87 Foxbody 351w Timing issues

[rovere351]

Hi guys, new to the forum here. I've been searing around and have not found a solid answer to my issues. I got a 351w(1984 block .03 over) in a Foxbody like the title states. I have a 268h comp cam installed along with the rebuilt springs on a stock heads (e7 heads) it's running through a msd 6al with a blaster 2 coil, Autolite 23's and a stock style rebuilt duraspark dist and street demon carb.I also have a performer rpm intake on it. right now my timing is 6 degrees initial with 30 centrifugal obviously making that 36 total the issue I'm having is that i can't set my vacuum advance (turning the screw in the vacuum) without the engine pinging at around 2500-3000.

The cam kit i bought came with a timing set. Being a single roller, I opted it out for a double rollar that could possible problem number 1 if that timing set was made specifically for my cam ( i still have it) but don't see the issue unless the gears differ. possible problem number 2 is that i installed the cam straight up that already has a 4 degree advance ground into it so maybe i'm more around 40 degrees timing instead of 36. My rad is stock. Problem number 3 is that i have no EGR hooked up because of the svo shorty headers and the performer rpm intake. I have a 195 thermostat installed i'm going to try a 180 see if it's a heat problem. But i can time it to 36 all in and not hear a ping but then that's 0 initial 36 centrifugal and if i bring down my centrifugal and run 8 degrees initlial and 28 centrifugal it still pings. but like i said under light load 2500-3000 in that range. i'm pretty sure i'm at the end of my vacuum advance cause i keep turning it counter-clockwise and it stays the same. problem number 4 is probably the issue is running the stock heads and not having any egr hooked up. Any input would be greatly appreciated.

Thanks Mike

 

[mikestang63]

i'm still trying to understand E7's on a 351 with a cam

 

[rovere351]

well stock 351w heads i thought they were still e7's on the 351's maybe a different cast number but with a comp cam 268 high energy cam. I figure that my problem may be because of the restriction at the heads. they are for sure stock 84 351w heads though. also my timing was done with the vacuum advance plugged but tested with it plugged in it does not ping with the vacuum disconnected but i get horrible mileage and drivability. i have been debating about some kind of valve to limit the vacuum to the diaphram maybe my cam has to much vacuum it's about 15

 

[hoopty5.0]

Not sure why a mechanical advance would be different that any other, maybe someone can explain that better. but base timing should be 10-12°

 

[KZGUNS]

Do you know what your compression ratio is and what fuel are you using (octane)

 

[rovere351]

I'm running 87 pump gas but i have ran up to 94 with same result. i'm not sure exactly at the moment what my compression is i ran a test a year or 2 ago on it i remember my results being normal but i will run one this week. I've been having this issue for at least 3 years changed carbs, new distributor, spark plugs and cam (had an old general kenetics cam in it before).

 

[rovere351]

you can change you mechanical advance though the distributor itself changing the rate (slots) and springs and spring rate. there's a great write up online. base timing on a 351 from what i read in the books is from 6-8 but that's stock.

 

[KZGUNS]

Your compression and compression ratio are two different things. If you have say 9.5-10.5:1 ratio you need 92+ octane. Are you using an old balancer? Confirm tdc and see if it lines up on the balancer.

 

[rovere351]

i have verified tdc using a piston stop and the balancer is correct. I guess I'll be learning how to do a compression ratio check and i'll let you know but it's all stock combustion chamber exept for the .03 over pistons i bought it as a stock .03 over short block.

 

[KZGUNS]

i have verified tdc using a piston stop and the balancer is correct. I guess I'll be learning how to do a compression ratio check and i'll let you know but it's all stock combustion chamber exept for the .03 over pistons i bought it as a stock .03 over short block.

You wont be able to do that without removing the heads. If its stock chambers and pistons you're prob. have 8-8.5 unless those heads were machined down. I dont think ur issue is with the cam gear set. the cam is mechanical valve timing and the distributor is ignition timing. How does it run with the timing backed off till it doesnt ping? in the current timing is it hard to start when warm ie, cranks slow?

 

[rovere351]

lol ya your right won't be removing the heads this season plus i'm not 100% sure what make pistons i have probably sealed power. Like you said the heads have never been ground.

I can run at it where i'm at without it pinging without the vacuum advanced hooked up. if it is hooked up and running 6 initial 30 centrifugal and i floor it, it's fine but once i'm light on the pedal it will ping. I know that is all vacuum related but i keep tunrning and turning this thing and nothing. i road test set timing till it pinged at 8 without the advance hooked up and had hard starts so i turned it back to 6 and it felt awesome and started nice but once i hooked my advance same ping. i got 71 km per 15l (sorry for the canadian metric system) and i jumped for joy.

 

[KZGUNS]

Are on the metered vacuum port on the carburetor?

 

[rovere351]

yes, but i have tried manifold it just adds more timing to idle same light throttle ping.

 

[KZGUNS]

Ya it needs to be on the metered port on the carb. You might have an issue with the distributor bringing in too much advance.

 

[rovere351]

I've slowed the curve down till it stopped pinging and just went a touch more for safe measure. After that i would plug in my advance to the metered port but the advance would make it ping.

 

[KZGUNS]

You’re absolutely sure you have a good balancer and that the timing pointer is correct? You’re using #1 on you light? I’m not saying you don’t know what ur doing but trying to have you double check yourself. I’ve spent tons of time chasing an issue only to find out I was making a mistake. Do you know anyone with another distributor you can borrow to rule that out?

 

[rovere351]

I'm absolutely sure that number 1 on the balancer and the timing pointer are accurate. I bought a piston stop gauge from Princess Auto and verified that it is correct. I ruled out the distributor by buying a rebuilt dorman duraspark out of a 84 f150 351w. It was only like 40 bucks. I verified that i am using the 15l slot (it also has the 10l) with good spring pressure. It fully comes in at around 3500 they say 3000 is good but like I said I road tested the timing until it pinged then backed it off a bit. I'm still debating about restricting the actual vacuum to the line. Maybe it's possible that my cam is adding to much vacuum but i already changed the cam because at first I thought it was a lifter rattling. Maybe i just wanted a good excuse to put in a new cam.

 

[KZGUNS]

I'm absolutely sure that number 1 on the balancer and the timing pointer are accurate. I bought a piston stop gauge from Princess Auto and verified that it is correct. I ruled out the distributor by buying a rebuilt dorman duraspark out of a 84 f150 351w. It was only like 40 bucks. I verified that i am using the 15l slot (it also has the 10l) with good spring pressure. It fully comes in at around 3500 they say 3000 is good but like I said I road tested the timing until it pinged then backed it off a bit. I'm still debating about restricting the actual vacuum to the line. Maybe it's possible that my cam is adding to much vacuum but i already changed the cam because at first I thought it was a lifter rattling. Maybe i just wanted a good excuse to put in a new cam.

If you are plugged into the metered vacuum port it shouldn't matter how much vac the engine is making.

 

[KZGUNS]

You may have to bite the bullet and have it prof. tuned.

 

[rovere351]

actually if i'm say pulling 18 insted of a normal 12 wouldn't that open it up more? it's deffinetly plugged into the meted vacuum port.