I know im going to get some stick for this from you lot but bear with me on it....

Basically im looking into building a new engine. 1.8XU bottom end with a gti head. Reason being, 1.8 engine is short stroke and revs very very nicely. problem letting the entire 1.8 down is the head. Its stupidly restricted, has crap cams and small valves. Looking to start building the engine next month with the intention of finishing it off with mapping this time next year (sort of a background project).
Biggest problem ive come across is the 1.8 bore is 83mm and the gti bore is 86mm meaning there will be a lip at the top of the bore of 1.5mm either side (so would look a bit like a mushroom in a cross section). Im not worried about valve clearance as i know its not a issue. The thing im not so sure about is will this lip in the combustion chamber be a problem?
Any views on this, im happy to listen to. This is going to be a big learning curve for me so any advice/criticism welcome!

i thought the gti engine was a 86mm bore? Mind you, i did get that info from the haynes book of lies so wouldnt surprise me if its wrong!

The gti valves are bigger than the 1.8 ones. Ive got both heads sitting in my shed at the moment so can get pics. As youve said, the 1.8 inlet ports are very restricted. I did port my old 1.8 head and it made a nice difference but never got as far as cams.
you sure the gti valves wont cope with more than standard? im sure ive read several people that have built quite high power gti engines still with the standard valvetrain!

Thanks for that. Both the RS and j4r engines have a 86mm bore correct? If so, surely the cutout (sorry not a technical term...talking about the dome in the head) will also be 86mm diameter meaning when bolting it to a jp4 bottom, there will be a 3mm difference?
Tbh it's been so bloody long since I've looked at the head, I've forgotten what iT looks like in detail.
Cheers

What do you mean running? Your car never runs does it! :

Good to know. Tbh I have also been looking into turboing it. Just deciding if I want to spend the extra money.
The whole point of this engine is to try something different. Most 306 owners just buy a gti lump and bang a supercharger on the front!

no, 86mm purely refers to the bore of the block, I just measured both XU7 and XU10 cylinder heads and the chambers are both 82mm across.

Stan's post is totally irrelevant as he's running boost (or would if he ever actually drove it, I don't believe it even exists tbh)

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Bring on the Trumpets.

It is getting ready to come back out mate, it'll be at FCS and Pugfest next year.

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"Supercharged - 454.1bhp/317.5lb/ft"
Peugeot 306 GTi-6
2000 (X), Moonstone

Don't assume anything read the links

________________________________________

need a part number? get on here - http://public.servicebox.peugeot.com

Bring on the Trumpets.