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350 SBC Build Help

22K views 25 replies 7 participants last post by  454C10 
#1 ·
i'm looking for some advice and help,


my son and i are going to build a 1971 Chevy 1/2Ton p/u, it has the original 350 in it with the three on the tree, this is going to be a strong budget build / weekend driver/no real hwy runs, prob might give it hell once :D . I would like to end up with a 10.1 CR motor, nice cam, roller rockers, edelbrock RPM Performer intake, Qjet, MSD ign, headers, 350 turbo tranny, torq converter around 2400 to 2700RPM and 373s in the rear, (the truck is in N Carolina and i'm in Nebraska, i won't have a dime in the truck or transport to Nebraska, grandpa gave this to my son, and we are in the car transport business) butt it's not here yet to get # off block ect. or see what the inside of the motor looks like.

Plan:
i can buy a set of SBC 76cc heads with stainless valves 2.02 160 they were off a 383 stroker for about 3000mi, and the guy traded them for a set of aftermarket heads, i can get them for $250.00 then i was looking at the speedpro hypereutectic pistons they are $240 a set that gets me into the 10.3.1 CR Range, (Speed-Pro Hypereutectic Piston # on jegs 844-H617CP30 http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=4394&prmenbr=361 this piston CR is not figuring head gasket & piston in hole for the quench.

right or wrong i would like the 10. to 10.5.1 CR range. i plan to just recondition my rods and do what ever work needs done to the block & crank, (i'm looking for budget priced pistons,cam, roller rockers, intake and torq converter, even a used intake & headers and roller rockers if i can find em is ok ) is there good pistons for less money ? what cam would you pick for this setup ?

ok what CC heads would you guys run on a 10.1 CR 350cid motor ? you like the 76CC heads ? is $250 a good price ? what setup would you oldschool guys recommend for what i'm building ?

i would like to hear everyone opinion on this build from carb to pan, where i some places to buy my parts reasonable (or cheap, not so cheap thay are junk)......

all help invited





thanks all
 
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#2 · (Edited)
i would go to racers outlet at ebay motors.i got my crank from jegs for 195.00.eagle cast steel good to 500 h.p.and they have know shipping charges.atracers outlet i got new eagle rods good to 500 h.p. for 179.00.i got the speed-pro hyper. pistons of your choice for your build 179.00.if you get it all at one time kevin will treat you right on the shipping charges.i think i paid 700.00 for my 406 rotating assembly.get the new much better heads just out from gm for not much more than you are going to give your buddy and you can't beat the power from these heads for the price.and i'm not a vortec person.you will do much better to buy all this stuff new for not much more than you were going to spend and not have to deal with some of the machine work.you should not have to grind the rods for cam clearance cause they grind the throws on these new cranks for piston and cam clearance before you get them so you don't have to but check the clearance anyway.trust me you will make out much better this way.compare racers outlet prices to jegs and you'll be amazed.i was.i live up the freeway 1 mile from jegs main store and like them alot,but you can't beat the prices at racers outlet.also i have 3/4 ton van and got an 11" pro street converter from coan engineering with 2800-3200 stall and it works great.you may want to check them out.
 
#4 ·
im in Elwood Ne, 15mi south of I80 at the Lexington Ne. exit. i worked for a company that had a main office in Holdrege Ne. and a office in norfolk too, i've spent my share of time in Norfork Ne. (i was in norfolk Ne this last march my wife bowled state there) been to the wine & wings in pierce too.



Go Big Red



Mustangsaly
 
#5 ·
Hard to get that much cr out of a 350 with 76cc heads. The head gasket adds 8cc and the piston in the hole adds about 4cc. Do the math.

You will need 64 cc on a 350 to make that cr.

76cc heads will do a good job with a 383 or 400.

You should set the cr to the cam that you want to use. First determine which cam you want then make the correct compression ratio (not the other way around).

A 10:1 engine needs a pretty big cam to run pump gas. Between 230 to 240 degree of duration at 0.050.

9.5:1 cr with a cam in the 220-226 range with a 383 rotating assembly and the 76cc heads would be a good combo for your truck
 
#7 ·
think 10.25:1 CR is to much ? or will it be that high cause, if 454C10 is right The head gasket adds 8cc and the piston in the hole adds about 4cc = 12cc + 76cc = 88cc heads. or is the 10.25:1 piston have the extra 12cc figured in ?

thanks

Northern Auto Parts said,

Yes, we can substitute pistons on these kits to roughly achieve a
compression ratio of 10.25:1. In order to accomplish this, you would
need a piston with a .275 dome (H617CP). The upgrade on the street
performance kit would be $106.40 for a total of $566.39.


