Repowering 1994 Alpha One 4.3LX with new Vortec Engine

[jkm3093]

Hi guys,

For clarity I decided to start a new thread from my original:

http://www.marineengine.com/boat-fo...297-Alpha-One-4.3LX-Won-t-Start-amp-Backfires

I bought a new GM Marine 4.3L Vortec engine with 4 BBL intake manifold and have been swapping parts over or replacing as needed, and is ready to drop back into the boat for final assembly / adjustments. I had a few questions that I hope you guys will be so kind to offer opinions:

Ignition: I plan to re-use my Thunderbolt IV ignition with normal 8 deg. BTDC initial advance / 22 deg total advance, wheras the sparce motor specs I got with the new motor calls for advance of 2 - 26 deg which I take to mean the later Thunderbolt V with knock sensing retardation, greater total advance, etc. Any thoughts if this is OK & how it will effect power output? With no knock sensing I plan to use 93 octane fuel.

Carburetor: I rebuilt the Weber 9600 series 4 BBL carb. The old set-up had a remote automatic choke where the coil is bolted to the manifold and linked to the choke plate. The new manifold does not have a mount for the coil. Should I change it out to an electric choke like the 2 BBL carb has? Any leads about what I need?

I am sure there will be more things that pop up as I continue, but that's it for now. Thanks for your input.

Jim

 

[bondo]

Ayuh,.... I think you'll be Fine with the T-Bolt IV...
Testing will tell ya, at that point....

And,...
For yer choke, the Edlebrock Performer carb electric choke conversion should fit right onto yer Merc/ Weber carb, as they're the same castings...

 

[jkm3093]

Thanks, Bondo. Is Summit Racing a good place to get the carb choke conversion?

 

[RicardoMarine]

Ignition: I plan to re-use my Thunderbolt IV ignition with normal 8 deg. BTDC initial advance / 22 deg total advance, wheras the sparce motor specs I got with the new motor calls for advance of 2 - 26 deg which I take to mean the later Thunderbolt V with knock sensing retardation, greater total advance, etc. Any thoughts if this is OK & how it will effect power output? With no knock sensing I plan to use 93 octane fuel.

Jim, I'm not sure that this is what you're after, but here's a friendly FYI for you;

When looking at OEM T-Bolt IV or V module specs, note that the module specs will be minus BASE advance.
So for any TA numbers, BASE must be added.
Examples (according to your numbers):
Thunderbolt IV ignition 8 deg BASE + 22 deg Module = 30 deg TA.
Thunderbolt V with knock sensing retardation 2 deg BASE + 26 deg Module = 30 deg TA.
Looks like both give the same TA, but the V offers the knock sensing retardation and re-calculation.

Conversely, when looking at OEM engine timing specs only, the TA should include the RPM and will include BASE.
These numbers will be exactly what you'll see when you strobe this at the higher RPM range where you'll be checking TA.
Set BASE, but always follow up with a dynamic TA and RPM check, and you'll be safe.

Your new OEM Vortec engine will likely be using the full dished pistons, of which means that you'll want to be careful as to not exceed the OEM TA per RPM specs.

.

 

[jkm3093]

Rick,

Maybe I stated it wrong, but my T IV has 8 + 14 = 22 deg total like this:



I guess I was asking if this will be OK with the Vortec engine or if it is more susceptible to knock than my old engine.

Thanks, Jim

 

[jkm3093]

Now that spring is here I am now making a concerted effort to wrap up this project and spent a few days last week working on it - engiine bay is nearly complete and am now in the process of outdrive impeller change and will then pressure / vacuum test / reinstall the drive.

A couple of issues if I can kindly get some comments:

I am embarrassed to admit I have never changed the impeller in the 5 years I owned the boat and I doubt the original owner did either so that could make this a 17 year old impeller. Amazingly it was in very good condition with no vane cracking, little tip wear, still pliable & following the contour of the pump housing. My question: There is a plastic sleeve over the water tube that looked like it melted - see photos looking up into the drive shaft housing and the removed sleeve. Did the hot exhaust do this? What is the purpose of the sleeve - align the water tube into the coupling assembly during installation and it has no purpose after that?


The real problem I have is converting to an electric choke on the Weber 9600S-0823 4-BBL carb. I bought Edelbrock Performer series choke kit #1478 and it is wrong. The shaft that connects the choike plate linkage is too short and there is no vacuum port on the side of the carb for the chioke piston. Any ideas? I am thinking it might be easiest to install a old-fashion manual choke with the choke knob in the engine bay since it only needs to be choked on initial cold start up.

Thanks, Jim

 

[bondo]

I am embarrassed to admit I have never changed the impeller in the 5 years I owned the boat and I doubt the original owner did either so that could make this a 17 year old impeller. Amazingly it was in very good condition with no vane cracking, little tip wear, still pliable & following the contour of the pump housing. My question: There is a plastic sleeve over the water tube that looked like it melted - see photos looking up into the drive shaft housing and the removed sleeve. Did the hot exhaust do this? What is the purpose of the sleeve - align the water tube into the coupling assembly during installation and it has no purpose after that?

