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Old 04-13-2010, 03:49 AM
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ok, I gotta ask... what is the deal with the bowtie? is it the newer version of the old SBC 400? to my understanding, acquiring a 400 SBC is almost impossible... i see pretty good deals for the 400 bowtie block but weary about pursuing it which is why i elected to build the 383 stroker. are there any advantages/disadvantages to this block. thus far, not too many people I talked to know about this motor.

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Old 04-13-2010, 08:54 AM
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the bowtie block is chevrolet's version of an aftermarket performance block. they can be made for anywhere from a 350hp rating all the way up to a 700hp rating in the SBC. but personaly if i were thinking about going with an aftermarket performance block i think that i would buy a DART SHP block and i wouldn't go with just a 400ci motor, i would end up buying a 3.875" crank and build a 415 (standard 4.125" bore, 421 @ 4.155") or since these blocks come pretty much ready to use at standard bore and only need to be honed to what the piston diameter is then i would probabaly go with a 4.000" crank and build a 428 (standard 4.125" bore, 434 @ 4.155") other wise i wouldn't waste the money on an aftermarket block, most people who buy them do it because they are capable of holding alot more hp/tq and mainy that they can stroke them out farther than you can stroke a stock block out. they can also be bored out father than your typical gm 400 block, a typical 400 block really shouldn't be bored out father than .040 but some push the limit by boring them up to .060 but i wouldn't recomend this, i've heard of these aftermarket blocks being bored out as much as 4.250" with a 4.000" crank creating a 454sbc. the bowtie block is good but just like everything else with the chevrolet emblem on it you're gonna pay for, and i've not heard of them doing what the DART or World aftermarket blocks are doing as far as hp/tq numbers and stroke and bore combinations.

chevrolet has come out with heads with the bow-tie emblem on them to, they perform ok, but todays aftermarket head manufacturers out perform them all day lone. last year i bought a set of L-84 (i think thats what they were) with tiatanium vales, and bookoo machine work done to them, they came off a circle track motor. i bought them for 300.00, took the valves out and springs out, sold them for 950.00 then sold the castings for another 200.00, that is what paid for the heads i have on my motor now.
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Old 04-13-2010, 10:11 AM
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very insightful, i've read alot about the dart SBC components... i'm curious to know how do you calculate displacement from from the type of crank used? in your last post about the 400ci SBC, said you would rather use a 3.875" and make a 415 (4.125 bore, 421 @ 4.155) I know the bore is the size of the diameter, but is the 4.155" the rod length? next, when choosing a cam and carburetor for your set up what are the critical things one must consider/know? for starters, lets say i want to build a 400-500 hp 350ci with 210 heads. how would i go about choosing the right carb and cam?secondly, it wouldn't be wise for me to put that power house you constructed for me in a convertible. with that being said, i'm going to construct a more milder 383 based of all of the teaching's you bestowed on me thus far and send it to you so you can let me know what you think.
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Old 04-13-2010, 05:58 PM
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ok for the 3.875" stroke crank in a 4.125" (4.125" is the standard diameter of a 400ci sbc cylinder) bore you would get a 415ci motor, most people know this motor as a 421ci motor because you normally see it with a 4.155" ( a standard 400ci sbc bored .030"/ 4.125+.030=4.155"). and for the 4.000" crank it is the same idea. typically you hear of them with a 4.155" bore which makes a 434ci sbc (sbc = small block chevy) but if it was only a 4.125" bore is would be about a 428ci sbc. the reason you would only need to have the bore 4.125 is because it is a brand new block but if you were trying to do this to a used block you would end up needing to bore it out, and stroker clearance it, but neither of these two stroker cranks is recomneded in a GM production 400 block, only in an aftermarket block. as far as rod diamete goes, a stock 400 uses a 5.565" rod but most will tell you not to use these in performance build a stock 350 has a 5.7" rod these can be used but i would still recomend going after a set of aftermarket rods, then you have the 6.0" rod these are typically for high hp motors, but honestly they aren't needed untill you get up into say 600+hp, but if i were building one of the strokers i menitoned above i would probably use a 6.0" rod and then compressate it with a shorter compression height of the piston. compression height of a piston is the measurement from wrist pin of the piston ( where the connecting rod connects to the piston) to the top of the piston. all of this goes into account when you caluculating your stack. stack is the center of the crank, we'll use a standard 350 for this so a 350 crank is a 3.48" stroke crank but you have to find the throw of the crank from the center of the crank which is 3.48 devided by 2 = 1.74" now you take the measurement of the rods which are 5.7", so 5.7+1.74= 7.44" now you take the measurement of the compression height which a standard 350 piston is 1.560", 1.560 + 7.44 = 9.000" a standard small block chevy measures 9.025" from the center of the crank to the top of the block so you would now take 9.025-9.000= .025" this would tell you how far down in the whole the piston will be once it reaches TDC (top dead center, piston all the way up in the cylinder) once you go to a 3.75" stroke ( to make a 383) now take 3.75/2=1.875" + 5.7= 7.575" and if you where to put a standard 350 piston in there you would add 7.575+1.560= 9.135" but a small block is only 9.025" so this can't be done. now you would need to go with a shorter compression height pistons, say 1.433" so now take 7.575+1.433= 9.008" now take 9.025"-9.008= .017 that your piston would be down in the whole @ TDC. so know do you understand the compression height, and stroker idea.

