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408 build... trying atleast

3K views 27 replies 9 participants last post by  my87Z 
#1 · (Edited)
buildin up a 408 and im lost in the motor world now. to start off, it was a built 406 with 305 heads and was suppose to take higher octane then unleaded... =cracked piston. so i bought it and bored to 408. i dont know the cam or specs though and that where i get lost at. i want 400hp on pumped gas to the wheels though and so far its just:

400 block bored .40 over with clean and all that extra stuff
stock crank thats been polished and balanced
.40 over piston but not too sure of the brand or specs at this point (10:1)
holley 750 carb
air gap intake
hooker headers, 3in exhaust and dump offs

would it be better to get a new cam (want a nice lope)that i know the specs and then gets the heads? also which heads (iron) will you think can accomplish this task? and what other parts should be bought to also do the 400hp?
 
#2 ·
You won`t reach 400 horses with 305 heads. Flow is the key to power so the heads play a big role but don`t let this mislead you, the whole combo must work together as a team to make max performance. Unless we know what pistons you have then we really can`t recommend a set of heads, to survive on pump gas the compression ratio needs to be in the 9.5:1 range, the 305 heads have small 58cc combustion chambers and if ran on a 400 with dished pistons and pump gas put the compression ratio over 10:1, detonation likely set in and that`s what took out the piston. Let us know what pistons you have and what your looking to do, street? street/strip? and we can line up a combo for you.
 
#3 ·
Sorry for the confusion, but the car no longer has the 305 heads. When it was with the previous owner it did but since then has been scrapped. Motor is strictly street use and if it ever sees the track, it'll be just to see what time it puts out. Ill go to the shop and see what the specs are one the pistons. Also is there any way to look at a cam and know the specs?
 
#4 ·
soon2be said:
is there any way to look at a cam and know the specs?
See if there's a manufacturer's stamp on the end of the cam, often that's enough to pull up the specs from their website.

If not, it can be carefully measured with it in the engine and with one cylinder mocked up, valve train-wise. You'll want to use a degree wheel and dial indicator.
 
#5 ·
cobalt327 said:
See if there's a manufacturer's stamp on the end of the cam, often that's enough to pull up the specs from their website.

If not, it can be carefully measured with it in the engine and with one cylinder mocked up, valve train-wise. You'll want to use a degree wheel and dial indicator.
seems like alot. think ill be better off going new and knowing what it is then playin the guessing game and being dissapointed when its running.
 
#6 ·
F-BIRD'88 said:
How will you be using this motor? Installed in what?

Are you willing to buy the right pistons to match the heads correctly?

Gear ratio, torque converter stall? willing to match them to a easy to build kick *** street 400sbc combo?

Budget for cylinder heads?

400+.040
O deck the block
stock reground 400 crank
5.7 350 rods. (chev oem type rods with thru bolts will require minor rod/cam lobe clearancing preparation)
KB 147 +.040 Pistons
the rotating assembly must be rebalanced.
felpro 400 heaqd gasket
Comp cams Xe284H-10 cam 1.5 rockers
GM big port Bowtie vortec heads GM pn#25534446
Performer rpm air gap (vortec) manifold. felpro #1255 manifold gasket
1-5/8" long tube headers.
750+cfm carb

92 octane gas
86 monte ss, street machine. No strip but will run a race on street. Thinking about starting over and getting new pistons and going from there. Goal is atleast 400 to the wheels. I have the block work done and crank turned. Is forged internals only necessary if going spray or power adders? Rear end is stock 7.5 with 4.10 gears. Going with 400 turbo tranny. Like I said pump gas is a must. Is aluminum heads only really needed to reduce weight?
 
#7 · (Edited)
Series 40 dual chamber

F-BIRD'88 said:
The trick is to figure out what you want to achieve.
For pump gas on a 400SBC you want a true 10.5:1 cr or less:

flat top 400 pistons: use a 70 to 76cc combustion cylinder head
so if i keep the flat tops and go withthe Brodix IK-200 itll would produce the power im wanting? also and if there forged i can use nos from tiem to time and be ok? will the cr have to change when using nos?
when looking for a cam, will the exact specs on the pistons effect what route ill need to take?

oh and by the way F-BIRD'88 and all that responded, your helping me soo much. appreciate it all.
 