Ayuh,..... That's all that sleeve is for,... alignment of the tube....

I'd suggest a Full water pump rebuild Kit, with a new housing...
If everything ran without water long enough to melt that tube, ALOTA things got Way To Hot....

The Shutters, just at the top of the y-pipe, are probably Smoked,....
The exhaust rubber couplers are no doubt Burnt internally, possibly even the bellows, if so equiped...

Donno 'bout yer carb, mine is/was electric from Merc...

 

[jkm3093]

I'd suggest a Full water pump rebuild Kit, with a new housing...
If everything ran without water long enough to melt that tube, ALOTA things got Way To Hot....

The Shutters, just at the top of the y-pipe, are probably Smoked,....
The exhaust rubber couplers are no doubt Burnt internally, possibly even the bellows, if so equiped...

Bondo, thanks for the response. If the cause of the plastic sleeve melting was from running without water for a long time, it must have been before I owned the boat, and no problems with the outdrive surfaced during those 5 years. I always heard that dry running would wipe out the impeller within a minute but it looked surprisingly good. The pump housing shaft seal was worn out but that's about it. I replaced the water pump impeller, shaft seal and gaskets but the housing looked shiny withoiut any scoring so I didn't replace it. I inpected the 2 bellows and they looked good but I'll check them closer. The exhaust rubber couplers at the risers looked fine too. I have never had water in the outdrive oil or oil level drop so it seems to be well sealed but I will confirm with pressure / vacuum test. So, I haven't seen any other supporting evidence of running dry. Is it that uncommon for the plastic sleeve to melt due to normal exhaust heat?

 

[kghost]

There could be many reasons why that plastic tube melted and many were allready listed........If all worked well then I would not think there is anyhting to worry about. A good inspection and a definate replacement of the impellor is needed as you are in there allready!!!


Becuase it was stuck upward on the copper tube I would suggest that the last person who replaced the impeller never looked UP.......

Is this a gen I or a gen II alpha? Do you know?

If not a pic of the impeller will tell us.....


As far as your carb goes do some google searching for carb rebiulder/parts there are a few that wil have almost every part needed.

You may also be able to find a used carb with the electric choke set up and just rebiuld it.

Is there the ability to mount the spring chimney in the same location on the intake manifold? One determing factor is whether or not they installed the heat passage block off plates when the intake was installed. This area of the manifold was/is used as a carb base plate heat source. That is why the choke chimney mount.

 

[jkm3093]

Becuase it was stuck upward on the copper tube I would suggest that the last person who replaced the impeller never looked UP.......

Is this a gen I or a gen II alpha? Do you know?

If not a pic of the impeller will tell us.....

You know, it is very plausible the original owner ran it dry causing damage, then a shop repairing the outdrive & leaving the melted sleeve there. That's maybe why the impeller looked so good.

This drive is an Alpha One Gen II with the square drive oil reseroir. That brings up a question - when I pressure / vacuum test the outdrive, what prevents venting out the overflow port?

As far as your carb goes do some google searching for carb rebiulder/parts there are a few that wil have almost every part needed.

You may also be able to find a used carb with the electric choke set up and just rebiuld it.

Is there the ability to mount the spring chimney in the same location on the intake manifold? One determing factor is whether or not they installed the heat passage block off plates when the intake was installed. This area of the manifold was/is used as a carb base plate heat source. That is why the choke chimney mount.

The old intake manifold had a mount for the coil and the new one doesn't. I just rebuilt this carb so I'd hate to start over with another one and don't relish the thought of a new one unless it brings some benefit like going from 625 CFM to ???. I don't want to let this carb issue to run costs up even more also delay the project so for now I guess I'll fit a manual choke to it and come back to this issue later.

 

[guyjg]

Check w/a KOI auto parts store for the automotive electric choke for GM V-8s for that year and 4 BBL carb. I never liked the fact that the elec. choke was receiving voltage the entire time the ignition was on...it just wears out the heater coil. You'll need a length of 16 ga. purple wire to light up the choke. When you get the choke have KOI match the choke terminal w/the correct terminal connector.

 

[bondo]

This drive is an Alpha One Gen II with the square drive oil reseroir. That brings up a question - when I pressure / vacuum test the outdrive, what prevents venting out the overflow port?

Ayuh,... The drive will be on the bench, 'n the oil bottle will be in the boat....

There's a spring check-valve on the drive, 'n bellhousing...

 

[jkm3093]

OK, I reassembled the outdrive and tested:
Pressure: 15 psig dropped to 12 psig after 30 minutes
Vacuum: 8" Hg (all my hand pump would suck) held steady for 30 minutes
Pass or fail?

Then later I was cleaning up the bench and found the upper case baffle sitting under a rag - DOH! That's what I get for 1st time assembling after leaving it apart for 2-3 weeks. Next time I won't forget it!

Jim