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Author
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Topic: 460 tuning questions
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Rustang
Gearhead Posts: 733
From: Clarion PA
Registered: Nov 2000
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posted 08-01-2002 10:40 PM
   
I finally got my new 460 in my truck last week, and I'm not quite sure what to think about it's performance. It seems lazy when you first hit the throttle. I expected it to break the tires loose every time I nail it from a stop! The other night (see earlier post) I replaced the open 1" spacer with a 1" 4 hole. this along with a stiffer spring in the secondary diaphragm. It made it worse! The result was a hesitation when I nail it from a stop where there was none before. Tonight I messed around some more. I removed the spacer entirely and locked out the secondary completely. Still hesitates! I put the light secondary spring back in. I also checked out the cranking compression tonight. #1 cylinder is around 138psi (is that low for a mild 9.0:1 to 9.5:1 motor??) Plugs are white with slight black specs. The electrode is grey about its full length
Here's some specs
stock bore/stroke 460
750 model 3310 holley, #76 jets, #35 pump shooter
C6 w/stock converter
Timing is 12@ idle, all in 35deg
Weiand stealth intake
Crane cam, 216/[email protected], .518/.513, 112 centers set at 4degrees advanced
hooker 2"primary super comps, 2-1/2" duals into single 3-1/2" flowmaster
truck weighs 4500lbs w/ 3.55 gears
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'68 mustang 351 clevor- 10.92@124
'67 Stang, 351W -11.18@118
'69 351C Torino-14.90@100
'78 Pickup 351W-15.56@88
'79 Pickup 460 ET=??
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Moneymaker
Administrator Posts: 25883
From: Lyons, IL, USA
Registered: May 99
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posted 08-01-2002 11:05 PM
Sounds REAL lean to me.  ------------------
Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
Professional Manwhore
The Barry of BarrysGrrl
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jsracingbbf
Gearhead Posts: 2751
From: Batesville,MS. , U.S.A.
Registered: Mar 2002
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posted 08-01-2002 11:14 PM
I don't know about the spacers and it has been a long time since I've run a Carb, BUT I think maybe you should play with the PRIMARY shooter ( squirter ) size to get your bog to go away, then fine tune that with the accelerator pump cam. I always started with a medium spring then went from there on the secondaries. EVERY time I had a bog right after launch it was ALWAYS due to either the vent tube letting gas spill into the venturi or wrong accelerator pump shooter size. (too small) Push a piece of vacuum hose over the primary vent tube and leave it open then try to launch the truck. I doubt this is it but it's worth a shot ( it's cheap ) You may have a really small accelerator pump squirter for that engine. Also leave one spacer on there until you are sure it is the problem, try to change only ONE thing at a time. ------------------
Jerry Smith
69 Mustang Pro ET Drag
Only 'lil boys wear Bowties
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Rustang
Gearhead Posts: 733
From: Clarion PA
Registered: Nov 2000
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posted 08-01-2002 11:14 PM
Alex, I'll have to double check the jets, but assuming they are 76er's should I try some 78's? What do you think about the cranking compression?thanks
LS
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Rustang
Gearhead Posts: 733
From: Clarion PA
Registered: Nov 2000
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posted 08-01-2002 11:18 PM
Thanks for the reply Jerry. I was thinking about the pump shooter, but suspecting maybe it was too rich? This is because I ran this carb on my low 11 second mustang and it worked great on that 351. I bolted it on the truck with no mods. It has #35 shooter with the pump spring shimmed up (basically stacked solid).
Since the open plenum spacer didn't have a detectable hesitation, and the 4 hole does, what I'm wondering is does an open spacer require more or less pump shot versus a 4 hole spacer? [This message has been edited by Rustang (edited 08-01-2002).]
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Moneymaker
Administrator Posts: 25883
From: Lyons, IL, USA
Registered: May 99
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posted 08-01-2002 11:19 PM
It seems pretty normal with that wide cam. 140 to 150 lbs is about right and I'm sure the rings have not completly sealed up yet either. ------------------
Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
Professional Manwhore
The Barry of BarrysGrrl
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jsracingbbf
Gearhead Posts: 2751
From: Batesville,MS. , U.S.A.
Registered: Mar 2002
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posted 08-01-2002 11:46 PM
LS, buy a hat for it and throw the carb away. oh yeah convert it to Alky also. I know I'm being a smart A$$ but hey you have to admit that HAt would look awesome on a Street truck!
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Jerry Smith
69 Mustang Pro ET Drag
"Even a blind hog can find an acorn every now and then "
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jkilroy
Gearhead Posts: 1808
From: Vicksburg, MS
Registered: Dec 99
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posted 08-02-2002 07:14 AM
First off, a 750 is marginal for that motor anyway, you would be better off with an 850. You should put a vacuum gauge on it and check it at WOT once you get it tuned. I would expect that 750 will be costing you some real power.It has got to be lean and I prefer to work from a slightly rich state backwards. I would start with 84's all around and work from there. You probably need a bigger shooter also, do you have a 50cc pump on it? ------------------
Jay Kilroy
68' Fastback GT 390
"No such thing as a cam thats too big"
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Big Block Capri
Gearhead Posts: 136
From: Essex, Ontario, Canada
Registered: Nov 2000
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posted 08-04-2002 08:36 PM
You said that you have the spring on the accelerator pump shimmed nearly solid. The spring is there to compress while the fuel is forced through the squirter. Since the spring is virtually solid and liquids don't compress, the only thing left to give is the accelerator pump diaphram. It's a possibility.------------------
Paul Garant
"No replacement for displacement."
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Rustang
Gearhead Posts: 733
From: Clarion PA
Registered: Nov 2000
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posted 08-04-2002 09:26 PM
When I had the truck to the track yesterday, I found a HUGE gain in response off the line. I replaced the 37 pump shooter (I mentioned above it was a 35, but I must be gettin' old!) with a 28. Now the truck lays about 20 feet of posi marks at any stop sign I choose! There's still a hint of the motor being soft at low rpm though. After the tires catch the motor has a little bog to it for a second or two. My theory of needing less pump shot with the 4-hole spacer must have been right! The open spacer tolerated the big shot of gas. Unfortunately the run after I made the change the truck spun hard off the line and I lost ET! Paul, the solid pump lever worked great with my 'stang combo. Ran it for years that way. I just left it alone when I threw it on the truck.
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jkilroy
Gearhead Posts: 1808
From: Vicksburg, MS
Registered: Dec 99
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posted 08-05-2002 09:41 AM
You probably didn't really need a smaller shot, but a looonnnnggggger shot. ------------------
Jay Kilroy
68' Fastback GT 390
"No such thing as a cam thats too big"
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