Engine and car shakes bad/ misfires on the road after cam swap (CL-12-249-4) 1988 Chevy C1500 aTBI 350

[dave s]

A very talented mechanic friend once had a similar issue. I stopped by one night on my way home and just double checked his plug wires. He had two wires wrong. He said he triple checked the damn things , lol. I'm not saying you did that but he had the exact symptoms you describe.

 

[Frank Enstein]

They might be, I tightened them down until I felt resistance spinning them as I hand cranked the engine then when they all had resistance I gave them a quarter turn, this is the first time I’ve ever set lifter pre load

Here is the procedure to adjust the valves on a new 8 cylinder engine:

Turn the crank clockwise while watching the number one cylinder pushrods.

Watch the exhaust pushrod go up and down and then the intake pushrod go up and down.

Continue to rotate the crank after the intake pushrod goes all the way down until the timing marks

Line up on 0 degrees.

(This will be LESS than 1/2 turn of the crank after the intake pushrod is all the way down.)

Install rockers and tighten the nut while rattling the pushrods up and down until the rattle just stops.

At this point you are at ZERO LASH.

Tighten further to add your preload ( typically 1/2 turn after the rattle stops ).

Do this to both rockers for number 1 cylinder. Cylinder number 1 is DONE!

Now turn the crank 90 degrees ( 1/4 turn) and set the rockers for the next cylinder in the firing order.

After the second cylinder in the firing order turn the crank 90 degrees and set the third cylinder in the firing order.

Repeat this procedure for the remaining cylinders, one for each 90 degrees of crank rotation

ending with the last cylinder in the firing order.

 

[Slade88]

Little update everyone, I called around and took it to the one shop that said they could work on it. I get there and they look under the hood for about 5 minutes, they then tell me that they can’t work on it because “too much has been done improperly” they didn’t even take anything apart.. they said they wanted to do a comprehensive test but they’d have to remove the headers and they don’t have enough time for that and that they don’t want to touch anything because they don’t feel comfortable with all that’s been done. This worries me a lot

 

[RichLo]

Have to remove the headers or heads?

Never go back to that shop, they said they will work on it knowing that you have done a cam swap and made you drive it there all to find out they wont touch it. I'd try to make them pay you for gas for wasting your time.

 

[Schurkey]

Welcome to modified vehicles and working on your own stuff.

"The Establishment" wants nothing to do with them; because they can't trust your workmanship or your parts choices; and they know that if they merely charge "clock hours" instead of "book" time, you'll be unable to pay. They'll end up owning the vehicle AFTER they go through the paperwork to process the Mechanic's Lein. And then they'll own a vehicle they can't sell for the labor cost they've got invested.

The only practical way out is for you to fix this yourself, most-likely with an on-site mentor who may--or may not--help you for free. (Expect to buy beer and pizza at minimum.) Internet mentors can only do so much.

If I'm understanding you correctly, the engine has never idled properly. It's just worse now, and with additional symptoms, since the cam change.

You said the distributor is in "pretty good condition" but you don't say how you know that.

I bet you could find a usable compression tester at most any pawn shop.

 

[Slade88]

Welcome to modified vehicles and working on your own stuff.

"The Establishment" wants nothing to do with them; because they can't trust your workmanship or your parts choices; and they know that if they merely charge "clock hours" instead of "book" time, you'll be unable to pay. They'll end up owning the vehicle AFTER they go through the paperwork to process the Mechanic's Lein. And then they'll own a vehicle they can't sell for the labor cost they've got invested.

The only practical way out is for you to fix this yourself, most-likely with an on-site mentor who may--or may not--help you for free. (Expect to buy beer and pizza at minimum.) Internet mentors can only do so much.

If I'm understanding you correctly, the engine has never idled properly. It's just worse now, and with additional symptoms, since the cam change.

You said the distributor is in "pretty good condition" but you don't say how you know that.

I bet you could find a usable compression tester at most any pawn shop.

Ideally I would like to fix it myself, I do have a mentor who knows just about everything about cars but isn’t familiar with chevys (ford guy). I think I should explain a little backstory of how I got this truck so y’all can maybe understand my situation a little better, my grandma bought me this truck about 3 years ago, I did not pay for any of it, so naturally her and my mother and father, are very upset at how I’ve screwed up an engine that ran perfectly for years, they no longer trust me and want it taken to a shop almost an hour from where I live, we can’t really afford it getting towed so I really hope it can make it there without blowing up on the high way. It’s not really my choice anymore since they don’t trust me working on it. The distributor is original so is the cap and ignition coil. I guess yes it’s never idled correctly but it’s never been this bad, the engine ran pretty perfect before all this cam BS I wish I could just press the un do button on this whole operation, still love my truck though, and I appreciate the help from all of you, if y’all are ever in Charlotte I owe you a steak dinner!

 

[Slade88]

Have to remove the headers or heads?

Never go back to that shop, they said they will work on it knowing that you have done a cam swap and made you drive it there all to find out they wont touch it. I'd try to make them pay you for gas for wasting your time.

Headers, and yep

 

[Schurkey]

my grandma bought me this truck about 3 years ago, I did not pay for any of it, so naturally her and my mother and father, are very upset at how I’ve screwed up an engine that ran perfectly for years,

Grandma has skin in this game. Mom and Dad don't.

And from what you've said...the truck did not run "perfectly for years", it had idle problems all along.

they no longer trust me and want it taken to a shop almost an hour from where I live, we can’t really afford it getting towed so I really hope it can make it there without blowing up on the high way. It’s not really my choice anymore since they don’t trust me working on it.

Who's truck is this? Are Mom and Dad going to pay for the repairs? If they're paying, they've got skin in the game. If not, and the truck is yours...all you have to worry about is getting Grandma happy again.

Your Ford guy would at least have access to diagnostic tools. He'll have to deal with the Chevy firing order; and the GM-style computer system. If he's smart...he'll do fine.

 

[Slade88]

Grandma has skin in this game. Mom and Dad don't.

And from what you've said...the truck did not run "perfectly for years", it had idle problems all along.



Who's truck is this? Are Mom and Dad going to pay for the repairs? If they're paying, they've got skin in the game. If not, and the truck is yours...all you have to worry about is getting Grandma happy again.

Your Ford guy would at least have access to diagnostic tools. He'll have to deal with the Chevy firing order; and the GM-style computer system. If he's smart...he'll do fine.

My grandma bought it, but my parents have payed the insurance for me since it broke down. My grandma is going to pay for the repairs with help from me and my parents. So everyone has skin in the game you could say. I’m hoping to get the idle issue resolved when everything gets fixed. I’m just worried the the engine will tear itself apart or blow up during the 26 mile drive to concord, nothing seems to be progressively getting worse at least nothing I notice

 

[Schurkey]

Keep an eye on coolant temp and oil pressure. Listen for signs of impending doom.

You'll probably be fine.

Let us know what they discover.