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Discussion Starter · #1 ·
I have a new 5.0 engine build as a 331 stroker. I put in in earlier this year but haven't driven it much. I've been fiddling with the carb (Road Demon 625) to try and get a smoother idle. I pulled the carb and set the t-slot to .020 and the four idle mixture screws to one full turn out each. The car started but would not idle. I turned the idle up 1/2 turn and held the gas until warm. I was able to finally get a reasonable idle with the idle mixture screws exactly 1/2 turn out from stop and the idle screw turned in one full turn. I'm not sure what the t-slot is open to now. My engine vacuum at idle is only 12 inHg. My cam is not that radical. I would expect to get closer to 20 in.

The cam is a Comp Cams Magnum 281HR.

.512 lift
220 duration at .050
281 advertised duration
110 lobe sep
1.6 rocker ratio

Any thought on the matter from the braintrust?

Thanks,
 

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I have the same carb on my car and had a heck of a time getting it to run right till I talked to this guy http://www.4secondsflat.com/ bought his 10 dollar tuning guide and talked to him all I can say is what a difference, first off you need to get your ignition dialed in then work on the carb
 

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Discussion Starter · #3 ·
My ignition is set at 15 degrees initial and 22 degrees mechanical for 37 degrees total. I have a MSD 6A with a Duraspark II distributor. I'll look into the tuning guide.
 

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Hi there, I have the same "basics" as your motor except my .05 is 238 degrees. Don at 4 seconds flat, in his book tells you how to set up your initial timing. Total Timing and Timing at full advance at cruze (w/vacuum adv).

Mine ends up at 22 Degrees BTDC. 15 degrees, I had a lot of trouble getting my carb to run at idle. Mine does not get better till after 18 degrees. Must get that set correctly, or any carb stuff you do will not be correct.

My total WOT ignition is 33 degrees. So, my mechanical advance is only 10 degrees total, comes full in by 2300 RPM's.

He also has a trick for finding what total cruze advance is( with a vacum can). ( not WOT advance...)

He is setting me up with a 575 CFM Mighty Demon with Annualr Boosters, and he promises it will solve all my issues.

I have been runing this 750 DP all summer, and this car already screams in the high 12's..... He thinks I will knock a second off with the annulars...

With such large heads on a short stroke like the 302, the atomization is too heavy, the annulars solve this. I am getting 8 MPG, it should go to 15 MPG.
 

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Well, I've got 8in Hg from my 302 with only a Xtreme 268H, so I'd say you're decent.
 

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Discussion Starter · #7 ·
Thanks guys. I guess I was worried over nothing.
 

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I also have a 625 Demon. I run a F-303 roller w/1.7 rockers which brings the lift to .540. I have talked to B. Grants staff and was told there is not enough vacumm to get it to run without being rich. They recommended I use a 575 cfm speed demon which has the new idle eze base plate. Or drill holes in my Road demons butterflies to let more air in at idle.
That would be the third carb for this truck so far. The 670 cfm Holley was worse.




1994 Ranger Splash 5.0L, Reworked AOD, 8.8 Dif, Moser Axles, Auburn Locker, FRPP 4.30 Gears, Balanced Rotating Assembly, FRPP Crank, Scat Rods, 10.1 Forged Speed Pro Pistons, P&P GT40P Heads, F303 Rllr w/1.7 Rockers, Air Gap Man w/Demon Carb. Hookers.






<font size=-1>[ This Message was edited by: 302splash on 10/23/06 1:52pm ]</font>
 

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With a stock cam the vacuum spec is 17 to 21 inches at an idle. Some of the RV cams will keep that vacuum but when you put in a performance cam that vacuum at an idle goes away. The average idle vacuum that I have seen in the Ford SB is 20" at idle.
Paul
 
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