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Old 05-22-2014, 08:58 PM
dark_viper42 dark_viper42 is offline
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Chevy 305 to 350 swap?

Hello,

Hoping someone can give me a little info. I've got 1998 Sportstar with a TBI 305. I'm in need of a new motor and someone brought up the possibility of a 305 to 350 swap. I've been reading online all day but I'm not finding much info on ECM requirements. Can anyone give me an idea if the engine computer would need changed/reflashed to do this swap? Thanks in advance!
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Old 05-22-2014, 09:15 PM
Jeff d Jeff d is offline
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If your engine is running as is I'd consider pulling the whole thing, wiring harness, ecu and all and selling it. Then find someone selling a turn key 350 with ecu and wiring harness. You might get enough for it to offset a lot of the cost of the project.

If you go that route then you won't have to worry about so many odds and ends like alternator brackets, pulleys, ecu reflash/replacement, wiring harness and sender compatibility, etc. Those are the things that tend to kill swap projects both in time and money. Find a full turn key engine and you'll likely have a much easier time.

Will your transmission bolt up to a 350?
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Old 05-22-2014, 09:37 PM
dark_viper42 dark_viper42 is offline
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Quote:
Originally Posted by Jeff d View Post
If your engine is running as is I'd consider pulling the whole thing, wiring harness, ecu and all and selling it. Then find someone selling a turn key 350 with ecu and wiring harness. You might get enough for it to offset a lot of the cost of the project.

If you go that route then you won't have to worry about so many odds and ends like alternator brackets, pulleys, ecu reflash/replacement, wiring harness and sender compatibility, etc. Those are the things that tend to kill swap projects both in time and money. Find a full turn key engine and you'll likely have a much easier time.

Will your transmission bolt up to a 350?
From my online research its a direct swap. I'm just concerned about the ecu. The 305 and 350 are made from the same block so all brackets, pulleys, ect should swap right over.
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Old 05-22-2014, 09:47 PM
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Rossterman Rossterman is offline
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Swap and have the ecu reflashed for a 350
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Old 05-22-2014, 09:59 PM
dark_viper42 dark_viper42 is offline
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Originally Posted by Rossterman View Post
Swap and have the ecu reflashed for a 350
Any idea what the cost for a ECU reflash might be? Plan to call my dealer tomorrow...
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Old 05-23-2014, 05:32 AM
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CantRepeat CantRepeat is online now
 
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The trouble with flashing the ECU is whether or not Indmar has a cal file for a 98 350 and if the 350 you get is the exact same specs as the one Indmar may have made the tune for.

I see one for a 99 5.7 - 57tbi99.cal

If you end up doing this you may have to get a custom tune done for the motor through someone like Arizona speed and marine.
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Old 05-23-2014, 10:22 AM
dark_viper42 dark_viper42 is offline
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Originally Posted by CantRepeat View Post
The trouble with flashing the ECU is whether or not Indmar has a cal file for a 98 350 and if the 350 you get is the exact same specs as the one Indmar may have made the tune for.

I see one for a 99 5.7 - 57tbi99.cal

If you end up doing this you may have to get a custom tune done for the motor through someone like Arizona speed and marine.
Thats a good point and something I hadn't considered. A point I have to bring up after your question is after reading online that Indmar will not release their specs on the cams in thier motors how does anyone who cracks a block and gets and new short or long block get by with their stock ecu. I'd say chances are the cam in any remanufactured motor or even a new motor from gm/ford are not exactly the same specs?

I believe 99 was the first year they offered a 5.7L TBI in the sportstar. Not sure when they started offering it in the prostars.

With all the people i've read about getting a winter freeze and cracked block. Even if their 5.7L TBI was replaced by a new/reman 5.7L TBI they could/would possibly have the same issue.

Thanks for the response, looking forward to hearing more about people's take on this.
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Old 05-23-2014, 12:37 PM
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Rossterman Rossterman is offline
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Basically there were. 2 tbi 5.7. Pre- vortech at 275hp and vortech at 310hp (also called the predator). Easy way to tell is by number of intake manifold bolts. 8 bolts is vortech which has much better heads the are responsible for the HP increase. There's vortech engines are very common as were used in millions of chevy vehicles over the years. The predator is essentially this engine with SS head gaskets, better cam (folks have posted equivalent aftermarket cams that are close)' and brass freeze plugs. Ther are no special pistons, rods, etc that are used in a "marine" motor.

