Rebuilding sbc400 ... looking for some parts advic - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 04-18-2002, 03:09 PM
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Rebuilding sbc400 ... looking for some parts advic

I have a '76 5/4 chev truck that GM canada built for the canadian army(sort of a hybrid 3/4-1ton setup as they didn't build 1tons in 76 atleast in canada). I changed out the stock 350 and swapped the 400 from my buddies drag car when he retired and sold the chassis. It was making way to much power at the wrong rpm when it came out of the car so i swapped out some of the more exotic parts for some pieces i purchased and had lying around. Changed the single plane tunnel ram with an edelbrock dual plane. Changed the solid high lift cam for an old RV crane (i think?) cam. Changed the roller high ratio rockers and pushrods for some stock arms and rods i had. Retained the GM Phase I Bowtie heads and stainless valves. Retained the shortblock 4bolt(yes i know they only made them for like 1-1/2years [img]images/icons/wink.gif[/img] with Speed-pro forged pistons .030 over. Anyways... i had a little underhood fire about a year and a half ago and finally decided to do something with the motor this spring. I pulled the motor and sent it down to the local engine shop in London Ontario so they could ensure the heat had not done any nasty stuff to the block or heads. Everything checked out ok.... but because i let i sit so long there was some corrosion in one of the cylinders. I have to have another .010 bored out of the block. Sorry for all the history finally here are my questions. I am trying to decide whether to purchase new speed-pro forged pistons or go with something like the kiethblack Hypereutectic guys. I have heard a few people saying that the Hypereutectic pistons are a much better piston even though they are a cast piston? I guess rings is my next question and i have got answers all over the board on this one. Some people say don't waste your money and go with inexpensive OEM like rings and others say this i something you should invest in.
Next is a cam. I have been fairly happy with the cam that i scavenged when i installed the motor but i believe there is a great deal of life left hiding in my motor. I have been looking at the Lunati 30111 but believe there has to be an even better cam out there. Lastly this motor has been apart sooo many time during its strip days that half the head bolt threads have been healicoiled. I'm thinking of tapping and healicoiling the remaining threads and installing head studs. I know about the clearence issues but i'm always messing and i want to be able to remove the heads repeatedly in the future. While i'm at it i thought main studs and a windage tray would be a good idea.

Sorry for the long winded post. Look forward to your reply.

Tavis
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post #2 of (permalink) Old 04-18-2002, 03:20 PM
 
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Re: Rebuilding sbc400 ... looking for some parts advic

<font face="Times New Roman">
<font color=green>Look into the Comp Cams Extreme 4x4 series. They pull good vaccuum and make real good power down low where it's important in a truck, they don't fall off on the high end, but the emphasis is on power in the low end.
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post #3 of (permalink) Old 04-18-2002, 03:37 PM
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Re: Rebuilding sbc400 ... looking for some parts advic

about head studs....might make life a pain to pull the heads in the truck if you ever need to. KB hypers are the best choice for the street or anything you arent going to put a bunch of spray on or a supercharger. Go with some good file fit speedpro or C&amp;A rings IMO(I would stay away from gapless). Windage try dont really help untill the higher RPM's. Main studs are kinda pricey and overkill but definatly wont hurt. I'd give crane or isky a call when you have your motor pretty well figured out and let them pick the cam for you
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post #4 of (permalink) Old 04-18-2002, 05:36 PM
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Re: Rebuilding sbc400 ... looking for some parts advic

Thanx for the input guys!!! And quick [img]images/icons/wink.gif[/img] wow i wasn't expecting to see anything until atleast tomorrow!!
Plugged some of the comp cam specs into dyno2000 and they seem pretty sweet 451ft/lb at 2000rpm <G> and doesn't really fall off until around 6K.... nice and flat all the way through.

