302 shakes and cuts out?

Hagan · Oct 24, 2015

I'm stumped on ideas of what to try. My 302 won't spin past 3-4k rpm depending on how much I'm getting into it. It starts cutting out and and has a vibration at 2k rpm. I'm worried it's out of balance but I have no idea if it is. I used an Explorer front end accessory drive (fead) and a new balancer. I got what I believe is the correct flywheel for a 5.0 powered 92-96 f150. It matched the flywheel I took off another 302. I checked my block and it's an '87 truck block. I converted it to a roller cam using another block I had. I cant figure out where I went wrong?

I am using a Quadrajet carb that I bought off CL. I rebuilt it and converted it from hot air choke to electric choke. My brother put my carb on his '72 GMC Jimmy and it ran far better than his did. I was thinking of making the secondaries not open to rule it out. Maybe its too big of a carb?

Any one have any ideas?

Picture of my 302. Spark plug wires are routed and in wire separators and all the wiring is cleaned up

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Hagan · Oct 26, 2015

Anyone?

dirtcowboy · Oct 26, 2015

I'm confused as to which block you are using, the sploder 5.0 or the 87 302. FYI the roller cam mod is drilling, tapping two holes that bolt on the "spyder". Why didn't you use the sploder flywheel instead of an F-150 unit? Well the engine should be a 50 oz package, I believe the 28 oz is before 82. There are two firing orders, one is the 302 order the other is the 351 or "H.O" firing order. Check your plug wires for firing order. Carb isn't the problem. Firing orders

302 1-5-4-2-6-3-7-8

H.O. 1-3-7-2-6-5-4-8

FYI, the 5.0 truck engines use the non H.O. firing order.

whitebroncoii87 · Oct 26, 2015

did you torque all the bolts to shop manual torque spec? I had put back my flywheel once without torqueing to spec and it would run rough and cut out, then I took the engine out and removed the clutch cover to discover the flywheel bolts were all loosened.

Hagan · Oct 26, 2015

dirtcowboy said:
I'm confused as to which block you are using, the sploder 5.0 or the 87 302. FYI the roller cam mod is drilling, tapping two holes that bolt on the "spyder". Why didn't you use the sploder flywheel instead of an F-150 unit? Well the engine should be a 50 oz package, I believe the 28 oz is before 82. There are two firing orders, one is the 302 order the other is the 351 or "H.O" firing order. Check your plug wires for firing order. Carb isn't the problem. Firing orders

302 1-5-4-2-6-3-7-8

H.O. 1-3-7-2-6-5-4-8

FYI, the 5.0 truck engines use the non H.O. firing order.

I'm using a roller ready 5.0 truck block. I believe it was '87 but could have been newer. I lost my pics of the casting numbers. I'm using the cam out of a non H.O. roller block. I didn't use the Explorer flywheel because as far as I know they never made a 5.0 5spd Explorer. I can't use the Explorer 5.0 block because its distributorless.

The cam determines what firing order is needed. I am using theither Non H.O. firing order. It would barely run the other way.

Sorry if I sound confusing. I had 4 302 blocks at 1 time and a 351w block.

dirtcowboy · Oct 27, 2015

O.K., square one. What reciprocating assembly did you use? What cam? Harmonic balancer, 50oz or 28? How was it installed? BFH or correctly? Flywheel, 50oz or 28? Loctite on bolts? Clutch pressure plate on correctly? Pull your distributor and check the teeth on it. Check the crank for cracks, snout and flanged end? Timing is good? Vibration means something out of balance or broken.

Might be overthinking this, how bad is your vibration problem? Misfire vibration or catastrophic? Really shaking the truck or less than that? Are all of your plugs good? Plug wires? Tested with ohm meter? Dist. cap tight?

I'm not belittling here, the only way I know to troubleshoot is to start at the beginning and work your way through.

Hagan · Oct 27, 2015

dirtcowboy said:
O.K., square one. What reciprocating assembly did you use? What cam? Harmonic balancer, 50oz or 28? How was it installed? BFH or correctly? Flywheel, 50oz or 28? Loctite on bolts? Clutch pressure plate on correctly? Pull your distributor and check the teeth on it. Check the crank for cracks, snout and flanged end? Timing is good? Vibration means something out of balance or broken.

Might be overthinking this, how bad is your vibration problem? Misfire vibration or catastrophic? Really shaking the truck or less than that? Are all of your plugs good? Plug wires? Tested with ohm meter? Dist. cap tight?

-'87 302 block/heads recent rebuild stock.
-90's 302 Roller cam, pushrods, and lifters.
-Front end accessory drive is all off a 98 Explorer.
-Harmonic balancer is new (Dorman) and installed correctly.
-Flywheel new spec'd for a 92 F150 w/m5od
-Clutch new spec'd for a 92 F250 w/ZF5
-Flywheel has loctite in bolts.
-Distributor has correct gear from roller block
-Spark plug wires are new 8pm Accel.
-Distributor is Skip White HEI

I'm thinking my issue is more of a misfire? The plugs are 3 months old about 200 miles on them. Possible I have fuel injected spark plugs and incorrect gap?

Vibration isn't really bad. But I can notice it when I start revving the engine to 2k rpm. Maybe I'm just too concerned with that.

