What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

why does my 383 suck? >> now a crack??

blazinzuk said:
Whats your daily driver. I mean if you drive a Ferrari 455 (:haha:) for a daily driver you might be disappointed in your 383
Click to expand...

We built a mild 351W for a buddy's off road truck and he kept trying to compare it to the EFI 460 in his F250. Took me a year to get him to understand the 351W and that you have to wind it up to make the power.
 
ashman said:
Unfortunately I don't have any specs on the motor. I'll just have to get whatever information I can by testing it.
I drive an SHO which is sweet, but certainly not enough to spoil me from massive power. :haha:

I've never done a leakdown test. what is involved? can I rent the tool?
Click to expand...

Should be able too. Its a dual gauge, it screws into the spark plug hole, you feed it compressed air and it shows you how much air is leaking out, obviously the valves need to be closed. I take the valve covers off and just rotate the engine with a socket. This will rule out any major problems with the combustion area. I suggest this because you said you replaced the head and weren't sure if there were problems there

I like most other on here think the pinging is a timing issue. Do you know your timing tab is correctly aligned? Check your advance mechanism make sure its not stuck. Maybe see if you can rent an advance timing light. So you can mess around with it a bit.

But more info would be nice
 
Definitely get a timing tape or a dial-back timing light to check your total advance. You'll also be able to get a look at your curve and see when your timing's "all-in" This is a good resource if timing is your issue.

http://www.73-87.com/7387garage/drivetrain/hei.htm

You could potentially be running too much advance, particularly if you have a high compression ratio.

Too much compression could easily be an issue. A 383 that might work great in a lightweight car with a high stall (high compression, rapid advance curve, lopey cam) just won't get the job done in a truck. Some people build engines by just throwing horsepower parts at them without building for the intended application or considering how the parts work together. Best of luck!
 
blazinzuk said:
Should be able too. Its a dual gauge, it screws into the spark plug hole, you feed it compressed air and it shows you how much air is leaking out, obviously the valves need to be closed. I take the valve covers off and just rotate the engine with a socket. This will rule out any major problems with the combustion area. I suggest this because you said you replaced the head and weren't sure if there were problems there
Click to expand...
I'll see if I can round one up and test it.

I like most other on here think the pinging is a timing issue. Do you know your timing tab is correctly aligned? Check your advance mechanism make sure its not stuck. Maybe see if you can rent an advance timing light. So you can mess around with it a bit.

But more info would be nice[/quote]
I'm assuming the tab is aligned correctly, but I don't know for certain. I do have a HF timing light so I guess I don't know for sure it's accurate. The advance mechanism is just spring loaded under the dist cap, right?
 
By the time I had time to mess with the truck tonight it was too late to be starting it up, so I didn't get to the timing, but I did gather some info.

carb. internet says 600cfm:
Carb_number.jpg


coil:
Accel_coil.jpg


head marking:
Head_marking.jpg

internet info:
3998991​
307/350​
68-79​
1.72/1.50​
76cc
​

inside the dist:
Dist_inside.jpg

advance springs seem ok? :dunno:

Is there any way of figuring out what cam I've got short of pulling it out?
 
Last edited by a moderator:
Well unless you've got domed Pistons your compression ratio shouldn't be too high with 76cc heads, (unless they've been milled down a bunch) and another sucktastick item is how small the valves themselves are. Still shouldn't be a pinging issue. Onto timing And AFR next.
 
Quick question, when you did check timing, you disconnected the vac advance right??

Speaking of vac advance which port on that thar edelbrock didja hook the vac advance to? The manifold vac side(drivers I think) or the passenger side throttle vac?
 
myk5rox said:
Quick question, when you did check timing, you disconnected the vac advance right??

Speaking of vac advance which port on that thar edelbrock didja hook the vac advance to? The manifold vac side(drivers I think) or the passenger side throttle vac?
Click to expand...
yes I disconnected it.
Just went out and checked. The vac advance is connected to the passenger side.
 
991s and 882s are decent heads. They flow well, even with the stock size valves.
 
Off the top of your head do you know what type of piston is on this engine?? Dished stock type or flat tops? Been reading and its saying stock dished type pistons and these heads may have tendencies for detonation.... Especially hopped up. What temp t-stat do you have?? I just realized after reading this that if you can cool your heads down it'll go a long way against pinging. Like my caprice with LT1 they are 10.5:1 c/r but I run 87 octane, because head cooling is soo efficient it helps fight detonation. So a 160 deg tstat might be of some help.... Along with decent heads to really wake the engine up

Post #7 gets to some details as why.

http://www.hotrodders.com/forum/3970010-block-3998991-heads-low-compression-motor-138756.html
 
the weights are messed up on that dist. You can see the one on the left has no bushing. Timing will go along way to fixing power. Get a curve kit for your dist and put on one med spring and one light spring. When do you hear this pinging exactly?
 
myk5rox said:
Maybe on more stock applications, however I dunno about here with the extra air the engine itself is pulling.
Click to expand...

John Lingenfelter recommended either of them with stock valves for mild 383s and good on mild 400+ cod motors with the 2.02/1.60 valve jobs. I have ported 882s with 1.94/1.60 valves on the 7000 RPM 350 in my Camaro. They are no AFR220, but they are good street performance heads if you have them laying around.
 
They are OK heads and Lingenfelter suggested them when aftermarket heads were hard to come by. I guess I am still waiting on what suck means but I am guessing with a proper tune this motor will run just fine. My bet is still on timing.
 
AND if you did spin a camaro 7K with those heads it is about 1000 past peak.
 
I agree that it is probably timing related. I'm just saying don't put down a set of heads that have good flow numbers (better than small valve double humpers) when they are plentiful in good condidtion.

I use the Accel Blueprinted distributors in all my motors. For the price of it and it has a timing curve kit and adjustable advance as well as Accel's hotter coil in it when you buy it, it is a no brainier vs rebuilding stock stuff with bad bearings, thrusts and worn weight shafts.
 
TerryD said:
John Lingenfelter recommended either of them with stock valves for mild 383s and good on mild 400+ cod motors with the 2.02/1.60 valve jobs. I have ported 882s with 1.94/1.60 valves on the 7000 RPM 350 in my Camaro. They are no AFR220, but they are good street performance heads if you have them laying around.
Click to expand...

You said right here why they suck, mr L recommends them with decent sizes valves, but as Ashman said they are most likely stock 1.72/1.55 valves.... So the work to put big valves and port them put ya close to a GOOD set of heads,
 
For a truck, driven like a truck heads and exhaust size aren't a huge deal. If we were at the sand or mud I understand but low end tq and lugging will be fine with what he has.
 
80' 427 said:
For a truck, driven like a truck heads and exhaust size aren't a huge deal. If we were at the sand or mud I understand but low end tq and lugging will be fine with what he has.
Click to expand...

Again, for a STOCK truck yes, but why would mr Ashman want a 383 for it to drive Stocklike? He says it sucks for a
Reason.... It's getting choked, on top of the pinging issue... This is why a lot of people I know dislike 383, they do not build them right, they do just this and leave stock heads on it. Chokes out the flow the striker needs, it's NOT a stock engine, and shouldn't be tuned as such.
 
You must log in or register to reply here.

Latest Posts

Top Bottom