1968 Changing carb

[mbsf1970]

What would the effects of a rebuilt carb be? When do you rebuild? What would be the advantage of changing from a 2 to a 4 barrel carb? My 289 seems so much more sluggish than my 302 was....
Stephen

 

[karolscali]

Just changed out carb on my 302 from a 600 holly to a elderbrock 500. very impressed, very crisp and responsive. I have a elderbrock manifold, more than enough for a 302. after reading some posts in the past, decided to try it.Happy with it.:cheesy:

 

[franklinair]

A 4BBL carb & intake will offer your 289 a little more oomph. But you must also remember your previous 302 model had not only the benefit of the 4BBL set-up, but also a different rear gear ratio (3.00 compared to a 289's ratio of 2.79).
When converting to a 4 barrel set-up I use an Edelbrock Performer intake manifold and Edelbrock Performer 500CFM 4BBL carburetor with electric choke. Anything larger for a stock 289 engine is a waste. The engine can't suck any more than 500CFM, if that much.

Neil

 

[mbsf1970]

@Neil: from the archives......(2007)

I've used Edelbrock 4BBL intake & 600CFM carb on 289's & 302's. Nice package.
Neil Hoppe


Change your mind?? Just teasing. Roughly how much would a swap out cost and how much oomph could I expect over the stock 195hp??
Stephen

 

[Mosesatm]

The main problem with the 289 isn't induction, it's compression. The '68 289s have something like 8.7:1 compression, while the 302 has 10:1.

 

[mbsf1970]

Is it worth the expense of a. New Edelbrock. 4 bbl?? Realistically, how much more hp will it bring?
Stephen

 

[dalorzo_f]

289 was 9.3:1. ('68 FoMoCo Shop Manual)

As for "how much more Hp.." wrong question. As most "Hp" is measured at the peak of the curve, its generally not used and mostly for bartop racing and bragging rights (how often to you run your engine at 6000+/-ish RPM?).

And are you running a auto or manual? Makes a difference in how it gets to the road and how the change will be felt.

IMO more important would be looking at how it impacts the torque curve across the 2000-4500 rpm range, where you mostly feel the effect of the change (as thats where most folks do the majority of the driving, unless you run fast on the freeway with small tires and typical low ratio rear, typically 2.79 as noted above). Your cam and heads will probably be a limiting factor and a stock 289 c code is not going to run at 5000+ rpm real well, too restrictive to gain the full benefit of a 4bbl and good intake.

It will improve somewhat, but without complimentary head work its a limited gain.

Find someone with a desktop dyno and run some numbers.

If you are running the typical C code single exhaust, swapping it to duals would also help a bit.

 

[Mosesatm]

'68 289 is 8.7
http://www.geocities.com/~mustangs68/eng.html
http://www.carmemories.com/cgi-bin/viewexperience.cgi?experience_id=131
http://www.mustangtek.com/engine/FordEngineAssemblyID.htm

 

[dalorzo_f]

I'll stick with the number from the Ford Shop Manual and multiple other Ford related docs and back-in-the-day car mag specs I have over a few random websites... none I have list anything below 9.3:1.

MustangTek is a nice site, but riddled with errors and unsubstantiated data...

 

[Mosesatm]

If the '67 289 had 9.3 compression with 53cc combustion chambers how can the '68 have the same 9.3 compression with 63cc combustion chambers???

'68 2V heads have huge combustion chambers, the largest of any Windsor engine. Large combustion chambers = low compression, small combustion chambers = high compression. That's why builders mill heads.

 

[mbsf1970]

Tx for all replies.
Sounds like limited benefit vs. cost. I'll stick with 2bbl and focus on getting a 302 4bbl for my next mustang.....

Stephen

 

[dalorzo_f]

Well... I went back thru a lot of FoMoCo docs. Most call out 9.3, but the '68 sales brochure and Mannel's guide call out 8.7... the beauty of this hobby, not even Ford docs can be trusted to determine what is correct....:undecided

 

[Mosesatm]

What would the effects of a rebuilt carb be? When do you rebuild? What would be the advantage of changing from a 2 to a 4 barrel carb? My 289 seems so much more sluggish than my 302 was....
Stephen

Sorry, we got sidetracked.

I had a 4V on the road warrior and the secondaries kicked in probably less than a half dozen times <Rob shakes his head is disgust> so I think the original Ford 2100 is a perfect carb for a 289 for relaxed driving. On the other hand, if you you want to stomp on the gas and unleash some extra power then you will certainly notice a difference with a 4V.

These guys do good work.
http://www.ebay.com/itm/1968-302-FO...Parts_Accessories&vxp=mtr&hash=item3ce3570b4a

 

[Jester]

The performance question on 2v to 4v conversion has been asked many times (I have asked it myself) and I think we have been over most aspects of C vs J code set ups like dual exhaust, heads and exhaust ports, rear ratio etc. Leaving the data and hard facts aside a second, would anyone dare to just make a gut feeling guesstimate of oomph increase in lets say percentage? I guess there are many like me that are on the fence doing this swap but really have no idea how it would show on the kick in the pants gauge. Personally I am most interested in low end torque and HP increase as I don't drive much on the freeway, just want to give the Camaro guys sharing the garage a challenge at the red lights... I promise I won't hold any guesstimates against you.

 

[rvrtrash]

For "seat of the pants" I'll say that once long ago I had an R code (HO) '72 Mach 1. I was broke and going to school, commuting long distance, and needed to save money, so I disconnected and tied shut the secondaries. One night coming home I came across a guy that wanted to race on a country road. We both went for it, and my car felt noticeably sluggish and the top end fell off at 120, way below what it would do. I hooked them back up the next morning. Keep in mind that the primaries on a 4 barrel are normally smaller than the venturi's on a 2V, but I'm a believer in 4 barrels.

Steve