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Input on new engine plan for 1988 G20 #733932
March 11th 2018 9:04 pm
March 11th 2018 9:04 pm
Joined: Jan 2014
Posts: 91
Houston, TX
V
VanEnvy Offline OP
journeyman
VanEnvy  Offline OP
journeyman
V
Joined: Jan 2014
Posts: 91
Houston, TX
I am in the planning process of my 1988 G20 project. The van currently has a 1990 5.7l tbi engine with a large rear main seal leak and leaks from a few other places, so I am going to replace it with a crate motor.

My goal is to have driver quality performance and reliability. I don't want to build a complete frankenstein that will require heavy modifications or fabrication. That's the primary reason I am eliminating an LS swap from my options.

I would like to maintain the current ECU and TBI system. From what I have read that basically leaves me with two options:

1. A direct fit replacement engine with TBI heads...or

2. Go a generation newer and get the Vortec heads

I am leaning towards option number 2, even though I will have to use a special manifold/adaptor and possibly get a tune for the ECU. The cost is slightly higher to go this route, but from what I have read the vortec heads are leaps and bounds better than the TBI heads. They also seem to have more upside should I decide to do a more aggressive performance build (cam, etc).

Have any of you had to make this decision or thought about it before? What did you decide and why? Is there another path I should be considering? Am I thinking about this correctly?

Thank you for any input that you have!

Re: Input on new engine plan for 1988 G20 [Re: VanEnvy] #733933
March 11th 2018 11:29 pm
March 11th 2018 11:29 pm
Joined: Feb 2002
Posts: 406
vanland Des Moines
Lionvan Offline
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Lionvan  Offline
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Joined: Feb 2002
Posts: 406
vanland Des Moines
I bought a 350 Goodwrench van /pu/suv engine from Jegs for.about $1800 a little over a year ago. It has swirl port heads and different cam than the car.motors. about 15 more .horses and more torque. Paid.a.guy a.grand to put it in,plus a few hundred in odds and ends like spark plugs and stuff. Oh.yeah it's a 90 G 20.
Stock new put the zip back in it. I.had 160,000 on the old one. I bought THE van new.in 1990.
Jegs has all kinds of engines that bolt n. Call them up they're real helpfully.On the phone.

Last edited by Lionvan; March 11th 2018 11:30 pm.

[IMG]A foolish faith in authority is the worst enemy of truth. Question Authority.
Re: Input on new engine plan for 1988 G20 [Re: VanEnvy] #733948
March 12th 2018 5:15 pm
March 12th 2018 5:15 pm
Joined: Nov 2013
Posts: 2,493
Michigan
Dyno_Dave Offline
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Dyno_Dave  Offline
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Joined: Nov 2013
Posts: 2,493
Michigan
I think you've done your homework appropriately to this point.

Your current RPO L05 350 with swirl port heads have their place. If you want HIGH horsepower and high RPM, they are not the head for you. But they are a good truck head, and make great low end torque, which is what gets you moving, hence why GM used them in heavy trucks and full sized cars. They were also used in some F-bodies, but mostly as a low cost way into a V8. It gave them an intermediate step to offer the Camaro/Firebird buyer that the Mustang did not have. But I digress...

The RPO L31 5.7L Vortec will ultimately make more horsepower, and have more "headroom" for future performance growth.

Which is right, or best? Depends on your budget, your goals, and your patience in tuning. Understand the jump to the later 5.7L Vortec will require a better fuel pump most likely and expensive intake or an adapter for a carb intake, a chip or tuning system like EBL Flash, etc.

I would seriously recommend you spend a few hours reading through the TBI section of the thirdgen.org forum. They have about the best TBI information you're going to find on the web today, including contributors Rbob, FAST355, Tuned Performance, Schurkey, and others.

If you thumb back far enough, you can find a LONG thread (lots of detail and questions/answers) from a fellow who made the jump from L03 TBI 5.0L to L30 Vortec 5.0L, and what some of the differences he ran into where (accessories, tuning, etc.).

TGO


Re: Input on new engine plan for 1988 G20 [Re: Dyno_Dave] #733961
March 12th 2018 11:48 pm
March 12th 2018 11:48 pm
Joined: Jan 2014
Posts: 91
Houston, TX
V
VanEnvy Offline OP
journeyman
VanEnvy  Offline OP
journeyman
V
Joined: Jan 2014
Posts: 91
Houston, TX
Lionvan and Dyno dave, thanks for your input.

I did a lot of my reading on the thirdgen forum, tons of info there.

My goal isn't necessarily just to have high horsepower and RPM. I just want the best balance for drive-ability. By balance I mean a decent throttle response at low and high speeds. The average highway speed around here is 70-75mph and I'm worried about feeling "topped out" at those speeds.

I have read that the benefit of the vortec heads is primarily over 4000rpm, which i assume I will not see much. If the drive-ability between the swirl and vortec heads is going to be negligible at low AND high speeds, I could be easily be persuaded to stay with swirl heads and avoid the intake, egr, fuel pump, and tuning issues. Any input?

Weather vortec or swirl, my build will include headers, intake, & upgraded ignition.

Thanks again for the feedback.

Re: Input on new engine plan for 1988 G20 [Re: VanEnvy] #733974
March 13th 2018 7:58 pm
March 13th 2018 7:58 pm
Joined: Nov 2013
Posts: 2,493
Michigan
Dyno_Dave Offline
veteran
Dyno_Dave  Offline
veteran
Joined: Nov 2013
Posts: 2,493
Michigan
With the right cam, OD trans, and efi, the Vortec is a great truck motor. It's what's in my '98 Suburban and my '97 Express van. Not trying to talk those motors / heads down. They are almost legendary as the best factory iron SBC head ever. Better than old Corvette heads, better than fuelies, better than camel backs...Hard to go wrong with that! I'm sure you'll be happy with the performance of either.

Personally, I really respect the opinion of Fast355 on that forum. And many of the performance numbers he talks about are in his G van, with Vortec heads and TBI. You'd have to read some of his posts, but I believe he's indicated that the swirl port heads can be good for 300 horse. So again, sort of depends on your goals. But the more aggressive the build, the more tuning work to be done. And the more parts to be bought. So it's sort of a balancing act.

Even though your build is for a van don't be afraid to post questions about it in the TBI section. Anywhere else there (like Electrical or Interior), and you may be encouraged to look for another forum, as their specialty is 82-92 F-bodies. But the TBI section is a little more wide open, and they get lots of truck questions.


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