Had my dad's 1977 Bronco at a performance shop by his house to help finish the build. It's been a 3.5yr frame off.

Shop called me yesterday after doing a test drive and said the engine was starting to scatter around 4000rpm when you stand on it. They brought it back and checked the compression and it was down to 70-90psi in all 8 cylinders where as previously it was 150-175psi in all cylinders. They did a leak down test and all cylinders showed 30-40% leak down (no previous numbers). The breather in the valve cover is full of oil and the plugs are black. He dumped some marvel mystery oil in a cylinder and checked again and nothing changed. Their thoughts are that when I was trying to get it to start previoulsy that I washed the cylinders down and the rings are toast and it needs new rings, hopefully, and they want $4500-5000.

I'm a bit skeptical. When I was trying to get it to crank I didn't try to crank it for more than 60-90secs total. I don't think that's enough to wash the cylinders down and the rings to not seal but maybe I'm wrong. I'm also wondering if maybe the valves were set when the engine was cold and once it warms up it's hanging the valves open and bleeding off compression. We are going to go ahead and pick it up tomorrow and we are going to do some of the test ourselves. We are planning a hot and cold compression test as well as dumping some 50w oil into a cylinder and retesting compression and leak down with that to try and isolate the issue.

I'm not knocking the shop as they've been great to work with and they've done awesome work. My brother in law and I built the motor so they are just helping us out but the price they are quoting me for putting new rings in is ridiculous. I can buy, and have found, assembled short blocks for $2500 that I can swap my top end on to it. Heck I've found 347 long blocks for what they are quoting me. I'm just looking for some ideas or thoughts that would cause all cylinders to suddenly lose all compression at the same time. That just seems strange to me.


Quick build sheet below:

Ford 302

Bored 30 over

Balanced rotating assembly

Forged flat top pistons

Chromoly rings

Stock crank

Stock rods

Trick Flow Twisted Wedge aluminum heads that have been CNC ported with 66cc chambers

Trick Flow 1.6 aluminum roller rockers

Trick Flow roller cam with .542/.563 lift and 286/294 duration on a 112* lobe seperation

Upgraded push rods

Summit Racing gear drive

Long tube headers

Weiand Dual Plane intake manifold

Custom carburetor (shop built one for us)

MSD Billet Distributor

Run time is minutes as this was a fresh build.

 

There is no way you hurt it in that amount of time. I've done exponentially worse in the past on 389's and 350's with no ill effects. I just don't see it. Gotta go for now.

 

Ok. This thing has some issues.

First - Checked compression and whether cold or hot the compression was between 120-130 on all cylinders.

Second - The coil is arcing BAD. It's arcing to the negative terminal on it through the boot and electrical tape we wrapped around it. It's a bright *** red and purple arc.

Third - It's running so rich it's literally puffing black smoke at idle. This plug is after 6 miles of driving and it was brand new.

Fourth - We checked the lash on the valves and that seems good.

Fifth - The vac pump they told us they put on it isn't there so it's no wonder our brakes suck.

We poured some oil in a cylinder when it was cold and compression jumped from 120 to 150-160. So the rings aren't out of the question but I'm thinking they just need to break in.

But until I get the carb tuned and coil to stop arcing I'm not going to be able to really break this motor in. Anything above 2500-3000 and it starts popping and missing bad.

 

Go get a new Edlebrock 600-650 carb and see how it runs.

Something is fucky with their custom carb.

 

They put a Holley 4150hp on here in place of the Edelbrock 500cfm we had.

 

What I was taught with old school engines was any miss under throttle was a coil wire issue.

 

Well the coil is arcing like a welder so we are working on trying to get that fixed.

We checked the float levels on the carb and the rear float was screwed so far down that it wasn't able to be adjusted with the nut and it's still pouring fuel out of the sight bowl. Fuel pressure is also at 9psi. We spoke to the shop and they are bringing out a new carb, coil, coil wire, and plugs to the house today.

 

Way to go. Hope you get it worked out.

 

**** it's been a day. Shop came out and changed a bowl out on the carb that we found was messed up. Fuel psi was at 9 so we installed a regulator to bring that down. They also brought us a new coil and wire as well as new plugs. We've popped the intake manifold off and verified all of the lifters are pumping up and doing good. Pushrods are all straight. Valve lash is good. Now we are reassembling everything. I also picked up an Edelbrock 600cfm performer carb if I can't get this fancy Holley to lean out.

 

Which model 4150 HP is it?