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Old 07-05-2005, 06:11 AM
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383 0r 406???

Hi

I'd like to know from the above 2 motors which to transplant into my AC Cobra replica with 350 turbo box.this is what I have been informed...

"The 400 cu has the same stroke than the 383cu wich is 3.750. The 400cu has a 4.125 bore and the 383cu 4 bore. So you see that the 383 is closer to a square engine than the 400 and the 400 is also closer than a 406cu. The 400 will produce more power and torque than the 383 but rev slower,so it will take longer again over a short distance to gain what the 383 can produce. If you use the engine in an off-road or pulling vehicle the 400 will be supreme, but not in street or drag racing."

Will the 383 rev faster due to it being closer to "square"..Please assume that the 383 and 406 are fully worked...

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Old 07-05-2005, 08:21 AM
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More cubes = more power potential... How fast the engine revs won't matter so much as this can be taken care of by gearing the car correctly. It you can get ahold of a 400 block that is in good shape but in need of a rebuild then go for it. If not the 383 is only a small step down.

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Old 07-05-2005, 10:02 AM
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400 vs 383

The 400 is easier to build. The 350 block can have clearance issues installing the 400 crank. The rod bolt to lower cylinders. They can both have rod bolt to cam issues when using 5.7 rods. The main problem with the 400 block is that in some years there are some holes not threaded and tapped. Such as power steering (drivers side) and straight starter bolt pattern is staggered instead. So you need to drill the hole for a mini-starter. Both will rev up, if both are balanced. Going to the 383 is a loss of at least 20 HP and as much torque.
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Old 07-05-2005, 10:06 AM
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Hi

Thanks for your replies.I know a 377 is a 400 with a 350 crank,has anyone tried a 406 with a 350 crankshaft?What cubic inch does that work out to?I assume one would have to rev this combination to 8000+ rpm to make the power the 383's or 406's make at lower rpm.The advantage of a 406 with a 350 crankshaft could be an extremely fast revving motor?
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Old 07-05-2005, 10:07 AM
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Who ever is telling you a 383 will rev better is a moron IMO. That does not a make a bit of sense.....AT ALL. The 400 has a larger bore diameter which gives it a heads up with breathing due to less valve shrouding. If any argument makes sense it would be for the 400 to rev faster.

That is hardly anything to worry about one way or the other. I would use the 400 if you can get your hands on one. As mentioned earlier you will get a little more power out of it. They also respond better to big port heads and big cam just because the extra cubes help swallow more air. More air equals more power.

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Old 07-05-2005, 12:20 PM
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Quote:
Originally Posted by Zubair
Hi

Thanks for your replies.I know a 377 is a 400 with a 350 crank,has anyone tried a 406 with a 350 crankshaft?What cubic inch does that work out to?I assume one would have to rev this combination to 8000+ rpm to make the power the 383's or 406's make at lower rpm.The advantage of a 406 with a 350 crankshaft could be an extremely fast revving motor?
The stock car guys use this combination because they are always up high in RPM. For drag racing you want the HP and Torque. How fast you rev up is not a concern. The convertor looks after that. A trick the stock car guys use is to buy 4 valve relief pistons and install them backwards. I can't remember the benefit to this but I'm sure someone on here can tell you.
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Old 07-05-2005, 01:17 PM
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There is no question, build the 406 if you have the choice.
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Old 07-05-2005, 01:26 PM
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4 valve pistons ..installed backward..are you retared
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Old 07-05-2005, 03:51 PM
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no i'm not retared, and I can spell

Piston pins in a sb are not centered in the piston. Thats why there is an arrow pointing to the front. If they have 4 valve "reliefs" they can be installed "backwards" arrow pointing to the rear.
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Old 07-06-2005, 01:34 AM
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Hi Guys,thanks for your your advice,however need some questions answered here:

If I am looking at obtaining +- 600hp from a 383 and revving to 6500-7000 rpm with 11.5:1 compression,what pistons should I look at?TRW?Venolia?

Which are the best performance heads?Dart II,Brodix,Camel?

What camshaft should I use?280,290 or 300 duration?Is mechanical roller rockers or hyraulic better?

Is the 350 turbo gearbox any good or is the 400 better for drag racing?What torque converter, stall etc should I use?

Will I need to go larger on the valves with the performance heads or do they come with it standard?

Is the Victor Junior High rise intake adequate or are there better ones?

Lastly what carburettor should I use?Is the Holley 750 double pumper adequate or small?

Have I left anything out?
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Old 07-06-2005, 07:58 AM
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Forget about using TRW pistons for a high RPM high power engine. They are just too heavy. I am not sure about the Venolia, but if were you I would be looking at JE, Weisco or SRP. Those companys all have off the shelf pistons for what you want and they will not break the bank. The Wiesco even come with rings which is a plus. I would also run 6 inch rods so that you have the added advantage of a shorter(and lighter) piston and better rod anglularity. It will do your cylinder walls a favor.

It is going to take a big set of heads and a big cam to get to your power goals. You can forget camel humps to start. Brodix, Dart, AFR, TFS and others all have big port heads that you will need. I have a set of Dart Pro 1 230cc heads and they are great. Anyone with the others will probably tell you the same. I think you need a head in the 220-230cc intake port range one way or the other. To match those it is going to take a big solid lift flat tappet or a solid roller cam to get the RPM range to make that kind of power. Hydraulics are not too good above 6000-6500RPM, but you might could find a roller that would do what you want. I think it will take a 250-260 duration at .050 cam to make that kind of RPM and HP numbers. Get as much lift as you can on the cam with a 106-108lsa. If you go with a roller you can probably use a little less duration since the big heads will flow better with more lift.

The TH400 will take more power and high RPM lauches with less modification. Either can be made to work, but you really need to talk to a good transmission builder about that. If you are going to buy off the shelf, I would go with a TH400. If this is a race only car(which is should be for what you are talking about building) I would use a 5500RPM convertor. It will launch very hard and keep the engine in the RPM range it needs to be in to work well.

The Victor Jr. will not match the big port heads very well at all. Dart and Brodix both make intakes to match the bigger heads. I am using a regular victor on mine and it sucks. I had to grind most of the intake port away to get a good match and the intake gaskets only have about 1/8 inch to hold on to on the top. I also had to use double thick gaskets to get it to line up better and hopfully keep gaskets in it. An intake designed for the heads will not have that problem. If mine was not EFI I would have switched.

I would go with an 800-900cfm carb for an engine like that. A 750 might get it, but 600+ HP from a 750 is starting to reach.

Just my opinions....


Chris
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Old 07-06-2005, 09:07 AM
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Thanks....I had a Ford 302W, years back that revved like hell and used 300 durations cams,so I assumed a larger motor would like something rough like that too...
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Old 07-06-2005, 09:19 AM
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Quote:
Originally Posted by Zubair
Thanks....I had a Ford 302W, years back that revved like hell and used 300 durations cams,so I assumed a larger motor would like something rough like that too...
It will take more than the old 300 duration cam you are thinking of. You are thinking about advertised duration. Duration at .050 lift is where the real meat and potatoes is.

Chris
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Old 07-06-2005, 09:41 AM
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yes the 4 reliefs can be installed backward. argubly it can make more power.

go 400 for more power. its a hot little mill.
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Old 07-06-2005, 09:51 AM
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You're probably going to need more than 11.5:1 compression to reach 650 HP.

The pistons installed backwards was an old Dodge "factory stock" trick for the 340's & 360's. It pushed the pistons up in the bore {offset pins} and yielded higher compression and near zero quench.
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