Warmed 454 Intake Mainifold Choices?
06-14-2006, 09:16 AM
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Re: Warmed 454 Intake Mainifold Choices?
Originally Posted by CayFomula
mtgbiker,
With that kind of horsepower you should have no problem turning those props close to 6000 rpm let alone getting over 5000. I have an 89 272SR1 and when it had stock 454 Mags 350hp I was able to turn 25p Hydromotives 5100 at 72mph. The only mods I had at the time was Stainless Marine manifolds and Imco Shorties. Without the Shorties or the Stainless manifolds (saw no increase with the manifolds) I was able to turn 23p Mirage props 5200 at 67mph.
I would suggest you check timing and make sure you are getting enough air both into the engine compartment and that the flame arrestor can flow adequately.
With that kind of horsepower you should have no problem turning those props close to 6000 rpm let alone getting over 5000. I have an 89 272SR1 and when it had stock 454 Mags 350hp I was able to turn 25p Hydromotives 5100 at 72mph. The only mods I had at the time was Stainless Marine manifolds and Imco Shorties. Without the Shorties or the Stainless manifolds (saw no increase with the manifolds) I was able to turn 23p Mirage props 5200 at 67mph.
I would suggest you check timing and make sure you are getting enough air both into the engine compartment and that the flame arrestor can flow adequately.
Timing is being checked this afternoon after the Tropical storm passes. Cay, I'm sure you know all about those storms!
As far as air flow, I have 11x5 K&N arrestors which should be OK.
06-14-2006, 01:46 PM
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Re: Warmed 454 Intake Mainifold Choices?
Yours sounds a lot like my engines. Started off as 420 Mercs, punched 30 over, raised compression to 10:1 ( 
) Comp 282 H cam, Gil exhaust, Holley carbs. And I have Merlin intakes. Boat runs great. I have no problem spinning to 5200.
Click here to watch 3-17b
) Comp 282 H cam, Gil exhaust, Holley carbs. And I have Merlin intakes. Boat runs great. I have no problem spinning to 5200.Click here to watch 3-17b
06-14-2006, 01:50 PM
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Re: Warmed 454 Intake Mainifold Choices?
I knew a boat mechanic back in St Pete that couldn't get a Merlin intake to quit leaking. He switche to a Dart, fixed his leak problem, but he lost 200 rpm.
06-14-2006, 01:54 PM
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Re: Warmed 454 Intake Mainifold Choices?
you could do better then what you have as far as intakes go but you still wont get what you are looking for I think you need a combiation of reproping and manifold
06-14-2006, 02:07 PM
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Re: Warmed 454 Intake Mainifold Choices?
did i just read here that someone is running a big block at 12.7 to 1 at 40 degrees of timing ???!!! what in gods name are you running for fuel ? hydrazine ?
06-14-2006, 02:08 PM
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Re: Warmed 454 Intake Mainifold Choices?
I built my 454 to 420 specs but i am running large oval port heads that were ported, bowl blended, and flowed with big valves. I first tried an performer acted like it ran out of air. So I have an rpm-air-gap on it picked up some more power and 200 rpm.
06-14-2006, 02:14 PM
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Re: Warmed 454 Intake Mainifold Choices?
Originally Posted by stevesxm
did i just read here that someone is running a big block at 12.7 to 1 at 40 degrees of timing ???!!! what in gods name are you running for fuel ? hydrazine ?
total timming or base.....I tend to think hes talking about total
or hed have a pile of alunimum in hes oil pan
06-14-2006, 02:52 PM
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Re: Warmed 454 Intake Mainifold Choices?
Originally Posted by cuda
Yours sounds a lot like my engines. Started off as 420 Mercs, punched 30 over, raised compression to 10:1 ( ) Comp 282 H cam, Gil exhaust, Holley carbs. And I have Merlin intakes. Boat runs great. I have no problem spinning to 5200.
Click here to watch 3-17b
) Comp 282 H cam, Gil exhaust, Holley carbs. And I have Merlin intakes. Boat runs great. I have no problem spinning to 5200.Click here to watch 3-17b
Thanks for the info. Your right.... Similar set-up except your cam has 110* lobe sep and the one I'm running is 114*. Thats a pretty big difference when it comes to where the real power can come on. Also, I bet your idle is pretty aggressive. My idle is fair to mild.
It seems that I can't get to the "real power" because of where the peak HP is. I am going to test some 4blade 22p Hydromotives on Friday. Same props I'm running now, but 1.5 pitch lower. Hydromotive down-pitched from 25 to 23.5 last year.
Hopefully prop swapping will supply more information about speed, slip, rpm's, acceleration, etc.
06-14-2006, 06:01 PM
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Re: Warmed 454 Intake Mainifold Choices?
I don't think it is a single issue - the combination is for an aggressive 502 or semi aggrressive 540cid.
These cams/heads/intake/carb is a bit much for 9.3:1 compression 454 installed in a heavy/ non-efficient hull that is being propped for a low rpm. BTW: you are propped almost at torque peak which Throttle Up states can load the drive, lift stern, and cause more prop slip.
============================
Before changing an engine part, I'd go a few sizes lower in pitch to see if:
1) Your engine/rigging doesn't have an issue and can make power up to it's hp peak
2) Operate your engine as it was built for.Throttle Up always states that best all round performance will be had if WOT RPM is at engine peak hp rpm.
Then evaluate what's happenning and if motor changes need to be done to make you more satisfied.
These cams/heads/intake/carb is a bit much for 9.3:1 compression 454 installed in a heavy/ non-efficient hull that is being propped for a low rpm. BTW: you are propped almost at torque peak which Throttle Up states can load the drive, lift stern, and cause more prop slip.
============================
Before changing an engine part, I'd go a few sizes lower in pitch to see if:
1) Your engine/rigging doesn't have an issue and can make power up to it's hp peak
2) Operate your engine as it was built for.Throttle Up always states that best all round performance will be had if WOT RPM is at engine peak hp rpm.
Then evaluate what's happenning and if motor changes need to be done to make you more satisfied.
Last edited by SB; 06-14-2006 at 06:04 PM.
06-14-2006, 07:36 PM
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Re: Warmed 454 Intake Mainifold Choices?
mtgbiker,
A few questions to help with the diagnosis. What drives and ratio do you have? How does the boat perform getting on plane and accelerate in the mid range? Does it accelerate strong up to 5000 and then act like it hit a limiter or does it climb very slowly to 5000?
BTW I found that my 272 respnded well to turning the props inward, I picked up 4mph on back to back runs by doing this.
A few questions to help with the diagnosis. What drives and ratio do you have? How does the boat perform getting on plane and accelerate in the mid range? Does it accelerate strong up to 5000 and then act like it hit a limiter or does it climb very slowly to 5000?
BTW I found that my 272 respnded well to turning the props inward, I picked up 4mph on back to back runs by doing this.
