merc 280 drag heads 220 lbs compression

[slippy0217]

I have a merc 280 that has a drag port job on it with the mad efi and 260 electronics. What would be the magic number for high compression heads, i hear everyone saying 220 lbs of compression any suggestions

[John Richied]

I am running something similar to yours… and for a magic compression high; good question?
The lowest compression I would want is 155ish lbs… premium pump fuel with a splash of race fuel.
As for the high… 185 lbs is good! 210 plus has to be BETTER!!! :D

[Jay Smith]

Has allot to do with what your goals are with this engine, how long your planning on it to "last" and how often and how long its ran during a session? Santioned Drag racing only ? Recreational , and sand bar racing ? A 220 lbs compression engine thats ran allot other than short burst is MEGA hard on crank bearings , block saddles , and overall long term health of the engine along with at least $7.00 a gallon race gas to your wallet.

Also the type of hull configuration comes into play with the amount of compression developed and chose to be successfull. IMO The popular VEE bottom boats that tend to "shine" in the mid range and top end portion of the quarter mile track can be hindered somewhat by the addition of tons of compression which will make one hard to set due to the violant nature of the BIG compression yields at the start , also allot of 2 strokes start to labor bind fighting huge compression cylinder head numbers in the upper rpm range , making their move that is normally their best portion of the track in the middle and top of the coarse hindered and lack lustered , as the motor stops pulling fighting the HUGE compression numbers the VEE bottom boat tends to then settle down getting deeper in the water as acceleration slows and quickly starts to scruff off speed and ET's will become slower at that time .. Tunnels I have found on the other hand
( boats with training wheels ) don't tend to roll so bad at the start with big compression and tend to make their moves very early in the coarse and mostly have estabilished an early lead and tend to wait out the oncoming VEE bottom boat that is coming on the top side hoping that the distance of slight lead created until the finish works on their advantage, works sometimes and sometimes it doesn't..

Thats my .02 and hope that helps, that was just a few things IMO to consider when choosing compression numbers..

Good luck,
Jay

[dez nuts]

If you plan to run 1/8 mile or 1/4 put the compression to it 21cc heads on that motor will give you around 220psi and come on extremely well for short runs. If you like to run top end i would keep your compression under 175psi i like to run around 165 psi for top end and lower for river running 26cc heads seam to be real good on realy ported 280;s for top end thats what i run and have never had a problem with them mixing my fuel 50 50 with 110 hope this helps it all just depends on what you are doing and your intentions. Keys Dave:rolleyes: P.S. I have ran my stock drag motor with 32cc heads for top end and ran 132 mph came in changed the heads to 21cc went right back out after changeing the fuel to straight 110 and lost 2.5 miles per hour so high compression isn;t always the ticket.

[slippy0217]

thank yall all. I have a stv river rocket and planning on running just a quarter mile drag racing maybe the 1/8 like at the byuboyz river run. i occasionally once in a while might drive to my camp but that is only 4 miles from the launch

thanks a lot
Cody Roussel

[slippy0217]

what cc heads yall think imma have to use to get 220 compression and what octane fuel imma have to use

[slippy0217]

any suggestions

[Jay Smith]

Stock port and deck height maybe a 21 CC head to yield 225 ish , fuel requirements has allot to do with altitude , I'd say safe 108 @ Sea Level when I raced I ran 225 + compression and when they would let you run your own fuel I ran 4 gals of 108 Phillips Racing Fuel and added 1 gallon of super unleaded , ran great and NEVER EVER detonated a piston turning 10,000 and 27 degress timing total..

Good luck,
Jay

[stoker2001]

. I have ran my stock drag motor with 32cc heads for top end and ran 132 mph came in changed the heads to 21cc went right back out after changeing the fuel to straight 110 and lost 2.5 miles per hour so high compression isn;t always the ticket.
2.5mph loose doesnt seem much when you are at a buck thirty:p
Could be your air/fuel ratio is off with the tight heads?
Bet your elapsed time to 130 with the 21s was alot shorter:eek:

[T-REX]

Could be your air/fuel ratio is off with the tight heads?


I kan back tha HI COMP/top rpm deel....When I run 180#s on my F-1, it will spin a 22Yamaha to 11K.(time'in @ 26*)....wit 320#s and same wheel(23* time'in) it will only muster up 9900....BUT, the power diffrence to 9900 iz well worth the loss ov rpm!!.....Oh, an juss fer tha record, time'in @ 26*/320# comp/112 VP= a bigger loss ov top end rpm, and sum very dry(verge ov burn) pistons...

[150aintenuff]

so whats the magic # for 170-175 PSI of a 260 ported 200 block 32 CC got me 150-155 will 28CC do it???

[slippy0217]

my 280 is ported to a drag motor

it has a drag cut on it

what would be the cc's to use

[T-REX]

Try 21's...If it ain't enuff, cut sum more!!!

wit 21's U kan alwayz cut sum more, if 19's iz too much, U SCREW'D...JMO

The same CC's don't always yield the exzact same compression from mota to mota!!

[dez nuts]

I kan back tha HI COMP/top rpm deel....When I run 180#s on my F-1, it will spin a 22Yamaha to 11K.(time'in @ 26*)....wit 320#s and same wheel(23* time'in) it will only muster up 9900....BUT, the power diffrence to 9900 iz well worth the loss ov rpm!!.....Oh, an juss fer tha record, time'in @ 26*/320# comp/112 VP= a bigger loss ov top end rpm, and sum very dry(verge ov burn) pistons...Thats why i told him to run 21cc if he was going to drag race and 26cc if he wanted to run top end i like the 26cc heads on my ported 280 with 26cc heads it still only has 168lbs of compression the ports are raised so much it won;t make alot of compression at cranking speed but boy does it come on around 6500rpm. That F1 of yours sounds like a nice mota thats alot of rpm you get out of that little 2.0 they are some great motors and can really spin up have always wanted to try one on my rocket maybe some day i will put on together daimond has 2 brand new F1 blocks that have been sitting there for ever never even put together maybe i can get one and give it awhirl. I would go with 21cc on that motor if you are going to drag race it IMO that should give you rt at 220 to 225com. Thanks Dave:rolleyes:

[T-REX]

Dave, Talk Joe outta one ov them lil F-1's...U won't be sorry!!....I am still leern'in thangz about this lil mota...For one thang, It iz SOOOO much tuffer than it'z big bruthers!!...This thang iz goin on it'z 3rd yeer of "Torcher", and still only haz 8-11% leekdown, and most ov them 3 yeerz haz been wit 320#s compression!!....I have found out tha big rpm ain't always tha answer wit this lil mota, and have still got sum more tricks to try...after I exhaust all my exsperiments, the last addition will be a new button on tha wheel...I have a Chaz Goodman button, connected to a lil blu bottle, dat I wanna see if'in it'z all what it's poz'd ta be...:D ....New bote iz almost ready, so I git a 100# weight break over that other 16' dat wuz so heavy(365# hull)......

Oh, on second thought, maybe ya betta tell Joe them lil mota's ain't no good, and give him my shipp'in addy, an I'll disguard them for him!!!:D ;)

[slippy0217]

thanks a lot yall for yall help imma try it out