#61  
Old 03-17-2021, 12:04 PM
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A better answer would probably have been the reasoning for the ICL’s we use. I start by using a event calculator, and adjust the ICL on the calculator until the EVC and IVO events are square. On a timing chain engine I always assume the cam timing events are running 2* behind, so what ever that ICL turns out to be, I subtract 2* for the installed ICL.

When we install a cam we start with the ICL found with it degreed in from the .050 down from each side of max lift. Then further check the duration on the opening side of the cam from .006 to .050. Then the closing side from .050 to .006. That gives me the cams span or asymmetric’s for most of the overlap triangle. If the cam is a modern performance cam, has no asymetric’s (Crower 60919, SPC-8, ect) and I want to bleed compression I find I can move the ICL timing and retard it, I.E. the exhaust events are running behind the intake events without sending a ton on heat into the intake charge, seems like the max is about 4 degrees. Which if I recall correct is on a SPC-8 or a Crower can almost be installed straight up. What ever the span is (closing side of the cam is longer duration than opening) I subtract that from that 4 degrees. That is the max retard I will use it it is assymtrical, which is easy on a Voodoo, because the EVC and IVO events end up being square.


If you end up using a 704 on a 110 with a stock head, keep in mind the stock Pontiac heads have a huge push on the low lift flows. Personally on a Pontiac I think it makes that 110 act like a 108 LSA . It does a ton of scavenging, then tries to move a bunch of air again when the piston is coming up and the intake is shutting. Which make good power and mid range tq. But add much compression with those things can be to much of a good thing, you will be running race gas. Paul Carter runs a lot of compression with the 704, but I am pretty sure he ports the heads. That cam and ported head combo is pulling the air in differently than a stock head. Harolds cams are very effective cams for cylinder fill, IMO, no need to get carried away on compression on the 110 LSA.
Thanks Jay, I appreciate it. I've got to cc the chambers still, but honestly, I'm hoping that it ends up only around 9.5-1, instead of up at 9.7 to 9.8-1. If the 6X4 heads would come in around 94cc chamber after the valve job and new Ferrea valves installed, it would have right at 9.5-1, zero decked, .039" gasket, and 8cc valve relief. I think I would be really happy with that, along with the 704 and 110 seperation.

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  #62  
Old 03-17-2021, 12:16 PM
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I don't have any number from a 704.

This shows the overlap area for a Summit 2802 114 LSA

The green (intake) and red (exhaust) are for an ICL of 114.

The blue (intake) and cyan (exhaust) are for an ICL of 111.

At 114 ICL the exhaust is open much more than the intake ATDC. With the 3 degrees advance both the intake and exhaust are open the same ATDC.

Stan
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  #63  
Old 03-17-2021, 01:42 PM
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I don't have any number from a 704.

This shows the overlap area for a Summit 2802 114 LSA

The green (intake) and red (exhaust) are for an ICL of 114.

The blue (intake) and cyan (exhaust) are for an ICL of 111.

At 114 ICL the exhaust is open much more than the intake ATDC. With the 3 degrees advance both the intake and exhaust are open the same ATDC.

Stan
I installed that cam on a 108 ICL. Care to be so kind as to map that?
Thanks Stan

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Old 03-17-2021, 02:04 PM
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I don't have any number from a 704.

Stan
Does this info help any? Lunati used to put the cam cards on their web site but have ceased doing that. AAAARH

Advertised Duration (Int/Exh): 276/284 ;Duration @ .050 (Int/Exh): 233/241 ;Gross Valve Lift (Int/Exh): .504/.527 ;LSA/ICL: 110/106 ;Valve Lash (Int/Exh): Hyd/Hyd ;RPM Range: 2000-6000

https://www.lunatipower.com/voodoo-h...8-276-284.html

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  #65  
Old 03-17-2021, 02:05 PM
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I installed that cam on a 108 ICL. Care to be so kind as to map that?
Thanks Stan
Sure not a problem. At that ICL both valves have the same lift about 4 BTDC.