i think your idea of going with a mild 383 is good, but 400-500hp is a broad range, a 383 making 400hp will be a bery street friendly motor, but a 383 making 500hp would not be so street friendly, but like the one i have it can be done, and is done all the time.

now for the heads, you menton using 210cc heads for a 350 making 400-500hp, like i mentioned before this is very broad range, if i were building a 350 for 400hp i would use a good set of 170cc intake runner heads, but if i were building a 350 for 450hp i would likely use a 190-200cc heads, and if i were building a 350 for 500hp i would use 210cc+ heads

now for a carb, we will use the 350 again, if i were building a 350 to turn 5500-6000rpm i would use a 650cfm vac sec carb, if i were building it to run 6000-6500 i would use a 750cfm manual sec carb, if i were building it for 7000+rpm i would likely use a 800+cfm man sec carb. for a 383 turning less than 6500rpm i would use a 750cfm man sec carb but if it were on the high side of that range say 6500 +/- 100-200 rpm i would probably use a 850cfm carb

as for a cam, this is very general and can be argued but your advertised duration is what will tell you what the high side of the rpm range the cam is capable of like 6000-6500rpm, but the duration @ .050 will tell you when the cam starts making its power like 2500-3000rpm, and this is also where you will figure out what kind of stall you will need to run as you want you stall speed to be about 500rpm higher than the rpm your cam kicks in so say you have a cam that kicks in at 3000 rpm then you will want about a 3500 stall. another thing about cams is that all maufauctures use the 350ci motor as their reference when they list the rpm range of the cam, so a 3000-6000 rpm listed cam in a 383 will acutally run more in the range of 2600-5600rpm, in 400 it would run more like a 2400-5400 cam, so you have to keep that in mind as well when you are picking out a cam for something larger than a 350. but say you were building a 327 motor then that 3000-6000 cam act more like a 3400-6400 cam. get it. you also have to be aware of what compression you want to run when picking a cam as a cam with more duration @ .050 has more over lap, and will bleed off cylinder pressure, so you would have to have more compression the higher you go up in duration @ 050.

put some parts together that you thing would work for a 383 and send them to me and i will analyze them and tell you what i think and where you are going wrong
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Old 04-15-2010, 07:07 AM
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ok here it is... it's perfect but i need to see where i'm going wrong before i start getting too technical.

www.competitionproducts.com
short block:
-item #CMB350HL-040
- I chose this block because it's fresh pretty much ready to go with all machining and stroker clearances done.

