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Discussion Starter #1 (Edited)
Hi everyone
I've been trying to get my re-built 351w started and its not going well at all. I'm using the original rocker arms and when trying to get the motor started for the first time one of the rocker arms broke. It broke on the pushrod side. I replaced it with a new one. Tried to start it again and this time it broke on the spring side. Same cylinder same valve (number 2 cylinder exhaust). Both times I had an exhaust backfire. Would a backfire cause the rocker arm to break? Does what side it breaks on tell me anything? I find it weird to have two rocker arms break on the same valve. What else could cause them to break? I just put the motor together and haven't had it running more than 10 mins. Forgot to add that the pushrod is straight.
 

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No - backfire should't cause it, but I'd say you have something wrong in your overall geometry....even if it
s just that particular cylinder I'd spend some time getting serious with double checking things - like PR length for one. Obviously it's binding or it wouldn't be breaking rocker arms.....that grind doesn't look to radical 214/224 but how did you go about setting it up to start with? Did you change pistons/crankshaft or anything else...? Lot's of things to to know before we can really give you much help....
 

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Discussion Starter #3 (Edited)
Here is everything I did for this build
Bored 30 over
New pistons
New bearings
Stock crank turned 10 (maybe 20) under
New camshaft
New lifters
New heads
Powermaster one wire alternator
Got the machine work done and ordered the cam from the same place. They also had my heads to order parts since I bought bare castings. They knew all the parts I was using and nothing was a cause for concern.

A little over a year ago I did
4 barrel carb
204/214 cam with springs and push rods
Weiand stealth intake
Double roller timing chain
Bought all this from local speed shop at the same time. Car ran great just had a oil leak that turned into my current build.

I'm using the same springs/pushrods as the 204/214 cam because the guy at the machine shop said it would work and didn't need to be changed. When i turn the motor over by hand with the valve covers off all the rocker arms moved up and down and didn't notice anything wrong. If I did have the wrong length push rods wouldn't all of them break? Could it be a bad lifter?

After a ton of researching the internet I read that if you have more than .450" of lift then you may need to lengthen the slot on the rocker arm. True? If it was and my rocker arm is hitting the stud and breaking why isn't all of them breaking?
 

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I have soooooo many questions. What year is the W block? What exact heads did you buy, along with valve size? What is the cam's rated valve lift? What type of valve stem seals were used? What type of valve springs were used? How were the valves adjusted? Are your rockers on a stud or are they bolted down? Were the heads and block decked? Are your pushrods for the year of block you have? And above all...was your machine work done by a shop in a GM dominated town?...believe me, it matters. After I get answers, I can probably walk you through a fix.
 

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^^ What he said - also exactly what pistons you have? They come in different heights as well depending on a few things......

It's really hard to see "spring bind" eyeballing things - you really need to do your homework when you make that many changes.....not saying your speed shop guy was leading you down the wrong road but he may have been going on memory rather than facts..? IDK Did he configure it - or just sell you the stuff..? It wouldn't be unusual for one cylinder to show you trouble - before others do....that's why you need to work/check every single one methodically when you make changes like that.

Some years of the 351W the piston actually comes out of the cylinder a tad (stock), so you can see why a tller piston could lead you into trouble if it wasn't dished/fly cut.....that's just the tip of the iceberg for examples. Let's see what you have and work it out top to bottom
 

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They will...................

Time to get a decent set of roller rocker arms.

Here is everything I did for this build
Bored 30 over
New pistons
New bearings
Stock crank turned 10 (maybe 20) under
New camshaft
New lifters
New heads
Powermaster one wire alternator
Got the machine work done and ordered the cam from the same place. They also had my heads to order parts since I bought bare castings. They knew all the parts I was using and nothing was a cause for concern.

A little over a year ago I did
4 barrel carb
204/214 cam with springs and push rods
Weiand stealth intake
Double roller timing chain
Bought all this from local speed shop at the same time. Car ran great just had a oil leak that turned into my current build.

I'm using the same springs/pushrods as the 204/214 cam because the guy at the machine shop said it would work and didn't need to be changed. When i turn the motor over by hand with the valve covers off all the rocker arms moved up and down and didn't notice anything wrong. If I did have the wrong length push rods wouldn't all of them break? Could it be a bad lifter?

After a ton of researching the internet I read that if you have more than .450" of lift then you may need to lengthen the slot on the rocker arm. True? If it was and my rocker arm is hitting the stud and breaking why isn't all of them breaking?
 

