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Donziweasel
05-08-2007, 12:44 PM
I am currently in hell. A quick recap. Last year got a 1997 16 with a 5.7L. Not happy with the performance at 6000 ft plus, I ordered a set of Vortec heads, edelbrock intake, comp 264 marine cam, and edelbrock 600 cfm carb. Got it all put back together and it had a bog in the mid range. Played with jets, etc... and finally gave up. Sent it to Presicion Marine where they have a lot of experience in this type of setup. They tried everything and could not get the bog out. They did put a drive with 1.62 gears on it and a 23 pitch prop (mine are 1.47 w/ a 19 pitch) and it got 95 % out of it.

They are telling me that re-gearing to those gears will cost $1,500.00, plus a new prop! This is after I have already spent over $2,000 on the initail upgrades. Although they said Comp said the cam would not change the torque curve, they said it did. I am so pissed I do not know what to do. I am ready to say to hell with my Donzi, sell it and buy something else. Any help would be most appreciated to save this loyal Donzi owners sanity!

Rootsy
05-08-2007, 12:56 PM
1500 would be about right... stings a bit...

still playing with the edeljunk?

Carl C
05-08-2007, 02:09 PM
A blower should compensate nicely for the thin air. Not cheap though.

Donziweasel
05-08-2007, 02:16 PM
Stings a bit? Kinda stings like a damn rattle snake bite.

Jamie, any ideas on why it has the bog? As you know, I have been fighting this since last year. As far as re-gearing, all I can think is that simply changes the rpm range of the engine. It does not fix the problem, it only covers it up. Help!

mrfixxall
05-08-2007, 03:47 PM
Stings a bit? Kinda stings like a damn rattle snake bite.
Jamie, any ideas on why it has the bog? As you know, I have been fighting this since last year. As far as re-gearing, all I can think is that simply changes the rpm range of the engine. It does not fix the problem, it only covers it up. Help!

weezzzzz,,,what sparkplugs are you running?? if your running too hot of a sparkplug your cylinder temps could be to hot in the upper rpm range abd could be causing your fuel to burn before its soppose to....

Donziweasel
05-08-2007, 06:05 PM
Plugs are fine.

I started thinking about it in a different way.

1. The heads- new vortec heads machines to accept dual valve springs comp recommended for the cam. All this does is create more airflow. Wouldn't make a bog.

2. Camshaft- Comp cam 264. Pretty mild and comp says would not change torque curve. I wouldn't think this would create a bog

3. Intake- can't screw up an intake- no bog

4. Which brings me to carb- Edelbrack are pretty cheap and simple carbs. Since this is where fuel and air mixed, I am thinking this might be the cause. I might have a dead spot in the carb. Perhaps a Holley or BG Marine Demon would be a better match for this setup. The BG is almost twice the Holley. What are the benefits of a BG 650.00 carb vs the 400.00 Holley? Do any of you think I am on the right track?

BigGrizzly
05-08-2007, 06:10 PM
Lose the Edelbrock. The altitude and depending where you are is a problem. €€The holly can be set up better for the altitude. Since you snomobile I am sure you know about altitude jetting. I takes a super man and a dyno in your altitude to fix that carb. The gear set put a bandaid on the real problem. I know you didn't hear this but better now than later

BUIZILLA
05-08-2007, 06:19 PM
it's no secret that manufacturer's use higher # gear sets for torque multiplication at higher altitudes...

Cuda
05-08-2007, 06:28 PM
Which intake? There's a guy on another site going through the same problem when all he changed was the intake to an Airgap intake, and to no small suprise to me, an Edelbrock carb. I'm thinking the other guy's problem is maybe the carb isn't getting the proper signal (vacumn or back pressure) that it needs for the carb to fuel the engine properly. He was sure it was a timing curve problem, I told him I doubted it, but he bought a new distributor and different (non Merc) module anyway. He took it out Sunday, and now it runs even worse.

