my car back from the garage who fitted my new clutch, replacement engine & reconditioned PI equipment today. The engine is of unknown provenance beyond that it obviously hasn't done many miles, the rotating assembly has been balanced, the bearings are of good quality and there is a vernier cam disk fitted. It is reasonable to assume that the head has probably received some work and there was a phoenix manifold & sports exhaust fitted. Without removing the cam, we obviously can't tell which type it is, however, I have very little power below 2.6k RPM, obviously this makes moving off a dangerous exercise on the road. Once I hit 2.6k the engine transforms, goes to 5k in no time and it feels like there is more to give. Could this be a race cam and therefore unsuitable for road use I wonder?

[stuart]

Sounds like it, what tappet clearances is it running?

Stuart.

[iani]

Sounds like it, what tappet clearances is it running?

Stuart.

I don't know, they were set by the garage, not me, the top end sounds quiet.

[stuart]

I don't know, they were set by the garage, not me, the top end sounds quiet.

Large tappet clearances often give a clue to a non standard cam, Thats what they are supposed to be and would be quiet.

Stuart.

[Austin Branson]

+1 for Stuart's diagnosis.

[Steves_TR6]

Yes, my cam runs 24thou clearances, i couldnt believe it was right but it is.

 

Think you jeed to identify the cam to know how to proceed?

[iani]

Yes, my cam runs 24thou clearances, i couldnt believe it was right but it is.

 

Think you jeed to identify the cam to know how to proceed?

Yes, I think you're right, I don't want to waste any more money on labour charges though, I need to consider how I approach this. I currently have issues with the PI system too, it has all been reconditioned but came with a modified throttle linkage, it seems to be binding once warm, I need to sort this too.

[Graham]

could you not use a dial gauge to determine peak lift at what deg for inlet and exhaust, then from that you could determine the duration. Once you had all this then it would be a case of looking at all the cam specs to find what cam you have fitted. Would say this is quite important as if you have a 'hot' cam that need large gaps and you are running it with to tight clearances you risk burning valves or ruining the cam.

 

I know that in the 'Locost' race fraternity they have a jig of some sort that they use track side to determine what cam is fitted to the competitors engines as some competitors where taking control cams and having them reground to a 'hotter' profile

[TriumphV8]

Its very easy to determine what type of cam is in:

 

Measure the valve lift at the TDC where both are open.

 

Beyond 2.5 mm I would say reason can be the cam.

 

Also you can check if lift of both is same height.

Only Kent or Bastuck has Inlet a bit more open.

If more than 0.5mm is found I would check the timing.

 

Next is ignition, at 2000 rpm 20 degrees ist not bad.

 

Next is AFR it should be 13 in the are where the engine

should perform.

[iani]

Thanks for the tips, a much more knowledgable register member is coming round later to have a look with me. I did go for a run earlier with my AFR sensor in the tailpipe, at low revs the reading was everywhere from 12.5 - 20, with the car sat at 78mph, I had a tighter range of 14.5 - 14.9. The throttle linkage is binding when hot on at least two of the rods, I have a cold idle of 1k RPM but when hot it is c. 2k due to the rods expanding, I'm mulling over changing them for rods with spring loaded ends, I'm also trying some high temp lubricant.