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350 EFI TBI Mods, cam, heads, intake, tune, 383?

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350 EFI TBI Mods, cam, heads, intake, tune, 383?

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Old 04-24-2018, 09:06 AM
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Default 350 EFI TBI Mods, cam, heads, intake, tune, 383?

I have a 97 Maxum 2100SR with the 350 EFI/TBI engine in it. Its going to get some upgrades real soon.

Heads I am going to use are GMPP Fast Burn Vortec aluminum, already have.
Intake I am looking at is the GMPP TBI to Vortec Intake, will need to bored to 2 inch to fit the big block Merc TBI
The cam I am thinking about is the Comp XR276HR 224/230 110 LSA. I have read posts by Dennis Moore saying this cam will work with no reversion
The exhaust will be side exit, eliminating the prop exhaust all together.

Other options are:
If the block has little to no wear when I pull it down, I have a set of stock GM LT4 flat tops I could install
383? I have a fresh .030 over late model roller block that I could short block and install with the same top end, but maybe use dish pistons to keep compression in check.

As far as tuning, I have an Inovate wide band and I am an established tuner. I have been tuning for years. I would either have to purchase MEFI Burn or change the ECM.
I know the TBI may hold me back some, but I would like to keep EFI if at all possible. I also have a set of bick block TBI injectors that I can install.

Other question I have is will the stock Merc electric fuel pump keep up?
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Old 04-24-2018, 10:14 AM
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Originally Posted by Paxtonspeed View Post
I have a 97 Maxum 2100SR with the 350 EFI/TBI engine in it. Its going to get some upgrades real soon.

Heads I am going to use are GMPP Fast Burn Vortec aluminum, already have.
Intake I am looking at is the GMPP TBI to Vortec Intake, will need to bored to 2 inch to fit the big block Merc TBI
The cam I am thinking about is the Comp XR276HR 224/230 110 LSA. I have read posts by Dennis Moore saying this cam will work with no reversion
The exhaust will be side exit, eliminating the prop exhaust all together.

Other options are:
If the block has little to no wear when I pull it down, I have a set of stock GM LT4 flat tops I could install
383? I have a fresh .030 over late model roller block that I could short block and install with the same top end, but maybe use dish pistons to keep compression in check.

As far as tuning, I have an Inovate wide band and I am an established tuner. I have been tuning for years. I would either have to purchase MEFI Burn or change the ECM.
I know the TBI may hold me back some, but I would like to keep EFI if at all possible. I also have a set of bick block TBI injectors that I can install.

Other question I have is will the stock Merc electric fuel pump keep up?
I would go 383 if it was all apart.

MEFI burn will work fine. Although the TBI setup may work, it may also be somewhat limiting. I tuned a TBI big block and even with a bored out TB it was pulling vacuum at WOT and 5000 rpm. Injector sizing becomes limiting as well with a TB.

The stock merc pump should work. Your fuel demand won't be that much more.

I'd like to see a wider LSA on the cam.
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Old 04-24-2018, 12:37 PM
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Originally Posted by Trash View Post
I would go 383 if it was all apart.

MEFI burn will work fine. Although the TBI setup may work, it may also be somewhat limiting. I tuned a TBI big block and even with a bored out TB it was pulling vacuum at WOT and 5000 rpm. Injector sizing becomes limiting as well with a TB.

The stock merc pump should work. Your fuel demand won't be that much more.