So ATDC the intake will have about 0.020" more lift than the exhaust

Stan
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  #66  
Old 03-17-2021, 02:54 PM
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Originally Posted by 1968GTO421 View Post
Does this info help any? Lunati used to put the cam cards on their web site but have ceased doing that. AAAARH

Advertised Duration (Int/Exh): 276/284 ;Duration @ .050 (Int/Exh): 233/241 ;Gross Valve Lift (Int/Exh): .504/.527 ;LSA/ICL: 110/106 ;Valve Lash (Int/Exh): Hyd/Hyd ;RPM Range: 2000-6000

https://www.lunatipower.com/voodoo-h...8-276-284.html
Thank You. I have those numbers and some others. I but they don't tell the story about how asymmetrical the lobes are. This is based on generated numbers for a 704 and not from Cam DR number.

This shows the overlap for 110 112 114 lsa with ICL = LSA.

Stan
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  #67  
Old 03-17-2021, 03:41 PM
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^ Nonethe less, that is helpful info. Thankyou, Stan.

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Old 03-17-2021, 04:17 PM
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As far as I can tell Harold never put a terrible amount of velocity off the seat on his high speed designs like the Voodoo. The seat durations at .006 for the 704 are 281 on the intake and 289 on the exhaust. Probably someday someone will have decimal place behind those numbers. I can’t remember for sure what the 704 specs at .004 tappet, seems like it is 287 intake and 295. The further down to the base circle the more asymmetric’s show up though. Supposedly it has 8.33 span at .0045 or .004. Can’t recall now which it was. I have not seen quite that much, it may not all get translated to the profile from the cam grinder. I would not put any stock in the 276 and 281 like the Lunati sales literature says. I just did my first 904” dia lifter version on a 704, it is like a 704 on acid. It is a beast.

Thanks Stan. You are correct, 114 is putting the exhaust events pretty far behind. At 114 that would be equivalent to the ICL installed at 112. Lol. Which is where a lot of cheap timing sets end up after 10,000 miles when the were installed at 108. That is pretty much where I think the point of diminishing returns is for that Summit cam. Where as the cams like the Voodoo pull harder in the intake, and I think hit that DMR point 4* sooner than the symmetrical type cam. The 4 is just my guideline, I am sure there are exception to it. I was thinking the 60919 or the SPC-8 could run even more retard yet because the smaller split and less acceleration on the exhaust than the intake. But I could be wrong, haven’t looked at those for awhile.

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Old 03-17-2021, 06:36 PM
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Sure not a problem. At that ICL both valves have the same lift about 4 BTDC.

So ATDC the intake will have about 0.020" more lift than the exhaust

Stan
Thanks Stan,

That's nearly identical to what I found when I degreed it. I was trying to follow Paul's advice and see how far I could get the intake open more than the exhaust at ATDC. I just kept going until I got to 108 ICL and just didn't want to go further, as Paul said he likes to see .030 to .035"
It's really hard to get that number with a wide LSA cam though.

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Old 03-17-2021, 07:44 PM
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Would have been fun to know Harold Brookshire like Paul Carter did.

About 25-30 years ago some Dyno sim software came out and we bought it. Don’t recall now what it was. We thought it was cool. Used it a lot for picking cams at the time. It told us all the cams we were running at the time would make more hp with the cam timing retarded. Of course we tried it on several engines. LOL...didn’t exactly work out how it said.
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Old 03-17-2021, 08:22 PM
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Yep I had similar software about 30 years ago that said the same thing. Didn't matter what cam it was, every time you retarded the camshaft it made more power. It never worked out that way in real life though.

