anyone ever run a reverse split camshaft on Na log head

[autoX65]

so with a ported exhaust runner on the log head classic inlines fliw test says they can both flow equally about 140cfm so i would hink single pattern would be ideal except for all the 90 degree turns on the intake ports.

could a higher intake lift and duration intake help flow charecteristics. id like to try something with an intake in the 264-268 range with exhaust in the 258-262 range on a 108 lobe center. shooting for around 1800-5300 rpm range what are uour thoughts with this on a modified log with 500 cfm holley direct mount, 1.75 stainless intake valves and 1.5 " exhaust valve. 1800 rpm stall converter with race built c4, with exhaust and header. and 3.73 rear gears in a 8 inch rear.

ive heard a reverse split can help a poorly designed intake. any thought on this?

 

[80broncoman]

Never seen one run on one these sixes with out a turbo/blower.

In fact I've never really seen one run on much of any N/A engine unless the builder was paling on the turbo/blower and ran out of money.

 

[autoX65]

I know its more common in boosted applications but there are some good article online that have had good results with it in naturally aspirated so I plan to just try it so do those specs sound about right or any thoughts on it

 

[rbohm]

it depends on where the intake flow is compared to the exhaust flow, and the balance between the two. lets say the ideal balance between intake and exhaust flow is where the exhaust is 75% of the intake flow. that would mean that a single pattern cam is ideal for the engine. let us also assume that we can fudge the ideal flow by 5 points either way, meaning that as long as the flow balance between the intake and exhaust falls between 70-80%, we can stay with the single pattern cam. but lets say the exhaust flow goes below the 70% mark, then we want a dual pattern cam that favors the exhaust to improve flow. same with if the exhaust flow exceeds 80% then we want a cam that favors the intake side to improve cylinder filling. what we are looking for is a balance of flow intake to exhaust.

but realize that even changing the cam to favor one side or the other has its limits as well. for instance if your exhaust flows 55% of what the intake flows, then a cam design isnt going to help you, as you need to improve the exhaust flow.

 

[wsa111]

it depends on where the intake flow is compared to the exhaust flow, and the balance between the two. lets say the ideal balance between intake and exhaust flow is where the exhaust is 75% of the intake flow. that would mean that a single pattern cam is ideal for the engine. let us also assume that we can fudge the ideal flow by 5 points either way, meaning that as long as the flow balance between the intake and exhaust falls between 70-80%, we can stay with the single pattern cam. but lets say the exhaust flow goes below the 70% mark, then we want a dual pattern cam that favors the exhaust to improve flow. same with if the exhaust flow exceeds 80% then we want a cam that favors the intake side to improve cylinder filling. what we are looking for is a balance of flow intake to exhaust.

but realize that even changing the cam to favor one side or the other has its limits as well. for instance if your exhaust flows 55% of what the intake flows, then a cam design isn't going to help you, as you need to improve the exhaust flow.

This makes very good sense.
Why would you want a 108 L/C with a 1900 rpm converter.
You need a 2500 stall converter & a camshaft closer to 110 or better yet a 112 L/C.
If you use a clay smith camshaft you can try a 224I @ .050" & a 214E @ .050"
You need at least 9.5-10.5 static compression or no more than 190# cranking compression on pump gas.
108 L/C cams are fine for a race car, but you will hate it street driving.

 

[xrwagon]

would be interesting, i would like to know what happens to camshaft when the log is removed, as it then allows the head to go where the log can’t go, i reckon another 100 thou lift over the max for a log

 

[autoX65]

I agree wagon I've heard nothing but good things about modified logs. I've seen pictures of a few milled off and the intake runners and ports are actually huge so a custom intake is one of those possible upgrades that requires a lot of time and fabrication plus some money at the machine shop but I bet the log could get closer to 280+ hp with a nice custom intake. they remind me of the huge runners on boss 302 and 351c heads. I'm going to run the two barrel direct mount first but its nice to know there is the option of modifying the log if you want to go all out.

I should be ordering a cam this week and was debating between schnieder racing and clay smith. just read mike had some issues when he was set up with the degree wheel on his engine with lobe centers off.

