Dyno a 7.5:1 400? Sure, why not?

-
dukeboy_318 said:
Ok, my concern is that I am wanting to go to ebby RPM heads at some point when I can, mainly for weight savings as well as power. Would that affect the CR enough to actually hurt the performance? I currently have regular Silvolite 1263 flat top pistons but was thinking of jumping up to 6-pack piston with valve cuts, L2335 is it?
Click to expand...


Well the piston is L2355. If you went to the RPM cylinder head it will only make everything better. With that piston, zero deck height, .039 gasket and the 84cc head you'll only be at 10:1 compression. Check piston to valve clearance carefully as I had to flycut the L2355 pistons on 'Pop's 440' when we went to the roller cam.
 
Nice info, thanks for sharing this.
I've recently wrenched together a bone stock 400 as a simple cruiser engine.
Didn't change much on the stock internals, except for a different stockish cam and new cambearings.

I used steel headgaskets and 915-heads to up the CR a bit but I didn't cc or measure anything to find out where I was at.

Overal vacuum is fairly low still so I suspect the piston rings have seen better days.
Also still need to play with the ignition curve a bit as the engine doesn't feel strong at low rpm and also runs hot after some highway-time.
 
IQ52 said:
Well the piston is L2355. If you went to the RPM cylinder head it will only make everything better. With that piston, zero deck height, .039 gasket and the 84cc head you'll only be at 10:1 compression. Check piston to valve clearance carefully as I had to flycut the L2355 pistons on 'Pop's 440' when we went to the roller cam.
Click to expand...

Ok, I was thinking of the Comp Cams XE285HL cam as well. If I had the coin, I'd ship this thing off to you and let you work your magic. Sucks being on a budget. :wack:
 
whitepunkonnitro said:
One of the things I've been wanting to experiment with are shims or pucks that can be attached to the piston head with taper head allen screws...positioned more or less the way gas ports are. The weight would be insignificant considering where in the assembly it is positioned, and it would open up a universe of possibilities as far as compression and more importantly quench is concerned. It sounds off the wall, but I can't see any reason why it would not work.
Click to expand...

Weight would be significant. Better option would be quench 'turtles' in the combustion chambers, they wouldnt move and being a wedge head, the could be away from the valves. Would have to be fastened somehow and butt against the cylinder wall as they sure would want to move over with every power stroke. You could manufacture them with a .040 ring that would overlap the cylinder in the fire ring of the head gasket so it would be a captive fit..too many fitment issues but....?
 
pishta said:
Weight would be significant. Better option would be quench 'turtles' in the combustion chambers, they wouldnt move and being a wedge head, the could be away from the valves. Would have to be fastened somehow and butt against the cylinder wall as they sure would want to move over with every power stroke. You could manufacture them with a .040 ring that would overlap the cylinder in the fire ring of the head gasket so it would be a captive fit..too many fitment issues but....?
Click to expand...


A couple of years ago I welded up a quench head for a Slant, but never got to finish the project. I did consider what you are talking about, but wasn't crazy about the thin shell of combustion chamber they would be attached to...and the water behind it.
I'd like to get the opinion of someone who is versed in balancing reciprocating assemblies. Would the weight of say, a .150 thick slice of aluminum the diameter of the piston head adversely affect the balance of the engine?...at what RPM would it become critical?
 
Welding up and machining a pair of open chamber smogheads would be a lot of work for usually only a .5 point of compression gain.
Great if you have (access to) a mill and some spare time to do the work yourself.
 
I'm running a 400 in my duster. Honed, stock pistons, steel crank, same summit cam, iron adjustable rockers, wind age tray and baffled pan, 906 heads with a valve job and decked just to clean up. Steel shim head gasket, Performer intake, 750vs, and headers. Stick with 3.73s. It's an ok combo. I took it to the track but it was kind of embarrassing. With some wheel spin went 15.1 @ 99mph. I put on some drag radials went back and had some issues with clutch pedal setup. I never got a good run out of it and haven't had the interest in going back, was kind of a buzzkill for me. This was something I put together with junk I had, just to set the car up. I wasn't expecting to go 12s with what I have, but I thought mid 13s would be achievable. I put almost 10,000 trouble free miles on it so far, so it's serving it's purpose.
 
jamesdart said:
I'm running a 400 in my duster. Honed, stock pistons, steel crank, same summit cam, iron adjustable rockers, wind age tray and baffled pan, 906 heads with a valve job and decked just to clean up. Steel shim head gasket, Performer intake, 750vs, and headers. Stick with 3.73s. It's an ok combo. I took it to the track but it was kind of embarrassing. With some wheel spin went 15.1 @ 99mph. I put on some drag radials went back and had some issues with clutch pedal setup. I never got a good run out of it and haven't had the interest in going back, was kind of a buzzkill for me. This was something I put together with junk I had, just to set the car up. I wasn't expecting to go 12s with what I have, but I thought mid 13s would be achievable. I put almost 10,000 trouble free miles on it so far, so it's serving it's purpose.
Click to expand...

