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Old 04-26-2013, 12:10 PM
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full port and polish with bigger valves?

Helo everyone.
Well its that time of year to feel the need again to drive our prized possessions.

I have a question that I cannot answer my 1980 Z28 has a 406 sbc 10.75-1 comp,hydraulic roller setup 241@50 int-246@50 ex 571int-565ex lift, 110lsa 106lca stock crank reworked lightened cross drilled chamfered, scat I beam forged rods ,speed pro forged flat tops 7cc valve reliefs, rpm intake 1/2 spacer cant go more due to hood clearance Holley HP 750 cfm DP carb 74primary jets 82 secondary,.balanced drivetrain with a M-21tranny. 3:42 rear end,RHS pro action aluminum heads 200cc runners 2.02 -1.6 valves with comp987-16 springs and comp roller rockers 1.6-1.5 they flow 280cfm @600 lift 395 cfm @400 lift the car drives great ,highway and city driveable. It last ran 12.91@106mph,my dilemma is on yhe dyno it showed 437ftlbs of torque @4700 rpm but only 339 hp @6100 rpm thats at the wheels,A/F ratio at full throttle is 12.0 at cruising rpm it is 13.8, Im very happy with the torque numbers but not satisfied with the HP.I feel that when driving from 2200 rpm it pulls very hard but after 5000 rpm I feel the power not climbing although it will rev easily to 6500 rpm. I run 20 degrees initial timing and 37 degrees total MSD street fire HEI ignition tayor 8mm wires they have the best clearance for the plug boot for my setup and champion plugs all to specs from RHS.Fuel pump is a edelbrock rpm flowing 120gph @6psi.Ive tested everything using process of elimination to rule out any stumbling blocks that could be holding the power back but eveything is working like a clock.Yet for some reason the motor seams to not breath above 5000rpm, Should I decide to,
For better flow will a weiand team G single plane intake flow better vs the rpm intake,as well to have the heads fully reworked port polish bowl blending etc as well as installing 2.08intake valves and possibly, 1.65ex valves if there is room for it.
Id like to get flowing 320cfm if possible money wise Ive had it priced out and will cost 1000.00 for everything.The head reworking will not cost me a dime due to my mechanic doing it as a gift for me we go back 40years from kids.So I will pay pay for parts and machining only. he has been trained at Joe mondelos for head porting.His victor junior heads flow 360cfm which he worked on himself and counless other heads for his customers
Any advice will be thankfully received and faithfully applied,and much appreciated,This forum has helped me alot with my Z28 from day 1.

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Old 04-26-2013, 12:16 PM
How fast is fast enough?
 
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If you can get the head work for free, and don't mind calling in a favor (which can sometimes be harder than just spending the money) having the heads done certainly won't hurt anything. I would look for a better intake manifold choice though.

What do you have for exhaust? That can make a huge difference in peak power.
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Old 04-26-2013, 01:11 PM
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More cfm

I have headman elite 13/4 headers 3 inch x pipe into 3inch flowmaster 2 chamber mufflers. AS for the the intake rather than the rpm I have did you mean the team g intake would be better or something other than the weiand
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Old 04-26-2013, 01:13 PM
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more cfm

What intake would you suggest
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Old 04-26-2013, 01:28 PM
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Originally Posted by sapsz28 View Post
Helo everyone.
Well its that time of year to feel the need again to drive our prized possessions.