However, there is one note of caution in using this configuration. Compression ratios in excess of 9.5:1 are NOT recommended for use on pump fuel unless you are running aluminum heads. The extra 5 horsepower you may achieve may not worth be the trade off of $5 per gallon race fuel. If you have any more questions, feel free to call us at
800-831-0884.

-----Original Message-----

Mustangsaly Asked:

i was looking at this kit, Chevy 350 (to 1985) STREET PERFORMANCE -
HP350KHW Hypereutectic Pistons with Scat Crank.
http://www.northernautoparts.com/ProductModelDetail.cfm?ProductModelId=1
1497 Hypereutectic pistons... can substitutions be made on pistons ?
pistons i need are .30 over, and i'm wanting around 10.1.1 to 10.5.1 CR
Hypereutectic Pistons with 76cc heads, a i haven't picked a cam yet, .......






http://www.northernautoparts.com/ProductModelDetail.cfm?ProductModelId=11497
 
#8 ·
No, 10.25:1 is not too much if the cam your use is over 240 degrees duration at 0.050". However, it would be too much if you plan on using a smaller cam. And I think you should use a smaller cam if this is going into a truck with 3.73 gears. Like I wrote earlier, a cam between 220 and 226 duration at 0.050 would be about right.

That "9.5:1 cr using iron heads with pump gas " is a VERY general guideline and depends greatly on the valve events (cam). A super simplified guideline for the novice engine builder.

I have a 11.0:1 350 sbc engine with iron heads that runs great on pump gas without the need of any timing retard because the cam is large enough to bleed off cylinder pressure (late intake valve closing point).

On the other hand, I have a 9.0:1 cr 454 that will detonate if I turn the timing past 40 degrees even with 93 octane. The reason is because the engine makes a lot of cylinder pressure from a short duration camshaft.

Both engine produce about 180 psi on the compression gage. Don't confuse cylinder pressure with compression ratio.

So, you should figure out the dynamic compression ratio, which uses the static compression ratio and the valve timing events. Buy a how to modify a sbc book and you can read it for yourself.

FYI, when buying pistons, the cc of the head should be listed along with the compression ratio of the piston.
 
#9 ·
I'd go with a milder stall converter if you want any decent mpg, or swap in a manual, I'd go with typical 3.55s for a good balance of performance and affordability.

gas isn't cheep anymore. If it were, I'd say run 4.56s for all I care.
 
#11 ·
You can do this cheap without any problems.

A summit racing cam and lifters for 100.00
Get a summit racing double roller timing chain
Get the oil pump and gaskets from autozone (melling pump and felpro gaskets)
Have the rest done at the machine shop. (resize the rods, press on the pistons, clean the block, install the freeze plugs and cam bearings, turn crank, bore the block, freshen up the heads)
Get the bearings from the machine shop (M77's)
Could have the machine shop asssemble the engine also for 200.00.

Make sure the springs on the heads can handle the cam profile.

Get a high volume fuel pump.

A little bowl smoothing under the valves at the head/valve seat inferface will make another 20 hp!

No need to balance the engine.

I don't think a q-jet is a good choice for the performer rpm intake. The performer rpm is set up for a square bore carb (holley) not a spread bore carb (q-jet). A holley 750 w/vac secondary (3310) would make a nice combo with the performer rpm intake. The regular performer (not rpm) intake will mount to a q-jet.
 
#12 ·
i have a fresh set of 76cc heads that come off a 383 that had 3000 mi on them, is a 10.25:1 CR SBC Motor with 76cc Heads with stainless 202 160 valves a good choice ? Heads cost $250 think thats a deal ?
(if im right it will end up less than the 10.25:1 CR when you figure the piston in the hole & head gasket)

does anyone have any sbc heads that are runable or don't need a much, or won't cost a bunch at the machine shop they want to sell ???