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Old 03-18-2021, 02:23 AM
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Nice combo TransAm 474 ! Seems there are quite a few running a stroked 78/79 w72 . I have one ...bent wheel bob on this site has one too

Here's my combo (almost same as yours)

1978 400 XX WC block
Bore- 4.21"
Eagle 4.250" crank
Eagle 6.800" H-Beam rod
Mahle pistons and rings
Melling 60 psi 3/4" pickup
1978 stock 6x-4 heads - done by SD Performance ..CNC ported 260 cfm, 7/16" Studs, Ferrea Valves?
SD Performance Stump Puller roller cam 230/236 at .050, .567/.578 lift
Comp hyd rollers - no issues / ticking
crower 1.5 steel rockers
sims roller bearing timing chain set
original qjet- has elec choke, used Cliff qjet kit...his kit top quality..and got Cliff's qjet book for tuning (use one of his recipes)
Stock Cast Iron intake
original HEI distributor
1 3/4" headers, dual 2.5" exhaust
Super T10 4-Speed Manual transmission
canton road race pan
mcleod scattershield
center force DF clutch
original 3.42s

I figure my Compression ratio is around 9.25:1. When I got heads back from SD Performance I cc'd em. I seem to recall they
were either 97cc or 99cc? little more volume than i figured. I had original Super T10 rebuilt by local guy - he used a good kit.
Tranny was in good shape. But nothing special like better gears or cast iron side plate. I am little paranoid about the Super T10. It shifts fine and I beat on it a lot. But , Im not sure how much abuse it can take.

I have only had car at 1/4 track once. It ran 13.70s at 108mph. I had zero traction coming out of the hole - car will just blow away the tires when launching. I have old hard 255/60/15 tires that are likely pretty crap. I try and get into throttle gently
while on edge of breaking loose. I think my car weight is around 3550 lbs (3750 with me) Car has no ac , no pw or pdl, tilt.
Fairly basic 78 ws6, w72 , 4 spd car - though has deluxe interior which I like.

I have to say from around 60 to 120mph...its awesome I have it in 4th - at 60mph the rpm is around 2900?.
and then foot on floor and max to about 5500rpm. My tach sticks a bit. So, sometimes needle is pegged at 5500
Only on nice straight highway at night Also had to add pusher elec pump. Was kinda falling on its face at high rpm
I added carter elec by gas tank and that resolved. I use stock fuel lines and return line with big can stock type
mech fuel pump (from napa? like $40?). I use STP SA136 air filter - 3" height and $10 at autozone. My shaker is original
and not opened.

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Old 03-18-2021, 09:42 AM
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Originally Posted by pippintook View Post
Nice combo TransAm 474 ! Seems there are quite a few running a stroked 78/79 w72 . I have one ...bent wheel bob on this site has one too

Here's my combo (almost same as yours)

1978 400 XX WC block
Bore- 4.21"
Eagle 4.250" crank
Eagle 6.800" H-Beam rod
Mahle pistons and rings
Melling 60 psi 3/4" pickup
1978 stock 6x-4 heads - done by SD Performance ..CNC ported 260 cfm, 7/16" Studs, Ferrea Valves?
SD Performance Stump Puller roller cam 230/236 at .050, .567/.578 lift
Comp hyd rollers - no issues / ticking
crower 1.5 steel rockers
sims roller bearing timing chain set
original qjet- has elec choke, used Cliff qjet kit...his kit top quality..and got Cliff's qjet book for tuning (use one of his recipes)
Stock Cast Iron intake
original HEI distributor
1 3/4" headers, dual 2.5" exhaust
Super T10 4-Speed Manual transmission
canton road race pan
mcleod scattershield
center force DF clutch
original 3.42s

I figure my Compression ratio is around 9.25:1. When I got heads back from SD Performance I cc'd em. I seem to recall they
were either 97cc or 99cc? little more volume than i figured. I had original Super T10 rebuilt by local guy - he used a good kit.
Tranny was in good shape. But nothing special like better gears or cast iron side plate. I am little paranoid about the Super T10. It shifts fine and I beat on it a lot. But , Im not sure how much abuse it can take.

I have only had car at 1/4 track once. It ran 13.70s at 108mph. I had zero traction coming out of the hole - car will just blow away the tires when launching. I have old hard 255/60/15 tires that are likely pretty crap. I try and get into throttle gently
while on edge of breaking loose. I think my car weight is around 3550 lbs (3750 with me) Car has no ac , no pw or pdl, tilt.
Fairly basic 78 ws6, w72 , 4 spd car - though has deluxe interior which I like.

