Author Topic: Lunati 704 or 705 Cam? (Read 6012 times)

usraptr · « **on:** March 10, 2016 - 03:49:54 PM »

'70 'Cuda with a 440, .30 over with 440 Source 512 stroker kit with dished pistons and valve reliefs. ProMaxx aluminum heads 84CFM (not ported). Either Edelbrock performer, or Holley SD, or Mopar dual plan intake (Shaker hood clearance issues so can't run a high rise intake) and probably an Edelbrock AVS 800 CFM carb (I haven't decided for sure on Carb. I'm trying to get something that won't require modifying the shaker base plate) and Headers. '70 4-speed with Dana 60 4:10 gears. Power brakes. BTW I have access to 100 octane gas at a local station. Car with be a car show, cruise night, weekend driver/warrior.

With 4:10 gears I won't be going on many road trips.

I asked Lunati support for cam recommendations. Originally, I told them all of the above with stock 440 stroke with 440 Source rods and pistons and they recommended the 10230704 Cam. Then I changed my mind and decided to get the 512 stroker and they recommended the 705 cam. I have three concerns with the 705 cam. It says it requires a minimum of 10:5 compression. 440Source web site says the 512 stroker with 84 CFM heads makes 10.05CR. It doesn't specify iron or aluminum heads) However, I know the aluminum heads reduce the compression about a point so will I have enough compression for this cam?
Secondly, the 705 has a .533/.552 lift. Is that going to cause any clearance issues with my pistons with valve reliefs? Lastly, will either the 704 or 705 pull enough vacuum for the power brake booster or am I going to have to use a vacuum canister?
Lunati describes the 704 as a "Hot Street cam" and the 705 as a "Very hot street/bracket race applications." Don't get me wrong, I have no problem running a hot cam but just wondering from those with more experience with these cams if the 705 is going to be too hot for my application, if there is such a thing?

734406pk · « **Reply #1 on:** March 10, 2016 - 07:58:40 PM »

The piston to valve clearance will need to be checked no matter which cam you choose. Aluminum heads don't decrease the compression ratio, they allow you to run a higher compression ratio before detonation due to their greater thermo-conductivity and possibly combustion chamber shape. .040-.060 quench would be necessary and most likely a manual secondary Holley type carb with around 950 cfm IMOH. Good luck on your 512 build!

Chryco Psycho · « **Reply #2 on:** March 10, 2016 - 09:40:06 PM »

we really need a lot more info. What gearing & tire size ,auto or 4 spd
the 512 will make the cam seem smaller & will lower the rpm range of the vam by about 500 rpm but you still want the combo to match up so it is making power where you want it tith the rest of the package .
As stated above Piston to valve needs to be confirmed but with notched pistons generally you are OK at 5.50 lift & you need quench

usraptr · « **Reply #3 on:** March 10, 2016 - 09:58:56 PM »

Chryco Psycho, gearing is 4:10, OEM 4-speed with E60X15s + 25.5" tall. Can you explain what you mean by I "need quench" please? I'm confused about just what quench is and specifically what needing it is?

Chryco Psycho · « **Reply #4 on:** March 11, 2016 - 07:56:36 AM »

Quench is having the piston close to the head , less than .040 is too close but more than .080 you lose quench .
Quench creates a lot of violent turbulence in the combustion chamber squeezing the A/F mix towards the spark plug & effectively killing detonation this is more important than actual compression ratio when dealing with detonation problems

usraptr · « **Reply #5 on:** March 11, 2016 - 10:54:44 AM »

Quote from: Chryco Psycho on March 11, 2016 - 07:56:36 AM

Quench is having the piston close to the head , less than .040 is too close but more than .080 you lose quench .
Quench creates a lot of violent turbulence in the combustion chamber squeezing the A/F mix towards the spark plug & effectively killing detonation this is more important than actual compression ratio when dealing with detonation problems

Thank you. Based on the 4-speed and 4:10 gears which cam would you run, the 704 or 705?

