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post #1 of (permalink) Old 08-12-2002, 10:54 AM
logan_ut
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Buying New Heads, Need Some Advice!!!!

Well, I found out why I broke a valve spring in the truck I just bought. I had a mechanic that I know look at it with me and the problem is my cam has too much lift for the current set up in the heads and it is pushing the rocker arms up too much. He basically told me that the bottom end is too built for the top end. I think I am going to buy some Trick Flow aluminum heads with 195cc intake runners but I'm not sure what ones too get. The problem is that I don't have a cam card and the guy I bought the truck from is no help. It's got to have more than an RV cam but I don't think it is extremely high because I still have smooth idle and low-end power. Will a 1.25" valve spring (cam up to .500" lift) be enough or should I go with a 1.47" spring (cam up to .540" lift)? Will it hurt to have too big of a spring? Also, should I go with 64cc or 72cc chambers? Can I make a good decision without pulling everything to get to the cam and pistons?
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post #2 of (permalink) Old 08-12-2002, 02:13 PM
ratlover
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Re: Buying New Heads, Need Some Advice!!!!

OK.....the chamber size will alter your compression. If your existing heads have 72cc chambers and you go to 64cc you will gain compression. Thats good for power but bad because you *might not be able to run on pump gas. It depends on what cam you have and what pistons. You need to find those out. What are the rest of the specs for the motor?

On the trick flow heads.....I would not go with aluminum heads. Aluminum will allow you to run more compression but what they dont say is that aluminum requires you to run more compression to make the same power as an iron head with the same runners This is because heat=power and aluminum wicks heat away from the combustion chamber. Aluminum heads can be coated to help hold heat in the cumbustion chamber but its kinda spendy. Aluminum weighs less but saving 80 lbs isnt important in a 4x4.....80lbs might be good in an all out race car but not a street car. I would go with some dart iron egals(I was also looking into pro action heads with my sbc build up but didnt fully investigate.....you might want to, they seem good too) Iron egals are also much cheaper than the trickflos.

Tell us the rest of the specs of your motor(and hopefully you can give us some cam info)and we can help you pick some heads but right now we would be shooting in the dark.
post #3 of (permalink) Old 08-12-2002, 03:21 PM
logan_ut
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Re: Buying New Heads, Need Some Advice!!!!

Sorry I don't have more info for you yet. I am going to pick up the truck tonight and pull off the old heads to get a better idea of what I've got. What I do know is that the 350 block is bored 30 over.

On the heads, if aluminum is not the way to go would it be worth buying a complete head or just changing the valve springs, etc. in my existing heads?
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post #4 of (permalink) Old 08-12-2002, 04:22 PM
ratlover
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Re: Buying New Heads, Need Some Advice!!!!

You can have your heads taken off and have screw in studs installed. The cam you have might require valvesprings that are larger than the pockets in your head are cut for(but I doubt it)

I dont buy assembled heads for 3 reasons.
1. You dont get valvesprings matched to your cam.
2. Sometimes you dont get the quality parts installed
that you would if you picked your own.
3. Even the good head companies can have bad assembly
practices. Alot of the assembly work is farmed out.
Bad valve sealing, poor giude clearance, all kinds of
stuff.

Buy bare heads and have a competent machine shop do the set up if you cant do it. JMO

EDIT: it sounds like not having screw in rocker studs is your problem. Valvesprings coil binding will do alot more damage in a hurry.
post #5 of (permalink) Old 08-13-2002, 12:01 AM
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Re: Buying New Heads, Need Some Advice!!!!

I know most people do not have a camshaft degree wheel. So having said that, here is what I'd do with your truck if it was in my driveway. I'd use my degree wheel and dial indicator and measure the camshaft (lift & duration).[img]images/icons/smile.gif[/img] I've been know to just change the valve springs on an engine, and solve the valve train problem. I've also been know to replace the valve stem seals at the same time I replace the valve springs to a positive type valve stem seal with teflon inserts. Heck,[img]images/icons/smile.gif[/img] I might even do a leak down test on the old heads before I decided to remove and replace the old heads.

Buying new/rebuilt heads is still an option, and an expensive one at that. I'm sorta a fan for using World Products S/R cast iron heads on a pickup engine. I'm a super huge fan for using roller tip rocker arms.[img]images/icons/smile.gif[/img][img]images/icons/smile.gif[/img]
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post #6 of (permalink) Old 08-13-2002, 09:09 AM
logan_ut
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Re: Buying New Heads, Need Some Advice!!!!

