Looking for Little Tweaks

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Bookmaker

Bookmaker

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I have a 1974 Duster survivor w/318 auto. I'm trying to keep it stock-looking for the shows, but at the same time I'm wanting to tune it as best as possible for better performance. I will be changing out the 2.45:1 gearing in the 8.25 rear end for 3.21:1 with track-lok. That should make it a bit more fun.

With regard to the engine, I've bypassed the OSAC so that port vacuum goes directly to the distributor. For the distributor itself I have a set of lighter springs from Mopar.

Question 1: Where should I set the base timing, and should I use the FBO limiter plate so that I can set initial timing higher? (Factory timing spec is TDC)

At the end of the season this year I plan to upgrade the silent timing chain with a double-roller chain and magnum tensioner. If I am into it that far, I might as well upgrade the cam too. I will probably upgrade to dual exhaust also as the original Y-pipe is not going to last much longer.

Question 2: Would a stock 340 cam help this engine much given that I will be keeping the stock 2BBL carb on it?

Thanks.
 

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Can't answer your questions, but wanted to say....
That's a beautiful clean engine!


:burnout:
 
I would get a custom grind, the off the shelf grinds wont be much help. Make sure you tell them you are running factory snorkel air cleaner as that will be your restriction at this point. You could always run a better flowing filter on the street then put stock back for shows....just a thought. Talk to Don at FBO about timing a 318 2bbl with his plate.
 
Keep in mind you might be getting more than you bargained with the 2.45 to 3.21. The carriers are different and you may need to clearance the case with a die grinder... As far as cam the Summit K-6900 is popular with the low comp 318 and 360 guys.. Any way you go be sure to roll each cylinder to TDC to change your springs and valve stem seals!
 
Woods74 said:
Keep in mind you might be getting more than you bargained with the 2.45 to 3.21. The carriers are different and you may need to clearance the case with a die grinder... As far as cam the Summit K-6900 is popular with the low comp stock converter 318 and 360 guys.. Be sure to change your springs and valve stem seals while your at it!
Click to expand...



Just looked it up. Units with 2.45:1 have a different case. Guess I'll be shopping for a whole rear end now.
 
I have done the same on a factory stock low comp 318. I used a Comp 268H, Hedman tight tube headers that have been coated black with the heat riser fitted, 2" twin exhaust, same dissy set up as yours, Wieand 8007 & 625 road Demon all looking factory. It made 206.9rwhp with a tune and is a ball to drive with reasonable fuel economy.


 
Www.doctordiff.com is a good source for the suregrip carrier and gear sets of your choice. Keep in mind you should have 27 spline axles, need to know that when ordering your carrier
 
You can do the cam swap and use the 360 2bbl intake and carb and get a good gain. Still looks like a sleeper too.
 
Woods74 said:
Keep in mind you might be getting more than you bargained with the 2.45 to 3.21. The carriers are different and you may need to clearance the case with a die grinder... As far as cam the Summit K-6900 is popular with the low comp 318 and 360 guys.. Any way you go be sure to roll each cylinder to TDC to change your springs and valve stem seals!
Click to expand...

As far as the die grinder job on that case, is there a lot of material to remove? I have the same 2:45 gear in an 8- 1/4 and plan on doing a similar swap. Are there other caveats to be aware of in regards?
 
racerdan80 said:
Www.doctordiff.com is a good source for the suregrip carrier and gear sets of your choice. Keep in mind you should have 27 spline axles, need to know that when ordering your carrier
Click to expand...

I had a great experience with Dr. Diff!
He hooked me up....plenty of phone support and great price!

Highly recommend.

:coffee2:
 
I would go ahead and put a 4bbl on it, there are plenty of factory iron manifolds that will wake it up, factory 340 bbl exhaust manifold with a full duels will help it breath.
 
