Getting the jetting right -500hp - 454
 

Man was that costly!. Rebuilt 454's last year, had popping on top end, turned out previous owner (with run out engines) had the Holley 4150 dual pumpers set-up with #70 jets in primary and #80's in secondary, that's stock for this model Holley. At 12 hours, started stepping up the secondaries two steps at a time; popping moved each time to higher rpm before it occurred and plug color began moving from bright, bright white to touch of brown on most of them till we finally settled in at #88 jets on the secondary. That all occurred over a period of about 22 hours of running time. At about 35 hours, dropped an intake (SS Manley) valve at 3900 rpm and BAM, hydro-locked the starboard engine and the rest is history. Amazing how much damage that causes in a matter of about 3 seconds! During rebuilt, noticed excessive wear on a couple of valve guides, a few seats and valves. Mechanic and I decide, long story made short, we had to have ran them to lean to long during the re-jetting process, at least that's what we think.

So, here's the question. When trying to get the jets right, how do you determine whether the primaries should be increased? I mean, it was popping on the top end and plugs were white white, so we increased the secondaries till that solved the popping and plug color began sow trace of brown, engines performed great, even had better throttle response in the last 1/3 of throttle which didn't real have before. The fact is, we run at about 3600 rpm (cruise) most of the time just before those secondaries begin to open. So, how do we know we're not running them lean up to the 3600 rpm range. Engines idle perfect, response well and never popped in those mid-range setting.

Before I fire these new rebuilt GM 990 heads with fresh SS valves, seats, guides etc. up, I could sure use some fresh input here?!?!?. While the plugs were showing a touch of brown, this experience is telling me increase the secondaries another couple of steps say #92. If the plugs go black, we back off a set or so, at least I don't run them lean again. Thanks in advance for any suggestion or thought you may have.

Al

Re: Getting the jetting right -500hp - 454
 

The primaries are still 70's and as I began to think this thing through, it makes perfect sense that the primaries should be change as well. I have sets of jets ranging for 80's to 90's now. I agree, I need to change those primaries so what do you think about me sticking those 90's in the primaries as a starting point and a seat of 92's I have in the secondaries. Al

Re: Getting the jetting right -500hp - 454
 

Well, then that's what I'll do. I've got a set of 86's I'll put in the primaries and see waht I get. If you think of anything else, let me know. I really appreicate your response. Al

Re: Getting the jetting right -500hp - 454
 

Thanks again for the help, I'm strapping all the accessories on today and should have them running by the end of the day at least in the garage, my trucks gone for the weekend so can't put it in the water till next weekend. Will let you know how I make out. Al

Re: Getting the jetting right -500hp - 454
 

Don't get a One track mind here and just think about jetting. Where is your total advance at on your timing? Also when do you bring in your total timing? Be sure and start with a clean set of plugs. Check for blueing on the electrode. Do plug checks starting at 2000RPM's run for 1-2 minutes then chop throttle be sure to be careful of water coming in the exhaust or over back of boat, however avoid idling as much as possible to get clean plug reading. Then check your plugs. If you do this in 1000RPM increments, and know how to read plugs, all the way to WOT you will have a well tuned motor, not just the same jets as everybody else runs. Remember, when you are at lower RPM's and just running off the primaries only adjust the primary jetting. What kind of intake system do you have Single plane, dual plane, high rise? Believe it or not all this stuff is extremely important.

Re: Getting the jetting right -500hp - 454
 

I have dual plan intakes. Interestingly enough, I noticed that the the Thunder Bolt ignition packs have different numbers; one is 1622A 16-14 and the other reads 5B71A 16-14. I've always understood that the total time should be in the 32 degree range although I've never figured out how to check that in the boat given the tight quarters. The engines seemed to run good when the timing was set at about 16 degree at 1000 rpm. If you set the timing much lower than that, when I took the engines up to about 3000 rpm to get on plane, they seemed to hesitate as if they were flooding or something like that eventually "catching" and running ok at cruise or better rpm's. If you came off plane and went at it again, I get the same results, thus the way I arrived at setting them at about 16 degrees at 1000 rpm. For some reason I remember someone telling me these packs advanced the timing 14 degrees. Any thoughts on that? Al

Re: Getting the jetting right -500hp - 454
 

i dyno every motor that i have built. takes out all the guess work.

