Yes. That is my next step. Thanks.

FBO has a plate to help set up the distributor. another thought would be the valve train. stock iron heads won't support the lift that cam has. you might want to take a good look at springs and seals. also, if your using stock rockers and push rods you may have too much pre-load on the tappets.

Call me what ever you want... the reason I don't ask questions here is ive NEVER gotten a correct answer to anything ive asked. oh and you still don't know whats wrong do you? nor does anyone else, I told you what I would check so there you go good luck

IMO the shortening the slots (whether by welding or using the FBO plate) is putting the cart before the horse. First see if changing the initial timing resolves some or all of the issue. Then see what the rest of the timing curve looks like. With that info, adjust the spring perches and/or the slots as needed.

What was done to freshen up the engine?
Were the pistons replaced or heads milled?
Just curious as the piston to valve clearance might be tight with 242 exhaust duration @ 0.050?

I think you said cam was installed straight up? So we really don't know the exact installed position? You could maybe just do a quick check that the intake valve is at max lift around 102-degrees ATDC?

I'd start with the basics, pull the plugs and inspect them, then do a compression check. Leak-down check if you have the equipment.

If that looks good, you do need to re-curve the distributor as mentioned earlier for maybe 18-20 degrees mechanical advance in the plate, and around 16-degrees initial timing at idle (with no vacuum advance.)
Idle will likely need to be higher than normal too, and at idle the carb may be exposing the transition circuit. Check how much of the transition slots are exposed. You might have to drill the throttle blades if exposing to much of the transition circuit. Not sure if the drilled throttle blades is still the correct tuning adjustment? I think the Demon carbs have an adjustable idle air adjustment, and there may be a better way to correct that?

Agreed. Bumping the initial just to try it is free, quick and easy. I would play with that before spending money or going deeper.

Freshening up consisted of new rings and bearings, gaskets and a valve job. The head surfaces were straight and flat, so surfacing was not needed. Pistons are a mile in the hole, so I'm not too worried about piston to valve clearance. I degreed the cam and it was installed to Hughes recomendations. I haven't been able to work on it for a week, because of the weather. Maybe soon, it is spring in Oregon!

I did a 383 for a guy with that hughes cam, lifters, and springs, straight up, pistons a mile down, milled heads got it to 8.9 to 1 measured, pocket ported heads, old weiand dual plane, 100% stock older 3310, 18 degree in dizzy, 20 on the crank, exhaust manifolds and it runs fine. Its a bad combo but a bunch of old parts he wanted to use up, it sounds meaner than it runs, but will idle all day on cheap gas no matter how hot it is, which is what he wanted. Best advice all the initial timing you can get.

Sounds good, likely just need to work on the tune.
Was asking because on my 383, I used the pistons that are at zero deck height and no valve reliefs, and the heads were milled. when I checked piston to valve clearance (smaller cam than yours) the clearance was closer than I thought it would be.

Make sure that if the vacuum advance is hooked up it's on ported vacuum, not manifold vacuum. You may loose timing when put in gear with manifold vacuum

First step, purchase a vacuum gauge. Give us the reading @ idle and while in gear.

Second step, add more initial timing.

Then let's go from there!

Hope you get it sorted out.

Thanks for all the input. I have been wrenching on mopars for nearly 50 years and this is the first cam change that's ever given me problems. I have installed many cams over the years without so much as a hiccup, this one should have been a no brainer as well. I must be getting old.

Really that cam is pretty big for a stock 383.
Too much advertising hype about it "working" with stock engine.

How have you worked out your actual compression - 8.5 and "way down the hole" dosent sound right - if its got less cr than that then yes it would be a turd

The factory rated that motor at 8.5 compression. I have found Chrysler's numbers to be very optomistic and it is probably closer to 7.5, since it has the stock pistons in it. The car belongs to my brother and I was trying to help him out. We settled on this cam because of the claims made on the website. According to Hughes website, that cam is supposed to build cylinder pressure and shouldn't be put in anything that has much more than 8.5 compression. It sounded like the perfect cam. Perhaps it is hyped up advertising I don't know, I do know that I'm rather disenchanted with the whole fiasco and probably should have gone with much less duration but similar lift.