rotating assembly:
-item #350F40
-balanced 383 flat-top 2 pc rms .40 over 4 relief valves
-what's the difference/advantage between the 2 and 4 relief valves?

heads:
-item #AFR1040
-195cc/65cc angle plug
-what the difference between angle and straight plugs?

cam:
-item #CL110971
-hyd flat tappet
-lift .470/.470
-duration @ .50 .236/.236
-adv. duration .302/.302
-lobe center 108
-is advanced duration the max for that particular cam?
-for lobe center, how does it angle affect combustion? also, is lobe separation the space between each lobe?

carburetor:
-item:0-80670
-650 cfm
-electric choke
-what are the advantages of man/elec choke?

intake:
-item #52020
-6500 max rpm's
-dual plane

-it didn't state the rpm's for the cam but I figured i'd run a 3500-4000 stall to be on the safe side...

I found all items on competitionproducts...
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Old 04-15-2010, 09:24 AM
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okay here we go, i would recomend not going after an block out of a warehouse, i when you get home i would lolk on craigslist and your local classifieds for a 1 peice rear main seal block a block that is a roller block say 1987 and newer so you can run a OEM style roller cam and lifters, even though you will need to get it machined you will end up spending less money, and i would never pay 1100 for a block that is already bored .040 over.

the rotating assembly you listed is for a standard 350 not a 383, the crank in the kit you listed is a 3.48" stroke crank you are looking for a 3.75" stroke crank, look into scat for one of their nodular steel kits, scat is the best you can buy as far as steel and iron cranks go, that is untill you get up into forged cranks, i dont think you need forged.

a typicall 2 valve relief piston has a negitive 4cc valve relief notches cut into the top of the piston, a 4 valve relief typically has about a negitive 7cc valve relief cut into the pistons, i would look more for a negitive 18cc D dished piston, not a flat top for your application if you want to run pump gas, the -18cc will put your compression around 9.6:1 look for a rotating kit that uses keith black hyperuertic pistons, eagle also makes good nodular steel 383 kit, and i know that most of their kits use the KB pistons.

the heads you picked are good but stay away from angle plug heads you want straight plug heads, and angle plug head makes it hard to run a large primary header due to clearance issues.

as far as your cam, the duration @ .050 is pretty good with 236/236 and it was a smart move going with a single pattern cam cause the AFR heads flow very well on the exhust so the added duration from a dual pattern cam is not not needed but you will want to run headers with atleast 1 3/4" primaries so you can get that exhaust flow to the exhust pipes. but i would like to see you use a roller cam, they are far more durable and you will get a lot more lift out of one, the heads you picked will due better with cam that has atleast .525-.560" lift.

i would recomend a holley 4779 750 double pumper carburator, the 670 might do but since you plan on running this up to atleast 6000rpm i think a 750 would be better and you will get better performance out of a double pumper than you would with a carb that has vacuum secondaries.

the stall you mentioned is a little high you would want to go with about a 2800-3000 stall, remember that you need to look at the recomended rpm range for the cam, i had to go to summit to look up this specific cam to find it but it's 2500-6300, but with a 383 the extra cubes will eat some of the range up so it will act much more like a 2200-6000 cam so remember that you want you stall speed to be about 500 or so rpm above your cams rpm range

this is something like the rotating kit that you are looking for, yo should be able to find one just like this from scat, but remeber you will need to buy the block before and take it to a machinest before you buy the rotating kit so he can tell you what size pistons to get, then you buy the kit, take the pistons to him and have him size the bore to what the pistons are as not all pistons are of exact equal size, example not all 4.030 pistons are the same exact diameter, some piston manufactures recomend different piston to cylinder way clearances so the cylinders will have to be matched to the piston, it can't be dont the other way around ( i guess it could but it wouldn't be smart)
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Old 04-16-2010, 01:01 PM
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I agree that a used 87'-later 350 is the cheaper route, but I figured that if i go through a reputable dealer the I should be good and less work; basically assembly ready motor is the route i was aiming for.

pistons:
-I looked on summit (which is awesome)at those KB pistons but couldn't find one (-) displacement, is normal? as they were all (+).

heads:
-the single plane was unintentional but I learned something.
-as far rockers, I've seen kits with 1.5 and 1.6. is this normal? and what is the advantage of having different rocker sizes?
- i know that .600 is max lift and it is suggested that you stay at least .020 below, with that being said, how do you set the springs and measure lift/height?

carburetor:
-what the difference between having a electric choke vs. a manual?
-what are vacuum, secondaries?

