camshaft specs? The brake issue is easy to fix. Is this a Corvette or other car that might have a vacuum leak in a headlight system,,,etc?

 

I wish I did have the camshaft specs but I do t.. Did you see the photo of the camshaft anylisis? Does that even help? Yea I'm pretty sure I know what I need to do to fix the brake booster bc it just doesn't have enough vacuum .. What I'm wondering is 6 inches at idle and 16 max inches seem right for my setup?

 

Yes that sheet you posted gives you all the info you need about that cam.

 

It's. 1972 c-10 truck. Don't believe I have a vacuum leak bc they are all new line all I have is one to the brake booster one to the Pcv valve and one to the th350 tranny..

 

from what I can read and isnt obscured,I would toss that cam in a trash can. Im not saying its a bad choice in profile. Im saying a cam that big needs a wheel on the follower. It will have a rough idle and poor vacuum at idle and wont impress me with its performance. With out more information its all going to be a guessing game. If you gave me that engine for free I would not use it. I would take it apart and measure everything and make changes as I saw fit,,,
what is the brand name of the heads,intake,distributor,pistons,rockers? what are the exact specs of everything.You own the engine,they should supply exact info right down to the balance specs, piston to wall and piston to valve. They should say exactly where the ICL is and why

How is the power? does it melt the tires etc?

 

I would take it apart and measure everything and make changes as I saw fit.

Vinnie, I should have paid more attention to you in the first place.

 

It's not the cam. Matter of fact, if I were building the motor, I might have used more cam than they did for 10.5:1 static compression ratio. Only difference is, I wouldn't use one of those fosdick XE cams and I sure as hell wouldn't have used a flat tappet cam.
Here's the cam card....
21-227-4(Single Bolt) - Xtreme Energyâ„¢ Hi-lift Hydraulic Flat Tappet Camshafts

Here's what I would do:
Find zero on your damper by following the wiki article I linked for you here, then dial in 12-14 degrees or more initial timing at the crank and dial in total timing (initial at the crank plus centrifugal) based on the heads you're using. Without knowing EXACTLY where top dead center is on the damper, you will be shootin' in the dark. Maybe some of the Mopar guys will jump in here and suggest the total ignition timing you should shoot for, because I'm not a Mopar guy, but that's my best guess as to the lack of manifold vacuum, that the motor is seeing too little ignition timing, assuming that the valve lash is correct.
http://www.crankshaftcoalition.com/wiki/Determining_top_dead_center

EDIT: I just went back and read that this is a Chevy truck. The cam card you linked is for a Mopar 383, not a Chevy 383. What's goin' on ???????? Did the builder give you the wrong cam card or have I slipped a cog ?????

.

 

What is the timing at idle? Sounds more like a tuning setup issue. Camshaft is not a bad selection at all. Your basic comp cams style XE 275. 230 231 @.050 .521 .522 110lsa. Not a bad grind for a hot street 383. It has some moderate overlap at 13 degrees. It is going to idle a bit rough. Should be a responsive nice little engine. How does it run off idle?

 

So at around 780 rpms it's running pretty rough and it doesn't feel to reliable the initial timing is about 10 degrees if I bump it up to say 1000 rpms it's around 18 .. It's defiantly has the power at WOT can't keep the tires from spinning . Wondering if I should mess with the centrifugal advance and take some of it out . I'm really green to all of this so I'm pretty hesitant to try it for now. Haha also it's pretty hard to adjust this holley carbs idle circuit seems like it doesn't do to much to the idle or the vaccum ( although it's pretty bounce vaccum reading with this cam). Wondering if I should open the secondary blades a little too

 

Thanks I will look into it. Mopar? Isn't that dodge.. I'm running a 383 chevy

 

Yes I assumed it was a chevy cam card as well. Not sure why they would give you the wrong card. Im betting that the specs are almost exactly the same. But I would call the builder and verify to be 100 percent certain.

 

Problem is, if they sent the wrong cam card, what cam did they put in the motor? Jeez, I think I'll go back to bed and start over later. ain:

 

You really need to figure out what you have in that engine before you proceed.