Chryco Psycho · « **Reply #6 on:** March 11, 2016 - 12:59:14 PM »

well with the 4 spd you have a lot more latitude , so at 70 mph you will be at 3800 rpm you do not have to wrry about stall speed as you can load the engine at any RPM you want so either will work 704 is rated 2200-6500 705 is rated 2500-6500 so the 04 will have a bit more vacuum at idle & more low- midrange
& the 705 will be better mid - top end ..... your call

usraptr · « **Reply #7 on:** March 11, 2016 - 01:31:14 PM »

Thank you

734406pk · « **Reply #8 on:** March 11, 2016 - 07:25:16 PM »

I would not recommend using the Carter style AVS carb for this engine. Tuning parts are limited for them. A Quickfuel with adjustable air bleeds etc (or equivalent) would be a nice match. Easy to tune and plenty of parts available. The AVS is a good carb but should be used on a stock to lightly modded engine for best results IMO.

Chryco Psycho · « **Reply #9 on:** March 12, 2016 - 06:08:04 AM »

totally the AFB/ AVS are very hard to tune for the low vacuum engines

usraptr · « **Reply #10 on:** March 12, 2016 - 11:03:16 AM »

Thanks, I will probably go with a Quick fuel then.

dfrazz · « **Reply #11 on:** March 12, 2016 - 11:15:36 AM »

Quote from: usraptr on March 12, 2016 - 11:03:16 AM

Thanks, I will probably go with a Quick fuel then.

Check out Proform carbs. QF and Proform actually swap parts when assembled, and Proform's are less expensive (for now). I have one on my 440 and love it!

1 Wild R/T · « **Reply #12 on:** March 12, 2016 - 01:07:19 PM »

Quote from: Chryco Psycho on March 11, 2016 - 07:56:36 AM

Quench is having the piston close to the head , less than .040 is too close but more than .080 you lose quench .
Quench creates a lot of violent turbulence in the combustion chamber squeezing the A/F mix towards the spark plug & effectively killing detonation this is more important than actual compression ratio when dealing with detonation problems

Your numbers are wrong... Period... .080??? Seriously? Your begging for detonation at that point.... .055 is the iffy zone... .040 is the standard number.. I've seen guys run as tight as .024, generally you stay away from tighter than .035.. But if your gonna wind up at .065 you might as well go for .100....

The trend these days is the tighter the better, the more turbulent mixture makes more power & eliminates detonation...

This cut & paste is pretty old at this point but very good info...