But mid 80's and low 90's sounds like a good starting point.

Re: Getting the jetting right -500hp - 454
 

Thanks again Formulaz583. It was an expensive lesson but I'm glad I check-in with you guys. Finished the install last night. As soon as the neighbors wake-up, I'll crank them up and see what happens.

I'm still trying to figure out how theses carbs ever ran on these engines prior to me buying it. Makes me feel like there may be a rat here somewhere. On the other hand, everything else was such a mess, perhaps the I engines where run out (plugs where always black when I bought it) guess the engines where running rich due to oil, low compression, etc. I'd rather believe that than the rat theory.

You think changing these jets this much will help actual performance? you know, Spppeeeeeddddd. Thanks again to all you guys!

Re: Getting the jetting right -500hp - 454
 

32 degrees should be a good place to start with the timing. Try to bring the full advance in by 3000rpm's. Crane makes an excellent ignition system for carb motors. You can set any timing curve you want. This will work with your distributor also. Good luck hopefully there is no rattle snakes in your motor.

Re: Getting the jetting right -500hp - 454
 

I know I am new to this forum but I have some great advice for this particular application. As soon as I get to the office I will post a tuning guide which I drafted up myself. Yes I am a pro-carb builder and I often hang out in the Hotboat forums. Nonetheless I will post it here online which should allow you to reset those carburetors back to zero for tuning purposes. It covers alot about the idle/off-idle and proper jetting with respect to timing.

Remember one thing...fuel pressure and setting the valves are critical here. Sorry for the tease...I should have this posted by this afternoon.

~Ty

Re: Getting the jetting right -500hp - 454
 

My 500hp 454,s Ran Holley 850,s With 82 Primary And 84 Secondarys With Power Valves Front And Rear .my New 540 Has A 950 And Likes 80,s And 82,s.go Figure

Re: Getting the jetting right -500hp - 454
 

Thanks z.zuperboat and I'm looking for the post TPC Racing. Well had a bit of an oil leak at the remote oil plate, you know, the one underneath everything that you can reach without taking the exhaust risers off. Anyway, got that handled. Ran both of them, set the initial time at about 16 degrees at 1000 rpm. Had #86 in the primaries and 92's in the secondaries. Ran the engines about 2 minutes (in the driveway, no load) and the plugs are black as they come and dry, first time I've seen them black since the intial re-build. Changed the primaries to #80's, change plugs, ran it about 2 minutes, plugs are Gray/black. I think I'll run them there for now, better safe than sorry and I'm running low on boat money according to the wife! Will post after an in the water run this Saturday. Thanks again guys.

Re: Getting the jetting right -500hp - 454
 

I have a 540 bull dog with 89prim 91sec, 34deg @3400rmp elevation 4500ft
One question, When checking the plugs for a sweet tan color, which plug to check, do you check them all or is there one cylinder that will run leaner that you need to watch for.
Bryan

Re: Getting the jetting right -500hp - 454
 

Formulaz583, what makes the #5 & #7 run leaner than the others? Seems like I remember someone telling me that these dual plane intake manifolds (that's what's on these engines) would cause #7 & # 8 to run very lean if the engine was already on the lean side, is that true and if so, why? What is it about a dual plane manifold that causes that? Thanks.

Re: Getting the jetting right -500hp - 454
 

formulaz583 sounds good to me and since the intake valve I lost was in #7 I guess I can attest to which one goes lean first, #7! Putting it in the water tomorrow, will let you know how I make out. Won't have smaller than #80 jets for primaries till Tuesday but I'm going to see what the 80's look like under a load.

Re: Getting the jetting right -500hp - 454
 

When your done jetting those motor lets make a EFI map for those motors and get rid of those carbs. Hah just kidding you.

Re: Getting the jetting right -500hp - 454
 

A fellow boater and I have both installed egt's in our exhaust. We have never pulled a plug and can tune a motor to a T. They take the guess work out. Money well spent.

