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#2381772 - 10/04/17 11:49 AM Re: 408 help needed [Re: Mirada 408]
EV2Bird Offline
On Vacation

Registered: 06/23/14
Posts: 2966
Loc: Kansas Roads Between 0 and 140...
Looking at this...Engine is 408ci. eagle crank and rods, kb hyper pistons, comp cam hydraulic roller xr-292hr-10 duration 242/248 lift .545, 1.6 ratio rockers, edlebrock rpm heads, airgap intake, and 750 Holley dp. Car is consistently 12.20-12.30 @108-110mph.

You have a very very mild entry level cookie cutter stroker, your 2.08 heads are probably not helping you yet.


So you have a mild motor that happens to have a 4 inch crack, a much lesser motor as you found can easily equal that.

Id start at the big red flag to me and dump the hydro roller cam for a better "performance" cam, turn up the rpms to use the heads you have.

But as many has mentioned, when you start down the faster road, how fast is fast enough for you and how often do you like to drive the car?

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#2381789 - 10/04/17 12:26 PM Re: 408 help needed [Re: Mirada 408]
fast68plymouth Offline
I Live Here

Registered: 01/20/03
Posts: 10410
Loc: So. Burlington, Vt.
Quote:
...don't know the I/SA min weight but thats 440ish hp from that mild set up.


That car runs around 111mph, min weight is 3410.
At 3450 the Moroso chart shows 362hp.

If the car were really way overweight, you'd just run it in the next class down (H, 12.5lbs/factored hp), which would be 3545 min weight.

There is someone who does run that combo in "H", and that car has run 11.40's.
_________________________
68 Plymouth Satellite, 383, stock 906's, 3550lbs, 11.18 @ 123, 1.51 60' PRH is a Comp Cams W/D......competitive pricing on entire line. Custom cams available. ** dealer for Indy Cylinder Heads **

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#2381819 - 10/04/17 01:03 PM Re: 408 help needed [Re: B3422W5]
Crizila Offline
master

Registered: 10/31/03
Posts: 7490
Loc: Az
Originally Posted By B3422W5
Sounds like low cylinder pressure, low compression. And definately more convertor.
Doubt the carb is hurting more than a tenth.
How far in the hole are the pistons?
What is the cam lsa?
iagree Double check the CR to be sure. Whats the cranking compression. Ran a very similar set up to yours ( engine and car weight )in my 79 300 for a while. Ran a little larger cam and 3.90 gears. Think my CR was around 10.7:1. My car ran consistent 11.80's and a best of 11.53 with speeds in the 118 - 119 range. Yours should be able to do that.


Attachments
2006-08-02 14.53.10.jpg


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Fastest 300

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#2381825 - 10/04/17 01:11 PM Re: 408 help needed [Re: Mirada 408]
fast68plymouth Offline
I Live Here

Registered: 01/20/03
Posts: 10410
Loc: So. Burlington, Vt.
Too late to undo it now, but I would have just done a nice mild clean up on the heads, kept the 2.02 valves(keeping the ports for the most part, as small as possible), swapped to a solid lifter cam, went for 4.10's and a 4500 converter.
_________________________
68 Plymouth Satellite, 383, stock 906's, 3550lbs, 11.18 @ 123, 1.51 60' PRH is a Comp Cams W/D......competitive pricing on entire line. Custom cams available. ** dealer for Indy Cylinder Heads **

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#2381832 - 10/04/17 01:38 PM Re: 408 help needed [Re: fast68plymouth]
B3422W5 Offline
master

Registered: 01/20/03
Posts: 9929
Loc: Portage,michigan
Originally Posted By fast68plymouth
Too late to undo it now, but I would have just done a nice mild clean up on the heads, kept the 2.02 valves(keeping the ports for the most part, as small as possible), swapped to a solid lifter cam, went for 4.10's and a 4500 converter.



That advice sounds familiar Dwayne..... lol
Just bought me a nice 904 with low gear, billet drum and A&A brake.
Still need convertor and driveshaft, will swap over in the offseason. Also going to install my hemi dart glass hood and paint it to match. Hoping to get her to threaten the 10's.
_________________________
69 Dart GTS, performance upgrades in progress
11.26@ 118.40 best so far. Stock 360 shortblock with eddie heads.