I would look to see if they have an MEFI flash for your year ecu and the 5.7 vortech motor (possibly a 205 or other model if not offered on the 190). If they are available, reflash it and build a low cost 5.7 vortech and purchase an edelbrock marine vortech intake to mount your existing tbi. As others have said, there 2 engines are 100% dimensionally identical so all parts from current motor will swap over. There is virtually no cost difference over what it will cost to rebuild the 305 (other than the MEFI reflash ($50) and manifold ($200) and cam ($200) which will be around $500). If your 305 turns out to be a vortech motor, you can reuse the heads and save the manifold cost. In exchange you will and easy+50hp increase but more importantly, tons more torque.

Here's a fairly recent post with someone parting one out:http://www.mastercraft.com/teamtalk/...ad.php?t=58755

Last edited by Rossterman; 05-23-2014 at 01:09 PM.
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Old 05-23-2014, 01:16 PM
dark_viper42 dark_viper42 is offline
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Quote:
Originally Posted by Rossterman View Post
Basically there were. 2 tbi 5.7. Pre- vortech at 275hp and vortech at 310hp (also called the predator). Easy way to tell is by number of intake manifold bolts. 8 bolts is vortech which has much better heads the are responsible for the HP increase. There's vortech engines are very common as were used in millions of chevy vehicles over the years. The predator is essentially this engine with SS head gaskets, better cam (folks have posted equivalent aftermarket cams that are close)' and brass freeze plugs. Ther are no special pistons, rods, etc that are used in a "marine" motor.

I would look to see if they have an MEFI flash for your year ecu and the 5.7 vortech motor (possibly a 205 or other model if not offered on the 190). If they are available, reflash it and build a low cost 5.7 vortech and purchase an edelbrock marine vortech intake to mount your existing tbi. As others have said, there 2 engines are 100% dimensionally identical so all parts from current motor will swap over. There is virtually no cost difference over what it will cost to rebuild the 305 (other than the MEFI reflash ($50) and manifold ($200) and cam ($200) which will be around $500). If your 305 turns out to be a vortech motor, you can reuse the heads and save the manifold cost. In exchange you will and easy+50hp increase but more importantly, tons more torque.

Here's a fairly recent post with someone parting one out:http://www.mastercraft.com/teamtalk/...ad.php?t=58755
My 305 is the vortec model. It has 8 intake manifold bolts, 2 vertical in each corner.

Based on that I'm thinking if i can get my MEFI reflashed for a 350 I'll buy a new GM 5.7L vortech and then part my old 305 out to recoup some of the costs.

Any easy way is to find out if the 99 sportsstar used the same MEFI as my 98, because i know they offered the predator motor in it. If its the same MEFI i shoudl be able to have it reflashed to that and everything else would be a direct swap over. Just having a little trouble finding a exact answer, mainly because the SS isn't all that common.
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Old 05-23-2014, 01:52 PM
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Rossterman Rossterman is offline
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Quote:
Originally Posted by dark_viper42 View Post
My 305 is the vortec model. It has 8 intake manifold bolts, 2 vertical in each corner.

Based on that I'm thinking if i can get my MEFI reflashed for a 350 I'll buy a new GM 5.7L vortech and then part my old 305 out to recoup some of the costs.

Any easy way is to find out if the 99 sportsstar used the same MEFI as my 98, because i know they offered the predator motor in it. If its the same MEFI i shoudl be able to have it reflashed to that and everything else would be a direct swap over. Just having a little trouble finding a exact answer, mainly because the SS isn't all that common.
That's what I would do. You will need to contact indmar and give them the numbers off the back of the ecu. I'd be amazed if it is any different than what is used for the other models (just a different cal file). Don't forget you will need the indmar (or equivalent cam) as the standard cam in a car/truck wasn't a performance grind- unless you buy a new marine specific engine. There are some very reasonable long block prices that aren't much more than a rebuild and you start with new everything! Let us know how it works out!

Here's a new one at a reasonable price:http://www.michiganmotorz.com/350ci-...FcQ7Mgod-QcAyA

Last edited by Rossterman; 05-23-2014 at 02:07 PM.
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