383 help!!!! our motor combo needs suggestions

[c00nhunterjoe]

With the 4.30's you might get int the 12's. One way to find out.

[694life]

What spark plugs and gap should we be running? the car has a msd dissy a 6Abox and a msd blaster ss coil

[c00nhunterjoe]

I run the "stock" champion copper cores gapped at .045 running msd old school msd 6 box. Ngks are reccomended frequently on here. I ran them in my mustang and had good results on spray.

[694life]

something let loose in her so she's knockin real bad. gonna open her up over the weekend and see what we got. This guys got bad luck. I think the bottom ends been weak and when we got the cylinder pressure up it couldnt take it. Firefighter was dead on with the cam it ran awesome with tons of low end grunt (for a week) then bang she let loose just normal driving too. early in the week we did a couple 1st 2nd gear pulls from a stop but didnt romp on it real hard.

[c00nhunterjoe]

Man, that sucks. Pictures when you find out what went wrong

[694life]

four bent pushrods on #1 and #3 cylinders the rest are pin straight.

[lukedukem]

did you figure out what happend to the bent rods. what caused this
luke

[694life]

doing a slow top end disassembly starting with checking piston to valve and degreeing the cam. Weird it was only two cylinders on drivers side. Thinking weak springs or improper spring install height. We will see this week.

[Budnicks]

Not knowing the whole story, I would say either coil bind or clearance interferences, piston contact, too stiff of valve springs for stock weak push rods or even valve float or lifter pump up w/incorrect pre-load &/or lash when installed, etc., were the valve guides on the heads clearances for the added lift ??, {the stock guide height, is only good for about 0.520" gross valve lift, max before issues can accrue}, what valve spring pressures ??, what retainers were used ??, are they cheap stock 5/16" push rods, with stiff aftermarket valve springs ??, {that could do it easily}, what valve spring combo was used dual or single or ??, what installed heights ??, have the heads been shaved ??, how thick of head gaskets ??, did you check to see you had adequate valve to piston clearances ??, was the cam degreed properly ??, did you check to see you had the proper length push-rods to begin with ??, what kind of rockers were used ??... Just a few possibilities it could ultimately be... Good luck & I hope it isn't too bad, something simple or just overlooked...

[firefighter3931]

doing a slow top end disassembly starting with checking piston to valve and degreeing the cam. Weird it was only two cylinders on drivers side. Thinking weak springs or improper spring install height. We will see this week.

Sorry to hear that 

I doubt it's piston to valve because the 509 cam has a ton more duration and that cam cleared fine. The valve spring rate might be insufficient...what valve springs ?


Ron

[694life]

well im finding out some of that info soon. It ran for a week before they bent and it was at 3-4000 rpm so i doubt it was float or piston contact. I'm just found out they were stock push rods. The car ran for 7yrs with the pushrods with the 509 cam though. was the .513 lift the straw that broke the camels back?

[694life]

they were comp 911-16 valve springs  not sure of seat pressure or installed hieght. we didnt do much figuring because the 509 to 303 cam was less duration and figured if it worked for years with the 509 in there

[firefighter3931]

The stock pushrods are a problem, inmo. 

The 911 springs are fine for that application but they do have 330-340lbs of open pressure and coupled with the more agressive valve action of the voodoo cam can tax "stock" parts that are designed for more modest ramp speeds and spring pressures.

Mancini carries a chrome moly pushrod for the lowdeck that is heavy duty and designed for 300lb+ open spring pressures....with stock non-adjustable rockers these are the hot ticket ! 

http://chucker54.stores.yahoo.net/hydbchromemoly.html


Ron

[694life]

we were gonna "maybe" go with some adjustable roller rockers. Are there any recommended for this setup with the right pushrods? 1.5 or 1.6 ??

[firefighter3931]

we were gonna "maybe" go with some adjustable roller rockers. Are there any recommended for this setup with the right pushrods? 1.5 or 1.6 ??

If you have your heart set on a set of roller rocker arms i would suggest the Crane Gold race rockers....they have nice geometry with an oem head. Some guys like the PRW rocker arms but i have no personal experience with them but the reports are good. 

