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Old 04-04-2010, 04:46 PM
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350 chevy heads 1.6 rocker arms

first off this is my first post, though i have browsed here quite often as a guest, and have found a lot of good info.

anyways i have a set of stock 350 heads about 1977' or 1978, im building a pretty peppy motor for my 78 nova i plan on keeping it on the track.

heres the cam i have http://www.summitracing.com/parts/LUN-30108/

and here are the springs and rocker arms im looking at http://www.summitracing.com/parts/CCA-982-KIT/
http://www.summitracing.com/parts/CCA-RP1416-16/

the comp cams manual says i have to have guide plates with these rocker arms but i have been told by others i may not need them. could anyone help me with this?

i know the best thing would be get a new set of heads but budget for now wont allow it.

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Old 04-04-2010, 05:34 PM
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Hi,
For what your spending for cam, springs, & rockers, you could buy a set of vortecs, then save for the smaller priced items.
Rich
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Old 04-04-2010, 05:56 PM
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Quote:
Originally Posted by zackary027
first off this is my first post, though i have browsed here quite often as a guest, and have found a lot of good info.

anyways i have a set of stock 350 heads about 1977' or 1978, im building a pretty peppy motor for my 78 nova i plan on keeping it on the track.

heres the cam i have http://www.summitracing.com/parts/LUN-30108/

and here are the springs and rocker arms im looking at http://www.summitracing.com/parts/CCA-982-KIT/
http://www.summitracing.com/parts/CCA-RP1416-16/

the comp cams manual says i have to have guide plates with these rocker arms but i have been told by others i may not need them. could anyone help me with this?

i know the best thing would be get a new set of heads but budget for now wont allow it.
Hi Zackary. First off, do you have the 10.5:1 to 12.0:1 static compression ratio that it will take to support this cam? Next, will you have suitable fuel available to run the motor at this static compression ratio? Next, I would never use those fosdick rockers. The rollers will skip across the valve stem and not do any better job than a conventional rocker, other than maybe having a true ratio. The trunnion still uses the 50+ year old ball and socket technology that heats the oil and produces excess friction. If you want to spend some money on roller rockers, get some that have a roller trunnion. They will free-up about 20 hp and will also lower oil temps.

The other question I have is....why us some oddball Comp springs that require cutting the spring seat in the heads? Lunati makes a spring that is a drop-in that is specified for that camshaft....
http://www.summitracing.com/parts/LUN-73943K1LUN/

As far as controlling lateral movement of the rocker tip, is there some reason the stock pushrod guide holes in the head will not work? I mean, this cam has little more lift than stock. And by the way, don't start with some dismal lift like this and then try to crutch it with higher ratio rockers. The lifters have enough of a job to do without having to fight with the shorter lever length of a 1.6 rocker.
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Old 04-04-2010, 06:23 PM
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thanks for the quick answers, the cam was given to me brand new, was the only reason i was going to use it, if you have any suggestions im open to all and any, this is the first one i have ever built by myself. my block is a 350 4 bolt main, 40 over, a stock stroke crank, with 5.7 rods machined for arp rod bolts, edelbrock performer rpm intake power range from 3500 - 5500 i would like to match my top end to this.

id like to have a strong cam

want to run a set of flat top pistons, been told the summit racing rebuild kit is nice any advice?

i know this is a little off my main topic and i apologize, but from the answers i received looks like i need to alter my game plan.
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Old 04-04-2010, 10:33 PM
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What is the casting number of your heads? All the 77 78 production SBC heads were pretty sad in terms of performance.

Yes they can be set up for 1.6:1 rockers. Many 78 era heads have a pushrod guide slot machined right in the cylinder head. This slot often must be lengthened a bit towards the rocker stud when using 1.6 rockers. The push rod gets closer to the stud.
Some, with screw in studs and guideplates. (L-82 corvette) have guide plates that can be readjusted if nessessary.

With .517 net valve lift, the retainer to guide boss/seal clearance must be checked. The guides may need machining to shorten them.

If you want to use these heads keep your performance expectations modest.
The ports suck, the 76cc chamber shape sucks. The casting quality sucks. Doesn't leave much to work with.
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Old 04-05-2010, 06:35 AM
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so my best bet is to go ahead and pony up for a set of vortecs, which kinda sucks, being i have an intake,headers, and valve covers for the older style heads.
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Old 04-05-2010, 07:14 AM
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Quote:
Originally Posted by zackary027
so my best bet is to go ahead and pony up for a set of vortecs, which kinda sucks, being i have an intake,headers, and valve covers for the older style heads.
If you want a streetable 325 HP, those heads can deliver it. If you want more, the Vortecs or aftermarket are the best way to go.