I've already pulled my heads off because if I decide to keep them I have to have one of the heads fixed because the threaded rocker arm stud has been pulled out and stripped. I know new heads is an expensive option but I need to get it fixed asap and it is the quickest and easiest solution at this point. I've decided that the cam in the motor is more than I want for a four wheel drive so I'm going to change it and match it up with the heads I buy. I know now that I have flat top pistons but I have no idea what size compression chambers. Do I need this to match the correct heads? I pulled off some numbers from my old head to see if you guys know if they will tell me anything about the heads on it so I know what to replace it with. Any cam/head combination reccomendations would be appreciated. The numbers I found are as follows:

3932441T GM 8
H5 8
441
post #7 of (permalink) Old 08-13-2002, 09:44 AM
ratlover
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Re: Buying New Heads, Need Some Advice!!!!

I'm not a fan of the s/r heads(they stand for stock replacement) and thier flow #'s pretty much suck IMO.
World's sportsmanII are good heads IMO and close to darts.

Dont the heads need to be removed to install the teflon seals? A degree wheel and a dial indicator would give you a pretty good idea on what you are dealing with but to use one the motor has to be pretty tore down. Might as well yank the cam and pull the # off it.

Regardless you need to pull the heads. Either to intall screw in studs or to throw some new heads on it.

Roller tip rockers are nice but thier main advantage is that they are just generally better quality. The rockers ratio is more accurate and they deflect less, thats were thier power comes from IMO. You also need to make shure that you dont need long slot rockers.

<font color=red>*this is makeing alot of assumptions and there is no garantee that things wont get f-ed up, this is the cheap route and a way to cut a few corners. I dont recomend it but here is some food for thought* If long slot rockers werent used before and there are no signs of contact you should be ok with out them. You can assume the Bozo that put your motor together used the right springs. To heavy of a spring will wipe a lobe, if it hasnt yet it shouldnt be to heavy. To lite and it will float the valves sooner than it should. If your motor floats the valves easily especially if the cam seems to want to pull much higher there is a chance you got to lite a spring. If you only run your motor to 5 grand and it dosnt float the valves then you should be ok. It sounds like your only problem is that you needs screw in studs. It sounds like you should be able to pull the heads and have screw in studs installed and put the springs rockers and whole shot back together. Notice all the shoulds and sounds and words like that.</font color=red>

Now is the time you need to decide how deep you want to dive, there is some extra performance potential here but you need to decide if you can afford it. Money wise and also being out a vehicle and doing the work and all that.

<font color=red>Note</font color=red> I dont know what you know so sorry if I insult your car knowledge. If you are going to reuse your valve train you need to make shure everything goes with its mate. Take note of were it came from and were it goes. Lifters must go on the same cam lobe and pivot ball needs to go with its rocker. Everything needs to go back were it came from. I would go through the proper break in procedure even though the cam is broke in.


post #8 of (permalink) Old 08-13-2002, 10:12 AM
ratlover
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Re: Buying New Heads, Need Some Advice!!!!

What size reliefs do the flat top pistons have? Generally a flatop will give you around 10:1 compression with a 64cc head and around 8.5 with a 72cc head. It depends on how big/ if you have 2 or 4 reliefes. It can vary quite a bit, thats just a generalization. The compression ratio to shoot for massivly depends on what octane you want to run on and what kind of cam you want to run. So you got to answer that question first....whats "too big" about the cam now? What do you want your motor to perform like and what are you willing to give up?
post #9 of (permalink) Old 08-13-2002, 10:16 AM
ratlover
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Re: Buying New Heads, Need Some Advice!!!!

I would still go with the dart iron egals 275 ea bare....chamber size depending on what compression you want

Cam depends on lotsa things....

What intake do you have? what do you have for exhaust?
post #10 of (permalink) Old 08-13-2002, 12:54 PM
logan_ut
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Re: Buying New Heads, Need Some Advice!!!!

Ok. I don't know very much about all of this so bear with me! How do I tell what size reliefs the flat top pistons have? Also, can I get the numbers from the cam by just removing the timing chain cover and not the entire cam? I bought the truck how it is and can't get any information on what is in the motor. The rocker arms on it were Comp Cam Roller Rocker's with a 1.52 measurement. I "think" that the cam is too high just by comparison to my old truck with a crate 350 and RV cam. I have alot less braking in this truck and although it has more power it doesn't seem like it is as responsive at low-RPM. The truck is a daily driver and I am more concerned with strong low-RPM power for driveability and would also like to get as much power from the motor as possible without having to put my foot into it all the time. I want it to drive like a truck. The intake is an Edelbrock Performer and the exhaust consists of long headers and dualed Flowmasters. Thanks for all the help!
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