Help...fresh built 355 "dieseling" or running on...

[1970witha355]

Ok heres what i have. The block is a 1975 350. It is bored 30 over. It has flat top pistons. The block has been decked to zero (the pistons come up level with the block). It has stock iron "441" heads with 194/150 valves. The cam is an isky "201SL1". This is a circle track cam im told. The specs are: 390/410 lift, 228/232 duration @ 50, and a 108 lobe seperation, 2000-6500 rpm range. I dont know what the compression would be, im guessing around 10:1. I am running 87 octane gas. I have a TH400 tranny with stock (1300)rpm converter. The problem is the engine should be making 300hp give or take. It sure doesnt feel like it. I should be able to floor it and rip the truck sideways. It feels weaker than an old worn out stock inline 6. It doesnt feel like the 4 barrel is opening (new edelbrock carb). When I shut the truck off, it stumbles for a second or "deisels" then shuts off. The timing is set at 10 btdc. WTF!!!!!!!!!!!! I am so frustrated that I am sick! Is the answer better gas, stall converter, NEW ENGINE???????????? OH MAN AM I PISSED! HELP HELP HELP!!!!!!!!!!

[70cst]

Sounds like a timing issue ... others

[70cst]

Oh yes 1970witha355 ...

to the forums and from Ohio. I am sure there will be others who are more informed than I.

By the way... I luv 1970 C10's

[Lattimer]

Edelbrock 4bbl is mechanical secondary (at least mine is), so you should be able to see if they are opening by looking without the engine running. Mine wouldn't open at first until I figured out the PO installed too long of a throttle linkage rod. Pedal didn't travel far enough to make them open.

Your problems really could be any number of things. If you are really at 10:1 compression you probably won't want to run 87, you will need premium. Lack of power could be a cam timing issue, vacuum leak, or carb issue.

Which carb are you running? If its too much carb for the engine or set up way rich you can get lousy performance.

First thing I've learned to look at is vacuum. Have you hooked up a vac gauge to see what you have?

[TBONE1964]

Many questions:

What type of ignition?
Where is the base timing set?
What type of exhaust? Headers / Manifolds / Dual / Size of pipes?
Did you break the cam in correctly? Run for 20 minutes at 2,500 rpm. This varies depending on cam manufacture.
What are you running for fuel pump? What is your fuel pressure?
Is this a fresh build and what is the valve lash set at? Is it hydralic or solid cam. Do you have the correct lifters for the cam?

Yes the dieseling is usually a result of to much advance in the timing. Your base timing should be around 10 degress give or take a couple.

[Kid]

sounds like a timing issue. Don't trust your timing mark on the balancer. I suggest you find true TDC (top dead center) of # 1 cylinder, then check your timing mark on the harmonic balancer, you will prob. have to put a new mark on your balancer at actual TDC. Once you determine true TDC, set your timing using your actual TDC mark. If problem still exists, then I would pull the timing cover looking cam to crank timing error

[geezer#99]

No timing.
Try 20 degrees initial, 14 in mechanical and another 10 from vac advance.
And with that super low lift and too much for the cam duration don'e expect tire churning performance or 6500 rpm.
Once you get the timing set if it still diesil's hook your vac advance to manifold vac so you can close down your idle.

[bonnieclyde100]

i would get a stall converter closer to the powerband of your cam. 1300 is a little low for that cam to really hook up . also with that cam you should be able to have more timing than 10 degrees maybe 12 to 14. my truck diesels somtimes to so i shut it off while still in gear it shuts right down.

[1972RedNeck]

How does timing have anything to do with dieseling? When the key is shut off, there is no ignition, unless it is compression ignition. The lower the octane rating and higher your compression, the more likely the motor is to diesel. Setting your idle down helps.

[1970witha355]

The ignition is stock HEI distributor. Base timing is at 10 degrees. Full length 1 5/8 headers with 2.5" piped true duals through flowmasters. The cam was already in the engine when I tore it apart so it is broke in already. And yes I put all the lifters back in the exact same hole they came out of. It is a flat tappet cam, hydraulic lifters. I dont know what the fuel pressure is or the vacuum. Ill have to check it tomorrow and let you know.

[ole dollor]

just to start with. what does it idle at .how many rpm....if its idles to high its going to diesel after you shut it off..

[1970witha355]

Not sure on idle, good question. I dont have the tach hooked up yet. Ill hook it up tomorrow and find out. Man, this forum is great, you guys jumped right on this with me. Thanks everyone! Keep your input coming.