Heres a Link You Pick what you think is right 4 my build,
what cam , lifters , timing chain , gaskets , oil , pump , would you pick 4 my setup ? motors not apart yet, so woud wait & see or just put new rods & crank in ? there not big bucks. scroll down to pick ...........
http://www.northernautoparts.com/Pr...ductModelId=380
what do you think of my cam choice ?
Comp 1800-5800 RPM # 12-211-2 270/270 adv duration .470/.470 lift Valve Springs must be changed,Not Computer Compatible + $76.55

Are the 76cc Heads the Best Choice for a 10.1 CR motor ?
engine asembly isn't a issue,

Thanks

Mustangsaly
 
#13 ·
Yes, that is a pretty good cam. However, if you are on a budget you should get a summit cam and lifters for 79.95. sum-k1104 or sum-k1105. Comp lifters are another 86.00.

It is a good idea to run more cam duration on the exhaust valve due to typically low flow ratios (intake/exhaust) on stock exhaust ports, plus heavy cars with small engines like more exhaust duration. (good for a truck with a 350)

The heads sound like a good deal but they still need to be freshened up even through they have low miles. A valve job is really cheap if the heads are in good shape (less than 100.00). Plus I would add 1.5" OD springs with new retainers which will require machining. If the heads have 2.02/1.72 valves, the springs may already be 1.50". I would also install screw in studs. When spring pressure get higher, the studs will pull out if they are the press in type.

Here is how to figure compression ratio:

355cid (+0.030 over 350) is 44.375 cid for each cylinder. (355 cid/8)

44.375 cid is 727cc's (1 cid = 16.387cc's)

CR = biggest volume/smallest volume

biggest volume is: (volume with piston at bottom of stroke)
cylinder = 727 cc
head = 76 cc
gasket = 8 cc
piston recessed in block 0.020" tyipical for sbc = 4 cc
piston recess (+) or dome (-) = flats top about +1cc because of valve relief

smallest volume is: (volume with piston at top of stroke)
head = 76cc
gasket = 8cc
piston recess in block = 4cc
piston recess or dome =?

so a 350 with flat tops, 76cc heads, standard felpro gasket, and the piston in the cylinder 0.020" at top of stroke will have a cr of:
(727 + 76 + 8 + 4 + 1) / (76 + 8 + 4 + 1) = 816/89 = 9.17:1

So, to get 10.0:1 you would need more cylinder volume or smaller cc heads or a dome in the piston.

a 64cc head would give you:
(727 + 64 + 8 + 4 + 1) / (64 + 8 + 4 + 1) = 804/77 = 10.4:1

a 383 cid stroker kit with 76cc head would have:
(784 + 76 + 8 + 4 + 1) / (76 + 8 + 4 + 1) = 873/89 = 9.8:1

a 350 with 8cc dome pistons and 76cc heads would have:
(727 + 76 + 8 + 4 -8) / (76 + 8 + 4 -8) = 807/80 = 10.1:1

A 350 with a zero deck height block (block deck cut so the piston is flush with block), flat top pistons and 76cc heads would have:
(727 + 76 + 8 + 1) / (76 + 8 + 1) = 812/85 = 9.6:1

A 350 bored 0.060 with a zero deck height, flat top pistons and 76cc heads would have:
(737 + 76 + 8 + 1) / (76 + 8 + 1) = 822/85 = 9.7:1

It is always better to use flat top pistons because flame travel is quickest across a flat surface. Domes and dishes slow down flame travel and require more ignition timing advance to complete the burn.

A zero deck block, +0.060" bore, 76cc heads with flat tops might be a good way to go. 9.7:1 will work well with a moderate street/strip cam (220 to 230 degree duration).
 
#15 ·
I went to that site and the piston spec doesn't spell out the dome volume. It specs out the dome height which is not a lot of help because the height is not uniform. However, it does give cr when used with a wide range of cc heads and bore amounts. I would assume the cr given does include the standard 0.040" head gasket and piston recesses. So, that 30 over piston will give you 10.25:1 cr with a 76cc head, but that may be a little high for the cam you want to use. Can you find a piston with a little less cr using 76cc heads? 9.5 to 9.8 would be about perfect.
 
#16 ·
454C10,

what cam would you pick ? theres a bunch of cam choices, i picked that one for the 1800 to 5800RPM Range, thats why i'm askin so i get the right combo, you help is appreciated ! what cam would you pick ?

scrol down to see cams
http://www.northernautoparts.com/ProductModelDetail.cfm?ProductModelId=380

i'm guessing you have a big block C10 P/U ? you have any pics ? any advice about building one ?


thanks

mustangsaly
 
#17 ·
Do you need to buy it from northern? Because summit racing is cheaper for this cam. Cam and lifters for 79.95. The sum-k1104 or sum-k1105 would work for you. I like the k1105 because, like I wrote earlier, "it is a good idea to run more cam duration on the exhaust valve due to typically low flow ratios (intake/exhaust) on stock exhaust ports, plus heavy cars with small engines like more exhaust duration. (good for a truck with a 350)".