Re: Getting the jetting right -500hp - 454
 

As a pilot and flight instructor, I couldn't agree with you more. At night I could look out through the cowling's of a Cessna 421 I flew and watch the red glow of the exhaust pipes through the vents as the EGT's went up. While beautiful, peak EGT was not a good place to be for long. Not a bad idea. Where did you find the system for your boat, how much trouble to install and about how much $$$$ did it cost you? Thanks for the thought, that's a great way to go for those of us who don't have dyno's.

Re: Getting the jetting right -500hp - 454
 

I have a similar power motor to yours and my jetting was all screwed up. I have a dart manifold like the 500hps (staggered tubes) so all my jets needed to be a different size. I used the 500hp carb specs and now it runs, idles and top ends better. I ganed 3.2 mph also. I don't know what your manifold is. My carb is an 830 holley. Here's the specs.

Primary - Port 81, Stbd 75, power valve 6.5
Secondary - Port 89, Stbd 93, power valve none

Re: Getting the jetting right -500hp - 454
 

Alcor--Call Livorsi or look at their catalog. They have everything you need up to 3" guages. Toughest part is that you need a bung to attach the probe to.

Re: Getting the jetting right -500hp - 454
 

Check out the Innovate Motorsports web sight. Their air fuel meter will allow you to not only do your jetting but to dial in your entire fuel curve by adjusting your high and low speed air bleeds. I don't sell them I just bought 1 and like it.
http://www.innovatemotorsports.com

Re: Getting the jetting right -500hp - 454
 

Ok guys, I.m confused here. In the driveway, they nearly fouled the plugs out with #86's after 2 mins at 2000 rpm. So I put the 80's in the primary and down to the lake we went. Ran it 2 minutes at about 3,000, pulled them off, pulled the plug white white white. So in teh drive way with no load means nothing when it comes to find teh right jets on teh primary side. Don't understand why but obvious they run a whole lot different in the water with a load.

Immediately installed the #88's in the primaries,left #92's in secondaries. New plug in each number #7 cylinder, ran them them at 2,000 fora bout 2 minutes and pulled the plugs again. No sign of change in color of the electrodes, porclines dull dull white, maybe beginning to go gray. Reinstalled plugs and ran them up to about 3800 rpm for about three minutes, secondaries actually begin to open at 3,200 rpm. Pulled #7 plug in each one, plugs look like they are going gray on porcline. The base (Metal edge) of the plug appears dry black.

My confusion is that I believe I can go to 90's on the primaries but when i got back to the dock after idling for about 3 minutes, I pulled the same plugs and they were black black black. Look like they would foul running like that. Is there another adjustment I should be making to keep them running to and from the dock?

Re: Getting the jetting right -500hp - 454
 

you said the carb had 70 pri and 80in the sec. which make the carb a750 -4779. so you should start with 75pri. and a5.0 power valve and 84 and no powervalve in the sec. make shore the fule line to the motor and filter are at least 3/8 id. total timmingshoulbe 34 dregeesby 4000 rpm and then fine tune from their I DUE A LOT ENGINE PACKAGES WITH 750 HOLLEYS AND THAT IS A GOOD STARTING POINT

Re: Getting the jetting right -500hp - 454
 

Thanks for hanging in there on this one formulaz583. Your last comments along with CMS Racing are interesting.

First, yes these are twin 454's in a 1984 36' Coyote, early Sonic as I understand it. They have been responding (plug readings) the same to the changes we have been making. Since formulaz583 mentioned the PV early on in this thread, I noticed I have 6.5 PV at least on the primary side, haven't been back into the secondaries since then but will see what PV I find in there today, if any and will let you guys know.

Timing is still concerning me. Here's the deal. The indicator on the block runs up to about 16 degrees BTDC. These engines seem to start and run good at about 18 degrees at least at about a 900 rpm idle. I managed to sit in front (face about 12" from the belts, scary) of one of those running about 3000 rpm (in the driveway) and watched the timing retard but of course there's nothing for me to read. If I used the indicator increments as a guide and had to guess based on how far the timing moved, I would guess about 32degrees but again that's just a guess. How do you guys check total timing under these circumstances? And are you checking this under load or is the "driveway" ok for this check?

