383 mag w/ new cam bogs down when put in gear

[Ray70Chrg]

new lunati 703 cam, lifters, springs, timing gears & chains. Degreed cam and properly break-in process with lighter springs, then put in proper strength springs. I have no concerns about the new parts and their operation. Started engine, set initial timing to 15*btdc, connected distributor vacuum hose to manifold and that brought advance to18*,rpm's are 950/1000. Adjusted both carb screws for 20 inch vacuum. Idles nicely. Rev it up and release, idle returns to same values. Cam that came out of car is unknown. No manufacture id. Certainly no purple marking. When I put in gear rpm's reduce 300-400 revs and idle is unsteady and ready to stall. Put back in park or neutral and idle returns to normal. Carb is a Carter 625 Performance Series and I had no problem like this before. Is it possible carb is now a mismatch for this higher performance cam? Intake manifold, 906 Heads, & hp exhaust manifold are all stock. Trans is 727b. Any ideas appreciated.

 

[Lionized]

Idle should be set in gear, vacuum advance should be ported, not manifold.

 

[wyrmrider]

what's the lca on a 703
stock exhaust do not ike a lot of overlap
you can make it work
post your compression and vacuum when you get a chnce for the record
you are in the area where you are goingto have to limit total advance
carb can be tuned it's fine

 

[Ray70Chrg]

Hey Wyrmrider. Thanks for replying. I chose Lunati on your recommendation back in May. Lobe separation for 703 cam is 110. center line is 106 with 4 deg.advanced built in. I degreed it 3x and came up with 107 centerline. Installed camshaft straight up with new chain and gears. Compression tested at around 170 with 1 cylinder at 155. Vacuum is at 20 inches @ 950 idle.

 

[Wietse]

Idle rpm too high? what is the stall speed of the converter?
Maybe try to get it to idle lower in rpm, seems like you have plenty manifold vacuum to do so.
Do you have an AFR meter by any chance?

For the carb, check the secondaries are not open too far and your PCV valve is working correct.
Mine had same issue as you described where putting it in gear the rpm drops far down.
I found my secondaries cracked open too far (too much dry air) and my pcv valve started to provide lots of air, but i have a very low manifold vacuum where you might not have the pcv valve issue.
Likely yours is doing same as mine did, drops to very lean when thrown in gear.

 

[Ray70Chrg]

Hi Wietse, Thanks for replying. Converter I assume is stock for 383 magnum. Something like 26-2800 stall speed. Don't have a AFR meter. I'll check carb secondaries and PCV tomorrow. I had no problem sitting idle to 700 rpm with old camshaft, but this new cam seems to like 950 range better. The old cam didn't seem to be a HP cam and it was unknown age. This engine had no gitty-up for a 383 magnum and that's why I changed it. My 20 year old 4 cyl. Frontier PU could beat this 383 and that's no ****.

 

[1 Wild R/T]

Have someone with a timing light watch the timing when you drop the car into gear.... When you drop the car in gear the RPM's are gonna drop, if there is any mechanical advance "in" at idle when the RPM's drop the advance will "fall out".. When the advance "falls out" the RPM's will drop even further.... This can easily lead to the engine stalling....

 

[BSB67]

It appears the term "installed straight up" has three different meanings. Why is it the go to phrase I wonder.

Anyways, its hard to diagnose these issues without being there. Could be things already mentioned. Maybe vacuum leak but 20" of vacuum suggests otherwise - is the gauge correct? The overlap is not huge but the Carter might struggle with the larger cam. Could be simply in the timing/carb tune details. I would suspect that it should idle in gear, but probably not real clean at 700 rpm loaded against the stock converter.

Like mentioned, first items are ported vacuum, and making sure timing is not dropping out from neutral rpm to in gear rpm.

 

[66Satellite47]

May be off base here, maybe try plugging the PCV, try both ported & manifold vacuum advance, idle mixture screw adjustment combined with the secondary throttle idle opening. I'm not a Carter guy(never learned all the component/design functions well enough) so my suggestions are real general. Wild's comment on mechanical advance is sure worth a look. The 107* CL install should be OK, could advance that couple degree's, but doubt that's the issue. Hate to say it, could be a converter problem, previous cam performance problem could point to that. Broken stator converters go slow & "slip" into gear well. A 10" converter from a quality manufacturer could really perk that combo up, especially if the existing converter is suspect.
Edit: 1 low cylinder could explain some lack of overall power, not the idle issue.

 

[Don Frelier]

Slow down the idle and tune it in gear.
You should be able to get it to run well at 750 rpm. How does the exhaust sound? Hitting on all 8? Try pulling a plug wire at a time (use rubber gloves).
A real longshot but I had a problem once where my distributor bushing became really tight and the car wouldn't idle. But it would still run well at cruise.

 

[PRHeads]

A 383 with:

Intake manifold, 906 Heads, & hp exhaust manifold are all stock.

And probably a stock converter as well...... with a Carter 625 carb...... and then adding a fast rate cam like the Voodoo 703...... sounds to me like a combo that could easily present some challenges to get the low rpm operation sorted out.

I also wouldn’t really expect the motor to “come to life” at WOT until it got up into the 3000rpm range........ especially if it doesn’t have much rear gear in it.

As has been mentioned, see what’s happening to the vacuum and timing when going from idling in neutral to idling in gear.

A little looser converter would help some with the rpm drop when putting it in gear.

This engine had no gitty-up for a 383 magnum and that's why I changed it. My 20 year old 4 cyl. Frontier PU could beat this 383 and that's no ****.

A cam change to an otherwise stock engine isn’t going to make a night and day difference in the performance of the vehicle.
The farther you stray from the factory cam, the more likely it is you’ll need to make some other changes in the car to exploit the potential performance that might come from the cam swap.

