What Jets should I use??
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=12859
Printed Date: September-28-2024 at 12:51pm
Topic: What Jets should I use??
Posted By: MaddMarxx
Subject: What Jets should I use??
Date Posted: February-13-2009 at 12:11am
Does anyone have an idea on what jets I should run in my 715 holley duel feed carb, it has 65s in the front and 68s in the back right now, but I think I could go bigger!
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Replies:
Posted By: jbear
Date Posted: February-13-2009 at 2:22am
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I think this carb is not good for your boat in my expert opinion.....might make it to fast.
john ------------- "Loud pipes save lives" AdamT sez "I'm Canadian and a beaver lover myself"... |
Posted By: 79nautique
Date Posted: February-13-2009 at 12:14pm
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bump them up one - two sizes, I believe I had 72's in my single pump, but if you still have the stock cam then I wouldn't get to crazy, maybe one size larger on the secondaries. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: TRBenj
Date Posted: February-13-2009 at 1:30pm
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MM, is that a 4160? I assume so. Sounds like you have a rear metering block conversion on that thing? You must if you have replaceable rear jets instead of the plate.
If thats the case, then (by memory) I think Im running 68 in front and 74 in the rear. I posted my numbers on here at one point- Ill see if I can find them. The rear needs to be ~6 steps bigger to make up for the lack of PV. I turn up to 5200 without any problems. Admittedly, I havent done a good plug chop yet, but performance seemed to improve as I went from overfat (72/82) down to this point. Holley's general recommendation was to go marginally fatter than stock (66/72), so this is pretty consistent with that. ------------- |
Posted By: backfoot100
Date Posted: February-13-2009 at 5:54pm
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Tim,
I talked with Mark last night about this. I completely forgot about the lack of a PV without the metering block. Good call!!!!!! ------------- When people run down to the lake to see what's making that noise, you've succeeded. Eddie |
Posted By: LaurelLakeSkier
Date Posted: February-14-2009 at 9:44pm
| I'm quite sure the power valve only affects the primary side no matter if you have the standard metering plate or the conversion block. It opens to give the richer mixture to the primary circuit about the time the secondaries begin to open up. |
Posted By: TRBenj
Date Posted: February-16-2009 at 12:32pm
Thats correct. No PV in the secondaries means that the jets need to be larger to balance them out. ------------- |
LaurelLakeSkier wrote:Posted By: reidp
Date Posted: February-28-2009 at 11:36am
Mark, while all of the previous jet suggestions sound good, if your main objective is to run with the Boatdr, I suggest your only option is to go with one made by Pratt and Whitney. Just in case....... http://www.pw.utc.com/vgn-ext-templating/v/index.jsp?vgnextoid=c3ca34890cb06110VgnVCM1000004601000aRCRD - http://www.pw.utc.com/vgn-ext-templating/v/index.jsp?vgnextoid=c3ca34890cb06110VgnVCM1000004601000aRCRD ------------- ReidP /diaries/details.asp?ID=231&yrstart=1971&yrend=1975 - 1973 Mustang |
Posted By: eric lavine
Date Posted: February-28-2009 at 1:24pm
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I gotta laugh, im taking what appears to be a 650? marine and a 600 auto and combining the 2,i hope to end up with a good carb, im using the float bowls from the auto, drilling the base on the marine for vacuum, too cheap to buy another carb so I'll give this a shot on a buick 350. both carbs are in new condition. there definitely was a difference in the CFM of the carbs because the marine was around .050 larger. i need to run the numbers. will post in the future if it will even start lol ------------- "the things you own will start to own you" |
Posted By: jbear
Date Posted: February-28-2009 at 2:39pm
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Still think this is a bad idea...way to fast.
