Megasquirt on a 350 with a holly 4bbl carb intake

First off I don't know Chevys well at all. I always try and figure out what the fuck could have happened when someone tells me that their 350 blew an intake gasket and theres leaking coolant! (seriously)

A buddy of mine is getting seriously tired of tuning his rochester carb on his 350.. He's seriously thinking of ditching the whole car.

He's one of those guys who can't leave well enough alone (like most of us) and kept doing stuff to his motor etc. It's got a massive cam, roller rockers, some aftermarket heads blah blah.

The point is he's having a bastard of a time with tunability.

Until Monday he didn't know about Megasquirt. I'm wondering is there a fairly cheap and easy way he can get a throttle body, wide band O2 sensor and a megasquirt box on this thing so he can be a happy man again?

I know dakotas for the longest time had a holley throttle body. Anyone know if they have the same flange as a 4 bbl holley carb? There's probably some chev that came with a throttle body with the right flange??

I figure after getting ms and an O2 sensor he's going to have spent as much as he wants to.. so something junkyardable would be great.

Thanks for any input

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Andrew M
Onterrible
30ish



Edited 2 time(s). Last edit at 04/29/2008 07:15PM by hudson.

Well depending on the year you can get a TBI setup from a LT-1, like impala/z-28/trans am/Vette motor of the 80's vintage (85-93) or 90's vintage (93-97). IIRC it's L-98 and LT-1 respectively. Guess what? The later stuff is better.

See what you can find at a pick n pull. Might as well get the rest of the sensors for the motor because you'll need them too. Like MAP(or MAF) most are MAP, Intake air temp, o2 sensor, coolant temp, TPS, thermostat, Heck maybe Engine Harness, but they're easy enough to make custom and it always looks waaay cleaner. Painless wiring has to make a harness for it too. (The dash cluster may or may not be necessary to keep the ecu happy, but thought I'd mention it as a possible concern)

Personally I wouldn't use a megasquirt. There are tons of guy who are backyard tuners for stock PROMs for the factory ecus. They can make new maps for larger rate fuel injectors. Proms is out, tuned and back in in 20 mins.

I have a friend in Indiana who burns chips in his garage and does a lot of GM tuning on various GM ecus. He's done it over the phone and gets it real close in a few tries. You just tell him what it's doin. He makes corrections to a new chip, sends it to you, you put it in, and then send yours back. No down time. He's a hell Ohof a smart guy. He does forced induction tuning on factory ecus too. I can his number if you want let me know. Or find someone in your area.

These guys are the Original Gangsters - http://www.tpis.com/index.php?module=396sbc

Efi101.com should also help you in your quest.

That's the cheapest and best way I know of you can go EFI.
If you still want to use megasquirt just substitute it for the factory ecu and do the tuning your self.

But If that thing is really pumped up and you're going to flow more air than the stock induction system is capable of (My guess is not much over 400HP) you can get different intake runners, and plenums, and all that jazz. Flip through a summit catalog.

Dude help him out with this. It's not hard to get it workin right. Way easier than a carb in my opinion. You'll look like a God and it's a great place to get your feet wet with fuel injection conversions.

Innovate makes the best Wideband for the money hands down. HotRod tested about 25 of them and they voted it #1.

Hope that helps!

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Michael LeCompte

It'd be something like the one these guys sell for $3700. Only you pull the shit from the junkyard yourself for a few hundred bucks.

http://www.tpis.com/index.php?module=catalog_page&catalogPageNumber=9&catalogSubCategory=Fuel+injection+small+block

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Michael LeCompte

Thanks for the input..

First, he's a licensed mechanic who services/fixes my truck.. so I'm not going to come off as a good here

Second, he's been stuck using this camaro with a huge cam, etc as a daily driver as his brand new corolla has a mysteriously fucked up transmission (been at the dealership for months apparently).

He's about ready to just ditch the whole thing.. and I know he's been working on it for years and years so I don't want to see that. He also doesn't want to put a lot more cash into it.

Apparently you can get a throttle body off a 350 truck that will bolt to his Rochester adapter plate.. that's probably his best option.. he doesn't want to touch spark etc. I'll mention it to him at least.

I think the whole gas economy etc has got him hating on the whole project. Lately, he's always saying why bother with a V8.

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Andrew M
Onterrible
30ish

None of the factory t-bodies will fit a 4 bbl manifold. Depending on the year of his heads most factory EFI manifolds may not fit either.

Rochesters are great on a stock motor, but they are all pretty old and difficult to tune. . A new Edelbrock 4 bbl is a good route. They are easy to tune if needed. There is a 400 hp plus Malibu in my shop withan Edelbrock. It starts great, runs even better, good idle . I put a marine version on my boat 2 years ago. Out of the box, adjusted once and still fine.

Gene

heymagic Wrote:
-------------------------------------------------------
> None of the factory t-bodies will fit a 4 bbl
> manifold. Depending on the year of his heads most
> factory EFI manifolds may not fit either.
>
> Rochesters are great on a stock motor, but they
> are all pretty old and difficult to tune. . A new
> Edelbrock 4 bbl is a good route. They are easy to
> tune if needed. There is a 400 hp plus Malibu in
> my shop withan Edelbrock. It starts great, runs
> even better, good idle . I put a marine version on
> my boat 2 years ago. Out of the box, adjusted once
> and still fine.
>
> Gene

The heads are likely Edelbrocks.. they definitely aren't stock.