Im willing to have it made so how ill see what some grinders reccomend. I really had wanted something on a 108 lobe center but lets stick with 110 with this one. and wsa the 1800 rpm stall is already what I have built and ready to go so I want to build around that and I drive more in the mid to high rpm range so I'll be fine with a slightly lopey idle. so ill talk to clay smith and see if they are for it if not id probably so pretty standard with a 264/264 110.

 

[autoX65]

its already been measured at 8.7:1 compression ratio so I don't think at .050 lift I can go with the intake 224 exhaust 214. so do you think on a 108 lobe I can go with even a lower duration with more modern grinds should help. maybe like 262intake /256 exhaust advertised duration on a 108 or 110 lobe center?


I know this head hits peak flow early so I think toward a lower lift might bring on lower end torque early but I think max horse power would only be in the 4500-4800 range on the 200 with a modified log so I need the low end to be working to optimize all the extra air and fuel with the two barrel modifications so I don't get flat spots early in the revolutions on acceleration. its going to be all in early with lots of initial timing and its a quick raving motor that launches good as it rev up and carries well into the mid to high rpm range making hours power so its going to be pretty tuned thoughly.

I know its fun to get caught up in theories and dynamics of these engines and the talk can go on for years so I'm not trying to re invent the wheel because with out
heavy modifications to this six or spending a lot of time and money tracking down aftermarket and forgien parts there is really only a nice block with a complete
econonical non performance top end so I'm just trying use common bolt on parts known specs that work good.

 

[wsa111]

I believe you need more compression. Mill the head for a 50cc chamber & zero deck the block.

 

[xrwagon]

i wonder how many have offset milled the head, or moved the head around on a motor, thats a big trick in Australia with Holden sixes and can be applied to ford six inline, milling one side of the head makes sense, then re drill the head bolts, this enables a much bigger cam to be used. Its a bit of secret squirrel but i have seen it done, and the results speak for them selfs, 8 second qtr miles for blown Holden sixes is nothing to be sneezed at.

 

[autoX65]

that would be sweet xrwagon. I think it may be possible with the us log. main reason I want to increase intake lift is because I could not port the intake runners and only exhaust port heavily. so flow numbers say stock intake is 127 cfm and un ported exhaust 105 but ported its 129. so is that optimum for a cylinder head 127/129 intake/exhaust ratio? what effect would only ported exhaust have?

 

[xrwagon]

unsure of what effect that will have on anything, but those flow numbers you could pass onto a cam grinder when doing a custom camshaft, i am in Australia so we have access to 2V heads etc, an aftermarket company down here in the sixties did cut off log heads and had there own manifolds for triple carbs done, this is prior to 2V heads, that would be the optimum i think. There is a custom head porter here i race with, he wants to do a log head or a 2V head, i have a spare big log head i am giving to him to see what he can do with it, this guy knows his stuff and has helped others to very impressive times over the quarter with similar sized Holden six’s. He also said to me, we can move the head around, we can mill the head on one side as well, this will help to unshroud the valves etc and then get most out of it, this trick works on a Holden six head, it takes some time and some finnese and has to be a viable thing to do. His six cylinder dragster has run in the eights over the quarter and aspirated in the nines

 

[autoX65]

I really like the idea of milling the head on one side and I'm sure would help. shorter on the push rod side would help intake and exhaust flow in my mind. I really think just welding onto a cut off intake would be the ticket if you can't weld up steel tube too it instead of building some flange a lot of people go for but id rather stay all ne piece so there's no custom gaskets and especially intake leaks so if he can pave the way to any successful mods to the log I'm all ears.

 

[xrwagon]

you could quite easily do the flange, i have a book with photos of the flange plate that was welded/brazed on, cut out your own gaskets, exhaust is the same so that doesn’t change, i have seen 5 cut off log heads so far, 3 were done by Lynx, one is a home made one in a boat, and another is a Famous midget speedway car which was done by McGee and had mech injection on it, i have photos of another 2 heads and a injector unit in my private stash, some of these pics have never been published as the parts are in collections that won’t be sold

 

[autoX65]

so wsa I know you run the iskindarian cam and I'm thinking to for with the 256/256 super cam on a 112 degree lobe center. has a range of 1500-4800 so I think that about the correct power band and hopefully will have a little more off idle torque but do you think top end will be too affected with the lower duration. it does still have .450" of lift so I think that's plenty and its supposed to have best torque and economy. anyone run this cam?