***thanks for all the insight...
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Old 04-16-2010, 02:05 PM
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these are the pistons you want, i think the ones on summit are the same thing they just have a typo, KB135040 are the exact pstons i am running in my 500+hp 385 mid 11 sec car, but i have had my heads milled .040 to take the combustion chambers from 64cc to 58cc to raise my compression

http://www.kb-silvolite.com/test/kb_...etails&P_id=93

the difference between 1.5 rockers and 1.6 rockers is that 1.5 rockers are standard small block rockers and all cam maufacturers list their cam lift under a 1.5 rocker ratio, but a 1.6 rocker ratio is 1.0666 X the ratio of the 1.5 rocker, so you get more lift. example take a .500" lift cam and put 1.6 rockers with it and you will end up with a .533" lift, since i have a very good flowing set of heads and they have great exhuast flow as well as i'm using a dual pattern cam i use 1.6 rockers on the intake and 1.5 rockers on the exhuast, the cam i use is .525" so my acutal cam lift is int= .560", exhaust= .525". if i were running a stock or slightly modified stock head i would use the 1.6 rockers on the exhaust side as well.

if you buy heads already assembled then you wont have to put the springs in, but the way you would meausre how much clearance you have in your springs while the cam is at full lift would be to turn the crank untill the cam is at full lift, then take a feeler gauge and check how much space you have between your coils, you're safe at .010" as long as the coils dont get so supress that they bind.

as far as carburators go, i'm a holley man so i will tell you about them, an electric choke carb has an external part that electriclly closes the primary butterfly so you don't have to worry about it, these are good for regualer street use, a vacuum secondary is just how it sounds, there is a vacuum line comming from the intake manifold that hooks into the dristributor for the vacuum advance, but it also T's off and hooks to the carb so that when the rpms are raise the motor makes more vacuum and this tells the carburator to open up the secondary butterflies beacuse the motor needs more fuel and air, a manual secondary carb has a linkage that hooks from the primary butterflies and when the primary butterfly opens so far due to the throttle being pushed in farther then it manually opens the secondary butterflies cause the motor needs more and fuel to run the higher rpms. vacuum secondary carbs are great for street use and saving fuel, but they dont make them in a true double pumper so they dont make great high hp/ racing carburators, this is why most all racers go with a manuall secondary carb like the 4779 750cfm holley double pumper, this is what i have. the double pumper means that not only does it have a dual feed line (vac sec carbs can have dual feed lines as well but they are not double pumpers) but it also has an accelorator pump (50cc) in the rear bowl and one (30cc) in the front bowl. you can put a trick kit on a carb and put a 50cc in the front as well.

