aussie 408 combo

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tasvalowna

tasvalowna

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Hi , after pulling my 360 i found the bores oval and alreadty 40 thou over .I had tossed up the idea of building an engine myself but with a decent mopar friendly machine shop a long way away I decided to let an engine builder build the lot.
Im In Australia and have ordered most parts either from Summit or Mancinis.
The block is a LA 360 bored 30' , a Scatt 4'' stroker crank , rods and KB pistons machined to zero deck height .
A pair of Eddie heads ,1.6 Crane roll rockers , dual plane eddie manifold , crane ignition and a 750 vac sec carb.
The engine builder has recommended a retrofit roller howard cams part no. 710665-10 .
The engine will be a street /strip weekend cruiser and will probably run a 3500 stall with either 3.5 or 4.11 rear end depending if on the street or going to the strip.
Has anyone had any experience with a cam grind like this? how much difference will the 1.6 rockers make , is there any issues I should be asking about or looking for?
Itll be in a 69 valiant hardtop (dodge dart )
Any feed back appreciated
Ben
 
Nice ,thought out combo. The only thing I can ask,: Valve spring pressure. The stock Edelbrock head valve springs.575 lift max. Spring pressure open,roughly 320 lbs. That kind of lift (and rpm),might require more open max lift pressure . E mail Howards,you will get a answer. Howard's,my new choice in cams.Good luck.
 
nice size cam but i'd go a single plain but. the only thing that i have found is that people who build a stroker still think its a 360, when you look for bits or compare it to others think of it as it is a 400 or so cube engine, like a big block.
 
the whole engine was designed to see a max rpm of 6000-6500 .
I was looking for more torque than max hp . As with most things I guess theres some conflicting stories as to weather a single plane will produce more power than a dual plane at these revs.I think if it was to see 7000 i might agree but i will be sticking with the dual plane in the initial build at least and see what the engine dyno shows on the break in and keep it in mind anyway.
If the max eddie head lift is .575 with stock springs and the cam is 550 with 1.5 rockers , can any one advise me to how much lift it will be with my 1.6 ratio rockers? bit worried about any binding issues.
 
Your cam with 1.6 rockers will give a theoretical .5866 lift; just beyond what the stock Eddy springs will do. Time for new springs.
 
Your 408 at 6500RPM would induce the same amount of air as a 360 revving at 7360RPM and the same as a 340 at 7800 RPM

I would recommend a single plane.
 
If possible try to avoid getting packages where the value exceeds $1000AUD or you will get charged import duty, GST and an agent's fee which can add up to about an additional 35-40% of your package's value.

So I suggest order one cylinder head at a time.

Then the cam, lifters and pushrods

Then the intake manifold, valve springs, valves etc

Then the crankshaft and connecting rods.

Then the pistons, rings, bearings. etc.

Keep every package under $1000 AUD or it will cost you a fortune!
 
Also, if you haven't already purchased your eddie heads Amazon.com have a fantastic deal on bare chrysler cylinder heads.

[ame="http://www.amazon.com/Edelbrock-60769-Performer-Cylinder-Head/dp/B0006300VU"]Amazon.com: Edelbrock 60769 SBM Performer RPM Cylinder Head - Bare: Automotive[/ame]
 
1.6 rockers will marginally change the effect of the camshaft as if it were slightly longer in duration. This means it will move the RPM range up slightly however with a hydraulic roller camshaft like the one you suggested it will cause any potential for lifter pump-up to occur earlier in the RPM range.

So theoretically to get the most gain out of 1.6 rockers they should be combined with a lighter spring/valve. (beehive springs are good)

Or go solid roller.
 