DonziJon
05-08-2007, 06:49 PM
OK: I'm probably STUPID: ...BUT..I KNOW that Genearal Aviation Aircraft operate at altitudes from Sea Level to about 12,000 feet.... With carburaters. ALL these aircraft have a little knob on the dash/panel for adjusting the "mixture". A needle valve which can be screwed IN. or OUT... to Enrichen..or Lean out the mixture. At higher altitudes you want to LEAN out the mixture. There is less AIR (O2) at altitude so you WANT less GAS to keep the ratio in balance. Am I way off base, or can this idea be used with a boat at high altitudes? :bonk: John

PS: The engines in these planes are about the same displacement as what's in a Donzi.

I don't think this problem is all that complicated. :confused: :confused: :confused:

Donziweasel
05-08-2007, 07:00 PM
Intake is a performer. Still thinking a bad match between the carb and engine setup.

mrfixxall
05-08-2007, 08:24 PM
Intake is a performer. Still thinking a bad match between the carb and engine setup.

weeeeeze did you put a intake baffel under the intake???? If you didnt your boiling your fuel with the hot oil splashing the botton of the intake...

http://cgi.ebay.com/ebaymotors/NEW-MOROSO-LIFTER-VALLEY-OIL-BAFFLE-SMALL-BLOCK-CHEVY_W0QQitemZ260085654210QQcmdZViewItem

gero1
05-08-2007, 09:25 PM
very little help here... i have seen this problem many times on the street with edlebrock carbs. can you borrow a holly to run for day??? not a big one! maybe a 600- 750. no bigger. don cig runs in co maybe he could help

MOP
05-08-2007, 09:44 PM
PM Big Green ZX I sent him a small Holley that did not work out for his app, it may be Ok for yours. A 750 is to big for a 5.7 thats been said many times up here by some very smart guys, I have one on a 383 an feel it is a bit big at times.

smokediver
05-08-2007, 10:56 PM
you don't need to spend the money on new gears and labor . a new upper with the gear set is about 700.00 ...

DonCig
05-08-2007, 11:18 PM
very little help here... i have seen this problem many times on the street with edlebrock carbs. can you borrow a holly to run for day??? not a big one! maybe a 600- 750. no bigger. don cig runs in co maybe he could help

I run a Barry Grant Marine Demon, and I read and follow the tuning manual to the letter. No Bogs in my application, and if it did, I know how to tune it out on a Demon.

Don

yeller
05-09-2007, 12:55 AM
Have to throw in my 2 (uneducated) cents into the foray. To me, a bog is a fuel problem. The main fuel source being the carb, I'd beg, borrow or steal another carb for testing.

Mrfixxall, I'm not being confrontational, I'm just curious about your suggestions. I'm not a mechanic, but I have been around engines alot. I've seen the baffle plate increase hp due to a lower fuel mixture, but I've never seen it get hot enough to cause a bog. If it was boiling the fuel, wouldn't it be a problem in the upper rpms as well when the motor is working even harder?

LKSD
05-09-2007, 01:22 AM
Lose the Edelbrock. The altitude and depending where you are is a problem. €€The holly can be set up better for the altitude. Since you snomobile I am sure you know about altitude jetting. I takes a super man and a dyno in your altitude to fix that carb. The gear set put a bandaid on the real problem. I know you didn't hear this but better now than later


Sorry to chime in late here,, Griz & I are on the same page.. I too say go with a holley or BG.. Then worry about doing gears or other stuff.. Those Edelbrocks can not be jetted as easily as a H or BG can also the accellerator pumps in a H or BG are much bigger & you can also go with larger ones.. Lastly stay away from the vaccum secondary crap.. If you go with the H or BG get a mechanical secondary it helps to eliminate the bog.. Other than that how about a small 190 series blower & hatch scoop:lightning :bonk: :bonk: Jamie / Lakeside

maddad
05-09-2007, 06:09 AM
On a dyno, you can really see the effect of the edelbrocks secondary. It depends on a good signal to transition smoothly. In our boats(high load, low vacuum)that signal disapears as the secondary opens and so does the fuel you need. delaying the secondary opening till rpms and vacuum build up helps, but not as much as mechanical secondaries with their own pump. A dyno loads the motor at full throttle, like our boats, and you can see the torque curve go crazy from the "bog".
I switched to Holley.
Problem solved.:yes:

FOSTER
05-09-2007, 07:15 AM
Donziweasel, I can have this carb on a ups truck thursday if you want it, ran good two years ago. give me a call if you want. 603 387 5674
Bret.