as far as an assembly ready motor, there is no such thing the motor you were looking at will still need to go to the machine shop with the pistons to get honed to the correct size for the pistons, remember what i told you about that. you will spend less money buying a used block and having the machinest take care of it for you, you should be able to find an old roller block for around 100.00 then take it to the machinest, get him to tell you what it needs to be cleaned up, buy the pistons for that, take him the pistons, crank, and rods have him put new cam bearings and freeze plugs in it, bore, bake and glaze it, possibley deck it, and then he can balance the rotating assembly, all this machine work should cost you less than 700.00, 800.00 if you include the price of the block, plus you will have had the rotating assebly balanced. but if you buy the motor you were talking about you will still pay 200-300.00 the rotating assembly to be balanced and you will pay another 100-150 to have the bores honed to the pistons, so now with a 1100.00 block + 150.00 + 250.00 = 1500.00 that is twice as much, i can almost have the short block (block and rotating assembly) put together for that. and also like i mentioned before i would never pay 1100.00 for a block that is already .040 over cuase the possibility of it being rebuilt later is minimal as another .020" (to equal .060") over may not clean the bore up and you should never go more than .060" over on a standard block. i hope this makes sence, i would seriously stay away from a $1100.00 .040" block, serioulsy
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Old 04-16-2010, 02:17 PM
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Quote:
Originally Posted by my87Z
as far as an assembly ready motor, there is no such thing the motor you were looking at will still need to go to the machine shop with the pistons to get honed to the correct size for the pistons, remember what i told you about that. you will spend less money buying a used block and having the machinest take care of it for you, you should be able to find an old roller block for around 100.00 then take it to the machinest, get him to tell you what it needs to be cleaned up, buy the pistons for that, take him the pistons, crank, and rods have him put new cam bearings and freeze plugs in it, bore, bake and glaze it, possibley deck it, and then he can balance the rotating assembly, all this machine work should cost you less than 700.00, 800.00 if you include the price of the block, plus you will have had the rotating assebly balanced. but if you buy the motor you were talking about you will still pay 200-300.00 the rotating assembly to be balanced and you will pay another 100-150 to have the bores honed to the pistons, so now with a 1100.00 block + 150.00 + 250.00 = 1500.00 that is twice as much, i can almost have the short block (block and rotating assembly) put together for that. and also like i mentioned before i would never pay 1100.00 for a block that is already .040 over cuase the possibility of it being rebuilt later is minimal as another .020" (to equal .060") over may not clean the bore up and you should never go more than .060" over on a standard block. i hope this makes sence, i would seriously stay away from a $1100.00 .040" block, serioulsy
Just to prep a used block you're looking at an easy $750 at a good machine shop for just the block work- if they don't half *** it. He will not need to have that block from CP honed, just need to clean off the light oil (there to prevent rust), and assemble. Its actually a pretty decent deal for that block.
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Old 04-16-2010, 02:49 PM
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ok, sounds good. thanks for the insight/tips as all ways...
I will stay away from pre-bored blocks. I think i have the knowledge to put a better combination together for next post as I am en-route back to the states (3 weeks left) and i'm excited about putting together my first SBC. all the post have been truly insightful. I have never learned so much in a short a mount of time about a SBC as I have here over the last couple weeks... so thanks. like i said, my next post will better defined for my pending application...
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Old 04-16-2010, 02:50 PM
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like everything from area to area, machine shop costs are different, here where i live i can have the block completely preped for rebuild for about 500.00 then the balanceing is usually 200.00, and these guys come well recomended by the majority of racers in this area. we have a few machine shops right in town but i drive about 40miles or so just to go to this one. and i have never heard of a block not having to be honed for the pistons, as not all pistons are exacatlly the same in diameter even when it comes to buying one brand of .040 pistons to another brand of .040 pistons.

AP you're telling me that you would pay 1100.00 and then another 100.00 to have it shipped to a local parcel warehouse for a block that was already bored .040, i haven't looked into what the cylinder wall thickness of these blocks are or if there is anythng specail about them, i'm pretty much taking them as a standard GM block that has been bored .040" with new freeze plugs and cam bearings in them. but honestly would you pay that for one of these
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Old 04-16-2010, 02:51 PM
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Originally Posted by youngsavage
ok, sounds good. thanks for the insight/tips as all ways...
I will stay away from pre-bored blocks. I think i have the knowledge to put a better combination together for next post as I am en-route back to the states (3 weeks left) and i'm excited about putting together my first SBC. all the post have been truly insightful. I have never learned so much in a short a mount of time about a SBC as I have here over the last couple weeks... so thanks. like i said, my next post will better defined for my pending application...

okay shoot it over when you're ready
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