MM...did you see the thread about the distributor? I think I might need this...what do ya think? john ------------- "Loud pipes save lives" AdamT sez "I'm Canadian and a beaver lover myself"... |
Posted By: Rick
Date Posted: March-06-2009 at 2:56am
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Make sure the Carb is Marine. Automotive carbs are built so that if there is to much gas it spills it out of the carb down the intake to the ground. For obvious you don't want this to happen in a boat because it fills the bilge with gas... Not a good thing. You need to make sure the throttle shaft isn't grooved and the overflow is curved back into the front barrels. Holley sells this tube if you need it. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=250&yrstart=1996&yrend=2000%20" rel="nofollow - 2000 Ski |
Posted By: SS 201
Date Posted: March-10-2009 at 9:39am
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GOOD POINT
THE DIFFERENCE BETWEEN AUTO AND MARINE IS J TUBES TO PUT THE FUEL BACK IN THE CARB RATHER THAN BILGE. ALSO MOST MARINE ARE ALREADY SET A LITLE RICHER THAN AUTO. BEFORE JETTING UP OR DOWN BE SURE TO READ THE PLUGS FIRST. PLUG GAP AND ELECTRONICS CONTROL THE PLUG READING, SO TOO MUCH FUEL WITH A LOW VOLTAGE OUTPUT WON'T BURN PROPERLY. ALSO THE FUELS TODAY DON'T ALWAYS SHOW GOOD READ, ADD A LITTLE OCTANE BOOSTER AND IT WILL CLEAN UP THE BURN.WILL SHOW REDDISH COLOR WHEN JETTING, HELPS WHEN CHECKING PLUGS. |
Posted By: MaddMarxx
Date Posted: March-11-2009 at 1:50am
Yes it is a marine carb it was off of my buddys Donzi, and it had really big jets in it, so when we rebuilt it we down sized the jets, I just have not had the time to work out all the bugs out, I do have to do good plug check, but it seemed to be running lean!
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Posted By: SS 201
Date Posted: March-11-2009 at 9:14am
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MOST 600 CFM NON REAR PLATE USE STOCK 65 F 76 R.
GO TO MORTEC.COM IT CAN ANSWER MOST ALL OF YOUR CARB QUESTIONS. AGAIN REMEMBER YOU ENGINE CONDITION AND IGNITION CONTROL HULL ,PROP ARE FACTORS IN THE JETTING OUTCOME. BIGGER NECESSARLY IS NOT BETTER.WHAT ONE RUNS DOES NOT NECESSARLY FIT YOUR NEEDS. LOTS OF VARIBLES GO SLOW IT IS CHEAPER THAN MAKING RASH OR COPY CAT DECISIONS.BEEN THERE DONE THAT. |
Posted By: MaddMarxx
Date Posted: March-11-2009 at 11:17pm
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Its a 715 cfm! ------------- |
Posted By: SS 201
Date Posted: March-12-2009 at 5:06pm
| 715 72 f 84 r |
Posted By: boat dr
Date Posted: March-12-2009 at 10:24pm
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Mark , I may be out of line here , but why not put the 4160 back on it. You do not have enough mods on the motor that would require the extra CFM nor the hassles that go with the jetting.
One more thought , those bowls with the external float adj. are not marine complient.Did you not loose MPH by adding this carb? Unless there were major issues with the stock put her back on. My stroker is moving a lot more air and turning 5900 rpms with a stock, YES STOCK, 4160 and as you know who took the trophy home..........Boat dr ------------- boat dr /diaries/details.asp?ID=4631 - 1949 Dart /diaries/details.asp?ID=1533 - 1964 American Skier |
Posted By: eric lavine
Date Posted: March-13-2009 at 12:02am
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we did some calculations with boat weight to engine ratios doc, your boat should actually be doing around 70, you sure your plugs are OK? ------------- "the things you own will start to own you" |
Posted By: boat dr
Date Posted: March-13-2009 at 3:16am
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Eric, I have done more running than calculating. But read them and weep...
12x15 @5000 rpms =66.25 actual 53.02mph 12x15 @5100 rpms =67.61 actual 54.08 12x15 @5400 =71.59 actual 57.27 12x15 @5600 =74.98 actual 58.96 As you can see there is a big difference between theoretical MPH based on pitch and RPM and actual GPS speed. The slippage rate climbs very steeply after 4500 rpm's. 20% or so down low then climbing as you spin it higher........ ------------- boat dr /diaries/details.asp?ID=4631 - 1949 Dart /diaries/details.asp?ID=1533 - 1964 American Skier |