Mercruiser 420's single plane or dual plane??
05-10-2012, 11:14 AM
#12
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Thats not even close to the specs on any Merlin head or stock 990
Stock 990 head is 119 cc chamber, 325cc intake runner , 2.19" intake valve, 1.88 exhaust valve
NO Merlin head was a 208cc intake runner
360 is more like it
Here is the best advice you will get....
Ask a local engine builder not a mechanic or Internet guy.
They are all just guessing !!!!!!!!
I told you on your other post single plane intake is wrong for 5200 rpm, you loose torque which is what is really needed to spin the prop.
If you have the big merlin heads with a single plane intake manifold with a stock 420 bottom end your LOOSING hp and Torque from a stock 420
That's a fact I've run 420s on the dyno many many many times
Stock 990 head is 119 cc chamber, 325cc intake runner , 2.19" intake valve, 1.88 exhaust valve
NO Merlin head was a 208cc intake runner
360 is more like it
Here is the best advice you will get....
Ask a local engine builder not a mechanic or Internet guy.
They are all just guessing !!!!!!!!
I told you on your other post single plane intake is wrong for 5200 rpm, you loose torque which is what is really needed to spin the prop.
If you have the big merlin heads with a single plane intake manifold with a stock 420 bottom end your LOOSING hp and Torque from a stock 420
That's a fact I've run 420s on the dyno many many many times
05-10-2012, 07:14 PM
#14
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Thats not even close to the specs on any Merlin head or stock 990
Stock 990 head is 119 cc chamber, 325cc intake runner , 2.19" intake valve, 1.88 exhaust valve
NO Merlin head was a 208cc intake runner
360 is more like it
Here is the best advice you will get....
Ask a local engine builder not a mechanic or Internet guy.
They are all just guessing !!!!!!!!
I told you on your other post single plane intake is wrong for 5200 rpm, you loose torque which is what is really needed to spin the prop.
If you have the big merlin heads with a single plane intake manifold with a stock 420 bottom end your LOOSING hp and Torque from a stock 420
That's a fact I've run 420s on the dyno many many many times
Stock 990 head is 119 cc chamber, 325cc intake runner , 2.19" intake valve, 1.88 exhaust valve
NO Merlin head was a 208cc intake runner
360 is more like it
Here is the best advice you will get....
Ask a local engine builder not a mechanic or Internet guy.
They are all just guessing !!!!!!!!
I told you on your other post single plane intake is wrong for 5200 rpm, you loose torque which is what is really needed to spin the prop.
If you have the big merlin heads with a single plane intake manifold with a stock 420 bottom end your LOOSING hp and Torque from a stock 420
That's a fact I've run 420s on the dyno many many many times
I figure with a smaller intake (DUAL PLANE) maybe will help me get some back until I decide what to do about the heads...
I am gonna try to find my numbers on heads I had logged somewhere to see what they were...
05-10-2012, 07:41 PM
#16
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I run 34 degrees timing now... with 21P props I was spinning 5000, so I would have to use 19-20P props to see 5200, no boat I ever heard of with these engines spin that small a prop, I have an issue to resolve..
05-10-2012, 07:46 PM
#17
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Thats not even close to the specs on any Merlin head or stock 990
Stock 990 head is 119 cc chamber, 325cc intake runner , 2.19" intake valve, 1.88 exhaust valve
NO Merlin head was a 208cc intake runner
360 is more like it
Here is the best advice you will get....
Ask a local engine builder not a mechanic or Internet guy.
They are all just guessing !!!!!!!!
I told you on your other post single plane intake is wrong for 5200 rpm, you loose torque which is what is really needed to spin the prop.
If you have the big merlin heads with a single plane intake manifold with a stock 420 bottom end your LOOSING hp and Torque from a stock 420
That's a fact I've run 420s on the dyno many many many times
Stock 990 head is 119 cc chamber, 325cc intake runner , 2.19" intake valve, 1.88 exhaust valve
NO Merlin head was a 208cc intake runner
360 is more like it
Here is the best advice you will get....
Ask a local engine builder not a mechanic or Internet guy.
They are all just guessing !!!!!!!!
I told you on your other post single plane intake is wrong for 5200 rpm, you loose torque which is what is really needed to spin the prop.
If you have the big merlin heads with a single plane intake manifold with a stock 420 bottom end your LOOSING hp and Torque from a stock 420
That's a fact I've run 420s on the dyno many many many times