 

This ^^^^^^^^^^^^^^^^^^^
If you cant determine what the cam is for sure everything else is a waste of time. A real lopey cam is not going to give a steady vacuum reading.
If you do decide to adjust the valves with the engine running turn down the idle as much as you can. It will help to contain the mess

 

Having to adjust one valve after break in sounds suspicious. Hope you haven't wiped a lobe. If you don't have a lot of experience setting valves, then, yes, setting them running is the easiest way.
Basically, engine running, with valve covers off adjust each lifter by loosening the nut until you hear it tapping, then tighten until tapping just stops. Tighten 1/4 turn more. (I will get some argument here, some say 1/2 turn, some say 3/4. They all will work.) It is messy, but accurate. You can cut up an old set of valve covers to adjust through to help contain the mess. I hate doing it that way and haven't set valves running since I was a kid. Lots of experience.
At this point, you might as well start it up, set all the valves and see if that fixes it. If not there are other problems.
OH yeah, is it a flat tappet? ZDDP?

 

Having to adjust one valve after break in sounds suspicious. Hope you haven't wiped a lobe.

You're thinkin' what I'm thinkin'. That could account for the jittery needle on the vacuum gauge.

 

Dang everything I've read everywhere else says not to adjust these type of lifters this way.. Looks like I will have to give it a shot.. So to be clear you guys think the vacuum gauge needle should be rock solid at idle with a bigger cam? And what's this about maybe messing up the lobes? All info is very valuable ... Thanks again for your posts

 

You sure you don't have a vacuum leak? Under the base of the carb maybe?

 

Well, what kind of lifter is "these kind"?

 

Leave the valves alone and put some timing in it!
At least 20 initial. Then adjust the dizzy mechanical for 12 degrees all in at 3200.
Fine tune it and then be amazed at the vac reading.

 

put some timing in it!
At least 20 initial. Then adjust the dizzy mechanical for 12 degrees all in at 3200.
Fine tune it and then be amazed at the vac reading.

I agree this needs to be done. Only I would still run those valves all again, just because one valve had to be readjusted after break- in.
OP still hasn't (I don't think) revealed what type of cam this is, hyd roller or flat tappet. If the builder sent the wrong cam card, then what else did they do wrong? If it is a flat tappet, the OP was probably not informed of the need for zddp. Better to catch a wiped lobe now, than let it get worse in a brand new motor. That 383 cost the OP a lot of money. I would stick an indicator on there and at least check the lift on the valve that needed adjusting and compare it to a couple other valves

I might give it a little more total timing, maybe 34. 32 is safe.

My 383 is very similar to yours. It runs 11"Hg at idle. Rough idle.

 

It's a hydro roller... I guess I might readjust the valves seeing as it not to difficult... My start up procedures I got from the builder did say " valves HAVE BEEN PRE SET. and tested to be correct. They may need to be re-adjusted after 50 miles if they are ticking, very rare..."

So the motor was pre run and tested in the shop, but there was a break in procedure that I still had to do... Problem is I bought this online and out of state a year ago and now I haven't been able to get hold of the builder ..

 

OK, Hydro roller. Yeah, our engines are probably very similar. So, you're prolly good on the cam. I would still run all those valves. You can do it static, but be very careful about depressing the spring in the lifter. Cheap insurance for an hour's worth of work.
I don't understand when you say 6" @idle and 20" max. When are you getting "max"? Also, nobody asked, are you hooking the vacuum gauge to full or ported vacuum? I would guess full since you get 6"@idle. Just checkin'.
So, if all's well with the valves then your next step is timing. I don't want to do all that typing, but there are lots of threads on setting up your distributor. Do a search. Don't know what you have, but I think HEI's are the easiest to set up. I would start with 18 initial + 16 centrifugal = 34 total and work from there. You can play with vacuum advance after you get it running good.

There are also some good tutorials on using a vacuum gauge. Tells you what the needle fluctuations mean.

Carb work after timing is optimized.

 

Yea hei distributor ... 6 iches at 850 rpms and 20iches at around 3000 rpms... Not running it with the vacuum advanced hooked up

 

Oh and manifold vacuum I've used two different ports the one in the back of the holley carb (the one used for the brake booster ). And one manifold vacuum on the front of the distributor too.. Same reading on both...

 

Look at the cam card again gents, that is an electronically generated cam lift analysis card...the brand of cam listed is not the actual cam.

To the OP, that cam is quite big but not out of line for the power your stated, it will have a serious lope at idle which will require tuning to get right. Your vacuum will be low but 6 inches of mercury is too low...should be closer to 8-10 inches at idle and maybe even 12 if you really get it dialed in nicely. You will likely have to run a higher idle rpm to get a smooth vacuum without fluctuations, 900-1100 is about right for that size cam.

