rumblefish360
Well-Known Member
Sweet5ltr has good advise IMO, well said.
Waking up the old 400
- Thread starter 73Runner4spd
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kidmopar
Well-Known Member
i have a new 268 hi energy comp cam if u want to go smaller with the cam, it should improve over what u have, the 284 likes more gear and converter to run. let me know.
Sweet5ltr
Well-Known Member
Ebay (Early 80s Direct Connection Engine Manual, $20); http://www.ebay.com/itm/CARROLL-SHE...ure&vxp=mtr&hash=item56478c66da#ht_717wt_1388
Mancini racing (Engine manual from Mopar Performance, $10);
http://chucker54.stores.yahoo.net/mo9thedensps1.html
I own the vintage, D.C. Engine manual but ordered the newer 9th edition Mopar Performance Engine manual this evening. The 9th edition Mopar Chassis manual is also a great piece of literature if you currently don't own one. For $20 you could own both. It's well worth it.
Snoman
Well-Known Member
Thanks Sweet5ltr found them both, That is what i was looking for. Thanks
73Runner4spd
Well-Known Member
Well, first would like to thank everyone for their input on my set up. Unfortunately I did not build this motor. I bought this car pretty recently. I already have the Hooker Competition ceramic coated headers and a set of 3.91s. A stall wont be necessary due to it being a manual. I would be interested in swapping the cam but if it will perform well with the addition of the gears, headers, and a better carb than it may stay. Also this may be an extremely stupid question but I'm going to ask it anyways...The compression I am running is considered "forced induction" compression lol. How long do you think it would take for me to throw a rod or burn a piston by throwing a supercharger on it. As I was told all of the motors that came with the 4 speed consisted of having a forged crank? Is there any truth to this by any chance? I am not really serious about throwing a blower on it but would entertain the idea. Thanks again guys.
Sweet5ltr
Well-Known Member
I am sorry to say but their isn't much truth to the claim of steel cranks being put solely behind 833-4 speeds. Crankshafts were either Cast or Forged. In 1972 Chrysler started installing cast cranks in "B" and "RB" engines. Typically, if your car came from the factory with a four barrel carburetor or a performance package, you will have a factory forged crankshaft (post-1972).
If you plan to stay with the camshaft, a 750cfm (4150 series) carburetor would be mandatory. Your engine would possibly perform better with a 650cfm double pumper carburetor, but it doesn't leave you much room to grow for the future.
Do you currently have an LSD or an "open" carrier?
What intake manifold are you currently running? (Performer or Performer RPM)
73Runner4spd
Well-Known Member
The numbers decode that it was an hp car...well a 73 hp car which we all know is not quite what they were lol. It did come with a 4 barrel and like I said is considered to be a performance car. It has LSD but I think my clutch packs are wearing out cause Ive only been grabbing posi rarely lately. Idk if the guy that built it didnt put any lsd additive or what so I changed the fluid with lsd fluid but its at the body shop right now anyways. And I forget what intake it is. Its a dual plane if that makes any difference between the model of intakes.
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That depends on how much you stick your foot into it and if you tune it right. You can throw a rod or burn a piston with a carb on it but the blower might help 'force' the issue a bit sooner...
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You say that someone else built the motor and it has 915 heads which are way ealier than 72.
Do you know what pistons are in there now? That would need to be determined before any extreme mods. I'd pull the heads for a looksee before ramming air into it.
Do you know what pistons are in there now? That would need to be determined before any extreme mods. I'd pull the heads for a looksee before ramming air into it.
Meep-Meep
дворянин
There are lots of places to loose compression. Just because you have 915 heads you can't assume you are starting from 8.5:1 compression and ending up with 9:1. My 77 440 block has ridiculously huge bore chamfers that add a few CC's to the chamber volume. My KB pistons have what looks like the Grand Canyon for valve reliefs. Add all that up and I'm at 10.1:1 with a steel shim gasket, -.015" deck pistons and 915 heads. In the earlier 440 block I would be closer to 10.5:1 or better.