Hagan · Oct 28, 2015

Ok for shits and giggles I did a compression test to rule it out. Bought a new compression tester to do this test...here are my results:

1)178
2)172
3)176
4)175
5)171
6)181
7)177
8)178

Not perfect but far better than I thought considering my Bronco was running on 100 psi lol.

So...I can only assume this is a fuel or spark issue?

I did NOT time my motor. There aren't any timing marks on it. I used a vacuum gauge and adjusted the timing to the highest reading which was a steady 21in.

So, let's rule things out.

Carb - Tested on brothers truck ran perfect
Carb adapter - Don't see how it could cause issues?
Compression - Perfect
Spark plugs - Autolite 25 gapped to .045
Wires - Accel 8pm wires (new)
Distributor - Skip white (new) may be failing???

I think checking fuel pressure is the next step

85_Ranger4x4 · Oct 29, 2015

The 302 is rejecting the GM floodrajet :icon_twisted:

Hagan said:
I can't use the Explorer 5.0 block because its distributorless.

Neither here nor there at this point but you pull the camshaft position sensor and replace it with a distributor set up for a roller cam and HO firing order.

Hagan said:
Ok for shits and giggles I did a compression test to rule it out. Bought a new compression tester to do this test...here are my results:

1)178
2)172
3)176
4)175
5)171
6)181
7)177
8)178

Not perfect but far better than I thought considering my Bronco was running on 100 psi lol.

So...I can only assume this is a fuel or spark issue?

I did NOT time my motor. There aren't any timing marks on it. I used a vacuum gauge and adjusted the timing to the highest reading which was a steady 21in.

So, let's rule things out.

Carb - Tested on brothers truck ran perfect
Carb adapter - Don't see how it could cause issues?
Compression - Perfect
Spark plugs - Autolite 25 gapped to .045
Wires - Accel 8pm wires (new)
Distributor - Skip white (new) may be failing???

I think checking fuel pressure is the next step

I have '87 Mustang (EFI) plugs in my carbed Ranger, haven't touched them in 3 years.

I question fuel supply. I know when I forget to turn the fuel pump on mine is very dramatic shaking and running rough before it dies if I don't catch it in time.

What do you have for a pump? Filter(s)? Fuel tank vent?

And for timing it should at least have a line for TDC. If you have the pointer you can get a digital timing light to adjust the advance for you. It is a PITA to time a engine with the explorer FEAD (almost as if they didn't intend for it

) just because it it is so hard to see what is going on down there with all the stuff in the way. I just put a white line on the dampener to make it visible, set what I want on the timing light and adjust the dizzy until it lines up with the pointer.

BTW it would make oil changes easier if you switch the PCV and the oil filler cap. Put the one you rarely use buried in the back and the one you should use a couple times a year to the front.

Hagan · Oct 29, 2015

85_Ranger4x4 said:
The 302 is rejecting the GM floodrajet

Neither here nor there at this point but you pull the camshaft position sensor and replace it with a distributor set up for a roller cam and HO firing order.

I have '87 Mustang (EFI) plugs in my carbed Ranger, haven't touched them in 3 years.

I question fuel supply. I know when I forget to turn the fuel pump on mine is very dramatic shaking and running rough before it dies if I don't catch it in time.

What do you have for a pump? Filter(s)? Fuel tank vent?

And for timing it should at least have a line for TDC. If you have the pointer you can get a digital timing light to adjust the advance for you. It is a PITA to time a engine with the explorer FEAD (almost as if they didn't intend for it ) just because it it is so hard to see what is going on down there with all the stuff in the way. I just put a white line on the dampener to make it visible, set what I want on the timing light and adjust the dizzy until it lines up with the pointer.

BTW it would make oil changes easier if you switch the PCV and the oil filler cap. Put the one you rarely use buried in the back and the one you should use a couple times a year to the front.

I didn't use the Explorer block because it was sitting in the back of my truck for 2 months in the rain. Wasn't in "good" condition so I bought my current one.

I'm leaning towards fuel supply too. I was going to run a "T" in the fuel link at the carb and hook up my fuel pressure gauge but ran out of time.

I'm using a cheap Holley 5-8 psi fuel pump running in 5/16" steel fuel line and then using same thickness rubber line to the carb. My brother has this exact same fuel pump, and he is having a fuel supply issue too. His fuel pressure is dropping to near 0 at WOT.

The PCV is where it is because it's easy to remove and the carb has the vacuum port at the front. Also the breather is very tight.

Thanks for the reply...I thought this thread was about dead!

85_Ranger4x4 · Oct 29, 2015

I am still using my 2.8's 1/4" line with a Mr Gasket 12s (or something like that) fuel pump.

About $50 at just about any parts store, no complaints in 4.5 years.

Hagan · Oct 29, 2015

Your '85 was originally carb'd though. I put in a b2 tank with a single line on the passenger side of the frame.

I have a Holley mighty mite.

85_Ranger4x4 · Oct 29, 2015

Just saying I wouldn't blame the 5/16 line.

peganit2 · Oct 30, 2015

Convert that electric pump to mechanical. Fuel supply issues solved.

Why you didn't do it when you were building the motor has only one explanation, funding.

Mechanical fuel pumps can be had to support 700+HP. You're no where near the limits, and you won't be for a long time. A generic parts store pump will more than keep up with what you have.

peganit2 · Oct 30, 2015

5/16 fuel line is good for about 400 HP with a good pump.

Do the math.

302 shakes and cuts out?

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