Triumphrat

Motorboy · 03-25-2007, 11:21 AM

Does anyone have a source , such as magazine road tests, of the the plotted Torque curves of the stock 790 and 865 engines ????

As I have gathered from this forum, the exhaust cams of the 865 are timed differently which give more torque at the expense of high end power compared to the 790 cam timing....8% more displacement with 15% more torque for the 865

I have a 790 and have acquired a set of 865 barrels and pistons with which to play mix and match....any thoughts are welcome as to what setups would work best.....Robert

sweatmachine · 03-25-2007, 11:22 AM

I'd toss the 865 stuff in the trash and buy a wiseco 904 kit.

bonnieblackinfl · 03-25-2007, 11:55 AM

Sweat is right, if you are going to go through the hassle of a teardown, you might as well spend $400 on a BB. You already have a spare cylinder, so there won't be any down time.

Or you can send the spare to me so I won't have any down time :hihi:

I'll even pay for the shipping!

Greg :-D

rodburner · 03-25-2007, 12:53 PM

I think he meant to say that he has a spare 865 top end that is going to be bored for the 1100cc kit and he just wanted to rub your noses in it.
Right? :-D

Motorboy · 03-25-2007, 02:31 PM

The 1100cc setup is a hot little number alright....but I was thinking of advancing the Ex cam one tooth so it will open earlier in the power stroke and close earlier decreasing valve overlap.

After that 25 hp(and up) shots from the the blue bottle till the 790 pistons don't like it anymore then install the 865 barrels and repeat after tweaking the spark advance down a bit...

Lastly the 904 setup in the old 790 barrels and a back down off the juice to a sane NOS shot size determined from steps 1 & 2....

As I see that some are already on the juice,,,,I could forgo all this testing if NOS shots sizes are already common knowledge for this engine.....Robert

amanger · 03-25-2007, 05:54 PM

Id be just putting the 865cc pistons and barrells on with the 790cc camshaft.That way you will have the best of both worlds.The 865 extra grunt and the 790 top end.
:wink:

bonnieblackinfl · 03-25-2007, 08:53 PM

Quote:

On 2007-03-25 12:31, Motorboy wrote:
The 1100cc setup is a hot little number alright....but I was thinking of advancing the Ex cam one tooth so it will open earlier in the power stroke and close earlier decreasing valve overlap.

After that 25 hp(and up) shots from the the blue bottle till the 790 pistons don't like it anymore then install the 865 barrels and repeat after tweaking the spark advance down a bit...

Lastly the 904 setup in the old 790 barrels and a back down off the juice to a sane NOS shot size determined from steps 1 & 2....

As I see that some are already on the juice,,,,I could forgo all this testing if NOS shots sizes are already common knowledge for this engine.....Robert

As far as I know, I'm the only one that has went the nitrous route, I'm still in the tuning phase, but the rule of thumb is no more than 50% of the stock hp rating with cast pistons, therefore a 30 shot is max for me right now. I plan on building my 904 w/carrillo rods and run a 75 shot, stock rods are good to 100hp. A typical 904 kit produces 80-85hp, which would leave a 20hp shot on the table. If you go with the bottle, build your engine so you can play. :-D

Greg