 

[Ray70Chrg]

Hey Gang, Thanks for all your inputs. Today when I started using your suggestions my HF timing light took a dump and expired. I've only used it about 4 times. Oreillys is the only one that has a light in stock but the reviews on it are terrible. I might be a few days from getting a replacement, but I'll try some of your non light suggestions. Thanks
update from today: Looked at pvc and it was operating properly. Set idle @ 750 in gear but went back to park and idle was 1500. reduced it to 1000. there were some things that were different from yesterday. I had left the vacuum gauge connected to the manifold nipple overnight and when the car came up to tempt i noticed it was no longer at 20 in. but was now 8 in. (head scratch, WTF!). I must have a air leak somewhere. Checked all the usual places and found nothing. I had also left the port nipple disconnected but covered with a boot. For no good reason at all I reconnected the vacuum hose to the dist. vacuum unit and the rpm's jumped considerably. I know that in idle there is little to no vacuum at the port nipple. Well surprise,surprise there was 30 in. of vacuum at the port nipple. Something caught my eye and I noticed some small amount of liquid was seeping from under the right front corner of the carb. onto the intake manifold. Gasoline. I guess the carb is eating the gasket and hopefully this will be the solution. Luckily I inherited a Carter handbook with the car that shows how to take apart and rebuild their carbs. Now to find a good timing light, Carter rebuild kit and fix the carb. I have this car for 4 1/2 years and it stood in a garage for 15 years before I bought it so 20+ years and the gasket finally gave up. Thanks to all for your input.

 

[MoparGuy68]

Hey Ray. Is this the cam you installed?

Lunati Voodoo Hydraulic Flat Tappet - Chrysler 361-440 268/276 SKU #10230703

Hydraulic Flat Tappet. This high performance street cam likes 2400 RPM stall, 800 CFM carb, dual plane intake and headers. Makes un- equaled power to 6200 RPM with proper valve springs.; Advertised Duration (Int/Exh): 268/276; Duration @ .050 (Int/Exh): 226/234; Gross Valve Lift (Int/Exh): .494/.513; LSA/ICL: 110/106; Valve Lash (Int/Exh): Hyd/Hyd; RPM Range: 1800-6200; Includes: Cam Only

My engine has a bigger cam than stock in it. Don't know the specs or brand of it though. I was worried that maybe the HP Exhaust Manifolds, I now have installed, might create too much back pressure for the cam. I was only able to drive the car once, after completing the steering system swap (electrical system is apart now).

I did notice that the old curb idle setting on carb, is now too low to keep the engine from wanting to stall out when put into gear. It did stall out on me once backing out of the driveway. During the test drive, when stopping at stop signs, it almost died, but kept running.. But my drop in idle speed when going into gear doesn't seem to be as much as you are experiencing. With the headers, while in gear it used to idle ok at 700-750 rpm. With the exhaust manifolds I think I may have to raise that to about 800-850 rpm.

 

[Ray70Chrg]

Hi Steve, Yes it is that cam. I was afraid to take it on the road because it was so weak. I read something in Carter carb manual and it lead me to an adjustment on the accelerator pump bracket if the floats were out of adjustment and the fuel bowls weren't full to spec. Made the adjustment and it helped reduce the amount of rpm drop to where the engine seemed more steady. Since the floats appear to be out spec and the intake vacuum is low, I'm in the middle of carb rebuild and resealing the intake and the valley pan which had no gaskets at all. Just the joys of going down the rabbit hole on a car you have no history about. Tried calling you this a.m. but didn't leave a message. Ray

 

[fishmens67]

Initial timing and carb adjustments on a auto transmission car should be made in gear.
20 in of vacuum at idle seems awful high for that cam 170 # compression ? most are around 150 with less cam.

 

[wyrmrider]

20 inches in HIGH vacuum not low

 

[oldkimmer]

Use the ported vac port on the carb. When u use the full vac port the timing goes up at idle but drops excessively when in gear. Remove vac hose from dist. Plug it. Set idle timing to 15*. Check total timing. How does it run in gear now? Kim

 

[Ray70Chrg]

Hi Kim, Thanks for your suggestions. As I stated in post #14, I've decided to remove the intake manifold and valley pan and start from scratch to insure things are right. As we all know when you buy these old cars there's no telling what's been done to it so best bet is to cover all the bases.

 

[MoparGuy68]

Hi Steve, Yes it is that cam. Just the joys of going down the rabbit hole on a car you have no history about. Tried calling you this a.m. but didn't leave a message. Ray

Ray, I did see that you called. I had a busy weekend and didn't get around to calling you back. So I'm responding here.

I agree about the rabbit hole, as you dig deeper and deeper into the car which has had 50 years worth of **** done, and or not done to it. Then discovering all the hidden surprises that you didn't know about at the time you bought it. These cars were all 21 to 34 years younger when I last messed around with them, and the past two to three decades hasn't been kind to them. With the low quality replacement parts being made for them and many original parts either destroyed or in terrible shape, I think it's a bit masochistic to work on these cars today.

If I knew what I now know about my car, back in November when I bought it, I probably would never have gone back to "look at it" that second time. Since it arrived at my house, I've driven my car twice for a cumulative total of 3.8 miles.. That's it.. The rest of the time I've been working on it.. Hopefully, this time around, the car won't be sitting longer than about 2 months without being driven. After the first drive, it sat for 5 months while I had it apart. Then after the 2 months, there is still MORE stuff that needs to be fixed on it..

You're retired and can work on yours whenever. With me working full time, screwing around every weekend with this car and not being able to drive it, is getting old and tiresome. I need a vacation from my own half century old car! It turns 50 on September 3rd..