408 horse power?

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ramchargermike

ramchargermike

Mopar Garage Bar & Empori
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I just put together a nice 408 built from a 1977 360. It has a 4" Eagle crank. 0.030 KB pistions about 72cc heads with 2.02/1.60 30deg valves stock rockes and pushrods. between 9.5:1 to 10.0:1 comp. heavy valve springs good cam from comp. My boss or anyone else i know wont give me a rough horsepower rating. I also have a air gap intake and a 750 edel. carb hooker headers 2 1/2" exhaust 2:71 gear rear end 904 trans. This this is a rocket one it is broke in I will take her to the track but i at least want to know what horse power range I am in. Any one have any idea?
 
255+

No really, just how "good" is the cam from Comp. Specs or a part# will help us. 10:1 compression and a duration of 230 @.050 should have you around 1hp/cubic inch.

The cam that gives the most power won't be a good fit for your gears or converter.
 
Somewhere between 250 and 500 would be my guess. Don't mean to be a smart axx but there's no way anyone can guess the hp with what little information you provided. "A nice Comp cam"?? Since there are at least 1000 nice cams from comp that's not much to go on. Was the cam degreed in? That can have a profound affect on how an engine runs. Plus that's not much to go on with the description of the heads either. Are they 273 heads that someone installed 2.02 valves in, or 340 X heads, or Edelbrock heads, or Indybrocks, or RHS??? The cam and heads are really what makes the power package so it's imperative that you provide every aspect of the build. Flow numbers (or at least a real good description, such as the casting # and ALL work done on them) of the heads is a HUGE plus.

BTW: What the heck are 30 degree valves??
 
If you can provide the cam card and head flow figures....I can run it through Dyno 2000 for you. You'd need to take the results with a pinch of salt but it can be pretty close with enough data.
 
Your definetly gonna have to lose the low gears.Once you have your cam figured out,then you,ll beable to match a convertor and gears for max. performance.good luck
 
ramchargermike said:
I just put together a nice 408 built from a 1977 360. It has a 4" Eagle crank. 0.030 KB pistions about 72cc heads with 2.02/1.60 30deg valves stock rockes and pushrods. between 9.5:1 to 10.0:1 comp. heavy valve springs good cam from comp. My boss or anyone else i know wont give me a rough horsepower rating. I also have a air gap intake and a 750 edel. carb hooker headers 2 1/2" exhaust 2:71 gear rear end 904 trans. This this is a rocket one it is broke in I will take her to the track but i at least want to know what horse power range I am in. Any one have any idea?
Click to expand...

its impossible to even guess hp with the lack of information you posted.
 
I figured the lack of cam specs would hurt my question
Comp cam part number 20-224-4
Grind number : crs xe274h--10
Gross valve lift 0.488 on the intake and 0.491 on the exhaust
106.0 deg centerline
Springs are 995-16
Heads are 1977 360 truck heads polished and ported 4 angle valve job. I used 30. Deg. Intake valves instede of 45. Deg. For more flow. About 72cc chambers after milling the heads.
That's all the specs I have for now.
 
The work on the heads means very little with that cam unless they were barely touched, and that cam is not big at all for a 4" stroke. I think if it makes 400hp/inch that would be good, and torque around 430.
 
Grab a copy of 'How to build Big-Inch Mopar Small Blocks" from amazon.com. they have 6 or 8 sample builds in the back of the book using a variety of carbs, cams, pistons, compression, etc and have dyno reports for most of them. Very informative.
 
It should have real good low end torque but as Moper said that is a real small cam for a 4" stroke engine. If the heads were done right I'd guess about 400 hp.
 
pettybludart said:
Your definetly gonna have to lose the low gears.Once you have your cam figured out,then you,ll beable to match a convertor and gears for max. performance.good luck
Click to expand...

X2, the gears are going to drag it down. 3.55/3.91's will make it feel 1,000 lbs lighter.

Now coasting the freeways around 80 mph those gears will be great, its from a stop it be a pain
 
Hopefully you can read this:

I run the appx. same year head (ported) also with a 2.02 valve so I've used my flow figures and pumped them into Dyno 2000,

I included the 408 cui, 750 cfm carb and your cam specs.

I assumed a DP intake and small tube headers,

In my experience, the small tube headers/open exhaust works to be about what you should expect set of TriYs through open pipes prto produce in real life


Flow figures used were:

.100 - 75
.200 - 142
.300 – 170
.350 - 195
.400 - 219
.450 - 231
.500 - 240
.550 - 243

.100 - 55
.200 - 114
.300 - 130
.350 - 140
.400 - 142
.450 - 145
.500 - 148


408XE274H.jpg
 
autoxcuda said:
Well Brian at IMM got 480hp/500tq from this. It's got a lunati voodoo 60403 cam which seems smaller than the XE274h?



http://board.moparts.org/ubbthreads/showflat.php?Cat=0&Number=6780602&page=0&fpart=1&vc=1
Click to expand...

Hi there.

FWIW I've found with D2000 that the difference between a set of ported cast heads like mine, and some decent ported Eddies can be as much as 60 HP in a combo like we're discussing.

I enter the flow figs for my ported cast heads, then compare against some publicized ported Edelbrock flow figures I got off the Net, and the graph just goes ballistic........much more than with a cam increase or intake change.
 
