Finally got my new 383 to the track. Very disappointing. My best run was a 12.45 @ 108. The 357 ran a best of 12.01 @ 112.76. Every incremental was slower with the 383. Everything on the 383 is the same except the block, crank, rods, and the extra point of compression. I’m missing 100 HP somewhere and I don’t have a clue where to find it. Assuming there is nothing wrong with the rotating assembly, it’s either something really simple or a mismatch in the parts. I’ll start by ohming out all the plug wires, compression and leak-down on all cylinders, then timing and fuel. Maybe this thing just wants a bunch more fuel than the 357?

I had the exact same weekend as you. My previous combo was a 355 with Dart IE180's and a Comp XE262 hydraulic cam that went 13.70's at 97-98 in this kind of weather. I changed to AFR180's and an XS262 solid, everything else EXACTLY the same, and went a best of 14.23 at 94mph. The car was sputtering a little every few minutes on the way home from the track, I'm beginning to wonder if the fuel pump or distributor is laying down. How depressing, guess I have some troubleshooting to do like you.

Hey Mike,

I guess I can find some comfort in knowing I'm not the only one in need of a crying towel! graemlins/sad.gif

By the way - do I have to change my signature? graemlins/sad.gif

do you have a fuel pressure gauge you can see?

Sounds like you need to do timing/fuel loops.

Do a compression test?

Transmission? Converter?

Same transmission and coverter. I was only able to check compression on 4 cylinders without removing the headers. All 4 were between 197 and 200 PSI. I need to check the other 4 before I can rule out a bad cylinder.

Fuji, i know ive asked you before, where do you race at again?

I had similar results last week too!!!

I had a converter made for my combo, and I slowed down.
Boy am I upset.

hang in there, you will figure it out.


talk to ya later, mark

Scribner, Nebraska. About 35 miles north of Omaha.

Hi Chris, Sorry to hear about the less than expected results. :( Gotta' be something simple.

Rod

Might try a chassis dyno. I learned a few things about my 383. Biggest thing was it peaked at 5k.
Suspect my heads are too small. Or not enough cam.
Oh and my tach was low by 500 rpm. :(
At least I had 370ftlbs at 3k.

what were the 60ft and 1/8mi times for both the 357 and the 383? what shift points for each? how much timing for each? usually from what i've seen the extra 1/4" stroke helps by 2-4 tenths with all other parts remaining the same.
BTW, i think you could help it out a little with a 750dp, that extra shot of fuel in the secondaries helps off the line. ;)

383 - 12.45 run:

60' 1.765
1/8 7.917 @ 86.76

357 - 12.01 run:

60' 1.740
1/8 7.662 @ 90.57

I looked back through my timeslips from last summer and found a run with a 2.038 60' and an ET of 12.48 @ 111.84. So even with a .2 quicker 60' the 383 still barely keeps up with the 357.


Timing was 35 degrees in both engines. I shifted the 383 at 6000 and the 357 at 6500. I know I didn't put as much effort into trying to make the 383 run fast as I did the 357, but I thought it should run faster or at least as fast with very little effort. I might be wrong.

35 degrees? why?

ya something doesn't add up? My 383 with a milder combo traps 110mph. were probably close to same weight.

How many miles on that new 383? I wouldn't expect
a newly built motor to perform as well as a
properly broken in one.

Emil Dusek:71 SS-502

You might try backing down the total advance a bit.Keep the same amount of initial.

My old 383 ran the best
with... get this... 32 total.
That was setting it at the track for the best MPH.

My guess is that it will perform the best with a total figure somewhere between 32 and 34.

if yours ran best with 32 degrees then i'd think the timing mark, or the light was off.

every motor is different, i guess. my best friend's 383 likes 40deg total. most i've messed with like 36deg, but that's not a rule of thumb. fresh motor or not, i also would've thought the 383 would run quicker times even before it was fine tuned. :confused: it's gotta be something simple.

When you put the cam in you check it and make sure it was in the right place. Car sounds lazy like the cam is retarded.

if it's pumping 200lbs of cranking compression I'm sure the cam isn,t retarded, the carb may need to be jetted up or down, I'm sure the vacume signal is also different than the 350

I had a simular experience. I had my 355 running 12.8s. Built a 388(all good parts) with the same protopline 200cc heads. I used dish pistons to get the same CR. Stepped up to a comp xs282s10 from a xs268s10 cam..Increased the stall from 2500 to a 3500. The best time I could get was 12.8. Got PO'd and went back to a 355 with 282 cam and now im running 12.2. Maybe the combo didn't work with the 388..but I felt like I should of picked up some time..The CR was 11-1 with both engines

motors arent all THAT different, unless you're using SB2.2 heads, and something in the range of 18:1, i doubt seriously that the motor would want 32 degrees.

But then who cares what the tab/light says, set it where it will MPH best, move 1 degree at a time and find the spot it likes most.

Brian,
Alot of what deturmines how a motor will react to timing is the shape and design of the combustion chamber. The fast burns (hence the name), and vortecs usually only like 34 degrees with power falling off after that. I could see a combo liking 32. Is it common? No, but I don't doubt it. As you said, tune it for where it MPH's.
Happy Motoring,

Hmmm, cranking compression means the cam is in right??? Whatever you say but I would be checking the cam anyway. Dog won't move and it lays over the first half of the track.

Brian-

No the light was not off, nor was the balancer.

Both were checked because the 32 degrees threw me for a loop also.

I think it was because of the high compression combined with the Comp 268 High Energy cam, feuler heads and flat tops.