HEI redneck blueprinting LOL

turtlevette

turtlevette

The Turdle
Joined
Mar 24, 2008
Messages
1,492
Location
Marshfield, MA
Now i'm messing with my HEI. I've never used a timing light because the timing mark always slips and is never in the right spot. I've always set timing by advancing until i get a bit of knock under hard acceleration then back off a tad. I've recently rejetted the QJ so now it takes more timing. I can advance to the point where i can't start the car.

I believe the answer lies in getting more mechanical advance. If you look at the way the weights and cam are built, the weight arm flattens out against the cam limiting how much it will push the cam. I don't think i'm getting a full 20deg of mechanical advance. I don't think i've ever gotten any decent amount of advance which is kind of depressing as this thing has never seen it's full potential due to this shit HEI. I'll have to take a bunch of pictures. The cam is worn and looks nasty. The springs on it are the heavy ones. I went to the lightest gold springs.

I just did some experimenting by grinding off the tips of the weights. This allows the weight arm to continue to push the cam up to the point where the weighted end hits the inside of the rotor.

It's getting dark now so i'll have to wait to keep playing. Has anyone else ever messed around with this?

I have a timing cover and need to finally install it to get some quantifiable data.
 
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Send yer dizzy to Jeff, B2B, he kan fix it fer u....

Me, just get some majical parts in the mail, and whadda I no, it werks, more or less....

I need to send it out to him to C if my effarts wur right....

:clap::clap::skeptic::zzz:
 
Don't mess with the weights. Put in the gold springs, time it at 36* at 3000RPM, and let it idle wherever it lays.
 
You're on the right track by not trying to use bushings underneath.:clap:
Don't knock them, they're great dist and easy to set up.
There were different weights, but the key is the center plate profile also known as the curve plate.
GM had curve plates ranging from less than 10 crank degrees to over 25 crank degrees using the same weights. They not only set the min and max but also the middle of the curve by the way the weight arms contacts the curve plate as it goes to max.

Occasionally over the years, someone may have flipped the center plate over usually by mistake and with some of them you can do that and get a decent run, some not so great. You may check that.

Be sure that the weights return fully when your done.
Interesting to see what you come up with.
 
big2bird said:
Don't mess with the weights. Put in the gold springs, time it at 36* at 3000RPM, and let it idle wherever it lays.
Click to expand...

That's what i'm doing but getting there by seat of the pants tuning. Once it runs great under heavy throttle, the initial is so far advanced it won't start or is very hard to start warm.

It sounds like a wimpy starter trying to turn over a very high compression motor. You just can't crank against a lot of initial when warm.

Moving the stock and replacement weights and cam by hand its apparent its only moving about 10 deg. After the mod (grinding the tips off the weight arms) it moves through most of the range.
 
Junkyard HEI here for a SBC, when I pulled it apart I noted the weight pivot posts were really small, and worn damn near 1/2 way in he diameter, weight holes really messed up....pulled apart a old Pontiac HEI I had, stole the larger diameter posts from it, and installed on the Chevy unit, along with the Poncho weights, seems to work, but I not getting the full advance I need, really....

have to set initial at like 10* or less for hot start issues....

:eek::surrender:
 
mrvette said:
Junkyard HEI here for a SBC, when I pulled it apart I noted the weight pivot posts were really small, and worn damn near 1/2 way in he diameter, weight holes really messed up....pulled apart a old Pontiac HEI I had, stole the larger diameter posts from it, and installed on the Chevy unit, along with the Poncho weights, seems to work, but I not getting the full advance I need, really....

have to set initial at like 10* or less for hot start issues....

:eek::surrender:
Click to expand...

What's the number on the curve plate?
Try and find one with a greater range or if you have spares you can try and reshape one.
BTW, never throw those parts away, like gold to hei guys.
 
big2bird said:
Just a reminder here:
10* distributor advance =20*crankshaft advance:)
Click to expand...

OK Yes. Thank you. I've been thinking about this all wrong. It looks like the slot is good for about 20 deg rotation which is 40 deg crank rotation which would be way way too much. Even so i need to get just a little more which i think my mod will accomplish. I know i'm playing with fire. I had a buddy that did this years ago and cracked the ring lands on several of his pistons.

010752 said:
What's the number on the curve plate?
Try and find one with a greater range or if you have spares you can try and reshape one.
BTW, never throw those parts away, like gold to hei guys.
Click to expand...

i don't see any numbers on the original. I browsed through several brands of HEI kits on ebay. I just went for the cheapest since i thought they were all the same. The Spectre kit was 6 bucks with free shipping. Comparing the 2 cams the overall profile is the same. It's a matter of where the hole is drilled. The old cam pictured below has the hole offset towards the trailing edge giving more profile. The replacement cam's hole is drilled right in the middle giving less profile. So i guess i went backwards by putting in the new parts made in Taiwan.