What is the most, exact precisely defined occurrence in all piston engines? It isn�t ignition timing, combustion, crank indexing, or valve events. It is Top Dead Center. You can�t build an engine with an error at Top Dead Center because TDC is what everything else is measured from. Spark scatter, crank flex and cam timing can move, but TDC is when the piston is closest to the cylinder head in any one cylinder. The combustion process gets serious at Top Dead Center and about 12 degrees after TDC, most engines want to have maximum cylinder pressure. If maximum cylinder pressure occurs 10 degrees earlier or later, power goes away. Normal ignition timing is adjusted to achieve max cylinder pressure at 12 degrees after TDC. If your timing was set at 36 degrees before TDC that is a 48 degree head start on our 12 degree ATDC target. A lot of things can happen in 48 degrees and since different cylinders burn at different rates and don�t even burn at the same rate cycle to cycle, each cylinder would likely benefit from custom timing for each cylinder and each cycle. Special tailored timing is possible but there is an easier way��Magnificent Quench�. Take a coffee can � full of gasoline burning with slow flicking flame. Strike the can with a baseball bat and you have what I would call a �fast burn�, much like what we want in the combustion chamber. The fast burn idea helps our performance engine by shortening the overall burn time and the amount of spark lead (negative torque) dialed in with the distributor. If you go from 36 degrees total to 32 degrees total and power increases, you either shortened the burn time or just had too much timing dialed-in in the first place. If you have really shortened the burn time, you won�t need so much burning going on before Top Dead Center. Now you can retard timing and increase HP. Did you ever have an engine that didn�t seem to care what timing it had? This is not the usual case with a fast burn combustion but an old style engine with big differences in optimum timing cylinder to cylinder will need 40 degrees of timing on some and others only need 26 degrees. If you set the distributor at 34 degrees, it is likely that 4 cylinders will want more timing and 4 cylinders will want less ( V-8). Moving the timing just changes, which cylinders are doing most of the work. Go too far and some cylinders may take a vacation. Now what does quench really do? First, it kicks the burning flame front across and around the cylinder at exactly TDC in all cylinders. Even with spark scatter, the big fire happens as the tight quench blasts the 32 degree old flame around the chamber. Just as with the coffee can, big flame or small flame, hit it with a baseball bat and they are all big instantly. The need for custom cylinder-to-cylinder timing gets minimized with a good quench. The more air activity in a cylinder you have the less ignition timing you are likely to need. When you add extra head gaskets to lower compression you usually lose enough quench that it is like striking the burning coffee can with a pencil. No fire ball here and that .070-.090 quench distance acts like a shock absorber for flame travel by slowing down any naturally occurring chamber activity. A slow burn means you need more timing and you will have more burn variation cycle-to-cycle and cylinder-to-cylinder, result more ping. Our step and step dish pistons are designed not only to maximize quench but to allow the flame to travel to the opposite side of the cylinder at TDC. The further the flame is driven, the faster the burn rate and the less timing is required. The step design also reduces the piston surface area and helps the piston top stay below 600 degree f (necessary to keep out of detonation). All of our forged pistons that are lower compression than a flat-top are step or step dish design. A nice thing about the step design is that it allows us to make a lighter piston. Our hypereutectic AMC, Buick, Chrysler, Ford, Oldsmobile and Pontiac all offer step designs. We cannot design a 302 Chevy step dish piston at 12:1 compression ratio but a lot of engines can use it to generate good pump gas compression ratio. Supercharging with a quench has always been difficult. A step dish is generally friendly to supercharging because you can have increased dish volume while maintaining a quench and cool top land temperatures. You may want to read our new design article for more information. ".

By John Erb
Chief Engineer
KB Performance Pistons

72bluNblu · « **Reply #13 on:** March 12, 2016 - 01:38:10 PM »

I realize this for is a big block so it's not an apples to apples comparison, but I run the Lunati Voodoo 10200704 in my 340. The cam has the same specs, although obviously the different displacement, cylinder and valve sizes make a difference. My 340 is .060" over so 4.1" bore, 2.02/1.60" valves and iron 308 heads ported and flowing 264 cfm @ .500". Compression is 9.8:1, and I also run a 4 speed although currently with 3.55's and 26" tall tires.

With the smaller displacement the cam probably seems hotter, and in my combo it pulls about 10" of vacuum at idle, which is around 800 rpm (about as slow as it will go). I had a heck of time trying to tune it to work with a vacuum secondary carb, and did a lot of tuning trying to get a 670 and then a 770 street avenger to work. Even using a A/F gauge I couldn't ever get the transition into the secondaries right. They worked great on the primaries, or WOT, but going through the primary to seondary transition was never right, even after going through the entire line of pump cams, secondary springs, pump shot nozzles, etc. I went to a 750 double pumper with mechanical secondaries and had it sorted out a day, no problem. I'm not a carb tuning expert by any means, but that was my experience and using the wideband A/F takes a lot of guesswork out of the tuning process.

Even with 9.8:1 compression I pulled a few degrees of timing out of it to stop it from detonating on 91 octane pump fuel (best I can get in California at the "normal" pumps). I run 20* advanced at idle and all in mechanical at 34*, with everything in at a little over 3k. I also have an early 340 though, so the pistons are .018" over the deck and I run open chambers so obviously the chamber shape etc is different.

