Low Compression 440 Build Questions
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twostick
Senior Member
My 493 with a custom reverse dome piston, zero deck and Edelbrock RPMs came in at 8.97:1 compression. Round figures, it made 500 hp, 600 ft/lbs and is happy on all but the hottest days on 87 regular. If I were to add some RPM to the timing curve, it would probably be happy all the time. 34 degrees all in by 2000 is a little aggressive.
Kevin
twostick
Senior Member
If you were just wanting to wake up your current combo without a rebuild, a new timing set with the extra keyways so you can advance the cam 4 degrees plus a performance distributor recurve will get you some amazing gains for very little money.
A stock iron Thermoquad intake is more than enough for a tweaked stock combo and you said you have 3.23s.
2.5" duals to finish and it's going to be much harder on rear tires.
Kevin
A stock iron Thermoquad intake is more than enough for a tweaked stock combo and you said you have 3.23s.
2.5" duals to finish and it's going to be much harder on rear tires.
Kevin
496 polara
Member
If you have a sound motor then minor upgrades will surprise you.
Recurve the distributor for more initial and a quicker curve.Use vacuum advance.
2.25 minimum dual exhaust and 2.5 is fine also. Mufflers up to you but I like the longest case dynomax Super Turbo for better flow and not loud.
Don't need HP manifolds.Money better spent on headers or use the logs. I have run the Hedman shorty headers and the Hooker Super Comp 1 3/4 tubes on c bodies. The TTi 1 7/8 are too big for most C body engines. I would not be opposed to the Schumacher tri y either but have not run them on a c body.
If you get into modifying the engine I would rather have a good set of ported heads with a stock Cam than a bigger cam and stock heads. Airflow is power.Period.
Stock intake is fine unless you go to the next level.
Carb is up to you. Anything 650 or larger. Smaller throttle bores will help throttle response.
An interesting thread here to read. A lot of talking and the test starts at post 49
Iron head test starting on '78 440.
The single plane intake and larger cam don't necessarily jive with a c body and 3.23 gears but there is a lot of useful info here.
Recurve the distributor for more initial and a quicker curve.Use vacuum advance.
2.25 minimum dual exhaust and 2.5 is fine also. Mufflers up to you but I like the longest case dynomax Super Turbo for better flow and not loud.
Don't need HP manifolds.Money better spent on headers or use the logs. I have run the Hedman shorty headers and the Hooker Super Comp 1 3/4 tubes on c bodies. The TTi 1 7/8 are too big for most C body engines. I would not be opposed to the Schumacher tri y either but have not run them on a c body.
If you get into modifying the engine I would rather have a good set of ported heads with a stock Cam than a bigger cam and stock heads. Airflow is power.Period.
Stock intake is fine unless you go to the next level.
Carb is up to you. Anything 650 or larger. Smaller throttle bores will help throttle response.
An interesting thread here to read. A lot of talking and the test starts at post 49
Iron head test starting on '78 440.
The single plane intake and larger cam don't necessarily jive with a c body and 3.23 gears but there is a lot of useful info here.
wyrmrider
Member
Lots of good replies
I owned 2 Imperials and TWO 73 New yorkers and a 78 Maxivan
I helped design the Micey Thompson quench dome pistons now maybe also ICON which were suggest as from Hughes
If you are NOT going to change the pistons use the Mike Jones Motorhome cam 256@.006 204 @.050 .305 lobe lift or a similar one from HOWARDS run Rhodes you liftersas
you need keep the dynamic compression as high as possible 10 more degrees will kill your grunt with your gears and a stock converter
If changing pistons use the quench domes and you must deck block for close piston to head clerance
now you do NOT have hard exhaust seats so if you are going to run it hard or tow or if your exhaust seats are worn you need seats use the premium DURABOND sintered iron seats
you will need guides do a modern 5-7 angle valve job on the intakes and a radius job on the exhaust backcut the intakes viton seals
you might investigate beehive valve springs and retainers
you can use K line conversion guide sleeves and go to 11/32 valves but this is not a race car
if you need new valves the traditional way is the MOPAR PERFORMANCE oversize valves then open the bowls to 90 % leave the seats wider that a racecar the valves loose heat thru the seats
It may be cost effective to go to aftermarket heads with non open chamber not Hughes and there are better combustion chambers than Edelbrock unless they changed the were old wedge style
Trick Flows may be best but touch up the valve job and you may want to consider beehive springs and retainers
I'd as Eric Weingartner to buy and build the heads if I wanted a top notch job )I can do it myuself) Let Eric pick the heads
stock pistons will still be way down the hole and you need to find some D Dish pistons to get compression and tight quench
still heads and cams can be a cost effective answer you just need to watch you timing and gas