Now about that PV. CMS is saying I need to a 4.5 PV with 75's in the primary and 84's in the secondaries. I haven't a clue. Formulaz583 what are your thoughts, you had mentioned these PV previously. What do you think about the combination CMS is suggesting? I can order the PV (doubt the local part house has them) Monday and I already have jets in the 70 range coming in.

Thanks again guys, I'll get back to you today on the secondary PV situation.

Re: Getting the jetting right -500hp - 454
 

Forgot one thing that I haven't mentioned, I am running Champion RV15YC4 spark plugs. Thanks for the links on plugs formulaz583, makes me think the plugs are the right ones, just need to work through these other issues. The carbon cleaned up as soon as I ran them at mid range or higher settings, simply loaded-up when idling.

Re: Getting the jetting right -500hp - 454
 

no the are not the . you need a R5673-7 ngk or champion v63c or a equilvent to the plugs extended tip plugs are no good in a marine engine they can glow and cause pre ingition call me at my shop 410 335 2226 CMS Racing Engines from 9.00am/4.30pm if you have any questions concerning this matter

Re: Getting the jetting right -500hp - 454
 

try a MR42T OR MR41T AC PLUG IF THAT IS EASY TO FIND IN YOUR AREA. Rember the jetting recommendation I gave you is for a marine or auto 750 dp. I have dynoed many 454 and 502 in this power range and I have found if you go more than 6 numbers higher in jet you have to due major work on the mettering blocks and air bleeds to make the carb work properly . the jetting recommendation should give you a good exhaut temp and good air fule ratio. give me the list # on the carb and some more details on the motor and what altiude you boat at and I can help you get close. sounds like you are getting the timming set 32. to 34. total . set under no load is the easyest to due .you can measure the balancer and mark off 32. or 34. degrese or if it is a gen 5 or 6 the balancer is all ready marked and you dont need a advance type timming light.

Re: Getting the jetting right -500hp - 454
 

no I said the jetting would fit either the marine 750 or the automotive carb on the same engine the only diferance in the carbs is the j tubes and the 850 carb is going to use more jet than a 750 . if you run 93 squared in a 750 air fule ratio would be 6.1 or so. you have to compare apples to apples.

Re: Getting the jetting right -500hp - 454
 

Thanks CMS Racing for the time on the phone today. Thought I'd provide my cam information and see what you thought. They are:

Comp Cams
Part #11-000-5
Engine CB 396/454
Grind # CB 6084/6002 FT114
S/N: 2 6226 & 2 6227
Intake Exhaust
Valve adjustment: .018 .020
Gross Valve lift: .533 .562
Duration at .016 tappet lift: 268 282

Open Close
Valve Timing at .050
Int. 5 BTDC 45 ABOC
Exh. 56 BBDC 0 ATDC

Specs. are for cam installed at 110 intake center line

Intake Exhaust
Duration at .050 230 237
Lobe Lift .3140 .3310
Lobe Separation 114.0

Not sure if all that's good, bad or indifferent. All we did was get Comp to match a Crane cam supposedly made for Mercury Offshore Racing years ago for about 10 of these engines that were shipped to Miami, at least that's all Mercury Offshore Racing could tell me about the original Crane cam we found in the engines when I bought it. Since we could get Crane to run new one's (anytime soon anyway) we provided the information to Comp and they came up with these cams and solid lifters. If you have any new thoughts, please call me at 800- 727-1468, or post a reply. I'm usually in the office from about 9:00 to 5:00 CDT (New Orleans).

Thanks again for the insight. Trying to round up those MR 43T plugs you and Formulaz583 suggestioned along with a 5.0 PV. Will install this stuff, and some #76 in the primaries (I have those) and #86 in the secondaries (got those too), get the total time right (for sure) then take it to the lake get some vacuum and plug readings and see what I end up with with that set-up. Probably be the weekend before I make the lake. Thanks again.

Re: Getting the jetting right -500hp - 454
 

Quick update. Installed AC MR43T (#10 under the new numbering system). The best I could come up with on the jets were some #76's for the primary and I put #86's in the secondaries; better a bit rich CMS than lean, the pocket can't take anymore lean problems this year.