I use the Duster that the 340's in as my daily driver. It's probably a little hotter on the cam than I should be for what I do with the car. It runs great and stays cool, but it is definitely a little work to drive it in traffic. For a weekend car it would be great, and with the additional displacement and the stroker you could probably get away with the 705 if you're not frequently driving in traffic or using the car as a daily. Like I said, it's a small block so take it all with that in mind, but maybe it will help with your decision.

Here's a clip of my car at idle with the #10200704 in my 340...

https://youtu.be/62bjHlxzsoA

734406pk · « **Reply #14 on:** March 12, 2016 - 06:47:14 PM »

Quote from: 72bluNblu on March 12, 2016 - 01:38:10 PM

I realize this for is a big block so it's not an apples to apples comparison, but I run the Lunati Voodoo 10200704 in my 340. The cam has the same specs, although obviously the different displacement, cylinder and valve sizes make a difference. My 340 is .060" over so 4.1" bore, 2.02/1.60" valves and iron 308 heads ported and flowing 264 cfm @ .500". Compression is 9.8:1, and I also run a 4 speed although currently with 3.55's and 26" tall tires.

With the smaller displacement the cam probably seems hotter, and in my combo it pulls about 10" of vacuum at idle, which is around 800 rpm (about as slow as it will go). I had a heck of time trying to tune it to work with a vacuum secondary carb, and did a lot of tuning trying to get a 670 and then a 770 street avenger to work. Even using a A/F gauge I couldn't ever get the transition into the secondaries right. They worked great on the primaries, or WOT, but going through the primary to seondary transition was never right, even after going through the entire line of pump cams, secondary springs, pump shot nozzles, etc. I went to a 750 double pumper with mechanical secondaries and had it sorted out a day, no problem. I'm not a carb tuning expert by any means, but that was my experience and using the wideband A/F takes a lot of guesswork out of the tuning process.

Even with 9.8:1 compression I pulled a few degrees of timing out of it to stop it from detonating on 91 octane pump fuel (best I can get in California at the "normal" pumps). I run 20* advanced at idle and all in mechanical at 34*, with everything in at a little over 3k. I also have an early 340 though, so the pistons are .018" over the deck and I run open chambers so obviously the chamber shape etc is different.

I use the Duster that the 340's in as my daily driver. It's probably a little hotter on the cam than I should be for what I do with the car. It runs great and stays cool, but it is definitely a little work to drive it in traffic. For a weekend car it would be great, and with the additional displacement and the stroker you could probably get away with the 705 if you're not frequently driving in traffic or using the car as a daily. Like I said, it's a small block so take it all with that in mind, but maybe it will help with your decision.

Here's a clip of my car at idle with the #10200704 in my 340...

https://youtu.be/62bjHlxzsoA

Good info! As expected the 704 cam grind in a 340 will be more aggressive than in a 440 (512). Both the 704 and 705 should not be used with stock rocker arms and push rods. The correct springs (recommended by Lunati etc) 10 degree Chrome Moly retainers and locks would be cheap insurance.

Author Topic: Lunati 704 or 705 Cam? (Read 6012 times)

usraptr

Lunati 704 or 705 Cam?

734406pk

Re: Lunati 704 or 705 Cam?

Chryco Psycho

Re: Lunati 704 or 705 Cam?

usraptr

Re: Lunati 704 or 705 Cam?

Chryco Psycho

Re: Lunati 704 or 705 Cam?

usraptr

Re: Lunati 704 or 705 Cam?

Chryco Psycho

Re: Lunati 704 or 705 Cam?

usraptr

Re: Lunati 704 or 705 Cam?

734406pk

Re: Lunati 704 or 705 Cam?

Chryco Psycho

Re: Lunati 704 or 705 Cam?

usraptr

Re: Lunati 704 or 705 Cam?

dfrazz

Re: Lunati 704 or 705 Cam?

1 Wild R/T

Re: Lunati 704 or 705 Cam?

72bluNblu

Re: Lunati 704 or 705 Cam?

734406pk

Re: Lunati 704 or 705 Cam?