If your compression is up then get your head flows and just bite the bullet and ask Mike Jones to do a cam for your combination
maybe a feww more bucks than a shelf cam but his consulting is worth it and you will end up with more torque
Tranny Transgo reprogramming kit and if you do a rebuild choose between a 518 and a lock up pump and converter all well known mods I did both
I owned 2 Imperials and TWO 73 New yorkers and a 78 Maxivan
I helped design the Micey Thompson quench dome pistons now maybe also ICON which were suggest as from Hughes
If you are NOT going to change the pistons use the Mike Jones Motorhome cam 256@.006 204 @.050 .305 lobe lift or a similar one from HOWARDS run Rhodes you liftersas
you need keep the dynamic compression as high as possible 10 more degrees will kill your grunt with your gears and a stock converter
If changing pistons use the quench domes and you must deck block for close piston to head clerance
now you do NOT have hard exhaust seats so if you are going to run it hard or tow or if your exhaust seats are worn you need seats use the premium DURABOND sintered iron seats
you will need guides do a modern 5-7 angle valve job on the intakes and a radius job on the exhaust backcut the intakes viton seals
you might investigate beehive valve springs and retainers
you can use K line conversion guide sleeves and go to 11/32 valves but this is not a race car
if you need new valves the traditional way is the MOPAR PERFORMANCE oversize valves then open the bowls to 90 % leave the seats wider that a racecar the valves loose heat thru the seats
It may be cost effective to go to aftermarket heads with non open chamber not Hughes and there are better combustion chambers than Edelbrock unless they changed the were old wedge style
Trick Flows may be best but touch up the valve job and you may want to consider beehive springs and retainers
I'd as Eric Weingartner to buy and build the heads if I wanted a top notch job )I can do it myuself) Let Eric pick the heads
stock pistons will still be way down the hole and you need to find some D Dish pistons to get compression and tight quench
still heads and cams can be a cost effective answer you just need to watch you timing and gas
If your compression is up then get your head flows and just bite the bullet and ask Mike Jones to do a cam for your combination
maybe a feww more bucks than a shelf cam but his consulting is worth it and you will end up with more torque
Tranny Transgo reprogramming kit and if you do a rebuild choose between a 518 and a lock up pump and converter all well known mods I did both
volksworld
Well-Known Member
the problem I ran into was that most of the available pistons wound up with under 8-1 or over 10-1...for a mild factory air automatic barge I wanted to stay around 9-1...(cue the "my 11-1 motor runs great on regular" crowd)...I used the dished ICON's, but those only come with the .990 big block chevy wrist pins so I had to spring for new rods too...by the time I did that and had it balanced I have a feeling a stroker kit wouldn't have been that much more...rest of combo HP manifolds (for looks more than performance),TTI 2 1/2 exhaust, performer 440 and 750 Holley, Hughes 2024 cam kit (remember I wanted it to idle with the factory air)
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jim almond
New Member
more compression will definitely help. Also, hughes makes a whiplash cam specifically for low compression motors. A factory hi stall converter, along with free flow intake and exhaust, and recurved distributor will wake it up as well.
wyrmrider
Member
agree on the quench dome pistons, ixnay on the stock cams they have long close ramps to act like an EGR and reduce smog last thing you need is late losing good discussions on the converters or you can go lock up converter and pump
wyrmrider
Member
recurve dist will work noneed for morewith resonable compression BVVC on Whiplash style cams they try to make a hot rod sound at the expense of torque I make dynot tested suggestion later
wyrmrider
Member
Howard has a better choice that the rattler or whiplash unless you are just building for a hot rod sound
wyrmrider
Member
Iused the 6 pack pistons and 915 heads but milled a D dish in the heads like the old TRW TURBO piston best combi with a stock looking head
NO WAY to make open chamber heads work without quench dome pistons
wyrmrider
Member
Exactly but build good quench
wyrmrider
Member
If you want to use pump gas you need to loose the open chamber heads with dished pistons (with or without stroker) We had a production rebuilder line to redoo MOPAR
Transit bus 440's Puttin in quench and the right cam reduces EGT temp 800 degrees under a
continuous load like going uphill Open chamber reqheads require race gas or E85 and timing fudges in a vehicle with your converter and gears and weight
If you know how to tune that carb ok otherwise TQ is your best choice Alum manifold just saves weight no real HP gain with your rpm range
ANY cam with longer overlap will have a certain amount of internal EGR due to reversion in the chamber and intake manifold at lower rpms. That is usually where the "lumpy" sound comes from. BUT the longer overlap will help power over 3000rpms, as longer durations do to.