 

[xctasy]

Your better off building scavengability via the Winston Cup restrictor plate method detailed below,

It results in a higher required rev range, and won't improve anything except peak power...

if you extrapolate it out, a mech sec carb with 56% more cfm should give up to 230 hp with ease if its set up right. In actuality, we've seen 289's with 500 cfm 2300 Holley 2-bbls make 352 hp with the right kind of NASCAR style cam in Historic C Carerra Panamerica 65 Mustangs.

http://www.hotrod.com/techarticles/engi ... to_12.html
http://www.hotrod.com/techarticles/engi ... to_06.html

The cam is the heart beat to extracting the best out of the head you have. You need to look at how to pull more air through a stock 500 cfm carb like the Nascar guys used to with 390 cfm 6895 carbs on 355's and the above guys do with that bad a$$ 289.

 

[xctasy]

Your better off building and maintaing scavengability via the Winston Cup restrictor plate method detailed below,

It results in a higher required rev range, and won't improve anything except peak power...


They limit exhast flow to 78% of intake, and then amp the cam timing up to build cfm flow above 400 thou.

if you extrapolate it out, a mech sec carb with 56% more cfm should give up to 230 hp with ease if its set up right. In actuality, we've seen 289's with 500 cfm 2300 Holley 2-bbls make 352 hp with the right kind of NASCAR style cam in Historic C Carerra Panamerica 65 Mustangs.

http://www.hotrod.com/techarticles/engi ... to_12.html
http://www.hotrod.com/techarticles/engi ... to_06.html

The cam is the heart beat to extracting the best out of the head you have. You need to look at how to pull more air through a stock 500 cfm carb like the Nascar guys used to with 390 cfm 6895 carbs on 355's and the above guys do with that bad a$$ 289.


viewtopic.php?f=1&t=67266&p=515035#p515035

You have to see where your heading, using past precedents, then forwarding actions, then review that its done. Richard, your really looking at a T-code 200 Sprint engine with a special 2v carb, headers, cam/head/valve mods to get past the poor exhast flow.

Lets recap on a 352 hp net at 6700 rpm /316 lb-ft at 5000rpm C-code based 2-bbl 289 with K-code solid lifter cam, and show what a soft head/NASCAR restrictor plate tune would be like to draw out power and torque which tecnically wouldn't be there considering the carburation to cube ratio and air flow readings. Once that's pulled apart and understood, apply the concept to a 200 or 250.

Stock 2-bbl 289 power was rated back in the day as 195 hp gross, but was probably 156 hp at 4400 rpm, stock torque was most likely 225 lb-ft at 2800 rpm. Compression was about 9.2:1, which is elevated to 9.25:1 for his engine. It uses stock 2-bbl 2300 series #4412 Holley 500 cfm with 1.375" venturis, and stock 73 jets and two stock 62.5 thou power valve channel restrictions for this new found power. That means that the carb is being sucked within an inch of its life at 6700 rpm for its 293 cubes and at 85% VE, the carb 'sees' 482 cfm. Stock was the 2-bbl 2100 Autolite 1.14 = 300cfm, 1964 - '67, on 289's

Vizard and others use traditional power predictions that take peak head flow at 10, 25, or 28 inches on a standard piston size of 500 cc for 4 cyl, 625 cc for a 5 liter /305 cid engine, multiply by a factor, and thats your maximum power. A scala factor is applied to correct for engine sizes above or below. A 293 cub engine making 237.5 cfm at 28 inches can make 450 hp at 8500rpm if there is no choke point. For an all encompassing link, see http://www.wallaceracing.com/calcafhp.php

Now, the last kicker was the heads were based on a 237.5 intake, 185.6 exhast, and "because of the two-barrel carburetor, exhaust-port flow was intentionally limited to less than 80 percent of intake flow above 0.400 lift to maintain a scavenging effect. Read more: http://www.hotrod.com/techarticles/engi ... kYG0GTeI80%" Itallics mine, and its all based on 1.94 intake /1.60 exhast.

The intake manifold, a single plane Edelbrock Victor Jr. intake with an adapter that’'s hogged to match the carb’s bore size, is one of the best, so its not really feasible to copy it on a small six. It's like comparing a two hole 1.675" discharge to a nice square verses one 1.75" hole to a rectangle.