You could subtract 20 degrees of overlap Int & Exh and it would be a much better street cam. Especially with low CR.
Ran an Engle in a 406" SB street motor - 214/224 @.050, .470/.504, 110 CL - and it ran great: perfect throttle response even with stock converter, 3.23 gear, 28" tire, handled AC, pulled 17 MPG, but still sounded pretty rumpity.
Rarely have I seen a street car where the rumpity idle was the main build consideration actually run well @ lower RPMs.
I scaled that SB Engle up 1 lobe spec Int/Exh for a 446" RB street build, and got the same results in a 4-speed early-B wagon.

real compression ratio is probably high 7's with a .039" head gasket. that cam has over 70 degrees of overlap on the seat, a bunch for a 383. why hugh's would say this cam is ok for a low compression engine baffles me, especially a torque weak 383.

I went thru this getting the 440 whiplash to run

I have a stock TC 2.76 gears in a 4000lbs truck

what I did was get the fbo plate and lock the dist 0* and set timing to 36*

change the whole engine and became a street beast.

I tried 14* initial with plate on 18* light springs vac can or with out

sorta ran dies a lot/ temps go up at speed because late timing ect.. ran like a pig.

I used a holley street dominator (open plenum) new OOTB 750cfm edlebrock tunning** changed step up spring/ bumped the squitter up 1 size bumped 2ndary jets up 3 stages rich .113 jet

FYI..ididnt read all the post here but I have run 4 of the whiplash cams and they all want the most initial they can take and very little mech advance. they like a lot of gas so fatten up the carb.

I gave up on holley as I was not to good at tunning them.

but did learn about picking the power valve...as long as the throttle palates are not open to far it wont let gas thru port even though valve is open..

when choosing a # PV use a vac reading at a cruz speed and divide it in half.

mine was 20 inches at 55 mph so I went with a #10 pv it only has 10 inches to 7 inches at idle but does not flow fuel as the throttle blade are not at the transition slot yet.

edlbrock was way easy to tune with a vac gauge and watching the step up pistons at idle...change to weaker spring till they stopped bouncing at idle, upped the accel pump shot for off idle stumble, upped 2ndary jets to rid it of the transition bog of 2ndarys

only get 10 mpgs with 3.23sg but it fries the 29x15x15 M/Ts from a 15mph roll and flat out screams a 1/4 mile run.

once you get the timing dialed in and the carb fat enough it will work with a low stall TC 2.76 gears

I have a 900 rpm idle in N and drops to a 700 rpm idle in gear and has a nasty chop chop chop and a crispy snappy throttle.

my 318 roller whiplash has fbo plate- 14* initial with plate on 18* for 32* total.. MrGasket light springs - no vac advance hooked up.

junky did the 383 whiplash and had to recurve dist and fatten up the 750 holley then it became a street beast also.

very frustrating till I figured it out with the 0* lock out

IMHO, once it comes together the hype for a "STREET" cam is spot on.

I like mine NOW but was ready to yank it out and toss it.

the tuning book from fbo with the plate was the best 40 bux I spent. fixed all 3 of my mopars following the tuning guide.

now that I understand that the timing has to light the cyl early to get it all to burn in the cyl if key.

if not it burns going out the exhaust port/header tubes which makes temps go up and headers glow red.

also it has strong exhaust fumes leading you to think it is rich but is lean. the smell of strong fumes is the hydro carbons not burned because all the oxygen was burnt first.

this had me all confused at first as I kept thinking lean and need more fuel

nope more timing is whats needed

IIRC my 440 has more dur then the 383

230* @ .050
245* @ .050
.518/.518 lift


don't give up on it.

my speed shop said now way with stock everything..LOL!

750cfm eldelbrock
holley street dominator
440 whiplash cam/springs
headers-3" pipes/muffs
12" low stall TC 727
used 2.76 3.23 3.91 gears turning a 29x15x15 m/t all street friendly

dist locked 0* 36* total

I drive it daily/weekends and have clocke 10,000 miles now. great daily drive if you got gas $$