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Discussion Starter #1 (Edited)
355 to 383 Motor info Added

Im a little more than dis-satisfied with the performance of my car. the only difference between the 350 & 383 is a little over a point more compression, a single plane intake and i put the cam in straight up instead of 4 degrees retarded. the car is running the same times as it did with the 355. I don't get it. Any ideas on what to look for?

Motor Specs;
383ci 3.75" stroke 6.00" rods, flat top pistons .002"-.003 down in bore from TDC.

TFS 23* cast aluminum 2.02"int/1.60"ex, 1.5" full roller rocker, 1.95cc intake runner, milled to 60cc combustion chamber. .018" compressed head gasket with a 4.100" bore.

CompCam 12-224-4 Magnum Solid lifter, lift .525"in/ex, duration at .050" 248*in/ex.

Single plane intake.

Holley HP 750cfm.

Summit 1.625" coated headers.

TH350 4500rpm stall, leave of foot brake @ 2500rpm.

Rear: 4.56 gear, full spool, 28" tall slicks.

3350lbs w/driver.
 

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What else did you change? Anything? Did you just take the top end off the 355 and put it on the 383? How about the convertor? More stroke means a tighter convertor. Don't know your combo. Dave
 

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Need alot more info like Dave said
 

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Discussion Starter #4 (Edited)
What else did you change? Anything? Did you just take the top end off the 355 and put it on the 383? How about the convertor? More stroke means a tighter convertor. Don't know your combo. Dave
Nothing. I did exactly what you described. the whole car is exactly the same as with the 355, except the point higher in compression, same cam just installed straight up instead of -4°. What do you mean by "tighter converter", lower stall speed? I am using a 4500rpm stall right now(same as with the 355). 4° wouldn't make that much of a difference, would it?
 

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Nothing. I did exactly what you described. the whole car is exactly the same as with the 355, except the point higher in compression, same cam just installed straight up instead of -4°. What do you mean by "tighter converter", lower stall speed? I am using a 4500rpm stall right now(same as with the 355). 4° wouldn't make that much of a difference, would it?
How Much timing are you running?
 

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The 383 will need a better head and more cam to take advantage of the extra cubes. With all else being equal the 383 will make more torque than the 350 so if your converter is too loose then you are just wasting all that new found torque. Ofcourse this is a very general statement but it may be whats going on with your car.
 

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More info is needed. What heads? What cam? What carb? All motor or spraying it? What compression? What ignition? What rear gear? Leaving off foot or trans brake? Is the car spinning when you leave? Is this a street/strip car or just a strip car?

IMO You need at least a 215 to 230cc intake runner heads, 264 to 272 duration @ .050, a 850 cfm carb, a good ignition. A 383 will need more of everything to take advantage of cubes.
 

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It only makes sense that the combo feels the same as your 355" engine and a lot of people don't take those extra 30"+ into consideration. If your running a cylinder head and cam combo that maxes out on your 355" at whatever hp and rpm your 383" with tif same parts will make the same power. Your combo works well on your 355 but with the extra cubes and compression you'll need more cylinder head and probably camshaft as well to take advantage of the additional displacement. Also with the added arm in the stroke your peaks will happen sooner in the rpm band making gear and converter changes possible too. Remember its not the ability to throw all kinds of speed parts together to make your Nova fast its more important to find the right combo!
 

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Cubic Inches alone should give you a couple of tenths, given all other components are in good working condition, as Ryan stated. You should see a positive gain on a dyno or race track.

I would look at optimizing the timing and air/fuel. Shift points, most likely lower on the 383 then the 355 (peak torque lower in the rpm range). Is the 383 @ rpm limit before the end of the track? If no change, trans/converter. If you have a time slip post it along with another from the 355, it will tell the story.

No. 4 degrees will not erase 50+ lbs of torque
 

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Discussion Starter #12
According to desktop dyno, just the cubs and point higher in c/r, & everything else being equal, it's telling me about 75 more horsepower than the 355, except about 500rpm in the power band. The car does go a little quicker if i shift right at 6000rpm, but with a 4500 stall and 4.56 gears, im shifting as soon as im out of the hole, guess im still use to the 7500rpm shifts of the 355.:D:rolleyes:. I have a holeshot 3000 B&M converter. maybe i should try that.
 

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My 383 is still pulling at 6500(cam is 2800-6400 rpms) and that's where I shift mine at. Felt like it was pulling even at 6700 rpms, but I slung the belt and had to order a 3.25 inch deep groove pulley and put it on. Haven't taken it to the track yet, until front brake upgrade and some Hoosiers with some Weld rims for the back. I am running some AFR 195s with this one as it is just a street-strip car and mostly street.

I ran the Trick Flows on my first 406 and some AFR 210s on my last 406 and to me the AFRs work better. I went with the 195s this time because the Eliminator 195s flow what the older 210s used to flow and I figured that would get it done for me. Can always open them up in the future though.
 

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i would agree on the small runner of the head...but it depends on the head. I took my older 1094 AFR COMP ported heads off my 355 and had SR Springs installed and plopped'um on my 406. These heads flo 300+cfm....so the small runner thing isn't as much of a big deal.
I will get larger heads eventually...but for now they work fine.

I would increase int timing and limit your total. It will make a diff.
 
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