So this is know as a split duration cam which normally has more duration on the exhaust than the intake. This makes up for weak flowing exhaust ports and helps little engines in heavy cars. A how to modify a small block book will have all this information in it. You should get one at your local book store.

Yes, I have a 70 C-10. 454 cid with 8.75-9.0:1 cr, Holley 750, very mild roller cam, 781 heads with some flow work, msd ignition, cold air induction, BBC corvette exhaust manifolds, 2.5" exhaust, tachometer in factory location, 4 inch front drop and 6 inch rear drop, 1.125" front sway bar, all new bushings, 5 lug with 15x8 rallies, front disk, 3.08 with alburn LSD, 400TH, AC with 134b, power steering, power brakes, remote and power locks, 2.5" exhaust, runs mid 14's at 98 mph, 4100 lbs, 8 mpg city, 12 mpg highway, factory green but needs paint, sorry no pictures.

BBC's suck gas! The 350 that was in there before did 12/16 mpg.

My advice is to find a truck ready finished and buy it. No way my truck would sell for all the money that I have in it, not even counting the work!! I wish I had installed a used 6.0 LS1 and transmission for a heavy duty gm truck instead of the 454.
 
#18 ·
i just seen northern had that cam (Plus a Bunch of Others) but i liked the 1800 to 5800 RPM, this truck will run headers, (or is there a problem with headers fitting these trucks ? ) this will be a frame off 71, i seen the truck last fall butt didn't pay much attention. what about the 10.25:1 CR i want to run ? think thats good or bad ? ( i'm thinking it will end up being a little lower than that, it's not a daily driver ) 350 turbo tranny with a stall converter with 411s..











Mustangsaly
 
#19 ·
Headers fit fine on these trucks. The problem with these trucks is getting the exhaust around the rear axle.

Well, if you are running a 4:11 and 10.25:1 cr then you should go up a little in the cam. You were talking about using a 3.73 gear before so the smaller cam would be needed in a 4000lb truck. So now, look for a cam in the 230 to 235 duration at 0.050 range (around 280 advertised). But then the valve springs become even more critical. Weak springs with a big cam really kills performance. Valve float is an ugly thing. You need the 1.5" diameter springs (dual springs). Don't use the HP Z28 springs. If you go cheap on the valve springs with this cam, the engine could be down 50hp!

10.25:1 cr with a cam in the 225 duration at 0.050" in a 350 sbc will have detonation issues. Retarded timing would be required even with the high octane pump gas. Power drops quickly with timing retard, so any power gain from higher compression is quickly lost. A bigger cam bleeds off the cylinder pressure and allows normal ignition timing.

The better choice for the street would be, 9.5:1 cr pistons along with the smaller cam (270 comp), 2200 stall, and the 3.73 gear.

Just weekend hotrodding, 10.25:1 cr, 4.11 gears, 2600 stall, 280 cam with good valve springs!.
 
#20 ·
454C10,

sorry i posted 411s butt meant 373s,(thinking one thing and writing another) with 373s in your opinion is that 1800 to 5800RPM Cam a good choice ? plus i was thinking with a starting point of 10.25:1CR, i will end up around 9.7:1 to just under 10.1:1CR or so (i'm guessing) , with head gasket & piston in the hole counted in the formula, what did you do for tail pipes ? what did you do for a fuel cell ? are you running stock height Spindles or 2½" Drop Spindles ? you have a wood or metal bed floor ?

where did you get most of your body and interior and suspension parts ?

Thanks
 
#21 ·
I think the 10.25:1 cr in the piston spec does include the piston down in the cylinder and the head gasket.

Yes, that would be a good cam for a 3.73. You could try the 10.25:1 cr and if it is too high then use a 2mm thick copper head gasket to lower cr.

I ran 2.5" outside the frame rails then over the axle and out the back. This clears the factory style ladder bar suspension.

I used Early Classic Enterprise's rear drop springs and shock reallocator kit.

For the front, I used 2.5 inch drop spindles plus 1" drop springs. The truck has 73 to 78 Chevy truck front suspension (a-arms, 5 lug disk brakes, sway bar, brake lines, etc). Got parts from a local junk yard and the springs, spindles, and bushings from Summit Racing. The rear axles are also 5-lug from a 73 to 78.

