I just built a 383 stroker. It is a 350 block bored 30 over. It is a 383 crank, stock rods 5.7, dish .110 pistons for 9.7.1 compression ratio. It has 462 heads w/194 valves, performer rpm intake, 650 dp holley carb. I set the timing at 12 degrees but it idles too high in park but too low in gear. What can I do?
List the cam specs, carb and trans converter stall?
12 BTDC is modest
The cam is a comp energy cam flat tappet 507 lift, 650 holley double pumper carb and a 2000 stahl converter
Connect the vacuum advance to a full time manifold source for starters, this is a source that pulls vacuum full time, including at idle. Now recheck the timing, it should be around 20 to 24 degrees before top dead center. When you do so, the first thing it's gonna do is idle up, which you will lower on the idle setting on the carb. Once you have it at the correct idle speed, set the idle mixture on the adjustment screws. With just plain 12 degrees timing, it likely doesn't have enough advance so to get it to idle you have to open the carb up off the idle slots to get it to idle, this causes the carb to draw off the primary boosters which results in idle problems.
Most times a when U noitice a big drop in RPM from idle to gear is caused by a tight covertor and bigger cam. Sounds like a likely cause for your seanrio. If this in in fact the case then timing changes will help but never over come the root cause. A 2800+ stall will really help.
You can clean up the idle with more advance to help
What is the duration of the cam?
The duration is 284
Need more stall and more idle timing advance.
I run this cam in my street 406.
Lock out the distributor's mechanical advance system.
Set the now locked timing at 34 to 36deg BTDC.
Retain vacuum advance, but get a fully adjustable crane vac adv
and dial it in to allow 10 to 12deg of added vacuum advance at high cruise speeds
like on the hiway. Limit the max possible amount of added vac advance at highest manifold vacuum (like during deceleration) to 15deg.
The exact rate of vacuum advance has to be found by drive testing
and adjusting the diaphram spring tension.
use ported vacuum.
Get a 3.5" or 4.5" rated power valve for the carb.
Remove the carb and flip it over and reset the pri and sec
throttle opening at idle so that about .020" to .030" of the idle transfer slot is exposed at idle.
make sure the PCV is hooked up and functional.
The XE284H-10 cam needs a 10" high stall torque converter.
Get a 3500+ stall for max performance.
A stock 2000 stall will not work well at all.
Its way too tight at idle.
It will idle easily at 800-900 rpm in neutal-park
and will idle easily and rock steady at 750-800 rpm in gear and not load up.
It will now idle clean without fluctuation and the throttle response will
be much much better.
If its hard to restart when the einge is hot when using locked timing.
install a simple ignition power interupt switch to kill the spark during engine cranking. Make sure the GM rear starter motor mounting bracket is installed when running locked timing.
Are you using a GM HEI distributor?
Hei Distributor And A 700r Tranny.
on a HEI.
There are two ways you can go here.
You can simply lock out the mech advance.
Or you can limit the mech advance travel stop to about 10deg of travel.
This will allow a 24-26deg inital base timing at idle.
and a total mechanical advance of 340-36deg at max mech advance.
use a 1 medium and 1 light mech advnnce spring combo once the mech advance travel is limited.
The stock GM vac advance pot on your distributor will not be
right for you engine. Get the crane fully adjustable vac advance with
the stop limit for the vac advance and read the crane directions on how to set it up correctly for vac adv rate and limit.
Th700r4 high stall converter.
Don;t be temped to buy one of the cheap "2600stall" converters
They are just a restalled GM 2000 stall converter
All they do is bend the intermal fines over more to increase the
stall. the stall and idle will not be right for your cam.
This is a very inefficient way to get increased converter stall.
Get a real deal high stall lock up converter.
based on a 245MM converter size.
3500-4000 real stall.
ya get what you pay for. These th700r4 converters perform.
They have a fully function HD lock up clutch so the th700 trans
performs correctly in OD and retains full street ability.
get some 4.10's
If this is going to be driven on the street on anything like a regular basis, I'd strongly recommend you use a mechanical advance curve and not lock out the mechanical advance. If you use more than around 22-24 degrees of initial, there's no point in adding more advance at idle by using manifold vacuum- so use ported in that case.
This is going to require tailoring the curve to match the combination, so start at a safe baseline and work your way up from there. KEEP NOTES! You may think there's no way you won't remember the changes you made, but trust me- you will not remember them all.
I have been using locked out mechanical advance+ correct set up and dialed in vacuum advance (ported vac source) on my car for over 5 years. Its is primarily street driven.
same XE284H-10 cam. I don't change any thing to run at the track other than tire pressure. The tune up is exactly the same.
The locked out timing is very, very effective for this cam, on the street.
This is what this cam wants.
Didn't you just say yourself:
BTW that's total advance, not "total mechanical advance". Total is mechanical plus initial. Mechanical is the 10 degrees that comes in from the weights. Initial is the 24-26 degrees, the two added together is the total advance.
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