So running the numbers, we have a 289 V8 making really good power very high up in the rev range, and, at just over an lb-ft per cube, quite poor torque at 316 lb-ft. Scaled down to a 200 with 1.75" intakes and 1.45" exhasts, that's 244 hp and 219 lb-ft. Due to poor head flow and limited carburation, torque and hp occur at too high an rpm.

Back tracking to an EFI 3.3 non crossflow Holden engine in 1985, it had 195 lb-ft at 3000 rpm, and 142 hp at 4800 rpm, with a 264 degree cam with 8.8:1 compression. 1.625" intakes, 1.4" exhasts, 12 port head with similar head flow to a D7 head. Still less than 1 lb-ft per cube. A 250 EFI Falcon with 8.8:1 compression, 264 cam, 247 lb-ft, or less than one lb-ft per cube at 3000 rpm.

Somewhere between the two is where best low end torque curve lies.

I'd personally like to see 9.7:1 compression, maximum torque at 3500 to 4000 rpm( 207 lb-ft at 4000rpm being possible), power of 193 hp at 5750 rpm, and a 2-bbl 2300 series 350 cfm #7448 carbwith 1.1875" venturis, and a 280 degree cam which produces those figures with a head that meets 80% of the peak intake flow at 360 thou. Based on Wallaces website, which calculated 450 hp at 237.5 cfm, I'd punt for 249 hp flowing heads to get 193 hp. You'd only need 175 cfm at the intake. To get power at 5750 rpm, your internal port size outside the intake valve needs to be only 1.338", and a D7 head is about that already, but the intake runners are too small leading up to that to allow the 1.338 port size to be effective. Thats why people favour the large runner intake manifold, as the ports then have a chance to get good air flow from the carb.

With that combo, you'd still get power, but get excellent lower speed torque.

 

[autoX65]

I sure like those numbers of the 2 barrel 289. very impressive hp. nine years ago I had a 66 deluxe poney interior with afr heads, rpm air gap intake, comp cams extreme energy split pattern and a holley 650....with a 3:0 ratio it was a beast on the freeway and took down some street bikes at 140mph plus many time! smoked all the newer mustang gts, beat the v8 cameros, new challengers kept up with some vipers but this is street racing talk so a lot of it was the driver haha

I'm buying a small log head tomorrow in hopes to cut off only the log leave the stock exhaust and weld up a tunnel ram style intake with a four barrel or may try the 2305 holley 500 cfm.

I still haunt even run my fresh large log modified for the two barrel but I really want to get started on a custom log because that'll be in the power range I want hopefully if done right I think I can get 280+ hp easy out of the 3.3l!

 

[xctasy]

I'm totally with you. The big six guys have been using combos like you've suggested.

We have discussed this at length.

https://www.fordsix.com/forum/viewtopic ... highlight=

The 500 CFM 80095 is really just half a 6708 series 650 4-bbl double pumper with very slightly different venturis and throttles. These carbs conduct 390 hp in the Group A 1984 Fox Mustang 302 Dick Johnson use to race down here.

Stock primary and secondary jetting for non egr 350 and 400 small block Chevs was similar to the 54/73 jetting of your 80095. A 6708 is just two 500cfm mec sec carbs, more or less.


Split down in half, the 80095 is an easy 212 hp carb with the stock jets, and you can go up on secondary and squirters just like the auto version of the 6708, the 6708-1 with 85 secondary jets.


The restrictor plate cam details for the the Currie Historic C Mustang 289 above are:-

LCA is 109
Duration at 50 thou is 244 intake, 248 exhaust
With 1.6 roller rockers, and a lash of 18 thou intake and 20 thou exhaust, gross lift is 584 thou.
Sorry, don't have Competition Cams total at lash duration figures , but its very similar to the 240/300 I6 comp cam oval track
PN # 66-679-5

A 575 thou gross lift, 545 thou 290 intake/294* dur at 50 thou 255 in/256 ex , LCA 108.

Have to check it against the 132 page catalog.

http://www.compcams.com/Technical/Catal ... atalog.pdf

https://www.fordsix.com/forum/viewtopic ... 20#p551920

A small six cylinder engine with a 2-bbl like that and a proportionally lower cfm head flow would have a much lower rev range than 6700 rpm, and would give better specific power, maybee over 250 hp with the right cam and with a 200 I6 with 500 cfm of carb, it wouldn't be as undercarbed as the Currie Historic C Mustang is.

