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Questions about 440 tuning, Cam, and ignition! #973599
04/15/11 08:30 AM
04/15/11 08:30 AM
Joined: Jan 2003
Posts: 202
Johnson City, TN
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Haney Offline OP
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Haney  Offline OP
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Johnson City, TN
I just bought a 73 Cuda from a guy and I am trying to sort some tuning issues out on it and was hoping to get some help / opinions….. The car specs are:

• 71 440
• Stock rods and crank
• TRW Forged Flattops; approx. 10:1 Static Compression ratio
• Out of the box Edelbrock RPM heads (84cc)
• Stock style rocker gear
• Comp XE285HL Cam, comp lifters, Stock Edelbrock Head Springs
• RPM Intake
• 750 Speed Demon Carb
• MP Electronic Ignition
• Doug’s 2” Full Length Headers
• 3” Magnaflow bullet mufflers out the side like a AAR currently, coming a 2 ½ “ X-pipe exhaust system. Current system way too loud.
• 833 4-speed
• 8 ¾” rear 3.91 sure grip
• 275/60-15 rear tires (28” tall)

This is a new engine with very little run time. Once I ditched the vacuum advance hook up and got my total timing to 34 which put my initial at 15, the car starts and takes the gas really good. However the idle quality is very poor. I am pretty sure this is in the baseline carb adjustments. I have not addressed these yet other than a few minor trial adjustments. I do have the following questions.

1. Big Block XE285HL users: How is the idle quality of this cam? I know the comp spec card says ROUGH, but is it too rough for a 446 cube street car? I have to say that it does sound very aggressive for a street car. What RPM should this cam idle? How much vacuum should I have at idle? This would be good to know as I try to dial in this carb.

2. Will I be able to run power brakes with this cam? Brake booster seems starved right now.

3. Valve Springs. The Edelbrock springs have a seat pressure of 115 lbs and an open pressure of 280 lbs. The recommended comp 924-16 has a seat load rating of 112 lbs and an open load of 355 lbs. Coil bind is pretty close at 1.160 for the Edelbrocks vs. 1.175 for the comp springs. Should I change these springs? My gut says yes with the lift rate of this cam. I guess I could lose valve control up high in RPMs? Comments?

4. What is the best plugs and gap to run in this combo?

5. Any suggestions or good how to’s on dialing this carb in? I have never had a 4-corner idle carb. Is there a better carb for my application?

Thanks for any help or comments!


'69 Barracuda 340 4-speed
'73 Cuda PROJECT
Re: Questions about 440 tuning, Cam, and ignition! [Re: Haney] #973600
04/15/11 09:55 AM
04/15/11 09:55 AM
Joined: Jan 2003
Posts: 4,707
Moved to N.E. Tennessee
GomangoCuda Offline
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GomangoCuda  Offline
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Joined: Jan 2003
Posts: 4,707
Moved to N.E. Tennessee
Which TRW pistons do you have? What is the actual deck ht?

Your engine will like a bigger carb.

Carb adjustments are covered pretty good in BG's manuals. Here is the one for Speed Demons.
http://barrygrant.com/fromBarryGrant/Demon%20Instruction%20Manuals/Speed%20Demon%20Manual.pdf
Also look at http://barrygrant.com/demon/default.aspx?page=28
Better download them now as he has gone out of business and I don't know how long his website will be up.

That cams lift (.545) is a bit much for stock rockers and pushrods.

I would run about 18-20 deg initial timing with that much duration. You will need to shorten the advance curve so that you don't have too much total.

A friend has a similar spec Engle cam and he eventually converted his car to standard non-power brakes.

Last edited by GomangoCuda; 04/15/11 10:28 AM.

In theory, there is no difference between theory and practice. In practice, there is.
Re: Questions about 440 tuning, Cam, and ignition! [Re: Haney] #973601
04/15/11 10:30 AM
04/15/11 10:30 AM
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck Offline
Not enough dumb comments...yet
Mr.Yuck  Offline
Not enough dumb comments...yet

Joined: Jan 2003
Posts: 24,562
Brookeville, Md
I'd just start w/ the basics. Turn the mixture screws all the way in, then back out 1 1/4. Start the car and crank the idel up to 2500. Set your advance at 36* (w/ those heads you could go to 38*) Then run your idel down to about 900 or so. Turn the screws in/out until you get the best vacuum signal. Go for a romp and adjust from there. That carb should work well enough for what you have. What jets/squirters/PV are in it? I'd think you'd want 76/82 jets, 31 squirters and a 6.5PV to start with.