[Steeveedee]

Originally Posted by ole dollor

just to start with. what does it idle at .how many rpm....if its idles to high its going to diesel after you shut it off..

Yup. Crank up the idle to cover the low vacuum, get dieseling.

1970witha355- if you have true 10:1 compression, that 87 octane is going to ping your pistons into oblivion. It's going to take some tweaking to get our ride running well, but I think your cam is overkill for the rest of the setup.

[1970witha355]

Yeah i think the cam may have to go. I bought the truck with this engine in it. I paid $750 for the truck so I just tore it down, lapped the valves, put new valve seals in, and put it back together since everything else looked good. I have less than $1000 in the truck the way it sits. Since the cam is a "circle track" cam it may not have any low end torque which I would like since the truck will be a local cruiser. Sounds like this cam likes to be run at high rpms.

[Lattimer]

Originally Posted by 1970witha355

Yeah i think the cam may have to go. I bought the truck with this engine in it. I paid $750 for the truck so I just tore it down, lapped the valves, put new valve seals in, and put it back together since everything else looked good. I have less than $1000 in the truck the way it sits. Since the cam is a "circle track" cam it may not have any low end torque which I would like since the truck will be a local cruiser. Sounds like this cam likes to be run at high rpms.

That is true. Plus, more radical cams will make very little vacuum at idle, which causes poor off he line and slow speed driveability. And if you have power brakes they won't very well at idle.

Thats why I said check the vacuum first. That will show if your timing is advanced far enough or if the cam will create enough. Idle speed is important too when checking vacuum. These are things I have learned the hard way recently.

The dieseling is probably just a symptom of the real issue, as is the poor performance. It all sounds very fixable, but you just have to go one piece at a time until you get the puzzle solved.

[blue 72 gmc 4x4]

My truck did that for awhile when I was putting that ****ty 87 in it...383 crate motor spec sheet even said that it could run on 87. Started running 91 and it never did it again. I also gave it a couple more degrees in timing and that made a difference too.

[luvbowties]

Originally Posted by 1970witha355

Ok heres what i have. The block is a 1975 350. It is bored 30 over. It has flat top pistons. The block has been decked to zero (the pistons come up level with the block). It has stock iron "441" heads with 194/150 valves. The cam is an isky "201SL1". This is a circle track cam im told. The specs are: 390/410 lift, 228/232 duration @ 50, and a 108 lobe seperation, 2000-6500 rpm range. I dont know what the compression would be, im guessing around 10:1. I am running 87 octane gas. I have a TH400 tranny with stock (1300)rpm converter. The problem is the engine should be making 300hp give or take. It sure doesnt feel like it. I should be able to floor it and rip the truck sideways. It feels weaker than an old worn out stock inline 6. It doesnt feel like the 4 barrel is opening (new edelbrock carb). When I shut the truck off, it stumbles for a second or "deisels" then shuts off. The timing is set at 10 btdc. WTF!!!!!!!!!!!! I am so frustrated that I am sick! Is the answer better gas, stall converter, NEW ENGINE???????????? OH MAN AM I PISSED! HELP HELP HELP!!!!!!!!!!

Hey, got a friend who bought a built 383-powered Rambler--stole it, as owner could never make it run. Brought it home, degreed in the 'high-rpm-cam'(like yours is), and it ran so strong that po saw him take off in it and bought it back. You might give degreeing a shot before swapping cams.

Sounds like you could have the same issue. If the cam is retarded OR advanced, you'll never get it to deliver its potential, regardless where you set the timing. Also, as others have said, 1300 stall would be asking a lot from such a spec'd cam; it is not designed to have much low-rpm torque. (Plus, you may be underestimating hp potential at just 300; of course, it'll output its max at higher rpms than many of us like to twist our engines.)

You'd prolly enjoy a cam that puts out its hp & tq at a lower, more user-friendly rpm. But, for kicks it won't take a lot to degree what you've got now, just to feel what it can offer.

HTH,sam

[1970witha355]

Could someone recommend a good street cam for the setup I have? How do I know what cam I can put in the engine without hitting the pistons, etc?

[bonnieclyde100]

go to summit they have cams made for trucks in the truck section. that way you can get more power and still be able to tow.

[luvbowties]

Originally Posted by 1970witha355

Could someone recommend a good street cam for the setup I have? How do I know what cam I can put in the engine without hitting the pistons, etc?

This is a simple thing so many of US tend to overlook, myself included(in the past). Contact the cam mfg, give them your engine specs, and they will ask a couple more ???'s and then they will recommend a couple of options. Better than you and I could ever determine.
Hth,
sam

[1970witha355]

will do! thanks