Need Help Figuring Out An Engine Noise

Cody_94Cobra · Jul 25, 2014

Just put all new parts in a freshened up 86 model 5.0 for my 94 Cobra. Engine is making a weird noise and it sounds like it is echoing though the intake because it's louder through the upper than through the valve covers. Cars in time, checked pushrod length, checked valve clearance, rockers are right, running constant 50 psi oil pressure, car idles well and drives great, engine is broken in so i made a slight pull and the engine pulled fine until upper rpms it started to sputter and acted like it was hitting a rev limiter. Any help or advice would be appreciated .

jka · Jul 25, 2014

Is it a ticking noise ? if so check the header bolts. Also did you retorque the intake and the headers after you warmed it up? And can you post a vid of it. It would be helpful.

Cody_94Cobra · Jul 25, 2014

I retorqued intake and headers and checked for header cracks. I tried to upload a video but it won't let me. It's a tick and the noise increases when revved and becomes more high pitched.

jka · Jul 25, 2014

Are you running roller rocker or stock? And when you adjusted the rockers could you spin the pushrods easy or was they tight?Also what mods do you have done to the engine as far is heads/cam or mostly stock? I ask because you may have a preload problem and some rockers may need shims if you running the pedestal mount stock or pedestal roller rockers.

Cody_94Cobra · Jul 25, 2014

Running stock 1.7 cobra rockers. Gt40x 58cc heads g303 ford racing can stock 86 bottom end tf track heat intake 75mm tb with 75mm MAF cai and 30 pound injectors with Longtubes

Cody_94Cobra · Jul 25, 2014

jka said:
Are you running roller rocker or stock? And when you adjusted the rockers could you spin the pushrods easy or was they tight?Also what mods do you have done to the engine as far is heads/cam or mostly stock? I ask because you may have a preload problem and some rockers may need shims if you running the pedestal mount stock or pedestal roller rockers.

I'm currently taking the lifters out how would I be able to check them ?

Gearbanger 101 · Jul 25, 2014

Did you happen to check the piston to valve clearance with that cam (I'll assume that was supposed to be E or F 303, as I don't recall ford ever making a "G303" camshaft) and rockers? The '86 bottom end had flat top pistons with no valve reliefs. That means you're going to have limited ability to add lift. The last thing you want is high RPM piston to valve contact.

jka · Jul 25, 2014

Ford made a G-303 but i don't know anything about the specs it's kind of new american muscle and summit racing sell them. But i do what to know if those are the original 1986 pistons because the biggest cam to work with the 86 pistons is the b 303 or e 303 and that's with the use of 1.6 rockers. The G303 cam is like the trick flow stage 1 cam but the lift is 498/510 but that's for use with 1.6 rockers.

Cody_94Cobra · Jul 25, 2014

They are original 86 model pistons and they have been milled and fly cut to accommodate the camshaft and I puttied the pistons and checked with old head gaskets. The cam is .498/.510 lift with 1.6 so I'm assuming around .529/.541 with 1.7 and .226/.228 duration @50. The only thing that has recently been put into the engine are the cam, lifters, and pushrods. Everything was on the car with the stock cam lifters and pushrods and performed excellent.

jka · Jul 25, 2014

Did you take the valve covers off and check to see if any of the rockers had and play?

Cody_94Cobra · Jul 25, 2014

I've taken the entire top end off checking for play, improper torque, wrong pushrod length, bad lifters. It has perfect oil pressure.

Gearbanger 101 · Jul 25, 2014

Did you check the lifter preload? You should have between .020-.060 preload on the lifters after zero lash. That should equal 1/2 to 1-full turn of the torque wrench with the rockers torqued down to about 20lbs ft.

If you're getting much more than that, you'll have to add a shim. If you're getting it in under 1/2 a turn, you'll probably want to remove a shim.

Most shoot for somewhere in the middle....about .030 preload.

Here's a handy set of instructions for installation

http://www.stangnet.com/mustang-for...-other-stud-pedestal-mount-roller-rockers.28/

Also....check the inside of the valve covers and rockers for scuff and/or contact marks. The Crane "Cobra" 1.7 Roller rockers are a cast unit and fairly bulky. I haven't met anyone yet who hasn't had issues with them making contact with the stock aluminum valve covers in some spot. You'll either have to clearance the inside of the valve cover, or run a double valve cover gasket....or both in order to ensure there is no contact.

You also need to modify, or remove the oil baffle in order to install them, so I'll assume that's been done already, since I'm fairly certain they won't even bolt onto the head without doing so.

Cody_94Cobra · Jul 25, 2014

The rockers have been completely checked and the car is an original cobra so I'm running the stock cobra stamped valve covers so they haven't been an issue. I'm just going to remove the engine and disassembly it and redo everything.

Need Help Figuring Out An Engine Noise

Cody_94Cobra

Member

jka

Cody_94Cobra

Member

jka

Cody_94Cobra

Member

Cody_94Cobra

Member

Gearbanger 101

Straight Outta Locash

jka

Cody_94Cobra

Member

jka

Cody_94Cobra

Member

Gearbanger 101

Straight Outta Locash

Cody_94Cobra

Member

Similar threads

Need Help Figuring Out An Engine Noise

Member

Member

Member

Member

Straight Outta Locash

Member

Member

Straight Outta Locash

Member

Similar threads

Privacy & Transparency

Privacy & Transparency