Don't be so quick to write off your combination. The absolute truth is that MOST supposedly 10 second cars out there...all the good parts, lots of trick stuff...would be lucky to wheeze their way down the track in the 14's. Why? Because a car is a system, and if even one seemingly minor part is overlooked, or one important system is not tuned or matched correctly, the whole thing is rendered lame.
Is your carb jetted correctly? Distributor curved/timed the way it should be? Are you getting enough fuel to the engine throughout the entire run? I could go on and on..all simple stuff.
Spend some time tuning and optimizing all of the systems in your car, and there's no question that you've got a 12 second run in that combination. Many people have gone much faster with much less...you can do it too!
 
It's been a while, I actually think the mph was much lower. I didn't put this one together to race, I have another car for that.
 
My wife drives a '74 four door newport that we've had for 20 plus years and just for sh*ts and giggles I put on a performer intake, carter 600 afb, performer plus cam, mp distributor, a cloyes double roller timing chain ( just in time too, one tooth broke off and multiple cracks on the cheap stock one ) and a dynomax turbo muffler so it could pass slow traffic easier and you could really feel the extra power, you should hear her pulling out of the driveway, BAWWWWAAAAAA. I stopped there so it still has the stock manifolds and single exhaust, now I'm gonna put on a 750 holley and dual x pipe exhaust, all things just lying around anyway, she'll love it. She will want a bigger cam and headers next.

Jeff
 
The good thing about these Low CR builds it show people you don't have to tear into a decent short/long block to get some decent power levels. Of course the 400 would of benefited a bump of CR to 9:1 still would of been streetable and probably make 20 hp.
 
I'll second that.

When the time comes I would like to grab a set of E-streets and a small solid roller. Something that can take advantage of the heads flow abilities. 1.6 rockers are not out of the question.
I'm working with the same intake and I have a few TQ's to toy with that work very well. Love the flexable spreadbore. Plenty of CFM.

I like Moparlovers build. 470 HP ain't to shabby!
 
this also shows the importance of good flowing heads and a big carb! forget those cfm calculators to pick a carb!
 
Bump, for no good reason except a hope some one see's this.
 
I am getting ready to do a similar build on a 400 Ford engine but my compression will be blueprinted at 8.5.
 
Exactly! You never know (cough cough) who is running a 400 (cough cough) in there Duster.. (Ah-Chew! Cough cough!)

Lmao
 
rumblefish360 said:
Any updates?
Click to expand...

The customer called about a month ago and said the engine has a knock. So we went over and tightened the header bolts and the "knock" went away. Saw him leave the gas station a week ago in a cloud of tire smoke with a big grin on his face. Still running the 2bbl.
 
Jim yer full of it. You know low compression caint smoke tires. lol
 
I had a 383 Chevy I installed for a fellow along with a bunch of other work on his Camaro. He came back a day later with it "rattling like crazy". I looked at it, and said give it another 2 days and drive it both days". He called three days later and said "what did you do?" I said " those two heat cyclyes gave the Stage 8 fasteners time to tighten themselves up"...lol. At least it wasn't a knock tho Jim. That's terrible...lol.
 
Great info on the "smog" 400 and 440. With gas as it is now,even premium isn't what it use to be. Just goes to show ya, Bigblock mopars are beasts. Now if we could play with em AND get 20 plus mpg.....
 
I've got a 400 and an A833 OD I'm planning on putting in my 75 Dart. I got a stock bottom end with 30 over KB 240 pistons and lunati 10230703LK . Duration is 226/234 @ 50 and lift is .494/.513. planning on buying the weiand action+plus dual plane and 770cfm Holley street avenger. Any recommendations on a decent head that isn't too expensive? I've been looking at the 440 source stealth heads but Is there any other options that are a better bang for your buck?
 
Scott's dart said:
I've got a 400 and an A833 OD I'm planning on putting in my 75 Dart. I got a stock bottom end with 30 over KB 240 pistons and lunati 10230703LK . Duration is 226/234 @ 50 and lift is .494/.513. planning on buying the weiand action+plus dual plane and 770cfm Holley street avenger. Any recommendations on a decent head that isn't too expensive? I've been looking at the 440 source stealth heads but Is there any other options that are a better bang for your buck?
Click to expand...

I kinda like the standard 440 Source heads and a lot of people run them OOTB. But I think they need a lot of prep work. For another option in lower priced aluminum heads you could look into these.

mopartsracing - Sidewinder Cylinder Heads For Big Block Mopar
 
You must log in or register to reply here.
-

Back
Top