I am helping a friend of mine doing a upgrade on his 68 Road Runner he just purchased. Its stock except for headers and a M1 duel plane intake,Edelbrock carb. It idles smooth,not like a muscle car. Its a 4speed car,even has the Inland shifter yet. He wants a cam upgrade,poss head work to give it more of a muscle car feel,and better acceleration. He is on a budget ao he is not looking at pulling the motor,juat head work cam upgrade,something with a nice thumping idle,ideas?

Step 1: determine your budget

There are a couple of similar recent threads........ Do a search, there's some good info in those threads.

Has the engine been rebuilt prior in it's history ?
The reason I ask is because "rebuilder" Pistons for 383's can be notoriously lacking in any compression ratio to work with ?
just say'in....
it would be very nice to know what Pistons are present in the 383 before attempting a plan in Camshaft & Heads ?

Do you know the gearing? How much head work and does it have the stock 906 heads? Have you done a compression test yet?

It all starts with the cam choice. Everything else follows to match the cam.

Hughes
1.6 rockers and matching springs.
If your sticking with the stock heads, a good valve job, liners, guides cut to clear the valve lift and entry level bowl cut.

Obviously an aftermarket head can be had for the cost of machine work on the stock heads.

The dizzy will need to be recurved with more initial timing for these cams, and quicker advance rate.

A solid flat tappet cam would be better, but finding one that isn't too big will be a challenge. You can contact Jim at Racer Brown and he'll cut you one. The adjustable rockers and/or the solid cam will require new pushrods. Establish a budget first.

Interestingly, I do it the opposite way.
I determine all the other pertinent items I plan on using for the package, then use the cam to help tie it all together.
For me, the cam is basically the last thing I chose.

I should of said its running 3.55 gears. The previous owner said it had a bone stock rebuild with the exception of intake amd headers. This engine idles like a Imperial its so smooth. He wants a little attitude in it. Maybe stealth heads or a mild port,polish on the stock 906 heads.

He is going with a MP electronic ignition conversation also.

Yeah, I think Dwayne has the right idea here ?
Figure out what ya got to work with ?... then come up with the Cam to best fit and make it work.

Step 2. Determine you budget.

Step 3, determine your budget.

You get the picture.

I also agree with the question about the piston and compression ratio. If it is truly original, then we know pretty close where the piston is relative to the deck. If it has ever been rebuilt, the piston top/CR can be anywhere. I don't think original type pistons with the correct CD have been available for 40 years for the 383.

If nothing else, you should get a cranking cylinder pressure test now. Even though we don't know the cam, it might still be helpful.

To Russ's point, I don't know if correct height 1968/69 hp 383 pistons were ever available.
I've never taken apart an original 68/69 hp 383....... Did those motors actually have positive deck height pistons as delivered from the factory?

I took a few apart in my teens back in the 70's, and I twern't smart enough to actually measure much past a ruler ? LOL,
but seems to me from memory... if they weren't "positive", they were pretty darn close to, or at "zero" anyways ?

The few that I have measured are 0.003 to 0.005" below the deck. CD is 1.932".

My first rebuild was a 383 in 1977. I could not find a replacement piston with the correct CD at that time. I ended up having Dynamic Racing (for you old time Detroit guys) cut most of the dome off a high compression forged piston.

I suspect the "+.020" deck height spec was more for the NHRA than what the actual deck clearance was.
Seems like the tallest replacement piston I remember seeing for one of those has a 1.920 CD.

I think many of the rebuilder type pistons are more like the 1.848 CD variety, and some of those have a dish in them to boot.

If you want a little attitude in the idle fatten up the idle mixtures and set the base timing to like 2-3* BTDC. That'll give it some rumble rumble while idling.

Regarding cam; for me it's choose the cam I want first, then build everything around it.

One issue I had on my 383 was the lack of valve reliefs in the piston. Flat top pistons that appear to be zero deck height.
The heads were milled for compression which made the piston to valve clearance issue worse.

Edit: FWIW the pistons in this were sealed power forged replacement HP pistons, but engine built in the 1980's.

Right on the 1.920.

So, for the OP, if it has original pistons, there are some decent options, depending on budget. A 0.040" gasket, your favorite closed chamber head (915, or any of the aluminums out there) then fine tune chamber volume/cam to the best outcome.

At least there are a couple of reasonably priced piston options now to get decent compression, quench, and valve to piston clearance.
KB 162 flat top, KB 400 6cc dome.
The KB 400 works well with the 84cc edelbrock, sidewinder, stealth type heads.

Presuming typical streeter kind of a deal, he should be okay with some cam options. But you do make an important point that needs to be in the equation.

And if it has the typical rebuilder variety...... It's time for the hard decisions.

Using a 1.848 flat top in an uncut block with a steel shim gasket and the normal 88cc open chamber head, puts you in the 8.0 cr range.
That's going to limit how much cam you really want to stuff in there.

Maybe I'm missing it, but I thought that the dome/reliefs on the KB 400's were a wash, and they end up with low 9:1 with an 84 cc head and no quench w/o a bunch of milling.

I get about 9.9:1 with a KB 400, down the hole .024(stock deck height), .022 gasket and an 84cc head.

The KB 400 is listed as having 6cc effective dome volume.
If the dome and the reliefs were a wash it would be listed as a 0cc dome.