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#2381879 - 10/04/17 03:53 PM Re: 408 help needed [Re: Mirada 408]
fast68plymouth Offline
I Live Here

Registered: 01/20/03
Posts: 10410
Loc: So. Burlington, Vt.
There is no mention of the cr by the OP, but assuming 10.2-10.5:1, ported rpm's, that sized cam, intake, carb, on a 408...... Should be right in the 500hp range(if the valvetrain is stable enough to allow the motor to reach its natural peak).
And it should be over 500tq.

Assuming it weighs as much as my heap did when I first slid my 383 in it(3670 w/driver), if I apply the "90% rule"(the car should be able to run within 10% of the dyno crank hp, using the Moroso slide as the reference)......that's just shy of 117mph(450hp@3670).

If you had a 4500(or higher) converter, it's likely going to have some amount of slippage..... Seems like 7% is fairly typical.
Then if you have it geared right to use up all of what the motor has to offer, running a 28" tire...... 4.30's look about right.
4.30's, 28" tire, 7% slip, 117mph...... Works out to just under 6500 through the lights.

I'd be surprised if the current motor combo would actually "pull" through to 6500.

Each little step you take away from that scenario is ET you're probably not going to get back.

As a motor comparison, we did a 410 last year.
10.5cr, rpm's with mild clean up(265-ish), easy on parts sold roller, victor intake, qft-850 carb, pump gas.........538hp/524tq.
_________________________
68 Plymouth Satellite, 383, stock 906's, 3550lbs, 11.18 @ 123, 1.51 60' PRH is a Comp Cams W/D......competitive pricing on entire line. Custom cams available. ** dealer for Indy Cylinder Heads **

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#2382033 - 10/04/17 05:36 PM Re: 408 help needed [Re: Mirada 408]
fast68plymouth Offline
I Live Here

Registered: 01/20/03
Posts: 10410
Loc: So. Burlington, Vt.
Quote:
I was happy with it, but wanted to go faster. therefore send the heads out and have them cnc ported and 2.08 intake valves put in.


Just curious...... Who did you end up having the cnc porting done by?
_________________________
68 Plymouth Satellite, 383, stock 906's, 3550lbs, 11.18 @ 123, 1.51 60' PRH is a Comp Cams W/D......competitive pricing on entire line. Custom cams available. ** dealer for Indy Cylinder Heads **

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#2382156 - 10/04/17 09:39 PM Re: 408 help needed [Re: Mirada 408]
gregsdart Offline
master

Registered: 01/21/03
Posts: 8104
Loc: Frostbitefalls (Rocky&Bullwink...
What kind and brand valve springs are you running? A cheap straight spring might kill power and limit usable rpm you need to keep the motor up in the power band.
I just dynoed a very similar 408 with Airgap intake EQ heads and similar cam, made 504 up, 500 hp from 5700 to 6100. Torque was 520 at 4600. Something is definitely holding you back. If this is going to be a strip only car I would go with a 5,000 to 5200 stall converter. Get it to pull to over 6,000 so you can shift at 6,000( actual shift will be about 6200!)


Edited by gregsdart (10/04/17 09:50 PM)
_________________________
GREG
Educated at SHK U
Measure with yardstick
mark with chalk
cut with torch!



528 cubic inch alky injected 440-1 wedge, 3055 race weight.
8.779 at 153.16 mph. 1.289 60 ft. density altitude 1617 feet. Best 60 ft 1.24

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#2382161 - 10/04/17 09:46 PM Re: 408 help needed [Re: Mirada 408]
Mirada 408 Offline
member

Registered: 08/10/15
Posts: 14
Loc: West Virginia
I will try and answer some of the more asked questions. the cr is right around 10.7:1. The car started out with the goal as more of a street/strip car, with emphasis more on street manners. But over time its being turned into more of a strip/street car. Granted, its still full interior etc etc. And currently have no plans of gutting the car. I'm more of the Test and Tuner racer, I hit the track maybe 6 times a year and have some fun. As far as street driving it'll go out maybe a dozen times or so. And realistically if in my last outing the car would've picked up to say as fast as Crizila, 11.80's then I would've been content for the time being. The cnc porting was done by Hughes Engines. And other than more gear/convertor it seems as though many are saying camshaft. Is this the logical step in getting more rpms to be able to use the heads? If so would a solid roller be the way to go?