By 1972, the OEM cams had a bit more duration and more overlap, with the overlap being an emissions issue as the longer duration was to help better-fill the cylinders to help compensate for the lower CR. Ford also did this on their 1974 351HO motors.
Until more people got cyl head flow benches, all porting was done "by sight" and what was thought to look good. Just as the ports in the 906s were supposed to be better than the prior heads. Same on the Stage IV DC heads. When the main difference was the larger exh valve. As ALL B/RB heads, when ported with the MP Porting Templates, would all flow the same. THEN came the quench dome pistons and we learned that quench was better than not. By that time in the later 1980s, most of the older closed chamber heads had been scrapped as "bad", I suspect, when all they needed was the larger exh valve of the 1967 GTX 440. BTAIM
On our '72 Newport 400 2bbl, the exh temp was higher than our similar '66 Newport 383, open chamber vs closed chamber heads. The higher exh heat was used to allow the residue combustibles in the exh gases to more fully cook by the time they got to the end of the pipes. Without an external AIR pump, on non-cat converter vehicles.
I KNOW there has to be some engineering papers somewhere which indicates the emissions output of a stock 256/260 cam vs a similar aftermarket cam, as to which is cleaner, uses fuel better for better cruise economy, and ultimate power output. Everybody monitors air/fuel at WOT on the dyno runs, but none of the other stuff. Surely, with all of the cam lobes out there, there has to be a better combination we could buy and enjoy?
Such a test would be costly and time-consuming to do. Plus the additional instruments needed. I suspect the current "corporate" magazines would want to undertake such testing, either. Nor would the corporate cam vendors, I suspect.
I have seen some tests about lobe center separation specs affecting power below 3000rpm, but little else. For a stock, street engine, some minor changes can affect power more than not, it seems. A "torque" motor that is not shy about hitting 5000-5500rpm is the goal.
CBODY67
wyrmrider
Member
NO that combination will not work with your converter and gears andheavy car
Hughes stuff is way overpriced and do not even think about Whiplash or Rattler you look atg the specs of those cams and see that the rattler needs more compression and the whiplash will not idel and gas mileage will suck there is no free lunch
Without going into the short block the Jones cam or the similar howard is about all you can do
your carb and manifold will make no difference over stock but your choice the tq will give better gas mileage
if you decide to get into heads and block give me a pm
I've built hundreds of low compression 440s
second most economical thing ks going to quench dome pistons
changing to higher compression flat top pistons with open chamber heads without quench gets you into detonation easier ok if you have E85 or you convert to Propane but not on pump gas
Hughes stuff is way overpriced and do not even think about Whiplash or Rattler you look atg the specs of those cams and see that the rattler needs more compression and the whiplash will not idel and gas mileage will suck there is no free lunch
Without going into the short block the Jones cam or the similar howard is about all you can do
your carb and manifold will make no difference over stock but your choice the tq will give better gas mileage
if you decide to get into heads and block give me a pm
I've built hundreds of low compression 440s
second most economical thing ks going to quench dome pistons
changing to higher compression flat top pistons with open chamber heads without quench gets you into detonation easier ok if you have E85 or you convert to Propane but not on pump gas
fury fan
Senior Member
Yes, the author of that thread (IQ52) has done a number of low-CR builds and done A->B parts swaps and dyno'd the results.
He's done excellent work, much to be admired that he's put it out there for us to see.
While he does dispel some wive's-tale myths, there are 2 caveats:
1. I believe he blueprints those low-CR shortblocks, so he's therefore getting the max they can deliver. Someone else's rebuild might not perform as well.
2. #2, and this is the big one - he's not showing any dyno data below 3000rpm, and that's where you'll spend 90% of your time. You must pass thru the lower rpm before you ever get to the high RPM. That can be a VERY disappointing area for a heavy car.
You have a lot of possibilities, but the best bang for the buck is higher compression pistons! Even a stock 440 HP cam and heads will make a lot more power than anything with the lower compression pistons! For a distributor, I'd highly recommend getting in contact with Halifaxhops who rebuilds distributors and is on all the mopar sites.
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