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un fortuneately the motor is all together , but i'd remove the intake and install a set of checking springs on the front two cylinders---install a solid lifter in the front 4 holes and set up zero lash----now check for coil bind but most important , check roller rocker geometry to valve [email protected] 3/4 open , the roller s/b about centered on the stem---this can be corrected by using longer or shorter push rods---make sure the rockers clear the spring retainers and arn't binding in the pivot area
if all this checks good , there is a point you can check piston to valve clearance--i can't remember the exact # of degrees but if your @ the correct spot , you can push down on the valve with the check springs and measure the valve to piston clear
doctordesoto
 

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Discussion Starter #8 (Edited)
Let me see if I can remember/post every spec I know.

Engine - C90E-6015-B (.30 over) stock crank and connecting rods used. The shop put the new pistons on the rods

Bearings - Don't know the brand off the top of my head. The shop installed the cam bearings.

Cam - Elgin Pro Stock

Cam specs - Cam lift (int 296 exh 311) Valve lift (int 473 exh 497)
SAE dur (int 289 exh 300) .050 dur (int 214 exh 224)

Heads - Pro Comp 210cc (bare casting)
63 cc combustion chamber
2.02 intake
1.60 exhaust
Comp Cams spring Locators
Don't remember name of guideplates used
New studs
They had my heads for over a week while he ordered all the parts I needed. He also had one of my valve springs to make sure it would work for my application.

Valves - Elgin Pro Stock valves (using umbrella seals)
Intake - Head Diameter 2.020 Stem Diameter .3415
Exhaust - Head Diameter 1.600 Stem Diameter .341
Valves fit nicely into the guides. No side to side play.

Springs - Dont remember the brand. I bought them when I bought the previous cam a year ago from a different shop. They are stiffer than stock and have a smaller spring
on the inside of the main spring

Pistons - Have a oval shaped dish recessed into it. They are for a 69 block. I asked him numerous times on multiple days if I would have piston/valve clearance issues and he
said no because I didn't have enough lift for it to be a problem. When i had to motor almost running there was no knocking or ticking

Lifters - Don't know the brand. The shop had them in stock and brought out a bag with the lifters in it. They looked new and had no wear on them.

Rocker arms - Using stock non-adjustable ones. Guy at the shop said that wouldn't be a problem.

Push Rods - Bought a year ago. Hardened Rods. I believe stock length. I have a feeling they are probably wrong.

Intake - Weiand Stealth

Carb - Road Demon 625cfm

Thanks guys. If any more info needed just let me know and I'll answer to the best of my abilities. I just wanna drive my car again :( been working on it since February.
Jester, I don't believe I live in a GM dominated town lol.
 

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Hmmm...not crazy about stock rockers with higher seat pressure springs? Also if that's not a screw in stud I'd be leary under that circumstance too....and it doesn't look like they are in the pic on JEGS site? So a 497 lift on "stock" length PR (maybe?) with dished pistons on a 69 block should easily leave you clear of the piston. The question is what is the seat height of the springs on those heads (stock design)? Maybe somebody knows those heads....but I would at least verify the compressed and uncompressed height of the springs you have against some stock ones if you have them still. It might be as simple those rockers can't handle the pressure...or it could be the springs are bottoming out before the PR has met it's upper limit, and either the stud is gonna pop out or the rocker is gonna give in that cirumstance. DOC's method would be a down a dirty check to do a sanity check as well.....or you could even get one of those inspection scopes and look at the top of the pistons, but I bet you won't find anything....
 

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Discussion Starter #10
The studs are screw in. I'll check to see if the springs are bottoming out. If they are is that a pushrod length issue or having to get new springs?
 

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Discussion Starter #11
I just went and checked on the springs. Looks like they are bottoming out just before max lift. Can this be fixed with a shorter push rod or need to get new springs? Also it looks like the sides of the rocker arm are coming in contact with the retainer. I'll see if I can post a couple pics I took.
 