You think i should save these? LOL Notice the stepped wear on the cam and weights. You guys think i'm BSing when i say i drive this thing a LOT.


404fbfc744dc065.jpg
 
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Jim, you showing a nylon? bushing on there, I don't recall ever seeing one, just a Pontiac post of maybe 3/16 and a Chevy post of 1/8" and corresponding metal to metal weights....my motor home 350 engine weights are now old Poncho posts and weights, as I tried to say above....that post that limits the advance, years ago I remember them putting a bushing on it, then later on in the 70? them making the plate hole smaller, so the limit was much more permanent than just a bushing we used to slip off.....

shades of the EPA, I bet....

:flash:
 
turtlevette said:
big2bird said:
Just a reminder here:
10* distributor advance =20*crankshaft advance:)
Click to expand...

OK Yes. Thank you. I've been thinking about this all wrong. It looks like the slot is good for about 20 deg rotation which is 40 deg crank rotation which would be way way too much. Even so i need to get just a little more which i think my mod will accomplish. I know i'm playing with fire. I had a buddy that did this years ago and cracked the ring lands on several of his pistons.

010752 said:
What's the number on the curve plate?
Try and find one with a greater range or if you have spares you can try and reshape one.
BTW, never throw those parts away, like gold to hei guys.
Click to expand...

i don't see any numbers on the original. I browsed through several brands of HEI kits on ebay. I just went for the cheapest since i thought they were all the same. The Spectre kit was 6 bucks with free shipping. Comparing the 2 cams the overall profile is the same. It's a matter of where the hole is drilled. The old cam pictured below has the hole offset towards the trailing edge giving more profile. The replacement cam's hole is drilled right in the middle giving less profile. So i guess i went backwards by putting in the new parts made in Taiwan.

You think i should save these? LOL Notice the stepped wear on the cam and weights. You guys think i'm BSing when i say i drive this thing a LOT.


404fbfc744dc065.jpg
Click to expand...

You can but the weight nylon bushings at NAP for $3.00. Change them, file the weight wear smooth, and jamb them back in.
 
big2bird said:
You can but the weight nylon bushings at NAP for $3.00. Change them, file the weight wear smooth, and jamb them back in.
Click to expand...

Now i know how you guys feel when i mess with your heads.

I can't tell whether you're busting my balls or serious. Those weights and cam have about 1/16" wear.

Are you that dead set against using aftermarket kits? I took a ride to the chineese restraunt tonight and it ran real nice. I was able to get some preignition now at an initial setting that gives a smooth start.

With the mod, i am unsure how its coming in, ie what the modified curve looks like. I'll have to put that timing cover on and document it.

The Accel kit has a different cam and has white bushings. The springs appear to be painted. The Moroso looks the same but with black steel. Painted i think.

acc-31041_w.jpg

all the other kits Spectre, Mr. Gasket etc. have black bushings. The gold springs appear to be plated.

!CERz3hQCGk~$(KGrHqZ,!hoE0h2+9tkKBNRZ3-dJUQ~~_1.jpg

The MSD kit's cam looks similar to the Accel but has a set of black and a set of blue bushings. Both have the flat stop to ride on the plate.

M468428.jpg

Do you know what those extra bushings are for? I used the ones with the stops similar to the stock ones.
 
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All the aftermarket weights and cams are junk. Lars, and I , have tried them all.
The bushings are to fit various years. Some weight pivot pins are small, and some are larger. Can't tell you the year/models off the top of my head. All my dizzy stuff is buried during the remodel.

I'll look later to see if I have a spare GM set of stuff, but they too are buried.

Speaking of buried, boats suck hind tit.:sick:
 
Jim, the aftermarket weights are not hardened. They will wear very quickly.

Also, some earlier HEI's, the weights rest on nylon buttons. Later ones have a raised boss of metal.
 
Jeff, do you know much about the varying weight post sizes?? as in why??

makes no sense to me....Mike, you know anything??
 
The original 75 HEI advance mechanism froze up and it wouldn't advance. I guess this was a common problem with just the 75s. The current HEI is a 76 out of i don't know what. I bought it at a garage sale in the early 80s. I would guess this unit has 300k miles. The new weights with installed bushings fit very snugly over the posts so they hadn't worn at all. The plastic keeps them from wearing.
 
turtlevette said:
The original 75 HEI advance mechanism froze up and it wouldn't advance. I guess this was a common problem with just the 75s. The current HEI is a 76 out of i don't know what. I bought it at a garage sale in the early 80s. I would guess this unit has 300k miles. The new weights with installed bushings fit very snugly over the posts so they hadn't worn at all. The plastic keeps them from wearing.
Click to expand...

I have never seen one with bushings for the weights, just metal/metal, like this last one all worn to shit....

also I have seen different shape center pieces and different length on the 'beaks' of the bob weights....the tines actuating that center piece/plate....

:bonkers:
 
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