Degreed the balancer up to 34 degrees. Based on previous timing of 18Degree at 900 rpm, I was getting about 28 degrees total at 3,000 rpm, no load, driveway. Adjusted timing till I got 34 degrees total timing; again, seems to occur at about 3000 rpm, no load, driveway.

The PV's are 6.5 in both the primary and secondaries. Here's the twist this week. Placed a vacuum gage on the carb (vacuum port just under the primary bowl, front of engine). At 1000 rpm idle, it read 18. As I advanced the throttle, the vacuum went to 22. I thought as the throttles went up, the vacuum would move towards the 6.5 where the PV would eventually open.?.? Based on yours (formulaz583) being 12 at idle and 4 when going on plane, I confused again. Would appreciate a more advise about this. Thanks, Al

Re: Getting the jetting right -500hp - 454
 

Al,i'm going to jump in this for your latest question,when you free rev a motor(no load in driveway) the vacuum will go way UP (as long as your reving it steady). If you had your throttle linkage unhooked and blipped it with your hand on carb real quick,you would see the vacum drop temporarily then rise but it wouldn't tell you anything anyways,Hook your vacuum gauge to your carb with six or eight feet of vacuum hose and run it up to your helm temporarily if you want to see what it does under a load,Smitty

Re: Getting the jetting right -500hp - 454
 

AL smitty was right .running the engine with no load the vacuum will increase but under a load the vacuum will drop when you go in gear thenn when you add throttlethe vacuum will increase for rpms then as the load gets greater the vacuum will drop eventuality to 0 by wide open throttle. run the vacuum gauge on the next sea trial and you will see which way to move your power valve . but if you are to rich on the pri side the idle vacuum will be lower

Re: Getting the jetting right -500hp - 454
 

Sea trail results are in and based on what I think I've learned from you guys so far, they look way to lean to me, check out this photo. This is with #76 in primaries and #86's in secondaries; both have 6.5 PV's in them. Here's some under load reads:

Total time: 34 degrees at 3000 rpm, set at no load, both engines

Vacuum readings:
Port Eng. Starboard Eng.
Idle in gear, 900 rpm 18 19
2000 (load, nose way up) 9 10
3000 (load, on plane) 6 5
4000 (load, on plane) 4 3

The left plug in the photo (from #7 cyl., port engine) was new, never run at idle except for a few seconds, then run at about 4000 rpm for about 3 minutes. The right plug in the photo (same eng. and cyl.) was run from dock to the lake (say 5 minutes at idle) then at about 3100 rpm for about 3 minutes.

Obviously, the porcelain on both plugs are stark white. The ground electrode on the left plug (run at 4000 rpm) shows considerable bluing and the center electrode does too. The right plug ground electrode is not nearly as blue but still shows some blue, the center electrode is about the same.

To me, this says we're still very lean in the mid range and very very lean up in the 4,000 rpm range. Also, it appears those 6.5 PV's would not be kicking in till somewhere around 34-3500 rpm on the port engine and 32-3300 rpm on the starboard engine. What's the deal with the different vacuum readings at the same rpm? Even though I have them as close as I can get them, could it be that total time may be just a tad different between the two or would this be the result of something else. Let me know you thought but I'm thinking going back up in the 86 range on primaries and 90's on the secondaries and leaving the PV's alone for now. Al

Re: Getting the jetting right -500hp - 454
 

A Great engine information system that I use in both my airplanes and Boats! this used with a good three wire Air Fuel ratio guage is great!

model 2004 EIS http://www.grtavionics.com/

A/F guage http://www.turboimports.com/gredairgaugk.html

I had CMI build in a dry port for my o2 sensor. and EGT ports.

