The Cal-look Lounge

Currently in the process of upgrading the engine from my drag car ( The Jagerbug)

I’m changing the 2276 (82x94) engine from Cb 044 heads to some secondhand superflo heads I picked up a while back

The Superflos have been flycut somewhat so have a chamber volume of 30cc which is pretty small, I want a final cr of about 12:1

Current deck height is 0.90 mm

My calculations so far take me to using a 1.5mm copper head gasket (gives another 11cc according to my maths) which gives a top end volume of 41cc
Using a 0.5mm cylinder spacer drops the deck to 1.4mm

According to the Jmr calculator this gives a CR of 12.2

Does this sound correct ?

Engine runs FK89 , 48 Ida’s and is not street driven - just want to up the breathing with the bigger valve better flowing heads

Cheers Alex

I make that 12.4/1

Forget all the calcs for 1.5mm copper to cc, its just deck height in real world so

deck height is 0.9+1.5+0.5mm= 2.9mm[ which to me is way to much for a N/A race engine]

head cc 30
with 94x 82 on jmr calc shows 12.4/1

cheers Richie

So with a deck of 1.4 and 30cc chamber I get a comp ratio of 15.3 /1

To drop that further would I be better off machining pockets /dishing the pistons ?

Cheers Alex

If the superflos has been running a lot with 30cc chambers, they could be pretty tired.. Depending on the year of production, the aluminium is pretty "light"..

Hold a SF in one hand and a new competition eliminator in the other. The difference in mass is pretty obvious..

Would you need valve notches as well? Do you include the cc for them as well in CR calculation?

Hadn’t considered valve notch capacity - although thought they might be necessary, I suppose a decent pocket machined
In the piston crown would solve the need for valve notches and decrease CR

Ok - so rather than increasing the deck, if I machine a 70mm dish 1.5mm deep in the piston crowns then it will gain 5.6cc into the combustion chamber, then keeping the deck at 1.4mm that gives 13.4 compression - sounds more reasonable ?

If it was my engine, I would increase the deck height, notch the pistons accordingly  and the compression ratio is what it is. It’s a race motor so you’re going to be running race fuel so high compression ratios won’t be a problem.

For mine it was unshrouding the valve. Then, dishing the pistons to match.