The truck has a metal bed (LWB) and the stock tank. I plan on building a fuel cell for myself later and will mount it between the frame rails behind the diff (20+ gallon). The rear mount fuel cells that are made for these trucks are very expensive. So I will make my own from 1/8" aluminum plate.
 
#22 · (Edited)
tell me what you think of the $250 Heads i've found for a 350cid build ?

they have 2" stainless intakes and 1 1/2 stock exhaust valves. The intake ports are gasket matched and the chambers have been polished. They have comp springs and retainers. The heads are clean as the valve job had only about 3000 miles on it. They are 76 cc chambers. They do not have screw in studs or guide plates. Casting # is 3970126.


Thanks

Mustangsaly
 
#23 ·
If you're on a serious budget then those heads will work.
what is the spring diameter?
are the studs pinned?
If the studs are not pinned you need to add screwing studs. The heavy spring pressure required to runs a big cam will pull the studs out. Guide plates are nice while making high rpms.

But, those old heads just don't make as much hp as the new designs. The ports are small and don't flow well. A new set of AFR heads would make 50 more hp than those old style heads with the same parts!

If you can, get a set of 64cc trickflows, dart iron eagles, vortecs, or AFR's. The vortecs are cheapest but require some machining, special intake, special rockers, and special valve covers. But if you haven't bought any parts yet, using vortecs is no big deal.
 
#24 ·
re: heads

Just my opinion, but I don't think those heads are even worth $2.50!! Not to me anyway. 76 cc is to much. It's basically a smogger head. I think what you need for the compresion ratio you want, and for decent power would be a 64cc head with 2.02 intake and 1.64 exhaust. Also something around 200cc intake runners. I think the best "bang for your buck" would be the worlds sportsman 2 heads. both Summit and Jegs sell this head for as cheap as $879 american complete. The heads itself is $599 a pair bare. My dad purchases a pair of these before for his 350 race motor. they prove to be very good quality and you basically can't go wrong with the price. Their is room to port the intake runners if you decide to go a little bigger in you motor displacement or if you decide to turn your motor into something with more power. But the basic setup in my opinion is fine for the street aswell. I'm currently building a 327 for a street/strip car and these are the heads I personally will be using. Also, just my opinion, Their is lots of used carbs out there, I wouldn't use the quadrajet carb. Holly four barrel (or similar styles) are easy to tune and play with. sorry for running on here, good luck!
 
#25 ·
454C10,

i know what your saying, i like these http://www.paceparts.com/index.asp?PageAction=VIEWPROD&ProdID=24756

http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=4243&prmenbr=361

http://www.primediapowerpages.com/c...ages/Customer/Vanity/easy/competitionproducts

but i think i can make a strong street thumper with these $250 heads, those vortecs are $600+ then add intake. when my trucks ready for that serious power i will go that route and use this 350 in something else. i have plenty of other places to put my money in this truck. did you put late model stock type 3point harness seat belts in your truck ? i'm thinking of mounting or welding a seatbelt bracket in upper cab corner, and picking up some belts out of a salvage yard, might be good insurance or peace of mind with my son driving this with a 350 or 375HP motor in this SWB truck. how did running the exhaust on the outside of the frame rails work out ? did it take different headers ?

thanks

Mustangsaly
 
#26 ·
Running the exhaust over the rear axle is not a problem unless the truck is lowered. I'm not using headers so it is easy to turn the pipes quickly outwards to the outside of the frame rails. However, the pipes can always be turned to run outside the rails at any point under the cab.

Nope, just regular seat belts for me. But, I do have bolt holes in the upper cab corners already. ????

I have an idea for you..... Install a set pistons to make 9 to 9.25:1 cr with a 350 and 76 cc heads. Then install a mild cam, like a CompCam 260. This will get the truck running strong, even with the stock 3.08 gears. Good gas mileage, smooth idle, and safer hp for your son. Then you can up the hp later with 64cc heads and a cam after you have spent the money and time doing all the other things that you what to do with the truck. And will give you son time to get familar with the truck with a lower hp. FYI, good brakes, suspension, and tires will keep the truck and your son in good shape

It still would be a 300 hp engine with 350 ftlb of torque with the smogger heads and mild cam with headers. 325 hp with a little bowl smoothing in the heads.
 
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