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#2382168 - 10/04/17 09:55 PM Re: 408 help needed [Re: Mirada 408]
B3422W5 Offline
master

Registered: 01/20/03
Posts: 9929
Loc: Portage,michigan
If your compression is indeed 10.7 to 1, and the heads are at least decent, by far the biggest thing to fix is the convertor.
Nothing else even close.
_________________________
69 Dart GTS, performance upgrades in progress
11.26@ 118.40 best so far. Stock 360 shortblock with eddie heads.

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#2382170 - 10/04/17 09:57 PM Re: 408 help needed [Re: gregsdart]
Mirada 408 Offline
member

Registered: 08/10/15
Posts: 14
Loc: West Virginia
Originally Posted By gregsdart
What kind and brand valve springs are you running? A cheap straight spring might kill power and limit usable rpm you need to keep the motor up in the power band.
I just dynoed a very similar 408 with Airgap intake EQ heads and similar cam, made 504 up, 500 hp from 5700 to 6100. Torque was 520 at 4600. Something is definitely holding you back. If this is going to be a strip only car I would go with a 5,000 to 5200 stall converter. Get it to pull to over 6,000 so you can shift at 6,000( actual shift will be about 6200!)
Springs are Engine Pros, Dual with damper. And since you brought springs up, it reminded me. Hughes did tell me the springs seemed a little weak to them. could it be something as simple as the springs?

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#2382203 - 10/04/17 11:01 PM Re: 408 help needed [Re: Mirada 408]
fast68plymouth Offline
I Live Here

Registered: 01/20/03
Posts: 10410
Loc: So. Burlington, Vt.
It's not just the springs.
But.......it could be the springs, along with the converter and gears.

I've had one set of the sb rpm's in my shop that had the Hughes cnc porting.

Just an observation on my part, with no actual testing on an engine to see if it makes any difference or not.......but I don't care for the way they do the intake short turn on those heads.
It's as flat as a pancake.

Perhaps your cam and Gregs look somewhat similar on paper, but they are from fairly different lobe families, with yours being the more aggressive one, which would also tend to make it less rpm friendly.

Until you get some data(like from the chassis dyno), you're somewhat shooting in the dark.
_________________________
68 Plymouth Satellite, 383, stock 906's, 3550lbs, 11.18 @ 123, 1.51 60' PRH is a Comp Cams W/D......competitive pricing on entire line. Custom cams available. ** dealer for Indy Cylinder Heads **

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#2382355 - 10/05/17 10:19 AM Re: 408 help needed [Re: Mirada 408]
Crizila Offline
master

Registered: 10/31/03
Posts: 7490
Loc: Az
Originally Posted By Mirada 408
I will try and answer some of the more asked questions. the cr is right around 10.7:1. The car started out with the goal as more of a street/strip car, with emphasis more on street manners. But over time its being turned into more of a strip/street car. Granted, its still full interior etc etc. And currently have no plans of gutting the car. I'm more of the Test and Tuner racer, I hit the track maybe 6 times a year and have some fun. As far as street driving it'll go out maybe a dozen times or so. And realistically if in my last outing the car would've picked up to say as fast as Crizila, 11.80's then I would've been content for the time being. The cnc porting was done by Hughes Engines. And other than more gear/convertor it seems as though many are saying camshaft. Is this the logical step in getting more rpms to be able to use the heads? If so would a solid roller be the way to go?
I ran a Hughes HEH4650 AL ( .606 / .614 246 / 250 108 LSA ) Hyd cam with 1.6 rockers. Fully ported J heads W/ 2.02's.
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Fastest 300

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#2382377 - 10/05/17 11:02 AM Re: 408 help needed [Re: Mirada 408]
fast68plymouth Offline
I Live Here

Registered: 01/20/03
Posts: 10410
Loc: So. Burlington, Vt.
I guess if someone else who's looked at the heads has already mentioned the springs are a little light...... That may not be a bad place to start, but it will only affect the power curve above the point where the current springs are allowing some float(if that's even happening at all).