I have to say from around 60 to 120mph...its awesome I have it in 4th - at 60mph the rpm is around 2900?.
and then foot on floor and max to about 5500rpm. My tach sticks a bit. So, sometimes needle is pegged at 5500
Only on nice straight highway at night Also had to add pusher elec pump. Was kinda falling on its face at high rpm
I added carter elec by gas tank and that resolved. I use stock fuel lines and return line with big can stock type
mech fuel pump (from napa? like $40?). I use STP SA136 air filter - 3" height and $10 at autozone. My shaker is original
and not opened.
That is pretty sweet.

Curious on the big cc’s of your heads? Does the SD performance CNC program do some machining in the chamber?

I have a similar build. I am running a billet Al mid plate, that is all the t10 mods I have.. A couple friends said I should carry a bag of floor dry in the trunk. Lol I don’t think I will have to much trouble unless I go to the track, that or it will split the tranny in two going into second.


Last edited by Jay S; 03-18-2021 at 09:44 AM. Reason: Edit
  #74  
Old 03-18-2021, 09:50 AM
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Quote:
Originally Posted by pippintook View Post
Nice combo TransAm 474 ! Seems there are quite a few running a stroked 78/79 w72 . I have one ...bent wheel bob on this site has one too

Here's my combo (almost same as yours)

1978 400 XX WC block
Bore- 4.21"
Eagle 4.250" crank
Eagle 6.800" H-Beam rod
Mahle pistons and rings
Melling 60 psi 3/4" pickup
1978 stock 6x-4 heads - done by SD Performance ..CNC ported 260 cfm, 7/16" Studs, Ferrea Valves?
SD Performance Stump Puller roller cam 230/236 at .050, .567/.578 lift
Comp hyd rollers - no issues / ticking
crower 1.5 steel rockers
sims roller bearing timing chain set
original qjet- has elec choke, used Cliff qjet kit...his kit top quality..and got Cliff's qjet book for tuning (use one of his recipes)
Stock Cast Iron intake
original HEI distributor
1 3/4" headers, dual 2.5" exhaust
Super T10 4-Speed Manual transmission
canton road race pan
mcleod scattershield
center force DF clutch
original 3.42s

I figure my Compression ratio is around 9.25:1. When I got heads back from SD Performance I cc'd em. I seem to recall they
were either 97cc or 99cc? little more volume than i figured. I had original Super T10 rebuilt by local guy - he used a good kit.
Tranny was in good shape. But nothing special like better gears or cast iron side plate. I am little paranoid about the Super T10. It shifts fine and I beat on it a lot. But , Im not sure how much abuse it can take.

I have only had car at 1/4 track once. It ran 13.70s at 108mph. I had zero traction coming out of the hole - car will just blow away the tires when launching. I have old hard 255/60/15 tires that are likely pretty crap. I try and get into throttle gently
while on edge of breaking loose. I think my car weight is around 3550 lbs (3750 with me) Car has no ac , no pw or pdl, tilt.
Fairly basic 78 ws6, w72 , 4 spd car - though has deluxe interior which I like.

I have to say from around 60 to 120mph...its awesome I have it in 4th - at 60mph the rpm is around 2900?.
and then foot on floor and max to about 5500rpm. My tach sticks a bit. So, sometimes needle is pegged at 5500
Only on nice straight highway at night Also had to add pusher elec pump. Was kinda falling on its face at high rpm
I added carter elec by gas tank and that resolved. I use stock fuel lines and return line with big can stock type
mech fuel pump (from napa? like $40?). I use STP SA136 air filter - 3" height and $10 at autozone. My shaker is original
and not opened.
Thanks! that is a nice setup! I got the 704 VooDoo ordered last night, so we will see how it works, but from all of the reading I've done, I'm sure it will work great. We will install it at 104°. Roller would have been nice, but it wasnt in the budget.