You should make more than 408 hp , my 340 makes 412 hp and is almost stock except for some head work , air gap and cam and .30 over mahle forged pistons .
Good luck .

Forget those gears , unless you want to be cruising at 160 mph +
 
Read my thread on my 416 stroker. Simliar build to yours. I used my stock 360 heads with a light cleanup, XE484H cam, LD340 intake, and 750 Edelbrock. Best pull at machine shop was 420hp and 475lbs of torque. Last pull (in video) before I took it home with 14" chrome aircleaner was 408 hp and 460 lbs at torque. The maximum torque was at 4300 rpm and maximum hp at 5300 rpm... I was told the carb was holding it back. It was asking for more.
 
Rat Patrol said:
Hopefully you can read this:

I run the appx. same year head (ported) also with a 2.02 valve so I've used my flow figures and pumped them into Dyno 2000,

I included the 408 cui, 750 cfm carb and your cam specs.
Click to expand...

Could you run my combo in Dyno 2000 ??

416 cid ...4.00 stroke .030 over 340 block
Comp XE274-S solid with 236/[email protected] .502”/.511” 110 L/C
Edelbrock heads ported, stock valve job
M1 single plane, good port match, all cleaned up
9.8:1 compression measured
750 Demon Silver Claw
TTI 1 5/8 to 1 3/4 step headers port matched then coated
 
jerry6 said:
You should make more than 408 hp , my 340 makes 412 hp and is almost stock except for some head work , air gap and cam and .30 over mahle forged pistons .
Good luck .
Click to expand...

I've found D2000 to be really hard on heads that are "average" in flow #s.

At a guess I'd recommend adding around 20HP for any peak head flow figs below 250 cfm. Pretty rough but it's OK for a "ballpark" figure on the low side.:D
 
autoxcuda said:
Could you run my combo in Dyno 2000 ??

416 cid ...4.00 stroke .030 over 340 block
Comp XE274-S solid with 236/[email protected] .502”/.511” 110 L/C
Edelbrock heads ported, stock valve job
M1 single plane, good port match, all cleaned up
9.8:1 compression measured
750 Demon Silver Claw
TTI 1 5/8 to 1 3/4 step headers port matched then coated
Click to expand...

OK, a couple of notes:

1/ Small tube/ Open pipes setting works to about the same as a decent full exhaust in real life.

2 / D2000 doesn't recognise the type of head (small chamber vs open, alloy vs cast etc) so it underestimates a bit.

Headflow figs used are:

.100"--62.8 /44.4
.200"--134.2 /100.0
.300"--196.7 /146.6
.400"--233.6 /182.8
.500"--258.0 /203.6
.550"--267.4 /208.7
.600"--276.0 /213.9
.650"--280.8 /215.6
.700"--285.3 /217.4
.750"--286.7 /220.0


416_XE274S_SP.jpg
 
rob_robinson87 said:
Read my thread on my 416 stroker. Simliar build to yours. I used my stock 360 heads with a light cleanup, XE484H cam, LD340 intake, and 750 Edelbrock. Best pull at machine shop was 420hp and 475lbs of torque. Last pull (in video) before I took it home with 14" chrome aircleaner was 408 hp and 460 lbs at torque. The maximum torque was at 4300 rpm and maximum hp at 5300 rpm... I was told the carb was holding it back. It was asking for more.
Click to expand...

Mine is a very similar combo - I made 17 Rear Wheel HP more swapping from the LD340 to the M1 SP. One stage richer on the carb.

Worth thinking about with a stroker ....
 
fishy68 said:
That doesn't surprise me but what did the torque do?
Click to expand...

I can only give you an indication because it was a chassis dyno, not an engine dyno.

Basically it moved peak Tq from appx 3900 to 4500...and the figures stayed around the same. (Est. Peak hp of 420 is at 5500 currently)

What this told me was that the Tq that these SB strokers make is so much more than the std stroke equivalent.........the old rules about Single Planes only being for revvers just don't apply to them.

In fact, the strokers "need" a decent size runner and plenum like you'd find on an M1 SP (or an Air Gap).

The older intakes just can't feed them.

To be fair, I run 3.89 gears so streetability wasn't effected either.
 
Rat Patrol said:
I can only give you an indication because it was a chassis dyno, not an engine dyno.

Basically it moved peak Tq from appx 3900 to 4500...and the figures stayed around the same. (Est. Peak hp of 420 is at 5500 currently)

What this told me was that the Tq that these SB strokers make is so much more than the std stroke equivalent.........the old rules about Single Planes only being for revvers just don't apply to them.

In fact, the strokers "need" a decent size runner and plenum like you'd find on an M1 SP (or an Air Gap).

The older intakes just can't feed them.

To be fair, I run 3.89 gears so streetability wasn't effected either.
Click to expand...

Very good. TNX for the info
 
Rat Patrol said:
Mine is a very similar combo - I made 17 Rear Wheel HP more swapping from the LD340 to the M1 SP. One stage richer on the carb.

Worth thinking about with a stroker ....
Click to expand...


Yeah, I thought about a different intake and heads, but I was keeping things cheap and wanted the motor to have more of a "stock" look to it. (Yeah, it won't look stock to any Mopar guy). I was also concerned with location of my A/C compressor and how many intakes move around the heater fittings, etc. The car is going to be a street fun car- no real full out runs.
 
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