SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: jamiemwedmore1234 on September 11, 2013, 11:24:57 PM
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So I'm in need of some advice and I figured some one would have an good legit awnser I have a 496 stroker which started as a 4 bolt main 454 bored 60 over with a 4-1/4 stroke crank with H beam rods in it pretty stout bott end I have GM rectangle port truck heads on it 3/8 push rods roller rockers a stud girdle topt off with a edelbrock air gap intake Hei ign with a CID box lighting headers and a 750 dbl pump carp compression don't no gas I run is a min of 91 octane I have a JE serious pump with a A cutt impeller boat runs at 5000 rpms wide open if I GPS it on my I phone says 50+ mph don't seem right ????? Or does it I think I'm under carbureted and need a more agressive impeller WHAT DO YOU THINK plus when I accelerate out of the water to hard it cavitates I'm going to attached a pic of the cam card maybe some can meek sence of it and a big thanks for any advise
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I would say the 750 is way too small for the components you have going. You could probably get away with a tunnel ram and two 750's.
If you're going to stay with a single carb, you're going to want to go as big as you can find for the 4150 flange or go to a dominator (1100-1200cfm).
Also there is a lot of performance lost in tuning, be sure to get your timing and jetting right.
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Looks like the master has spoken, but the 750 is not enough by any means. I'm running a 750 on a mild built 468 and I'm under carbureted.
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Anybody got any complaints on quick fuel carbs. Does dominator carbs use the same flange as holly or demon
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I'm running a quickfuel and have had no problems choose it over the Holly hp
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Anybody got any complaints on quick fuel carbs. Does dominator carbs use the same flange as holly or demon
Dominator is a Holley, but with a very large mounting flange. Google "Holley 4500" and you'll see the difference.
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I'm looken at the 1050 quik fuel with the dominator flange and a adapter I'm guessing I'm going to need to up grade the fuel pump ! and a new flame arrester
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I know where there's an intake manifold with a dominator flange, let me check to see if it's for sale.
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So for$ reasons and that I don't want to change out my already new intake for a dominator flange I'm going to run with a QFT 850 marine carb so here shorty I will have a a demon 750 for sale more questions tho do I need to run a bigger/better fuel pump I've been running the stock one (mechanical )
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A stock mechanical type fuel pump will be good, as long as it is a quality performance piece, not some generic pump for a truck off the local kragen shelf.
I'd also recommend a good regulator and a fuel pressure gauge while you're at it.
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I have a gauge at the carb and I have No regulator now and if I'm not changing out the pump should I still get one if I remember is would run about 5-6 psi at a idle never did look at it while running it
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I have a gauge at the carb and I have No regulator now and if I'm not changing out the pump should I still get one if I remember is would run about 5-6 psi at a idle never did look at it while running it
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. And it is a marine fuel pump if that matters
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Wow 496 cid and a 750 cfm carb with square port heads that flow a ton of air ! Those heads will flow as much air as a HEMI ! That carb is just a big old restrictor plate you are way under carburated you need at least 1200 cfm into that motor , One thing with square port heads is they flow a lot of air but it moves slow , double carbs will help keep the air moving faster multibel smaller holes helps keep the velocity up 8)
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So for$ reasons and that I don't want to change out my already new intake for a dominator flange I'm going to run with a QFT 850 marine carb so here shorty I will have a a demon 750 for sale more questions tho do I need to run a bigger/better fuel pump I've been running the stock one (mechanical )
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An 850 is still very small for a 496. I run an 850 on my stock 460 ford motor. Hell my 468 chevy motor eats every bit of gas that the 1150 gives it.
they make a 4150 to 4500 adapter/spacer. I would do that with a holley 1050
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"plus when I accelerate out of the water to hard it cavitates "
When was the last time your pump was rebuilt, sounds like its time.
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It never cavitated until I put a modified moter in it I'm king to pull the bowl off it and check it out I think there's to much power in a stock pump with no up loader
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My 496 has two 750 quick fuels and feels like it wants even more. I'd love to be able to run some injectors like the set up Beaver has!!!
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My 496 has two 750 quick fuels and feels like it wants even more. I'd love to be able to run some injectors like the set up Beaver has!!!
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is yours a real 496 or a bored/stroked out 454 and is there even a diff
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I'm slightly confused on what I'm able to run for carburetors a QFT rep said to run the 850 marine carb and that should be more than enough but I here all you 496 guys running duel 750's or 1050's so what to do.?????.
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I'm slightly confused on what I'm able to run for carburetors a QFT rep said to run the 850 marine carb and that should be more than enough but I here all you 496 guys running duel 750's or 1050's so what to do.?????.
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My motor a 468 is 10.2 to 1 around 680 lift and I run an 1150. JMO 850 is too small. Find a 4150 to 4500 adapter and run a 1050. It will wake that motor big time.
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Mines a 13-1 stroker with a big cam 772" that's why I think it wants more.
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What's been overlooked here is that he is running 5000 RPM with the A impeller.
Some years back I built a mild 454 for my friend's jet boat that also turned an A impeller 5000 rpm, showing about 62 mph on a non gps speedo, but routinely beating 18 foot jets with headers, while his 20' open bow had through transom exhausts and covered engine. Made lots of guys mad.
The engine was installed into the boat with the 715 cfm (Yes, Holley made them) OEM carb, and did pretty well with it. One day he ran out and bought an 850 Holley without asking me first, and was surprised that the boat actually lost power until he and I did quite a bit of messing around with jetting, and in the end made no actual gains.
I have built some comp jet race engines that were turning smaller impellers into the 6200-6500 rpm range that did run single Dominators, and one of them out-powered the tunnel ram boats at Burley badly enough the other competitors were talking about protesting it. I assure you the engine was 16 cubic inches under the maximum allowable limit, with absolutely no porting in the heads or intake, they both still had APBA spec lettering in them. That particular boat didn't do well in rough water, or it may have shown similar results at other races. We are in the process of rebuilding that engine with new heads, and the ultimate plan is to dyno with both single Dominator and tunnel ram to determine the actual difference, but if the impeller limits an engine to a given RPM below it's actual maximum horsepower, larger CFM rating may not be doing much for it?
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What impellers were you running at 6200+ rpm?
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So still confused I'm going to dyno the motor in the next few months my goal is to do it with a new carb that is still not determined once it is dynoed the pump is going to mpd for them to do there magic but mpd wants accurate HP reading so back to square one need to no what carburetor to purchase based off motor parts that are in the beginning of this tread for more boat info it's a 88 commander mini day cruiser with a je serious pump I'm not drag racing just want to hall ass every once in awhile not worried about mpg but I also don't want it loading up on me because I'm over carbureted hope this helps hope I'm not confusing anyone just have gotten a large variety of awnsers just tryen to narrow it down a bit
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The grammar in this thread makes my head hurt. Sorry, I don't mean to be an ass.
Life is uncertain. Don't sip.
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I've had to get over grammar and spelling on forums a long time ago. I feel ya.