He's got a Holley mid rise intake with an adapter to the Rochetser QJet??? whatever it is.

I agree they are ancient and difficult to tune.. but he's just one of those mechanics.. likes to talk about how he can get a carb to run better than EFI. That being said, he's bloody sick of his carb right now.

My next door neighbour who's a big bow tie guy says you can put a TBI off a truck .. has the same bolt pattern as the rochester??

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Andrew M
Onterrible
30ish

Yeah guess you could go with a 82-93 TBI setup. Now we're talking throttlebody instead of tuned port.

Go find a 82-93 Chevy Truck and go get all the same sensors I told you about before and the wiring harness too. You'll likely have to get another adaptor plate for his high rise intake.

Get a megasquirt to tune it.

Dude it's about the same money either way and a Tuned Port setup is waay better.

Throttlebodys are only like 650cfm at max.

Oh yeah and you prolly need new fuel pump and FPR.

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Michael LeCompte



Edited 4 time(s). Last edit at 04/29/2008 09:31PM by pikespeakgtx.

pikespeakgtx Wrote:
-------------------------------------------------------
> Yeah guess you could go with a 82-93 TBI setup.
> Now we're talking throttlebody instead of tuned
> port.
>
> Go find a 82-93 Chevy Truck and go get all the
> same sensors I told you about before and the
> wiring harness too. You'll likely have to get
> another adaptor plate for his high rise intake.
>
> Get a megasquirt to tune it.
>
> Dude it's about the same money either way and a
> Tuned Port setup is waay better.
>
> Throttlebodys are only like 650cfm at max.
>
> Oh yeah and you prolly need new fuel pump and FPR.

I thought that's what I was always talking about? I knew you were talking about other things. He doesn't want to touch the intake, etc.. The car makes more than enough power as it is now.. I think all he really wants is drive ability and somewhat better gas economy -- without having to worry about tuning it frequently.

I agree there are better ways to do it.

Yeah he's going to be into a new fuel pump for sure, plus a return fuel line.

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Andrew M
Onterrible
30ish

it's going to cost about the same money to do it either way is what I'm saying.

The tuned port setup is going to give you all the MPG and efficiency. The TBI setups aren't that great. Plus theres no point in a high rise intake if you're only flowing 650cfm.

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Michael LeCompte

pikespeakgtx Wrote:
-------------------------------------------------------
> it's going to cost about the same money to do it
> either way is what I'm saying.
>
> The tuned port setup is going to give you all the
> MPG and efficiency. The TBI setups aren't that
> great. Plus theres no point in a high rise intake
> if you're only flowing 650cfm.


Word I hear you. This isn't my engine His rochester can't be flowing more than 650 cfm either (I'd imagine).

I'm just trying to help out a man who's tired of his carb, but doesn't want to change his intake

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Andrew M
Onterrible
30ish

put a new carb on it.

750 mechanical secondary holley carb.

buy it new. it should be just fine out of the box.


if you want to tune get a jet kit and a wideband and have fun.

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Michael LeCompte

650cfm is like 275 horse. Why the big cam? why the heads?

Personally I think he should just ditch the whole project! LOL! I mean this in the nicest way possible.

Either put a new decent Carb on it, or spend about a grand and get a tuned port setup and sell his old intake. Why's he so attached to it? Was it his granddaddys? Is he sentimental?

I'm trying to be funny, hope the humor comes across the internet.

---

Michael LeCompte

pikespeakgtx Wrote:
-------------------------------------------------------
> 650cfm is like 275 horse. Why the big cam? why the
> heads?
>
> Personally I think he should just ditch the whole
> project! LOL! I mean this in the nicest way
> possible.
>
> Either put a new decent Carb on it, or spend about
> a grand and get a tuned port setup and sell his
> old intake. Why's he so attached to it? Was it his
> granddaddys? Is he sentimental?
>
> I'm trying to be funny, hope the humor comes
> across the internet.

Hehe I hear you.

I don't know, maybe it's a big rochester. Like I said, I'm not a chevy guy.. and no one ever put a rochester on a volvo.

I think the honest story reads a lot like many guys I know.

They're chevy dudes. Love the 350, love the big cam, love the sound and torque of a V8.. are scared shit less of fuel injection.

I'd imagine 60+ percent of rodded motors out there aren't tuned right.

This story has a twist though.. He just started buying new cars and talking to people rodding new cars and has realized that he can have just as much fun with less fuel.. so I think he's just sort of given up on the whole thing.

I also think he just discovered turning.

Ah well, whatever I just hate seeing someone hate on a 10 year project.

---

Andrew M
Onterrible
30ish

pikespeakgtx Wrote:
-------------------------------------------------------
> put a new carb on it.
>
> 750 mechanical secondary holley carb.
>
> buy it new. it should be just fine out of the
> box.
>

Ha ha.

Hahahahaha.

HAHAHAHAHAHAHA....

Holleys are factory jetted incredibly pig rich in order to protect people who just throw the carb on out of the box.

IMO mechanical secondaries don't belong on a street engine, period.

A 750 is huge for a 350. We use 750s on 550hp stroker Pontiacs.


If you want drivability, the easiest way is port fuel injection. Not TBI, *port* injection. I am short of time but the LT1 intake (note not LT-1, that's different) will not work on a smallblock without massive rework of everything. The LT1 is essentially a different species that looks similar. Best bet is to get an open plenum carb intake and install bungs and rails for port injection.

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

why won't lt-1 port injection setup work? You need vortec heads or something?

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Michael LeCompte