Woods74 said:
Keep in mind you might be getting more than you bargained with the 2.45 to 3.21. The carriers are different and you may need to clearance the case with a die grinder... As far as cam the Summit K-6900 is popular with the low comp 318 and 360 guys.. Any way you go be sure to roll each cylinder to TDC to change your springs and valve stem seals!
Click to expand...

According to Dr. Diff, if I change the carrier there is no issue going from 2:45 to 3:21. I just ordered a 3.21 NOS gear set and Trac-Loc plus seals, shims, etc from the good doctor.
 
Successful swap from 2.45 to 3.21 gear set plus Trac-Loc in my 8.25 rear. Car is more playful now.
 
Glad the gear swap worked out. Is a higher stall converter in the budget? It will work well with the new gears. 2500-2800 stall would be a good upgrade. Could also have a custom converter made as well
 
Here's the thing about the cam.
To make more power in a NA engine of a given displacement,without digging into the heads, requires that engine to spin faster. That's just the way it is. That means the cam has to be redesigned to operate at that new higher rpm. That means the lower rpms are compromised or sacrificed. So now you have to get a hi-stall so your engine is not forced to operate in those lower rpms.
So now you have an engine that needs to rev higher to make it's power.
Is that what you want in A cruiser?
Is that what you want in YOUR cruiser?

Here's my 2 cents.
Forget the cam.
Get a Free-flowing exhaust and maybe a small 4bbl.
Get rid of every extra pound that is not contributing.Every ten of 'em is worth about a hp.
So where to start on the weight reduction?
#1,is wheels.Aluminums are about half the weight.
Exhaust. Forget full-length 3 inchers. My exhaust, just the pipes and Dynomaxers is 140pounds heavy. Stick with one large single exhaust on Trebleg manifolds.
Well of course there's the aluminum intake.
Get rid of the 5-mph bumpers if you got those turds.
And of course the spare, the jack, and everything else in the trunk. Be it gone!
Console/buckets?Gone. Radio? Gone for me, and the 4 x 10 too!
After that it gets harder..But 150 pounds is about 1 cam size right there, and you didn't give up any torque to get it.
If you want a bit more bottom-end (what SBMer doesn't), get the heads machined while the manifolds are all off. For a few bucks you'll get some Zing.
A slightly looser TC will make it a tad funner, but with the new gears, I would hold off on that. Why? Cuz going from 2.45s to 3.21s is a 31% increase in torque multiplication . That is a huge change. Turbo-boost! Once you get used to that, you may not need/want to make any other changes at all!
To get the equivalent torque and power from the engine to feel like that gear-change,would require the complete rebuild of the engine and a very substantial cash injection.And you still might not get quite the equivalent bottom end torque.You might end up having to ditch everything but the block, and the covers.
 
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I agree with the above. Get a nice aluminum intake manifold and small 4bbl. You will save weight there. Headers and good exhaust.
 
A low first gear set for the 904 will give you lots of jump off the line!
 
11.8% more jump!
And your starter gear would now be 8.8, versus the original 6.0. So that would be a 46.7% improvement. The low gear is worth about the same as going up one more gear size from 3.21s to 3.55s.
 
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Bookmaker,
If I may impose could You provide a tag # on the carb ???
Thx
 
image.jpeg
mech1nxh said:
Bookmaker,
If I may impose could You provide a tag # on the carb ???
Thx
Click to expand...
This is the tag on the original carb. I've got a rebuilt one on the car that I bought from RockAuto. If I decide to keep it stock I will rebuild the original and put it back on the car. However folks here are giving me the upgrade bug.

Also, I have a thermostatically controlled viscous fan to replace the direct drive fan.
 
:) under the radar upgrades,
$7.00 ? three pieces of sandpaper . progressively cut down
the Venturi's outside ring to 'Knife Edge' --- 800, 1000, 1200 ---
 
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I almost forgot! 1.6 ratio rocker arms! Basically camshaft light. Improves lift with very little effect on duration. Turns .421 lift into .449 which should still be within the margin of your stock springs. A well placed X or H pipe will also make a noticeable seat of the pants feel.
 
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