Does anyone know how you can tell if a carb base mod has been done?. I had a 1.7 previously that had had one done as i had the dealer paperwork proving it. I had so few problems with the car that i took no notice, i can't remember having to ever take the air cleaner off!. The 1.7 i have now has volvo history saying a carb mod needs to be done, but none confirming it has been done. I think it may be a thick piece of rubber between the manifold and carb but can't be sure. It is running so poorly and mpg is so bad that i think it may be the old warping problem.
I have tried everything i can think of all bolts are tight, all filters have been changed, new plugs, dizzy cap and arm. Unless i am missing something.

use a blowlamp or WD-40 spray round the baseplate area with the engine idling. If the engine running alters at all, then you've found an air leak.

If there's an air leak, the carb base is probably warped, you can confirm how much by checking against a straight edge. Check the flange on the inlet manifold as well. The new baseplate is a green colour and a thick chunky affair, about 2 inches thick. The original baseplates were quite a bit thinner. and a different colour....black springs to mind but I can't be sure.

You can get a thick piece of rubber between them, but not sure if that counts as Volvo's official mod! I thought they just put the thicker gasket on the later ones, but thats not substantiated I'm afriad!

Nice one thank you i will try the wd40 at the weekend. There is a very thin almost non existent gasket on there now. I really like the car (sold my first one in a crazy rash moment) but it is frustrating the hell out of me!

how did it go with the carb test?

great that volvo changed the colour of the gasket from old to new. easy identification - nice one!

Didn't get to do carb test as car is now off the road due to a problem with the prop - needs new one!!!, once that is done the carb is coming off so i can strip it down and hopefully find what the problem is.