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Discussion Starter · #1 ·
I recently swapped a 351 W based 408 stroker motor into my 89 F-350. When the engine builder and I discussed what my needs were we decided on a 3,500 rpm stall speed in the c-6. When we had everything built and assembled, it turned out that the stall speed was too high and on the highway, the tranny would heat up because unless I was doing 85 or faster, the torque converter would slip, creating heat. I went down to a 3,000 stall speed converter. The truck is better on the highway and does not heat up, but now...when I get on it off the line, I have a bog or a hesitation until the rpms get up, it does not happen if I pull away at normal speeds only when I'm on it. What my question is, does the carb have to be readjusted to suit the 3,000 rpm launch as compared to what it needed to launch at 3,500 and now the carb is dumping too much fuel in? Or have I now dropped the tranny below the powerband of the motor and now I have to powerbrake it until the rops get closer to 3,000 or higher for it to launch properly. The engine has no name aluminum heads (Strikeforce from PBM) that have 2.055 intake valves and 1.60 exhaust valves, they were ported and polished and flow 285 on intake, 185 exhaust @.700 lift, the cam is from PBM with a range of 2,200 to 5,600 rpm and is spec'd at 224/234 @.050, advanced duration is 290/300 valve lift is .496/.520 w/110 degree lobe separation. It has the Eagle stroker crank, I beam rods (6.200) and Keith Black D cup pistons (10:1 compression). It has a Edelbrock Performer RPM intake manifold and a holley 750 double pumper carb. I'm using a Holley HP 125 fuel pump that runs at 7 (lbs/psi?). The truck is huge and has 39.5 inch tires with 4:56 gears, it has a set of Stan's tri-Y headers and a short dual exhaust with dual flowmaster 40 series mufflers. With the 3,500 rpm stall, it would hit so hard I expected to lose the driveshaft every time, it would spins the tires for about 15 feet with no brake applied. Now it bogs bad unless I bring up the rpms then it only bogs for a short period of time. Could it be the carb is now overjetted and when the secondary kicks in it's flooding, or is the motor out of it's powerband?
 

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It is all in the carb. Big heavy cars(trucks) dont like double pumper carbs and tight converters. Try a 750 or 800 Edelbrock. I can say with confidence, it will fix the problem FOR SURE. JOE SHERMAN RACING
 

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Discussion Starter · #3 ·
I'm assuming when the secondaries opened and the stall speed was at 3,500, the higher rpm burned it off and kept it running without the bog but now that it's down to 3,000 it's too much fuel too soon, can you reduce the size of the jets in the secondaries? Would that solve the problem? I'm also hoping to fit the truck in this shop's dyno room. I'm expecting 400 RWHP from this engine, so once they get the carb situation fixed we'll see what it runs.
 

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On 2006-10-09 08:18, BIGJOE wrote:
It is all in the carb. Big heavy cars(trucks) dont like double pumper carbs and tight converters. Try a 750 or 800 Edelbrock. I can say with confidence, it will fix the problem FOR SURE. JOE SHERMAN RACING
250$ solution that I think will work as well.

Cris
 
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