If you know the engine is bone stock take the conservative route with the cam. Don't fuss over lift specs but select a cam with no less than 112 lobe separation and a fairly early intake valve closing point. Seek a cam that is specifically designed for low compression. Edelbrock, Crane, Comp all have something that will work. 600 CFM is plenty and the factory cast iron intake will do the job just fine.
Or put a motorhome turbo setup on it with EFI.
If you know the engine is bone stock take the conservative route with the cam. Don't fuss over lift specs but select a cam with no less than 112 lobe separation and a fairly early intake valve closing point. Seek a cam that is specifically designed for low compression. Edelbrock, Crane, Comp all have something that will work. 600 CFM is plenty and the factory cast iron intake will do the job just fine.
Or put a motorhome turbo setup on it with EFI.
racedodge
Well-Known Member
I disagree on the 600 cfm carburetor as a selection for usage. It is small for a big block IMO. Now with that being said, I take my cars up to 6000 rpm on occasion (more often than not) so a 600 would tend to lean out at the top end. So, with that being said, you need to identify what your driving style will be to determine the size of carburetor you plan on using as it is a variable just as much as camshaft, heads, etc. If you plan on cruising 99% of the time below 4500 rpm, then a 600cfm carb will do what you want, but if you plan on doing a 40/60% split above 4500 rpm (e.g. racing on the strip) the 600 is not the choice for you.
Sweet5ltr
Well-Known Member
272*/.455 Lift "Purple Shaft" Camshaft with 112LSA. 1,300-5,700RPM.
http://www.summitracing.com/parts/DCC-4286677/
Satellite65
Well-Known Member
That thought crossed my mind when I was going over my 440 last year. My pistons were TRW 2388's (long story) that yielded a whopping 7.8:1 compression with my 906 heads. This is a steel crank motor and would have made a great candidate for a turbo or supercharger. I decided the expense and complexity wasn't worth it so I ripped into it, swapped in a set of 2355's to up the CR to 9.6:1 and went with a more modern cam grind (Comp XS268S). The project has stalled due to lack of time and funds but I should have it running by spring. I think it'll have a bunch more oomph than it did before.
Wookie316
Well-Known Member
I have a new one of these I am not going to be using if anyone is interested. My build changed & I no longer need this cam.
Meep-Meep
дворянин
On the contrary a too large carb will tend to lean out at the top end because it's easier to move air than fuel. I agree 600 CFM may not be the ultimate for producing max power at 6000 RPM so the key is picking a carb that best suits your needs - as you have stated. All carbs work better with a stronger signal and it's usually best to be on the conservative side.
Meep-Meep
дворянин
I'm running that exact cam in my 440 and it's fantastic, however I don't know how it will respond with 9.0:1 CR or less. I'm running 10.1:1 and I believe any less is falling off the peak of efficiency. My car runs high 12's with that cam and a factory iron intake.
rumblefish360
Well-Known Member
Pm coming about the cam.
Sweet5ltr
Well-Known Member
I run the 509 "Purple Shaft" in my CME 9.75:1 451. I can tell you right now, with a basic 'untouched' Holley 750CFM 4150 series carburetor it ran completely off key. Installed another 750CFM 4150 series carburetor with a Proform Main body and Base plate (along with the correct jets, boosters, and power valve) that came off of an old friends 421rwhp SBF and it runs fantastic. The correct carburetor and tuning can make all the difference. Exactly like you are stating, if you don't build the car to be efficient in the camshafts power band then you are asking for a beating at the strip. In your case, you have a very well matched combination and the ET shows it.
droptop
Well-Known Member
This is what I did to wake up my 75 400. I used 383 intake, exhaust manifolds, and cam from a '69 Road Runner. I had the '69 906 heads milled 60 thou to help with the compression. Of course the intake had to be machined to these heads. I also used metal shim head gaskets instead of the composite gaskets. The rocker arms had to be shimmed with 30 thou shims, if I remember correctly. With the Eddy aftermarket elec. choke carb. it has a lot of low end torque and gets about 14 MPG. By no way is this a 1/4 mile bomber, but I am not afraid to pull out in heavy traffic, if you know what I mean.
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