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was it valve bounce?
02GF74 - 30/4/07 at 09:43 AM

got 1300 crossflow, twin dellortos, dunno about the internals so am assuming standard cam and standard head.

I am thrashing the engine a bit and have taken it to about 7,200 where it started to become much noisier and seemed to loose power - is that likely to be due to valve bounce? ( can't remember what the haynes book gives as red-line).

ned - 30/4/07 at 10:21 AM

at those revs the standard cams will probably stop making power won't they?

Fozzie - 30/4/07 at 11:29 AM

quote:
Originally posted by ned
at those revs the standard cams will probably stop making power won't they?


Absolutely right Ned!

02GF74, mine peaks at 6250, anything over that no more power, so no point!
I have my red line on my rev counter at 6200.

I rebuilt my engine to the limits of the 750MC Locost regs, so if yours is a standard engine, without any work, then I would be very surprised if your 'red-line' was quite as high

HTH Fozzie

DavidM - 30/4/07 at 11:58 AM

Peak power of a standard 1300 is at 5750 RPM.

I don't think mine would rev anywhere near 7200. Are you sure the noise you heard wasn't bits of metal landing in your sump?

David

procomp - 30/4/07 at 01:20 PM

Hi if it is valve bounce. It will have a definate change is sound when it happens and feel like a soft cut rev limiter comming in.

Almost all of the 750mc locost race engines rev to over 7k regular but need valve springs checking and installing correctly. When it is done properly a good engine will rev to 7800 before valve bounce occures but will need checking for spring poundage quite often.

For road car use 7k should not be a problem if valves and springs are instaled properly but as said above power is long gone.

cheers matt

Ivan - 30/4/07 at 02:25 PM

If memory serves me right - about 38 years ago I used to take my lightly modded 1300 GT Escort to about 7500 REVs.

Will agree that power fell of noticeably above about 6800 revs.

Eventually wrote it off going to work one morning by hitting a mountain head on and going A over kettel twice before rolling back down and ending on the very crumpled roof. - got the day off work to sort out mess so was almost worth it . Had cancelled insurance two months before

02GF74 - 30/4/07 at 03:38 PM

going by the things said, I don't plan to do it again but the noise change was very sudden - can't really describe unfortunately.

Read the crossflows can be pushed to 11 K (obviously proper tuned jobbies) so didn't think 7.2 K was that outrageous).

Memphis Twin - 30/4/07 at 04:50 PM

I really think that you need to read A G Bells book on 4-stroke engine tuning....

ned - 30/4/07 at 06:10 PM

a 10,000 rpm xflow is very very serious money to be put together properly with all the right bits to ensure some sort of level of reliability...

Ned.