Are the 4.9L intake manifolds interchangeable from the 1980s carb years through to the 1990s EFI years?

Best regards,
Rick C. Hodgin

 

Hello Rick. Not totally sure I understand your question.
But in general, yes, you can bolt a carbed intake to an EFI head and visa versa.

 

I'm in the process of converting my 4.9L from EFI to carb, and I'm looking at various parts. I found an Offenhauser after-market intake which looks very nice and says it fits the 4.9L and it's the same part for all years, but is $280. I found an old 83-87 stock carb intake manifold for a 4.9L, and it was $100. I looked at the gasket pattern and it was different enough for me to ask.

Thank you, AbandonedBronco. :-)

Best regards,
Rick C. Hodgin

 

The efi head has three extra bolt holes to help with installation but still had all the same ones as the carb. All carb manifolds will bolt right up.
The offenhauser intake is a much higher performance piece allowing for aftermarket carbs. If you just want the stock setup, go worth the stock intake.

 

What about replacing the EFI system in your truck with something like mega squirt or VEMS or other system?

 

I came across this thread tonight. This is looking exciting. :-)
Duraspark conversion for a 4.9 inline - FSB Forums

I've got it slated to get:
(1) 83-87 carb intake manifold $115
(2) Carter carb $100
(3) Pull off high-pressure fuel-pump, but leave low-pressure fuel-pumps in tanks.
(4) Miscellaneous other/custom fabricated connection hardware.

I have found some distributors online for a 1983 F-150 4.9L that have a vacuum line, and what looks like a 2-wire connector, all for about $50 to $80 each. Could I use one of those distributors? What are the two wires?

What else would I need?

Best regards,
Rick C. Hodgin

 

What year truck is this going into?
Kinda wondering if it's an EFI fuel system to the carb setup, which is doable.

The '83 Distributor sounds about right, a 2 wire connector to the signal trigger wheel sensor the Duraspark ICM uses.

 

1990 F-150.

As I understand it, if I get a prior year distributor, I'll need to change the gear to the one from my EFI engine. But would it work without hookup to a Duraspark ICM? Is it self-contained using only weights and vacuum? If not, what year do I need to go back to for that?

Best regards,
Rick C. Hodgin

 

If it's got a vacuum diaphram, it should have the advance and weights and stuff in it to work with a duraspark.

You might be able to get weights and spring kit to tune the spark curve, which maybe advantageous as you have a fast burn head.

I have heard of a difference in distributor gear (to camshaft) but do not know enough about it. I did the stab it in and see if it works, and seemingly lucked out and had a '96 distributor work in a '78 engine. (the '96 is OBD II era, and doesn't have a TFI module or weights or anything. Just a simple Hall sensor trigger I used for my VEMS)

 

Zarkeh- How would changing the distributor gear have a positive impact? The ratio has to be determined by the cam interface - if you change the gear all you can accomplish is throwing the engine out of time almost immediately, because some cylinders will be advanced or retarded in relation to how the distributor was set, and it will get progressively worse in a hell of a hurry. Changing the curve electronically or mechanically is one thing, changing timing is another - but changing the gear just sounds whacky. Or am I missing something?

 

Changing the distributor gear has more to do with the metals involved. A cam gear of one type of metal requires a distributor gear of a certain other type of metal. Otherwise, they'll chew right through each other.

I don't know if the EFI engine used a different type of cam gear than the carb'd engine, but I don't think so.
If you get an aftermarket cam, ask the manufacturer what type of distributor gear to use.

 

To change that, wouldn't the cam and distributor have to be a matched set? Maybe not the entire distributor, but the distributor drive gear?

Edit - I just realized that you're not talking about changing the gear ratio, just change it to a different type of metal.

Tom

 

I think at some point the distributor shaft diameter changed, necessitating a gear with a larger I.D.

But FYI changing the gear-to-rotor phasing on a distributor would just mean you would have to rotate the distributor in the block to maintain the same timing.

If you have a distributor with a vertical six-pin connector then you can use a Duraspark distributor using the bottom three pins on the harness only to hook up the Duraspark. I don't have the pin routing in front of me - a search would probably get it.

 

what AbandonedBronco said about the gear

What I said was in relation to the fast burn efi head, which has a better burn characteristic than the old carb heads. You could advance the timing on it to utilize this and get some gains from it, although if you didn't I doubt you'll have any problems.

I used a carb distributor in an EFI engine and didn't notice anything odd before ditching it all for EFI.

Once it's running, maybe talk to a tuner person about changing the timing curve if your willing to spend and work on it.

I only brought this up because there is a difference in the timing curves between heads, and if your building a performance engine, you might utilize this for some gains.

 

If so, I'd never heard that before. I've read of quite a few who convert their EFI engines to carb and all they do is drop in a carb'd distributor and I've never heard of issues.
Doesn't mean it isn't true though! Just hadn't heard that.