There is not one way to tune such a large cam for a heavy vehicle like a truck, there are two.

The first way is using a locked timing distributor and run large initial, this usually requires some sort of retard box and or a second switch to allow cranking before turning on the power to the distrubutor spark to get reliable starting when hot. This technique usually gives the most idle vacuum and the least lope at low rpm.

The second technique is too tune the distributor using weights and limiting the vacuum advance to get a fast ramp up on the timing curve typically having all the timing in around 3200-3600 rpm. Vacuum is usually the lowest of the two methods but the idle rpm can usually be the lowest since you don't have timing jacking it up.

Of course this all assumes your carb is setup correctly with the proper power valve, secondary opening, jetting, idle mixture etc. etc. etc. Don't underestimate the effect fine tuning the carb has on idle vacuum and quality though, getting that part of the equation right is first on the list of do's, timing is second.

 

Thanks for the response ... Tunning this holley carb has been a pain.. Starting with the idle mixture screws at 1.5 turn out if I turn them out more no real response only time I can get a response is I turn them almost all the way in.... Then it will die.. So then I start turning them back out and the idle goes back to normal then if I keep turning them out like to 3 or four turns out the idle stays the same... I've read something on the internet about the primary blades could be open too much already exposing a slot inside the carb and the I would need to take the carb off and adjust the secondary plates to bring them open a little bit allowing more air in . Then I could bring the throttle back down and covering up the slot by the primary plates which would allow the idle circuit to work better.. Any of this sound right?

 

This is the video that talks about the slot I am talking about at about 7.25 seconds in
https://m.youtube.com/watch?v=gag-Bg-X8cM

Does what this guy saying sound right?

 

Stop, there's way too much going on here. Pull the Carb, square your transfer slots, reinstall. Lightly seat your mixture screws, then come back out 1.5 turns each. Get it running, get a timing light on it, set your initial timing to 22* at app 850rpm.Now install your vacuum guage to a manifold source, adjust in equal amounts until you see the highest reading, its likely going to be 10-12*.
Now that the idle is clean, and vacuum stable, you can limit your mechanical to about a 12-14 curve. It will feel like a whole new animal.
If you find it hard to start when hot, search on here for a write up on ignition interrupt switch. Dead simple.
Once these steps are done, you can work on fine tuning the Carb and timing, it may want a couple degrees more/less initial or total. But this will get you close.

 

Get the carburetor tuned to idle with as much vacuum as you can get. I remember when I was starting my big block for the first time all I got for a vacuum reading was 8 hg. I took the carb off adjusted the primary throttle plates. Opened the secondary to about .040". I still didn't have but 8 hg of vacuum. I set the initial timing at 20* no change. I pulled the valve covers and adjusted all the valves again. (Mechanical Roller) This time when I cranked it and after adjusting curb idle I had 10-12 hg of vacuum. So my advice would be to adjust the valves while the engine is running. Loosen one rocker at a time until you hear it tapping. Now snug it down until it stops. After it stops tapping slowly turn the nut 3/4 to 1 turn, give the engine time to catch up. Then move to the next rocker and repeat the procedure. BTW if you have an old set of valve covers that you can cut the top off of it will keep the oil from splashing so much. If you dont, go to the junk yard and get a used set.

 

Yea I think I will have to adjust the valves if for nothing more than just to else eliminate one thing... I keep hearing about doing it with it running but with a hydro roller setup I've heard that's not the best way to do it.... Any input on this from guys with hydro rollers?

 

I run two small block chevy's with hydraulic roller cams and how I set my valve lash is bring the engine up to top dead center on the compression stroke on cylinder number 1. At that time both valves should be closed and I start by tightening up the rocker arm nut and move the pushrod up and down and not the spin method as unless you have done it enough you will end up past zero lash and once the pushrod will no longer move up and down and also the rocker arm will no longer pull up across the valve then I know I am at zero lash and give it a 1/4 to half a turn then lock the nut down.

Then I turn the balancer a 1/4 of a turn then proceed to cylinder number 8 in the firing order and both valves should be closed. You basically do the firing order of 18436572 and after you set the cylinder then you turn the balancer a 1/4 or a turn each time after your set then after two full revolutions you will have all your valves set.

There are several methods but this has worked the best and easiest for me.
http://www.hotrodders.com/forum/best-way-adjusting-valves-sbc-132599.html