#10 · (Edited)
Got back from shop and found out specs:
817 block from 71-77 truck bored .40 (but not decked)
stock crank thats been turned
stock 5.56" rods (doubt they were balanced)
TRW h400cp-40 flat top pistons.
brass freee plugs plugs
-------------------------
running those brodix ik200
a 750 carb
air gap intake
Comp cams Xe284H-10 cam 1.5 rockers
what type of numbers do you think itll put out?
 
#14 ·
based on the XE284-10 hyd flat tap cam, 9.5:1 c/r, high flow dual plane intake, 750 carb, and the idk200 heads, which i dont have flow numbers on but i put in flow numbers that came up to about 268cfm@.500 lift, a little more with higher lift and the numbers dynosim came up with were 499.8hp@6000rpm and 497.0tq@4500rpm, the numbers that i get on this simulator always seem a little inflated, so i would likely take about 5% off those numbers giving you around 474.8hp and 472.1tq, then after you take about 18% off those numbers for parasitic loss to the rear wheels you come up with 389.3hp and 387.1tq
 
#16 ·
another really good iron head you can take a look at is the DART iron eagle platinum 200, they flow a bit better than the idk200's, right out of the box they flow the same numbers as the AFR-195's, in my opinion dart makes the best iron heads on the market, i would bet you would get another 10hp/tq out of these head

since this is not going to be a street/strip can and just a street car why are you looking for 400hp to the rear wheels, those kinda numbers in a 3500lbs car typicaly will get you mid to high 11's in the 1/4, you also mentioned a th400 as a trans, any reason behind this, the th350 can be built to handle just as much for about the same price, and the 400 weighs more and has a higher 1st gear so it doesn't get quite as much pull out of the hole
 
#17 ·
soon2be said:
any suggestions? i dont know how or what to look for in cams to know what i need. jus know i want a nice noticable lope.

the XE284 will give a very nice lope, likely more than you think, comp's XE line are among the most aggressive hyd flat tap cams on the market, lunati makes a similar line called voodoo these cams open extremely fast for a hyd cam
 
#18 ·
my87Z said:
another really good iron head you can take a look at is the DART iron eagle platinum 200, they flow a bit better than the idk200's, right out of the box they flow the same numbers as the AFR-195's, in my opinion dart makes the best iron heads on the market, i would bet you would get another 10hp/tq out of these head
but will the added weight be that make that much of a difference?

my87Z said:
since this is not going to be a street/strip can and just a street car why are you looking for 400hp to the rear wheels, those kinda numbers in a 3500lbs car typicaly will get you mid to high 11's in the 1/4, you also mentioned a th400 as a trans, any reason behind this, the th350 can be built to handle just as much for about the same price, and the 400 weighs more and has a higher 1st gear so it doesn't get quite as much pull out of the hole
basically its having a car be able do do it if i wanted to. like having a vett and only for cruises. i put together vehicles that will resale and having a motor like this and able to put down these number will spark alot of interest of your basic "show car" that doesnt have a good motor or great motor but needs paint and bodywork etc.. the th400 was given to me in working order so why not use it? how much heavier is it? was always told it was stronger the the 350 and to build the 350 might as well build the 400... but i never understood building a car just for the track. if i invest time and money i want to drive it for more then 6-12 secs. but like i said ill take it to the track for times and the right amount of $$$
 
#19 ·
not sure about what you ment by the coment about the added weight, on the heads making much of a diff, cause i was recomending a set of iron heads, when the idk200's are made of a cast alm, and so are the AFR's, you would never notice the added weight of the iron heads, and they are a little cheaper and easier on head gaskets.

now for the th400 vs th350, the 400 is a great transmission, it weighs about 50lbs more and takes about 6hp more to run, but is a solid trans, and with the numbers you plan on running it may be able to stay together for a while in stock form, the 350 likely wont. the 350 has slightly shorter 1,2nd gears and can be built to handle just as much as a built 400 for the same price, on top of that the 350 is a little more commonm both are excelent transmissions to crank on if they have been gone through
 