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  #75  
Old 03-19-2021, 10:21 PM
pippintook pippintook is offline
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TransaAm 474 - I agree , the price of roller is a bit crazy. For my next build - i am likely dropping the roller and going with hyd cam. Roller cam and associated parts hike up cost a lot ...roller cam $500/600? roller lifters $500/600, composite distributor gear $120 - I also added crower steel rockers $500/600.
So, there is around $2000.
.
One of my fav builds was when I was in university (and low on funds)...I had '71 455 with cast rods (good bolts), forged trw pistons, HO Racing HC-02 hyd flat tappet cam, rhoads lifters, 1971 400 #96 heads (good valves, HO Racing VS11? springs (3 angle , tiny bit diy pocket porting, heads planed .050), edelbrock performer intake, '72 buick 800cfm qjet. I had this in 81 WS6 TA with THM350 and 3.08s and it flipping tore your head off and i could get it too hook a bit better on launching. I used BFG comp TAs 255/60/15. A lot easier to drive at track...ran 13.0s at 107mph. I used 1 5/8 headers and 2.5" duals and one big flowmaster crossflow muffler. Sure maybe only made 375/400hp? but made a boat load of torque. I seem to recall car weight being around 3900 lbs (with me in car).
.
My current 'higher end build' ...now that I have more $$...uses good aggressive roller ...but then I need better valve springs..and better pushrods...better rockers...making more power need scattershield...etc etc...everyone knows the game This build is about 2/3? times the cost...stroker kit $2000..heads by SD Performance $2500/3000...roller and parts $2000 - I think I got around $10000 in motor/trans with parts , machining , balancing etc...though lots of better parts (pretty bullet proof valve springs, valves, pushrods, crank , rods , scattershield etc etc ). I think this higher end pricey build could run mid 12s ...but I would need to get it took hook...and I suspect I would need to beef up the Super T10 to do that ....and then maybe the rear too.
.
Hey Jay re: "Curious on the big cc’s of your heads? Does the SD performance CNC program do some machining in the chamber?"
I am not sure if SD Performance machined the chamber. If they did it was just some minor light grinding or polishing. I dont recall the chamber looking too much different from stock. Maybe that added a few cc's...seems even some 6x-4 heads can be on higher end of cc volume,

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  #76  
Old 03-20-2021, 05:27 PM
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Ok, I've measured the 6X4 heads that will be used on this build, and they came out at 94.5cc. That is with the factory flat face valves and no valve job yet. So after the valve job and new Ferrea valves(which I believe have a bit of dish in the faces), we will probably be looking at somewhere around 95-96cc and 9.3 to 9.4-1 compression, with the block zero decked, .039" 1016 gasket, and 8cc Butler/Ross Flat Too piston. I think that will come out great for this pump gas 467 with the VooDoo 704 camshaft.

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  #77  
Old 03-21-2021, 07:23 AM
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It’s seams that in your compression calculations your forgetting to add in 1.5 CCs in top ring land volume.

This oversight seems to be happening a lot even by some long time engine builders who think they have all the factors nailed down.

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  #78  
Old 03-21-2021, 08:43 AM
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Steve, the real "oversight" is not factoring the camshaft into the equation, not missing 1.5 CC's during their calculations during the planning stages.....FWIW......

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  #79  
Old 03-21-2021, 08:52 AM
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Agreed, yes! But if every thing including how much for instance the top of a forged piston grows and with all other factors like you mention in that might have things sewed to maybe having too much compression, then to me it’s nice to know that there’s that 1.5 CCs sitting there!

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Old 03-21-2021, 09:00 AM
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Originally Posted by steve25 View Post
It’s seams that in your compression calculations your forgetting to add in 1.5 CCs in top ring land volume.

This oversight seems to be happening a lot even by some long time engine builders who think they have all the factors nailed down.
Steve, I believe the Diamond Pistons calculator that I use accounts for that, doesn't it? Below is a screenshot
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