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Discussion Starter #12
head resize.jpg
:cry:


Here is the spring at max lift. Looks like its bottomed out
 

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I stopped with the posts when I read all off your info in post #8. The thing I paused on first was the springs. You have no reason to be running a dual spring with that small of a cam. You need to be running a single coil with internal dampener. The next thing I noticed is the use of umbrella seals...you need a viton rubber positive seal, like the ones on a sm blk chevy intake valve (the ones from around '86 would be swell). The big Ford umbrellas are very thick from the top (under retainer), to the bottom (above guide). Increasing the lift much over stock will cause the retainers to come in contact with the seals. Pushrod length is a concerne, as well...your block is a 9.480" deck hight and you want to make sure that you don't have pushrods for a 9.508" deck. 28 thousandths will make a difference. You definitely don't want to cut costs with pushrods...they need to be one piece, hardened, unused. Next, you have "non-adjustable rockers" on screw in studs...that doesn't jive. There are only two types of non-adjustable rockers for a sm blk Ford...and they are the bolt down, sled type and the nut down, stud mounted that bottom out on the stud (rare). I would chuck any of the stock rockers staight to the scrap heap and get a good set of roller rockers...I have abused my Harland Sharp rockers to Hell and back with great results. The stock rockers are breaking at coil bind because the springs are installed at the wrong hight (too short), causing massive seat preasures at closed valve position. You should be running no more than 110 pounds of seat pressure for that size of cam...and that is plenty for up to 6000 rpm, which is all your bottom end should be doing anyway. Your guide plates also need to be of the new variety without wear...too much side to side slop will wear the valve tips out in a hurry. Now to adjusting the valves...the hydralic lifters on a small block Ford (and Cleveland) perform best at zero lash, plus a quarter turn (no more than 3/8 turn). This is from experience...remember my Hell and back statement. Now...what is zero lash? It is when the rocker is adjusted down to when the pushrod is just seated in the lifter with no up and down play. The spin method is NOT fool proof...the pushrod needs to be manipulated up and down until the rocker is adjusted down to zero lash...then taken a quarter turn more. Note: Adjust only the valves next to their paired open valve...that means if the intake valve on #2 is open, adjust the #2 exhaust valve. A sharpie helps keep things in order. Shoot me a pm, if you need anything else.
 

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I built a 302 and mixed up my push rods I had 351's 302 from different years and some older long Chevy ones laying in . I purchased two push rod measuring tools to order the correct ones since Ford listed a few that are possible . I also know some one who had the same trouble and the push rod was the culprit got the right one in and no more problems . It was a 302 some are .020 longer you won't catch that with the eye .
 

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Agree with jester I am fairly sure you really need to dig into it or you are going to be running in circles adapting or really breaking something. This is why valve geometry is SO important when you start to change things and turns into headaches very quickly. There are real good books that cover SBF builds/performance mods....I'd get one or find a shop that you can trust to help you out. In the end it will be money better spent. Ditch the stock rockers and get decent roller tips like Crane/Harland/Lunati/etc, some poly seals, and you will be in a much better place to start. There is still much that will need to be done to get it right.
 

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Discussion Starter #16
Thanks a lot guys.

So it looks like new springs, rocker arms, valve seals and checking pushrod length. When looking at springs what kind of numbers am I looking for (coil bind height, spring rate)?

Are these the type of valve seals i should be using? http://www.summitracing.com/parts/FEL-SS72861/?rtype=10

This sucks so much. The shop had me convinced that everything would work just fine. Before I buy anything else I'll post links here to get some feedback.
 

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don't know that you need new springs per se, you should verify the height open/closed (specs would have been given if you remember brand/part number. Example stock specs are around (lbs/height) 75lbs/1.79 installed and 200/1.34 compressed. A machine shop could measure all this for you as well - it's not a bad idea to be sure they are consistant. Then you would need a few adjustable PR's to help you figure out what the correct length is going to need to be....a dial indicator and a magnetic base would be very useful....and a good how to book to walk you through the process. Like jester says things need to be done in the correct sequence and checked every step of the way for anything that might be causing trouble. After you get done you will have a deeper appreciation of doing it right from the git go!! ;>) When in doubt consult with somebody as a sanity check.
 

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Thanks a lot guys.

So it looks like new springs, rocker arms, valve seals and checking pushrod length. When looking at springs what kind of numbers am I looking for (coil bind height, spring rate)?

Are these the type of valve seals i should be using? http://www.summitracing.com/parts/FEL-SS72861/?rtype=10

This sucks so much. The shop had me convinced that everything would work just fine. Before I buy anything else I'll post links here to get some feedback.
Nope...though they are good seals, they tear easy when being installed. These are the ones I like and use; http://www.summitracing.com/parts/FEL-SS72527/ . Using these depends on the outer diameter of you valve guide. I'll try to locate the ones for the smaller guide...the ones listed are for a .531" guide, but some are for the .500" guide...all using 11/32" valves.
 