#20 ·
soon2be said:
86 monte ss, street machine. No strip but will run a race on street. Thinking about starting over and getting new pistons and going from there. Goal is atleast 400 to the wheels. I have the block work done and crank turned. Is forged internals only necessary if going spray or power adders? Rear end is stock 7.5 with 4.10 gears. Going with 400 turbo tranny. Like I said pump gas is a must. Is aluminum heads only really needed to reduce weight?
you may want to look into beefing up that 7.5 rear. i just got done putting a 385 with an est. 490-500hp/470-480tq in my 87 camaro with a stock 7.5 posi rear with aftermarket 4.10's, the second time i got on it out of the whole, the inerds of my rear tore to bit's (literally), my wife reluctantly let me spend some more money on a strange 12bolt replacement, since then i've raced the 1/4 a few times, i'm still tryng to get everything dialed in but my best so far is 11.71@ 116mph, ive still got to work out some tire spin, and just keep working at it cause my mph doesn't really match my time so i know i can get into the 11.50's
 
#21 ·
my87Z said:
you may want to look into beefing up that 7.5 rear. i just got done putting a 385 with an est. 490-500hp/470-480tq in my 87 camaro with a stock 7.5 posi rear with aftermarket 4.10's, the second time i got on it out of the whole, the inerds of my rear tore to bit's (literally), my wife reluctantly let me spend some more money on a strange 12bolt replacement, since then i've raced the 1/4 a few times, i'm still tryng to get everything dialed in but my best so far is 11.71@ 116mph, ive still got to work out some tire spin, and just keep working at it cause my mph doesn't really match my time so i know i can get into the 11.50's
Yeah I figured. I want the 8.5, but the 7.5 came with the shell I got and had 4.10s. What's needed to "beefin" up a rear end? And on the tranny deal, if the tranny will hold up, ill look into builtdin up a 200. Ill use is as a everynow and the vehicle but if I ever sale, ill want the buyer to have the chance to run it on the highway.
 
#22 ·
soon2be said:
any suggestions? i dont know how or what to look for in cams to know what i need. jus know i want a nice noticable lope.
Here contact either one of these places and give them all of your engine specs and they can grind a cam just for your set-up, I like cammotion but both are top notch JMO. But not gonna guarentee a good lope they grind for the most performance out of your engine. Just tell them what you are doing and planning on doing with your ride they can help. http://www.cammotion.com/Default.aspx . http://www.bulletcams.com/ .

Cole
 
#25 ·
soon2be said:
Yeah I figured. I want the 8.5, but the 7.5 came with the shell I got and had 4.10s. What's needed to "beefin" up a rear end? And on the tranny deal, if the tranny will hold up, ill look into builtdin up a 200. Ill use is as a everynow and the vehicle but if I ever sale, ill want the buyer to have the chance to run it on the highway.
moser and strange do make stonger 28 spline axles for the 7.5 for around $250, a GOOD locker, i was going to ge an eaton before my rear busted for around $550, then i would get a good set of grears, as i have heard the pinion grears are actually the weak part in these rears

it may be much easier for you to put a 8.5 in that monte' but it's really hard to do this in the 3rd gen camaro's because of the torsion bar, atleast this is what i heard i didn't even try, i just paid about 2500 for a killer 12 bolt strange bolt in rear. even if you get a 8.5 in there i would still want to beef it up.

you mention a 200 trans do you mean the 2004R O/D trans that came in the 80's monte's stock. if so i would say this would be a great idea, otherwise you say you have a th400 and 4.10's, with a 28" tire (which will be about the max the car will fit) you will still run around 3100rpm at 60mph. i bought a 700R4 from monsters transmissions and i love it. the 2004r has about a 2.74 first grear while the 400 has a 2.48, the 700r4 has a 3.06. i run a M/T et street p275/65R15 on the rear which is 28" and i run around 1800rpm at 60mph, not to mention with the 3.06 first gear and the 4.10's in the rear, she is murder out of the hole, that the equvelent of a th400 with around a 4.70 rear gear, but just for the first two grears
 
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