You could have a couple of the ones currently on the heads tested if Hughes didn't provide that info to you.
I'd shoot for 150-ish on the seat, 350-375 open.

Then, if your goal is just high 11's, start with more stall(4200-ish), and if that doesn't get you quite where you want to be, put some 4.10's in it.
_________________________
68 Plymouth Satellite, 383, stock 906's, 3550lbs, 11.18 @ 123, 1.51 60' PRH is a Comp Cams W/D......competitive pricing on entire line. Custom cams available. ** dealer for Indy Cylinder Heads **

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#2382418 - 10/05/17 12:23 PM Re: 408 help needed [Re: Mirada 408]
Guitar Jones Offline
master

Registered: 12/18/09
Posts: 8950
Loc: in a cattle trailer down by th...
No mention of what you have for a fuel system or what it flows?
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W5 408 cid, 1.324, 6.155 @ 110.34, 9.756 @ 134.67 with a broken converter hub. Oh yeah, it's all Mopar too, 904 trans and an 8.75 rear!!

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#2382454 - 10/05/17 01:00 PM Re: 408 help needed [Re: Guitar Jones]
fast68plymouth Offline
I Live Here

Registered: 01/20/03
Posts: 10410
Loc: So. Burlington, Vt.
Originally Posted By Guitar Jones
No mention of what you have for a fuel system or what it flows?


Good point.
_________________________
68 Plymouth Satellite, 383, stock 906's, 3550lbs, 11.18 @ 123, 1.51 60' PRH is a Comp Cams W/D......competitive pricing on entire line. Custom cams available. ** dealer for Indy Cylinder Heads **

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#2382466 - 10/05/17 01:13 PM Re: 408 help needed [Re: fast68plymouth]
pittsburghracer Offline
Slowride

Registered: 02/02/05
Posts: 11979
Loc: PA.
Heck I had a 440 with two 750's on a tunnelram go high 9's with a Holley blue pump. I'm betting in todays world he has a better pump than that, BUT WHO KNOWS.
_________________________
1970 Duster
Edelbrock headed 408
6.143@110.89 mph
9.73@135.05 mph shifting at 6700 RPM
422 Indy headed small block
6.001@113.27mph
9.44@138.23


Untitled by John Cadamore, on Flickr





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#2382994 - 10/06/17 01:18 PM Re: 408 help needed [Re: pittsburghracer]
Guitar Jones Offline
master

Registered: 12/18/09
Posts: 8950
Loc: in a cattle trailer down by th...
Two carbs in that kind of application actually require less fuel flow to keep up because the jets are smaller. I know sounds weird.
_________________________
W5 408 cid, 1.324, 6.155 @ 110.34, 9.756 @ 134.67 with a broken converter hub. Oh yeah, it's all Mopar too, 904 trans and an 8.75 rear!!

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#2383051 - 10/06/17 03:14 PM Re: 408 help needed [Re: Guitar Jones]
pittsburghracer Offline
Slowride

Registered: 02/02/05
Posts: 11979
Loc: PA.
Originally Posted By Guitar Jones
Two carbs in that kind of application actually require less fuel flow to keep up because the jets are smaller. I know sounds weird.



I should have added it to my post but before I ran the tunnelram I ran it for 3 years with a 1050 dominator. Same pump
_________________________
1970 Duster
Edelbrock headed 408
6.143@110.89 mph
9.73@135.05 mph shifting at 6700 RPM
422 Indy headed small block
6.001@113.27mph
9.44@138.23


Untitled by John Cadamore, on Flickr





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#2383074 - 10/06/17 04:39 PM Re: 408 help needed [Re: Mirada 408]
Cab_Burge Offline
Too Many Posts

Registered: 08/23/03
Posts: 29731
Loc: Bend,OR USA
You improve the airflow into the motor and it ran the same as before, did you improve the fuel supply ?(not pressure,volume) work
I would look at that and IF you can jet the carb. rich enough to slow the MPH down in the 1/4 mile. If you can you have enough fuel supply to feed your motor in its current condition scope up
When changes don't help or the results don't make since, there is usually a reason for that work


Edited by Cab_Burge (10/07/17 12:34 AM)
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Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

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