But that cam is not what you need. All it has going for it is the price. Spending for a Summit brand (et cetera) cam and lifter set will put you light years ahead of the game, than using the free cam, IMHO.

You should look into the rebuild parts for your engine. One of several considerations is to get FT pistons w/the 1.560" pin height, not the "rebuilders style" slugs w/the pin at 1.535"- 1.540" (whatever they are). Or, if you do get them, plan on decking the block if needed to get a decent quench figure around 0.040".
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Old 04-05-2010, 07:24 AM
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so if i go with the pistons w/the 1.560" pin height, i wont need to deck my block?

oh and i will run on pump gas
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Old 04-05-2010, 07:39 AM
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Quote:
Originally Posted by zackary027
so if i go with the pistons w/the 1.560" pin height, i wont need to deck my block?

oh and i will run on pump gas
I can't say if the block will need decked, but the "taller" pistons will help allow good quench w/o the need to mill the block- or mill the block as much- if you follow me.
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Old 04-05-2010, 08:55 AM
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can a mod change the title of the thread to 350 build help?
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Old 04-05-2010, 09:28 AM
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You DON'T need to run Vortecs, there are a LOT of other good heads that you can run with the intake et cetera that you already have. Even a set of double humps with some bowl work would be good to 400hp and can be had for about the same price as used Vortecs, a little cheaper if you look hard enough.
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Old 04-05-2010, 10:02 AM
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Quote:
Originally Posted by zackary027
so if i go with the pistons w/the 1.560" pin height, i wont need to deck my block?

oh and i will run on pump gas
I'll explain what's goin' on.
The distance from the centerline of the main bearing bore in the bottom of the block to the flat decks of the block where the heads bolt on is called the Block Deck Height. On a small block Chevy, this distance is nominally 9.025".

When we choose parts for rebuilding a motor, we try to get close to the block deck height so that we will have a good squish without excessive cutting of the block decks. On a 350, for instance, we know that the stroke radius is 1.740" (half the stroke of 3.480"), the rod length is 5.700" and the compression height of a good quality piston is 1.560". If you add the stroke radius, rod length and piston compression height together, you will have the measurement of the "stack" of parts that you're going to use. The examples given here add up to 9.000", leaving the piston down in the bore about 0.025" at top dead center. When you add a conventional 0.040" composition gasket, the squish ends up at 0.065" (0.025" plus 0.040") which may be a little too wide for a good squish. So, you cut the block decks 0.025" for a "zero deck height" and the squish becomes 0.040", just the thickness of the gasket. You can see that if you used a shorter (cheezy) piston, you'd have to cut even more off the block decks to get a good squish. The more you cut off the decks, the more you have to cut on the heads and intake manifold to get them to fit properly and the whole thing turns to dog poo.

Squish is the distance from the piston crown to the underside of the cylinder head with the head gasket in place. A good target for this distance on a streetable small block Chevy is 0.035" to 0.045". A tight squish such as this will generate high turbulence in the chamber just as the plug is firing, homogenizing the fuel/air mixture for a complete burn. This in turn will allow the use of pump gas with a reasonable static compression ratio.

In my opinion, 9.5:1 to 10.0:1 is a reasonable SCR for a street motor on pump gas. The camshaft needs to be matched closely to the SCR.
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Old 04-05-2010, 10:16 AM
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ok that clears things up.
i have a few more questions.

i have already had the machine work on the block done. can the block be zero decked after it has been bored.

can anyone provide a link of a good piston to use.

and if i do have the block decked do i also have to have the heads done as well?
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Old 04-05-2010, 10:27 AM
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Quote:
Originally Posted by zackary027
ok that clears things up.
i have a few more questions.

i have already had the machine work on the block done. can the block be zero decked after it has been bored.

can anyone provide a link of a good piston to use.
Yes, you can cut the block decks after boring, but you need to measure everything to insure you cut the correct amount.

In order to choose a piston, you need to figure out the static compression ratio you will use in the motor. It takes 5 values to compute the SCR....
Cylinder cc's
Combustion chamber cc's
Piston deck height cc's (this will be zero if you choose a piston that will be at zero deck height)
Gasket cc's
Piston crown configuration cc's

Let's say you had a 350 that you bored +0.030". The cc's in the cylinder would be 727. What are the cc's in the combustion chambers? Will this be a street motor? Street/strip motor? Strip only motor?
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Old 04-05-2010, 10:35 AM
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im not sure about the combustion chambers i may be trying to find a new set of heads, vortecs, or double hump heads, im not sure i can get enough out of my curent heads.

i think my curent ones are 76cc with 1.94 - 1.60 valves

btw i really apreciate all the good info and help, this is the first "performance" motor ive built, i want it done right the first time.

im leaning towards street/strip a little heavy on the strip
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