Bryan

Re: Getting the jetting right -500hp - 454
 

al what did the plug look like down at the base of the porcelin the top only show color after a cupple hours running time.when we run a motor on the dyno for a day they barley show color on the top . thr eletrode will turn a rainbow color till it gets covered in carbon. change the power valve to 8.5 a run the boat agian. add fule addative of some nature and the plugs will color quicker. the jetting still should be close with your combiation

Re: Getting the jetting right -500hp - 454
 

formulaz583, the spark plug attachment/photo is at the bottom of post #50. Looking all the way down the porcelain, both of them are white all the way down. The boat comes out of the hole good and runs better than it ever has, I have to believe that has something to do with finally getting the total time up to 34 degrees, the idle timing has got to be up around 20 now as opposed to 16-18 at best in the past.

Everyone seems to be running high #80's on primaries and #90 to #92's on secondaries. Back in post #33 when I ran the 88's & 92's, the plugs did appear to be going towards gray but I swear it felt like it was going to foul the plugs getting to the lake and back at idle. On the other hand, having now marked the balancer and having moved the total time to 34 degrees, it must have been running about 32 degrees or less total timing back then, would that have made a difference on the idling characteristics?

These vacuum readings seem to be higher than everyone's, what up with that? Why? I agree, if the PV's are going to pass gas in the mid range, I've got to go to a 9 or so, but again, that sounds very high when compared to what everyone's running. Have you guys heard these high vacuum readings before? Are they unusually high or just a bit higher and no need to concern ourselves with why they are higher? If I heard CMS right back in post #48, jetting effects vacuum, does everyone agree with that statement?

It's hard to believe they ever ran with the #71's & #80's if this is range they need to be in, I mean your increasing the flow capacity by about 55-65% according to the Holly jet charts when you go the the 88's & 92's. But, unless there's something new, I think it's best to at least go back to the #88's and #92's and get some vacuum readings there with the new time, check the base of these plugs again and go from there.

Re: Getting the jetting right -500hp - 454
 

al the vacuum readings are high but you have a smaller size cam . hte .050 numbers arent that that big and the cam is on a 114. cnt. line which will give you a higer vacuum reading.please don't go to 88. pri and 92. sec. you will wash the walls with that jetting. if you must go up try 80.pri and 90. sec. but I have never put that much jet in a 4779. card even in a blower motor which made 745 hp . I only ran 78.pri and 85 sec. one of my race boats runs a 468.cid engine with a 4779. and 562hp . I run 75.pri 3.5pv and 85 sec no pv. and the engine package has been working just fine

Re: Getting the jetting right -500hp - 454
 

I hear you load and clear but with these plug readings something has got to chance. Based on limited knowledge I've gain from you guys on plug readings, they're lean. I certainly don't want to wash the walls either, makes no sense to save the heads and destroy the rings. There's got to be something else going on here with the plug color being what it is and at the other end of the spectrum, them not wanting to run at idle with big jets???? We've got to at least change the PV to a higher one if we are going to run the 76's & 86's because they're not opening til up around the 3400 rpm range and then only barely.

Re: Getting the jetting right -500hp - 454
 

change the power valve to a 8.5 will make it opne around 2350.rpm to 2500rpms dobble check your fuel psi while running you need at least 5.5psi at 5000. rpm and check fuel lines etc. one more time the plugs will color eventuly . it takes longer than 3to 5 minutes to color the top of the plug look at base of the porcelin it should be a gray band around it after making a run on them. due you have a egt metter you can install in the exhaut system. to help you tune your engines,

Re: Getting the jetting right -500hp - 454
 

Alcor,you need to check your fuel presure real well,ive ran a 4779 carb on a drag car (i know that a boat needs to be richer but NOT 12-14 jets richer). If for some reason you are getting some air thru jets mixed with fuel (low presure) then you'll band aid this deal with a ton of jet which isn't correct. Besides,if a motor has real good vacuum it pulls fuel(strong signal its called) thru the jets and booster venturis real well.People have been known to jet up a big carb on a motor with radical cam and heads to make up for low fuel signal and vacum,(the opposite of what you have). I would suggest also rigging some kind of air fuel mixture gauge or egt in your exhaust if at all possible,don't waste your money on gaffrig egt's though(i have them on #7&#8) on my boat and they read 200-250 degrees hot. I would pictur your eyes watering,plugs loaded up,transom black with 88 primarys in your boat(as someone said earlier-6-1 stoichametric fuel ratio!!!). Let us know what you find,Smitty