See http://www.iskycams.com/techtips.php

Tech Tip - 2004

Intake Restriction and Over Scavenging: "Waste not...Want not!"

It is certainly an over simplification to make the statement "that which is not wasted, should be inducted". However, in the case of restricted intake systems and in particular 2-BBL carb rules, it is not far off the mark. Engines with such restrictions are "choked off" to the point where they will not run much past 6500 RPM (if even that high) without dropping off sharply in power. You might have trouble running very fast yourself if someone had your windpipe choked down to say 50 or 60% of it's normal capacity. Under such conditions, would you volunteer to give blood at the Red Cross? Of course not, but without knowing so, racers often do the equivalent with their engines by running a camshaft better suited for a 4-BBL class! How So?

If you'll recall in last months tech tip: "Longer Exhaust Duration: Is This Really Necessary?" I discussed how, through habit, many racers and cam grinders alike are predisposed to running camshafts with longer exhaust durations, whether they need to or not! Well, in the case of restricted intake applications, if there was ever a situation in which you'd want to avoid the longer exhaust "trap" it's here! Especially the 8, 10, 12 or even longer degree spreads, I often discover people employing.

Use such a cam at you own risk - and don't be surprised to find that your exhaust temperatures are unusually high. Your headers in fact may even glow cherry red. There is a very good reason for this. Raw (unburned) fuel is burning "late" or in the pipe (header/manifold). You may have a good equilibrium of flow going here but there is just one problem. Much of what should be inducted into the cylinder is being scavenged out the exhaust! You see, although back pressure in an exhaust system can be restrictive, the only thing that could be even worse is a reduction of it to the point where you are now, in effect pulling a vacuum. In the case of an intake restriction, very slight back pressure is preferable to avoid "over scavenging".

Yes, Yes I know. You are probably thinking "what's wrong with a little scavenging?". Well, nothing if you can afford it. But with intake restrictions (either small 2-BBL carbs and/or restrictor plates) you must be very careful. You already have reduced intake potential and therefore simply cannot be cavalier about valve overlap and scavenging or you'll be way down on power and have those nice bright cherry red pipes to show for it! Case in Point: One racer who called me was in this exact situation and was running, not surprisingly, a 14 Degree longer exhaust duration. It was Friday afternoon and he needed a cam the next day for the last "points race" of the season and UPS had already picked up at Isky. "Too Bad" I said, "You don't have a set of those low ratio break-in rocker arms because they could really help in this case". " I do have some" he said "but they are only 1.2:1 ratio - is that okay?" I told him to use them (on his exhaust valves only of course) and he finished the race 2nd having come from the back of the pack. Later we made him the right cam so he could avoid this make shift approach.

Unfortunately, the symptoms are not always as obvious as in this case to allow for a speedy diagnosis. Also, it's not only longer exhaust duration that causes the problem. Although it is usually the primary offender, it is often coupled with too close a lobe separation angle of say 104 Degrees. A widening to 106 Degrees or preferably 108 Degrees (some go even wider) is usually prudent.

I am not absolutely dead set against a slightly longer exhaust duration in these cases as a 2-4 Degree longer exhaust lobe is permissible under some circumstances (if your running a completely stock exhaust system including mufflers for example). Each case is different, depending upon the equipment employed. I might even recommend shorter exhaust duration to some; if I feel they have "overdone" their exhaust ports and or exhaust system a bit. What matters is the end result and if you're out of balance on one side simply employ what I call the "Great Law of Compensation" to bring you back to that equilibrium of flow.

So, how can you tell if you may need to make some of these changes in your camshaft? Well, short of trying a lower exhaust rocker arm ratio, you can increase exhaust valve lash .004" - .008" temporarily to see if there is any improvement. You can also try and increase restriction (smaller headers or pipes, or in the case of open headers a longer collector) and simply observe the results. Remember, "One test is worth a thousand expert opinions". Keep this old axiom in your "tool box" and you'll be ahead of the game. How do you think Smokey's shop got to be "The best Damn Garage in Town" anyway? Yes, he had those country smarts, but his experiences in racing and his willingness to test are legendary!