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Re: Questions about 440 tuning, Cam, and ignition! [Re: Mr.Yuck] #973602
04/15/11 10:33 AM
04/15/11 10:33 AM
Joined: Jan 2003
Posts: 4,707
Moved to N.E. Tennessee
GomangoCuda Offline
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GomangoCuda  Offline
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Quote:

I'd just start w/ the basics. Turn the mixture screws all the way in, then back out 1 1/4. Start the car and crank the idel up to 2500. Set your advance at 36* (w/ those heads you could go to 38*) Then run your idel down to about 900 or so. Turn the screws in/out until you get the best vacuum signal. Go for a romp and adjust from there. That carb should work well enough for what you have. What jets/squirters/PV are in it? I'd think you'd want 76/82 jets, 31 squirters and a 6.5PV to start with.




I agree that would get you close and drivable if you haven't messed much with the idle speed screw. If you have then you probably should look at the first link above and read the part about transfer slots.


In theory, there is no difference between theory and practice. In practice, there is.
Re: Questions about 440 tuning, Cam, and ignition! [Re: Haney] #973603
04/15/11 01:50 PM
04/15/11 01:50 PM
Joined: Jan 2003
Posts: 202
Johnson City, TN
H
Haney Offline OP
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Haney  Offline OP
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Johnson City, TN
Thanks for all the input guys. I have no idea what is "inside" the carb. I plan on taking the carb off this weekend and looking at the base idle adjustments and the transfer slots to make sure I am not hosed on that. At that time I will check the the jet and PV size so I know.

So this should have a decent idle at 900?

Any comment on the valve springs? Also, what is the best plug and gap for this combo?


'69 Barracuda 340 4-speed
'73 Cuda PROJECT
Re: Questions about 440 tuning, Cam, and ignition! [Re: Haney] #973604
04/15/11 02:51 PM
04/15/11 02:51 PM
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck Offline
Not enough dumb comments...yet
Mr.Yuck  Offline
Not enough dumb comments...yet

Joined: Jan 2003
Posts: 24,562
Brookeville, Md
pretty big cam, I'd guess 900 would be a start. It might like more.


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Coming soon!!!!
Re: Questions about 440 tuning, Cam, and ignition! [Re: Haney] #973605
04/15/11 04:21 PM
04/15/11 04:21 PM
Joined: Mar 2008
Posts: 5,746
Ontario, Canada
Dodgem Offline
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Dodgem  Offline
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Ontario, Canada
I think I would recurve the distributor to have in gear idle 24 to 26 should help a lot!

Re: Questions about 440 tuning, Cam, and ignition! [Re: Dodgem] #973606
04/15/11 05:59 PM
04/15/11 05:59 PM
Joined: Jan 2003
Posts: 202
Johnson City, TN
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Haney Offline OP
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Haney  Offline OP
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Johnson City, TN
OK, how is the best way to determine the correct (highest) initial timing....


'69 Barracuda 340 4-speed
'73 Cuda PROJECT
Re: Questions about 440 tuning, Cam, and ignition! [Re: Haney] #973607
04/15/11 06:50 PM
04/15/11 06:50 PM
Joined: Jan 2003
Posts: 4,707
Moved to N.E. Tennessee
GomangoCuda Offline
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GomangoCuda  Offline
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Moved to N.E. Tennessee
Quote:

OK, how is the best way to determine the correct (highest) initial timing....




Here is one rough rule of thumb. I am sure there are others but this will get you in the ballpark. Remember every engine combo is different so concider this a starting point.


camshaft duration less than 220 degrees @ 0.050 needs 10-12 degrees of initial advance.

camshaft duration 220-240 degrees @ 0.050 needs 14-16 degrees of initial advance.

camshaft duration 240-260 degrees @ 0.050 needs 18-20 degrees of initial advance.


In theory, there is no difference between theory and practice. In practice, there is.
Re: Questions about 440 tuning, Cam, and ignition! [Re: GomangoCuda] #973608
04/15/11 08:38 PM
04/15/11 08:38 PM
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert Offline
Circle Track
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Circle Track

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Posts: 36,040
Lincoln Nebraska
I'd set the initial w the "vac gauge method". Vac adv (if used) unhooked/plugged. In gear w ebrake on & idle speed set close to what it needs and you are comfortable w, keep advancing the timing and at the same time keep reducing the idle speed back to where it was until you hit the highest manifold vac reading you can get then back off the timing till the vac goes down 1". W that initial figure in hand then you can shorten the slots to get 36-38 total. then springs then vac adv


live every 24 hour block of time like it's your last day on earth
Re: Questions about 440 tuning, Cam, and ignition! [Re: Haney] #973609
04/15/11 09:20 PM
04/15/11 09:20 PM
Joined: Mar 2008
Posts: 5,746
Ontario, Canada
Dodgem Offline
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Dodgem  Offline
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Ontario, Canada
Quote:

OK, how is the best way to determine the correct (highest) initial timing....




What I like to do is with vacuum advance unhooked and plugged advance timing by turning the distributor until I get idle set how I like it (most vacuum method will work) check and see what the in gear idle timing is at and put one or two light springs in the dizzy till you can achive this initial and still have the say 36 total.

I like to do this rather than welding slots as sometimes that gives you a hard starting car.







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