|06-14-2005 08:52 AM|
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.
|06-13-2005 06:47 PM|
i know what your saying, i like these http://www.paceparts.com/index.asp?P...D&ProdID=24756
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 ?
|06-13-2005 06:08 PM|
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!
|06-13-2005 03:57 PM|
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.
|06-13-2005 03:32 PM|
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.
|06-13-2005 10:54 AM|
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.
|06-13-2005 10:16 AM|
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 ?
|06-13-2005 08:32 AM|
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!.
|06-10-2005 05:32 PM|
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..
|06-10-2005 05:13 PM|
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.
|06-10-2005 04:22 PM|
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
i'm guessing you have a big block C10 P/U ? you have any pics ? any advice about building one ?
|06-10-2005 03:58 PM|
|454C10||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.|
|06-10-2005 02:59 PM|
1st thanks for taking the time to spell all that out for me. i Hate to ask more dumb questions, butt other wise i won't know. was you figures with this piston ?
http://www.northernautoparts.com/Pro...tModelId=10718 piston part # H617CP30 ? 10.26:1 CR not counting piston in the hole or the head gasket.
|06-10-2005 02:18 PM|
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).
|06-10-2005 01:07 PM|
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 ...........
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,
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