As for the ratio ; with a hyd cam i'd stick with a 1.5:1 ratio especially with the more agressive ramp speed on that VooDoo camshaft. High rocker ratios, agressive cams & hyd lifters are a bad mix. It will go into valve float sooner with the 1.6 vs the 1.5 so if you're looking to spin it up to 6k the 1.5 is your only real option. 

Don't expect any major power gains with a roller rocker....I'd be surprised if that swap netted 10hp 


Ron

[BSB67]

we were gonna "maybe" go with some adjustable roller rockers. Are there any recommended for this setup with the right pushrods? 1.5 or 1.6 ??

I believe in adjustable rocker gear as I believe that setting up a hydraulic with zero preload is worth it.  If you are just going to screw the adjusters another 1/2 or 3/4 turn past zero preload, stick with what you have and get the right length push rods.

If you want a good set of inexpensive adjustable rockers, find some used 25 year old Crane or Isky ductile iron units. These will be a far better product than today's low cost roller rockers.  The roller provides no measurable benefit.

[694life]

so i guess with that being said we will stick with the stock 1.5's measure the preload and get the proper length strong pushrods. Thanks again I will keep ya posted

[firefighter3931]

so i guess with that being said we will stick with the stock 1.5's measure the preload and get the proper length strong pushrods.

Good plan 


Ron

[694life]

ok so we used a scribe and a straight edge made a lin on the pushrod losened up the rocker shaft made another line, measured betreen the two lines and have 1/8th " cam card says preload should be .020 to .060 looks like we are at .125 how do i calculate pushrod lenght needed from here? did we do it right? things to look at?

[694life]

Anyone...

[firefighter3931]

I'm thinking that your measurements are off. If you had .125 free play in the pushrods then you would be able to move the pushrod up & down 1/4 inch with the lifter resting on the base circle of the cam ! 

The proper way to measure is to get the lifter on the base circle (heel) of the lobe and install the pushrod/rocker arm assembly and see if there is any vertical movement with the pushrod. If there is....your pushrods are too short. At this point you use an adjustable (checking) pushrod and install it until there is zero vertical movement (without preloading the plunger) and remove the pushrod. This will give you zero lash and you simply add .020 to the length of your checking pushrod for the correct length. 

Several companies sell the checking/adjustable pushrod : http://www.hughesengines.com/Index/products.php?browse=category&level0=VG9vbHMgJiBCb29rcw==&level1=UHVzaHJvZCBMZW5ndGggQ2hlY2tpbmc=

*Hughes will lend you the adjustable pushrod as long as you return it and purchase the pushrod set from them. 



Ron

[694life]

Thanks for the info. The pushrods we have seem too long it seems to me like we are bottoming out the hydro lifter with the pushrod. Im gonna look at it again late this afternoon.

[694life]

ok I made my own adjustable pushrod.... I have a stock pushrod at 8.590 (is that correct) it looks like that puts my preload on the lifter at .12121  If I go to a 8.5 pushrod it puts preload back in range at .032  should i go with that or do a custom pushrod to get it down to .020?

[firefighter3931]

ok I made my own adjustable pushrod.... I have a stock pushrod at 8.590 (is that correct) it looks like that puts my preload on the lifter at .12121  If I go to a 8.5 pushrod it puts preload back in range at .032  should i go with that or do a custom pushrod to get it down to .020?

I'd be happy with .032 preload 

In the past i've ran with .040 and had no problems. 

Not sure what the stock length on a lowdeck is supposed to be....it's been many years since i've had a hyd flat tappet cam. 


Ron

[JThotrodjunkie]

I like the new 850 hp series holley, adjustable air bleeds, no choke horn etc, totally tunable.  I had a 950 hp 3 sizes bigger jets needed! on my .065 over 440 (70 Charger R/T) diamond pistons, 11.25/1 edelbrock  performer rpm heads cam was solid lifter in the 550ish lift range but it was a road racing grind (wanted to to the silverstate but sold the car) That motor made 695hp and was the wildest thing I ever owned. I drove the car harder than anyone dared and it turned out a little lean.. upsized jets and no problem acted like it was injected! Good luck!