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don't know that you need new springs per se, you should verify the height open/closed (specs would have been given if you remember brand/part number. Example stock specs are around (lbs/height) 75lbs/1.79 installed and 200/1.34 compressed. A machine shop could measure all this for you as well - it's not a bad idea to be sure they are consistant. Then you would need a few adjustable PR's to help you figure out what the correct length is going to need to be....a dial indicator and a magnetic base would be very useful....and a good how to book to walk you through the process. Like jester says things need to be done in the correct sequence and checked every step of the way for anything that might be causing trouble. After you get done you will have a deeper appreciation of doing it right from the git go!! ;>) When in doubt consult with somebody as a sanity check.
Those springs look like they are around 1.750" diameter and probably have an installed hight spec near 1.850-1.900" at 125-135 pounds seat pressure...which is good for a solid cam.

On a side note...I need some part numbers on all of your parts, and I'll get you straight. Your shop may have also installed a set of sm blk Chevy valves, which will change your valve geometry, as well as your available spring installed hight.
 

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Discussion Starter #20 (Edited)
Unfortunately I don't know the specs on the springs and I don't know the part number. I wanna say they are Speed Pro springs. If it'll help I can post the cam specs of the smaller cam I was using with these springs on the stock heads. When I ordered that cam I told the guy I needed new springs and these were ordered. Anyway here are the part numbers that I have right now. If any other part numbers are needed I can see if I can get them.
Elgin Intake valve part # HPV-13
Elgin Exhaust valve part # HPV-5
Elgin cam part # E-960-P
Push rods are probably stock length but I'll measure them

I looked up the valve part #s and found this
HPV-13 Details <table border="1" cellpadding="2" cellspacing="2"><tbody><tr><th>Application</th><th>Part No.</th><th>Head Dia.</th><th>Stem Dia.</th><th>Install Ht.</th><th>Type</th><th>Stem Type</th><th>Chrome Stem</th><th>Seal Groove</th></tr><tr bgcolor="#FFFFFF"><td>Chev. SB 1 Piece</td><td class="partno" nowrap="nowrap">HPV-13</td><td>2.020</td><td>.3415</td><td>Stock</td><td>Int</td><td>Undercut</td><td>Yes</td><td>No</td></tr></tbody></table>
HPV-5 Details <table border="1" cellpadding="2" cellspacing="2"><tbody><tr><th>Application</th><th>Part No.</th><th>Head Dia.</th><th>Stem Dia.</th><th>Install Ht.</th><th>Type</th><th>Stem Type</th><th>Chrome Stem</th><th>Seal Groove</th></tr><tr bgcolor="#FFFFFF"><td>Chev. SB 1 Piece</td><td class="partno" nowrap="nowrap">HPV-5</td><td>1.600</td><td>.3415</td><td>Stock</td><td>Exh</td><td>Undercut</td><td>Yes</td><td>No</td></tr></tbody></table>
E-960-P Details <table border="1" cellpadding="2" cellspacing="2"><tbody><tr><th>Range</th><th>Part Number</th><th>Direction</th><th>Cam Int</th><th>Valve Int</th><th>Advdur Int</th><th>Timdur Int</th><th>Open Int</th><th>Close Int</th><th>Overlap</th><th>Lash Int</th><th>Center Int</th><th>Cyl</th><th>Footnote</th></tr><tr bgcolor="#FFFFFF"><td>C</td><td class="partno" nowrap="nowrap">E-960-P</td><td>INT</td><td>.296</td><td>.473</td><td>289°</td><td>214°</td><td>0° BTC</td><td>34° ABC</td><td>70°</td><td>HYD</td><td>107°</td><td>8</td><td>
</td></tr><tr bgcolor="#EEEEEE"><td> </td><td class="partno" nowrap="nowrap">
</td><td>EXH</td><td>.311</td><td>.497</td><td>300°</td><td>224°</td><td>49° BBC</td><td>-5° ATC</td><td> </td><td> </td><td>117°</td><td> </td></tr></tbody></table>High Output engine (Exc. Roller Lifters). Firing Order 1-3-7-2-6-5-4-8 These cams are used in the engines by rewiring the distributor to Firing Order 1-5-4-2-6-3-7-8.
I've been using the 1-3-7 firing order. Ugh....
 
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