Also keith black hypereutectic pistons require a significantly larger ring gap than normal. MAKE SURE whoever assembles the engine follows the specs supplied with the pistons or the rings will snap and lunch your motor.
 
ive already purchased the rockers and heads so theres no turning back on them . The heads and rockers were second hand and had done about 1000 miles and were set up with a solid roller prior to me buying them .The engine builder has measured up the lift etc and says the springs had already been changed and are good to go with my cam.The main thing by the sound is the inlet manifold . I might just buy a single plane M1 and when he is running the engine on the dyno , run it with both and see what the difference is and sell the other.
The reason i went with a dual plane was because of this

[ame="http://www.youtube.com/watch?v=i2DvnoHWagk"]Edelbrock Intake Manifold Dyno Test :: Single Vs Dual + Air-Gap Vs Regular - YouTube[/ame]

ben
 
Do you need to consider getting some heat into the inlet manifold? Cold starts in the middle of winter could be a *****. Use to **** me on the Melbourne winters.
I bought a M1 dual plane for this reason as it has water heating on the manifold but I've now shifted up north so this isn't a problem, so I'll probably sell it and get a chinese air gap copy from ebay.
What version of the edelbrock heads do you have?
 
No a heated inlet isnt a big deal , my 360 didnt have one and besides i dont drive it much in the winter.
Theyre just a RPM edelbrock , if theres more than 1 model then im not sure.The engine guy is going to take the inlets out to 2.08 , which in his opinion is easier and cheaper than going berserk with porting.
Im only hoping for between 450 and 500 hp and hes confident we should get that alright.
 
If you can't get 450-500fwhp out of a 408 with the parts you're looking at, something's wrong with the build or the machine work.
 
there will be nothing wrong with the machine work , im confident of that so thats good news.I hate to say it but he mainly builds chevs and fords but he has built mopars before so I hope we both get a surprise when it goes on the dyno .
 
That was exactly where I was going...unless the process was screwed up, those parts should have no problems making/exceeding your goal.
 
You said it was torque you were really after Ben.? I'd be staying with the rpm air gap. A good mate runs a roller cam in his 390 stroked with an air gap and runs 11.0s but it really street friendly at the same time. Something to consider...... Sometimes you need to consider more than the outright power ;)
 
thats right , itll be mainly a street car , with only the odd run at out 1/8 mile strip a couple of times a year. Outright hp is not really the goal , being able to do a rolling burnout is far more important to me !
The dual plane may hurt top end hp a little but if it gives me more twist down low , then thats the one that'll get the tick
Ben
 
tasvalowna said:
ive already purchased the rockers and heads so theres no turning back on them . The heads and rockers were second hand and had done about 1000 miles and were set up with a solid roller prior to me buying them .The engine builder has measured up the lift etc and says the springs had already been changed and are good to go with my cam.The main thing by the sound is the inlet manifold . I might just buy a single plane M1 and when he is running the engine on the dyno , run it with both and see what the difference is and sell the other.
The reason i went with a dual plane was because of this

Edelbrock Intake Manifold Dyno Test :: Single Vs Dual + Air-Gap Vs Regular - YouTube

ben
Click to expand...

What they neglect to mention in this video is that there is a relatively narrow spread in RPM between peak torque and peak horsepower and that's with a 360.

This flat-out indicates a restriction (for potential horsepower) in the heads/intake flow. Theoretically on a bigger cube motor such as yours it would be exacerbated.

IMO Getting a 408 to peak at or above 6500 is probably tunnel ram territory anyhow.
 
IMO - that cam is a mistake. It will be torquey for sure - but it won't carry up anywhere near 6K. A "low rpm" 4" stroke engine needs something that would be mid-size for a normal factory stroke just to be mild. The Crane 302-2 hysdraulic is a favorite of mine. With deceent heads it will idle at 800, have 13" of vacuum at idle, and pull to 5500. It also gets decent gas mileage if you can keep your foot out of it. That one is 242/252 @ .050. The Howards is 219/225. If you want to stay with hydraulic roller Howards then I'd recommend either the 710831-08 or 711351-08.
IMO - the 1.6 rockers are a mistake especially given the valve springs needed for the lifters and lobe design. I think they will also limit the rpm capability of the camshaft.
 
The Howards OP mentioned is 241/247 on 110.

I think for a stroker the 110 LSA will really help.
 
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