I'd like to see a wider LSA on the cam.
Thanks for the input the CC503 or Comp 276HR-12 is 224/230 112LSA.
I have been reading and realized the first cam may be too much. I forgot about the idle needing to be higher with such a large cam. This may not be good on the drive when putting it into gear. Tuning with fuel injection would help this problem some, with being able to get a lower idle with EFI vs. Carb.
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Old 04-25-2018, 08:02 AM
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Sell that motor and buy one already set up
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Old 04-25-2018, 11:39 AM
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Originally Posted by Paxtonspeed View Post
Thanks for the input the CC503 or Comp 276HR-12 is 224/230 112LSA.
I have been reading and realized the first cam may be too much. I forgot about the idle needing to be higher with such a large cam. This may not be good on the drive when putting it into gear. Tuning with fuel injection would help this problem some, with being able to get a lower idle with EFI vs. Carb.
I'm currently using a Crower 00483LM hyd roller in a 377 (stroker w/standard bore). Cam is a 221/230 @ .050" and .525/.545" with a 1.5 rocker on a 114 LSA. Several hundred problem free hours with this cam. I don't remember my exact idle setting off hand but believe its either 650 or 700 rpm. EFI definitely tames down the idle nicely, specifically if you get the AFR to reasonable levels.
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Old 05-04-2018, 10:15 AM
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Originally Posted by Trash View Post
I'm currently using a Crower 00483LM hyd roller in a 377 (stroker w/standard bore). Cam is a 221/230 @ .050" and .525/.545" with a 1.5 rocker on a 114 LSA. Several hundred problem free hours with this cam. I don't remember my exact idle setting off hand but believe its either 650 or 700 rpm. EFI definitely tames down the idle nicely, specifically if you get the AFR to reasonable levels.
Thanks, are you still running the stock exhaust manifolds?
I am leaning towards just running the LT4 Hot Cam. Its a proven cam, in a boat motor and does not have real aggressive lobes so it should do good at sustained high RPM.
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Old 05-04-2018, 03:52 PM
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Originally Posted by Paxtonspeed View Post
Thanks, are you still running the stock exhaust manifolds?
I am leaning towards just running the LT4 Hot Cam. Its a proven cam, in a boat motor and does not have real aggressive lobes so it should do good at sustained high RPM.
Yes. Stock GLM style manifolds.
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Old 05-08-2018, 07:57 AM
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I keep going back and forth on cam selection. With all the searching I have done, I keep seeing posts by Dennis Moore saying to keep the LSA tight on a boat motor.
So now I am thinking a Comp 218/224 110LSA. This cam only has 1 degree of overlap using the duration at .050. It is very close to the Hot Cam except for the difference in LSA, 110 vs. 112.

Dennis says that a 218/224 with a 110LSA will make close to the same power as a 224/230 with a wider LSA say 112 to 114. He also said it would have more mid range power and get better fuel mileage.
It seems a lot of guys want to only focus on LSA when trying to figure out what cam will revert water. What really matters is the total overlap of the cam, which is calculated with duration and LSA.

I got my motor pulled down and it looks like I have a bad cylinder on number 3. So, it looks like a total rebuild.
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Old 05-08-2018, 08:16 AM
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Also realized that my Fast Burn heads have raised D exhaust ports. My stock manifolds are not going to line up very good at all.
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Old 05-08-2018, 10:30 AM
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Originally Posted by Paxtonspeed View Post
I keep going back and forth on cam selection. With all the searching I have done, I keep seeing posts by Dennis Moore saying to keep the LSA tight on a boat motor.
So now I am thinking a Comp 218/224 110LSA. This cam only has 1 degree of overlap using the duration at .050. It is very close to the Hot Cam except for the difference in LSA, 110 vs. 112.

Dennis says that a 218/224 with a 110LSA will make close to the same power as a 224/230 with a wider LSA say 112 to 114. He also said it would have more mid range power and get better fuel mileage.
It seems a lot of guys want to only focus on LSA when trying to figure out what cam will revert water. What really matters is the total overlap of the cam, which is calculated with duration and LSA.

I got my motor pulled down and it looks like I have a bad cylinder on number 3. So, it looks like a total rebuild.
It is true that overlap, lift/duration and LSA are all a factor. Typically you will want to widen the LSA a bit when going up in cam size. Having said that the stock GM 395 cam that many SBC came with had a 109 LSA. But....the duration was tiny.

PM me for more thoughts.
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