Piggish 351m

[Mercmarquis]

Not sure if this fits this tech area but it is a 5.8 liter, But hell I got nowheres else to put it.


Today I titled, and tagged my new truck and shes runs reliably but has no grunt in it. I swapped over from the holley I was running to "GMN's official test carb" (eddy 1406). Its runs about the same reliable but crappy.

I've been kinda tinkering with it today. My coil scared the shit out of me because it had no ring inside to connect to, so it was shooting sparks and grounding to the coil bracket. So I swapped it over and fixed that mess.

I cant figure why this truck is so damn powerless unless I find the timing is absolutely whack. I didnt get a chance to check that today. But I dont hear any pinging or anything, has a misfire. But the damn thing is so loud I dont know if I could hear it. The plugs werent peppered or ugly either. Nice tan color. I'm gonna check the timing tomorrow, throw some new plugs, wires, cap n rotor on it. And hope that cures it.

I mean this thing sucks, I had to have the truck pretty much floored in 2nd to make it up this long hill we got...My mom's mini will cruise up at 40mph in 5th gear.

[1987cp]

Ask the older dudes about the cam specs that went into production "M" series motors (think of lowpo roller specs but less aggressive). Depending on how it's been treated, it could be worn down to even smaller than when it was new. Just my :p

[Dave84]

Try advancing the timing. My 77 F350 has a 400 in it and it was kind of a slug. But the problem it had was that the vacuum advance on the distributor wasn't hooked up. Once I plugged the vacuum tube back in you could stand on it and just melt those tires right off the rims.

[Mercmarquis]

Ask the older dudes about the cam specs that went into production "M" series motors (think of lowpo roller specs but less aggressive). Depending on how it's been treated, it could be worn down to even smaller than when it was new. Just my :p

Its got an aftermarket cam in there...Specs unknown. Sounds pretty healthy tho. I think the timing might be my ticket. By the way the vacuum lines were, I have a feeling they didnt know how to set timing either.

[Mercmarquis]

I should add that the motor has been rebuilt, .030 over. Has a performer 400 intake, unknown aftermarket cam. Rebuilt heads, longtube headers and a 600cfm carb.

[gadget73]

i'd say the timing is way off, and/or the advance mechanism isn't hooked up right, causing it to retard under load or something.

[Mercmarquis]

I think it is too, but I figured I'd see something on the plugs or hear some kind of detonation. But I've been wrong before.

[gadget73]

if its really late you won't hear detonation. it'll just be horribly gutless. if run long enough the headers might start glowing, and you may see some odd coloration on the plugs if you're one of those plug reading gurus. manifold vacuum will also probably be low. if its not ignition timing, its possible someone got the timing set in there wrong, that could also make it run pretty lousy.

[351wcrayz]

ok, question time:

1-Did you PERSONALLY oversee the camshaft bein put in/over haul/etc?

2-The Cam in my vic was worn so badly it was virtually a square w/ a round section (BAD) and when I first got it back on the road it had a slight feeling that the engine was dying, and I would let off and hit the gas again and it would work fine, found out the cam/lifters were the culprits.....

3-Has the truck sat an extended time/been abused badly?

Reason for the q's was that #2 was my problem, it got so bad w/ power loss that it wouldnt even turn the tires off, and after I passed 90/100MPH it wouldnt have any more "Go"......just check the cam mang.....might also be a bad timing chain.....

[Mercracer]

Check the basics including firing order and compression...... What gears does it have?

[Mercmarquis]

I just bought the truck so no, I did not witness any work being done to the truck.

[Mercmarquis]

Check the basics including firing order and compression...... What gears does it have?

Its got a 9in, not sure of the gears. I'll crawl under the truck and see if theres a tag. No locker in the rear tho. Open diff....bah

[turbo2256b]

timing should be around 18* initial and 36 total probably need to modify the distributor to do it. My 400 pulls aroundd 375 HP and with 25% slipagee due to 3000 Rpm stall at high way speeds gets 13 to 14 mpg with 4.11 gears and 33" tires. Truck is in no way a slug.

[Mercracer]

timing should be around 18* initial and 36 total probably need to modify the distributor to do it. My 400 pulls aroundd 375 HP and with 25% slipagee due to 3000 Rpm stall at high way speeds gets 13 to 14 mpg with 4.11 gears and 33" tires. Truck is in no way a slug.

You may do fine with it, but 18 degrees initial will ping like crazy with a 351M depending on the cam and pump gas......

[Mercmarquis]

I guess when your timing is nearly 60* off there is a problem...lol Set to 16*intial and 36* full advance. Must have 10l slots in the dizzy.

Runs alot smoother, and revs up nice and quick. Its alot easier on the starter as well. Has alot more power but is still kinda blah. Its more because of the transmission likes to stay in a higher gear. Its doesnt like to downshift. But when I put it in manual first and romped it, it wrapped up to 60 pretty damn quick, spinning the tires on the wet road the whole way.

Do c6's have a kickdown rod like a c4 does? Cause there is no rod anywhere. It has the vacuum soleniod, which I put all new vac line on. I also fixed another vac leak from a cap that just fell off, hopefully that will help. I also got a sticky linkage in the tranny, really hard to put the tranny in 1st or 2nd.