Thanx again

T.
post #5 of (permalink) Old 04-18-2002, 07:03 PM
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Re: Rebuilding sbc400 ... looking for some parts advic

Yes, the heli-coils are a good idea. They are stronger then when the block was new. For the street head studs and main studs are a waste of money, use it for something more helpful. If you do go with main studs the mains should be align honed with the studs.
The hyper pistons run a tighter clearance then forged so are quieter and seal better. They can withstand alot of pressure, but will shatter fast if rattled. So detonation and nitrous should be avoided with these pistons. Unless you plan on running nitrous, high rpm, or somekind of forced induction, I would say your choices should be cast or the hyper pistons. You will make better power due to the better sealing from the tighter fit.
I too say stay away from the total seal piston ring scam. The top ring is forced out by cylinder pressure to make the seal. The problem with total seal rings is the second ring is the gapless ring while the top ring remains stock style. So the cylinder pressure goes past the first ring's gap, but is then trapped by the gapless ring. The pressure equalizes between the two rings with the cylinder pressure. This causes the top ring to lose it's seal. So basically you are running on one compression ring. The second problem this creates is heat removal from the piston. Most of the heat is removed from the piston through the rings. Once the top ring loses it's seal it no longer transfers heat. And it is the ring closest to the heat of combustion.
Since this was once a drag engine, I would be interested in a couple of things like intake port CC's,and valve spring pressures.
post #6 of (permalink) Old 04-18-2002, 09:46 PM
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Re: Rebuilding sbc400 ... looking for some parts advic

Hey RolngThun
Thanx for the advise! I think i'll still go with the head studs they aren't all that much more expensive than new head bolts and i'm starting to get a little paranoid about stripping out head bolt threads on this guy. I like the idea of the hyper pistons so i believe i'll go that way.

I got lucky with the heads .... i had the same thought as you when i first bought the engine but the heads had just been installed before the car was taken off the track and no porting had been performed yet. I believe the heads are overkill for the motor i'm trying to build i think i read somewhere that the smaller valve heads are better somehow for low rpm torque. (increased airflow velocity because of the smaller valve size maybe?) They still have pretty huge Intake Runner Volume even without the porting 184cc i believe. Maybe they aren't the best choice for stump pulling or rock climbing but i like to yeehaa in the mud every once in a while soo i think i keep them on the motor.

I forgot to mention the springs in the original post as one of the parts that i replaced.... the spring that were in there for the solid cam would have eaten my cam in bout 10 secs ... i replace them with a set of stock springs from an old truck 350 that i had lying around.

Oh... i forgot to ask... you mentioned align boring if i go with new main studs. Should i have that done if i just purchase new main bolts?

Thankyou all for your help and advice.

I'll post some pics as i move the project forward... i just got a fancy new digital camera soo i'll finally get to use it for something other than family pictures [img]images/icons/wink.gif[/img]

T.
post #7 of (permalink) Old 04-19-2002, 06:04 AM
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Re: Rebuilding sbc400 ... looking for some parts advic

How would the 4x4 Comp Cam work with 10.5 to 1 pistons?
post #8 of (permalink) Old 04-19-2002, 07:58 AM
ratlover
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Re: Rebuilding sbc400 ... looking for some parts advic

About the head studs, you shouldnt have to worry about stripping the block. If you say that you will be yanking the heads much I would look into it further. Do you have enough room to pull the heads with the motor in the truck? With the studs you need to pull the heads staight off the studds and with the lenght of them sometimes you dont have enough room to clear booster and the like.then you gota unthread them all or yank the motor wich is all a PITA....just something to think about as a dissadvantage. And be carefull when installing heads with head studs....its very embarasing when you get your shirt over the stud and drop the head into place trapping yourself because you dont have enough azz to yank it off cuz it has bound with the shirt in there and you got to crawl out and get a friend to help you free your shirt[img]images/icons/blush.gif[/img][img]images/icons/wink.gif[/img]
post #9 of (permalink) Old 04-19-2002, 04:53 PM
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Re: Rebuilding sbc400 ... looking for some parts advic

Kendog, with 10.5:1....well, no Xtreme 4x4 cam needs THAT high compression. But if you run on race fuel I guess the 4x4 cam and 10.5:1 comp runs very good[img]images/icons/smile.gif[/img]

Andreas
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post #10 of (permalink) Old 04-25-2002, 01:38 PM
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Re: Rebuilding sbc400 ... looking for some parts advic

I should end up with between 10.5-10.8:1 with the pistons i am installing. I live in the great white north(canada) and pump gas with 92-94 oct is available at every gas station. Don't know how you yanks live with your pump gas [img]images/icons/wink.gif[/img] Hopefully it will run VERY GOOD!!!
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