rebuilt 350 stutter at wot

80chevy_shortman

Well-Known Member
Joined
Jan 17, 2010
Location
siler city, nc
recently bought a rollin chassis 76 k5, so i went and had a fresh rebuild on a th350 i had, and mated it to a np203. got a sbc 350 built .060 over, comp magnum cam that is rated at .470 lift with 1.5 rockers but i have 1.6 so im sure lift is now close to.500,aluminum heads 64cc 2.02 1.60 valves doubled valve springs, long tube headers, edelbrock performer intake, 600 holley vacuum secondaries, and msd street fire distributor. all out timing (2500-3000)rpm with dist vacuum unplugged is set at 35 and initial was like 16 i believe. cam is pretty lopey. problem is when i try to wot or open 4 barrels the truck starts stuttering and bucking like timing is off or its skipping. note that all engine parts are brand new never used besides block and carb which is rebulit. now with such a cam i should have used a bigger stall. but i used a new factory stall convertor and truck is factory geared 3.08. could this stock stall and such a high gear cause this problem maybe like its puttin a hell of a load on the engine tryin to move this ole heavy chevy. i plan on regearing soon waitin on some more cash flow first, any ideas r appreciated????
 
Whats the timing at idle? It could probaly take a little more timing, a carb adjustment won't hurt. Also those 3.08s need to go. What all the specs on the cam? Usally your ok on the stock converter until you get over 295ish total dur.
 
idle is at 800, timing is set at like 16-17 idle, 35 at 3000rpm. cam specs .470 gross lift, duration @ .050 224 224, lobe separation 110, duration @ .006 tappet lift 270 270,l obe lift .313 .313. but like i said i have 1.6 rockers instead of 1.5. yea i got a set of 4.10's i am about to swap asap. 600 holley does that seem kinda small
 
provided the outside ring of the balancer hasn't spun, 16-17 degrees btdc at idle is a little steep for a sbc; 8-10 with a max of 12 is more like it. your total advance at rpm (including the vacuum) should be in the range of 34-40 degrees, depending on tuning differences. the 600 hollet is ok for your use, it's probably the only thing keeping the motor from falling on it's face in a heavy chassis running 3.08's & 35s; a 750 would be even worse.
 
ithanks for the replys fellas, um yea i am startin to swap a set of 4.10's today, hopefully ill have her rrunning next weekend, i am sure i tell a heck of a difference in the gear set. so after i swap the gear set, if it still acts up, i need to check the tuning of carb and timing
 
I know you said you have an msd dizzy but what wires and plugs do you have. NGK's are really nice to have. Honestly I'm startin to think it's more of a carb issue than timing, holleys are very hormonal during weather changes.
 
yea it got accel wires from advance, and embarrased to say but cheap champion plugs the aluminum heads have a .750 plug reach and the day i went to get plugs and etc. they only had the champions in stock. and i always assumed ngk ran better with yotas and such. but i am swappin the 4.10's in asap and probably gonna put new plugs in cause during the intial engine break-in the plugs all got fouled. they r nice and blackkkkk.
 
put new plugs in but haven't had a chance to run it. in the process of swapping axles. and also trying to figure out my header problem. i have to pull the headers off everytime i change plugs and its aggervating as hell. the heads r pro comp aluminum wit straight plug hole design. and the hedman long tubes i used on that engine originaly with factory cast heads aint gettin her done for me. plugs # 6 an 7 are tucked behind the header tubes. any one ever seen that happen or any ideas on a different header i really dont want to use a stock manifold haha
 
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