LKSD
05-09-2007, 07:49 AM
If I remember correctly Weasel arent you at a high elevation?? That only can amplify the bad traits of that Edelbrock & a vaccum secondary.. That engine already has to fight to pull a vaccum with the thinner air.. ;) It is not something I think about much because I am closer to sea level, but high altitude makes it tough to get extra power & keep the laziness out.. :) Jamie / Lakeside

Donziweasel
05-09-2007, 08:38 AM
Jamie, yes I am up in the clouds. I run between 5000 and 8000 ft. The bog gets worse the higher in altitude I run.

Mr Fixall, I appreciate the advice, but the splash pan will not work with a roller cam, which I have. I think the manifold temps are fine.

It seems the general consensus is to try a mechanical secondary Holley or BG. Thanks for the ideas and keep them coming.

Cuda
05-09-2007, 08:51 AM
A splash pan will most certainly run on a roller cam application. HP 500's have a splash gaurd, and roller cams.

mrfixxall
05-09-2007, 08:56 AM
Have to throw in my 2 (uneducated) cents into the foray. To me, a bog is a fuel problem. The main fuel source being the carb, I'd beg, borrow or steal another carb for testing.
Mrfixxall, I'm not being confrontational, I'm just curious about your suggestions. I'm not a mechanic, but I have been around engines alot. I've seen the baffle plate increase hp due to a lower fuel mixture, but I've never seen it get hot enough to cause a bog. If it was boiling the fuel, wouldn't it be a problem in the upper rpms as well when the motor is working even harder?

I believe donziweasel stated that he was getting a boug in the upper rpm range....I had a similar problem with a boat years ago with just a plane jane performer on the boat and when the boat got to 3500 rpm it started bouging BAD....so i removed the carb and noticed a brown spot in the lower spot of the plenum which tells me that the fuel was burning in that spot before it had a chance to reach the cylinders...so all i did was remove the intake and installed a baffel and the problem went away....



Donziweasel,,,,,,, I dont see why the lifter valley baffel wont work,the lifters sit below the baffel,,or get rid of the performer and get the airgap intake where the baffel is not needed.. Trust me your manifold temps are as high as the oil splashing on it..look at your old intake,i bet theirs one mounted to the bottom of the intake....
good luck

Carl C
05-09-2007, 11:04 AM
:kaioken: :kaioken: Welcome to Hell.:kaioken: :kaioken:I needed some company. :kaioken: :kaioken:

Donziweasel
05-09-2007, 04:51 PM
Thanks for all the help. Just ordered a new carb and going that route first. I do not think the manifold is too hot and screwing up the fuel. Here is the reason- It does it when the engine has just been started as well as when warm. It simply has not had enough time to heat up the manifold. I did speak to some members today who I asked to call and they gave me some great advice. Amongst this post and my conversations today, as well as some PM's, the general consensus is I have a lean problem in the mid range and upper end. Secondaries are kicking in huge air and not enough fuel. This was determined due to no backfires when it would bog, indicating a rich condition. The edelbrock simply does not have enough tuning capabilities in this area to compensate for the lean condition.

I have also been told to get away from vacuum secondaries and go mechanical which makes since. Although many of you swear by the Sea Demon, as luck would have it, a buddy has a Holley 4160 in the box ready to go he said I could try first. Instead of spending $600.00 on a BG, I thought I would try it first.

Hell, if my company would sell, and I think I am getting close, I would be in an 18 Classic w/ fuel injection. Just out of curiosity, anyone know of a good relaible and inexpensive(yeah right) place to get a 5.7L fuel injected motor? Yes, I am considering a repower in the 16 if I can not get the "bog" out. I run anywhere between 3000-8000ft and the fuel injection would be nice. How about a fuel injection kit for my current 5.7L? JW, are you messing with them yet? How about a 5.7L fuel injected motor? Lastly, JW, if I sent you my motor as a last resort, can you put fuel injection on it?