I have a question that I cannot answer my 1980 Z28 has a 406 sbc 10.75-1 comp,hydraulic roller setup 241@50 int-246@50 ex 571int-565ex lift, 110lsa 106lca stock crank reworked lightened cross drilled chamfered, scat I beam forged rods ,speed pro forged flat tops 7cc valve reliefs, rpm intake 1/2 spacer cant go more due to hood clearance Holley HP 750 cfm DP carb 74primary jets 82 secondary,.balanced drivetrain with a M-21tranny. 3:42 rear end,RHS pro action aluminum heads 200cc runners 2.02 -1.6 valves with comp987-16 springs and comp roller rockers 1.6-1.5 they flow 280cfm @600 lift 395 cfm @400 lift the car drives great ,highway and city driveable. It last ran 12.91@106mph,my dilemma is on yhe dyno it showed 437ftlbs of torque @4700 rpm but only 339 hp @6100 rpm thats at the wheels,A/F ratio at full throttle is 12.0 at cruising rpm it is 13.8, Im very happy with the torque numbers but not satisfied with the HP.I feel that when driving from 2200 rpm it pulls very hard but after 5000 rpm I feel the power not climbing although it will rev easily to 6500 rpm. I run 20 degrees initial timing and 37 degrees total MSD street fire HEI ignition tayor 8mm wires they have the best clearance for the plug boot for my setup and champion plugs all to specs from RHS.Fuel pump is a edelbrock rpm flowing 120gph @6psi.Ive tested everything using process of elimination to rule out any stumbling blocks that could be holding the power back but eveything is working like a clock.Yet for some reason the motor seams to not breath above 5000rpm, Should I decide to,
For better flow will a weiand team G single plane intake flow better vs the rpm intake,as well to have the heads fully reworked port polish bowl blending etc as well as installing 2.08intake valves and possibly, 1.65ex valves if there is room for it.
Id like to get flowing 320cfm if possible money wise Ive had it priced out and will cost 1000.00 for everything.The head reworking will not cost me a dime due to my mechanic doing it as a gift for me we go back 40years from kids.So I will pay pay for parts and machining only. he has been trained at Joe mondelos for head porting.His victor junior heads flow 360cfm which he worked on himself and counless other heads for his customers
Any advice will be thankfully received and faithfully applied,and much appreciated,This forum has helped me alot with my Z28 from day 1.
Since you have a timing slip, if you know the weight of the car the horsepower can be calculated for another data point. I'm not much of an acceptor for chassis dyno data is a solid indicator of crankshaft horsepower. Bach when I was a young man in college, I accepted a couple summer intern jobs at Ford and as super good luck would have it ended up in the dyno rooms. What I discovered was that there can be as much as a 50 percent difference between the crankshaft power outputs as the engine is configured on the engine dyno compared to how it is configured when installed in a chassis on the chassis dyno. So when I hear chassis dyno guys talking about a 20 percent loss in the driveline, I just hold my nose and leave the room to find a place to puke.

You are going at the exact spot these guys want you to attack which is pour more money and technology into the engine. Don't get me wrong this will work; you can jack up the power till it overwhelms the installation losses. The problem is you have half a piece of information. From my reckoning by their formula to my experience you have an adjusted horsepower at the crank from 408 to 508. That's a huge spread and raises big questions in my mind as to whether the engine is down on power or whether that power is disappearing in the various installation losses. The installation is inclusive of ancillary drives such as the water pump, fan, alternator, power steering pump, possibly AC. Losses in the exhaust system. Losses in the torque converter, these can be significant as well as the transmission, drive shaft and rear end. Also the tires can eat a lot of power, especially when turning fast as they develop waves that move through the tire structure absorbing energy as they go.

So my opinion is that without a dyno run on an engine dyno, you're just pokin' at a pig while blindfolded.

Bogie
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  #6 (permalink)  
Old 04-26-2013, 01:28 PM
How fast is fast enough?
 
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If you can fit it, a Super Victor.

The team G intake has MANY different versions so you have to be more specific about that.

Better mufflers would help too, dynomax seems to make a decent one.

Also, has your carb been dyno tuned or did you just run it once for a power number? carbs need a lot of tuning by a pro to work well across such a wide RPM and loading condition.
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Old 04-26-2013, 02:52 PM
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Originally Posted by oldbogie View Post
Since you have a timing slip, if you know the weight of the car the horsepower can be calculated for another data point. I'm not much of an acceptor for chassis dyno data is a solid indicator of crankshaft horsepower. Bach when I was a young man in college, I accepted a couple summer intern jobs at Ford and as super good luck would have it ended up in the dyno rooms. What I discovered was that there can be as much as a 50 percent difference between the crankshaft power outputs as the engine is configured on the engine dyno compared to how it is configured when installed in a chassis on the chassis dyno. So when I hear chassis dyno guys talking about a 20 percent loss in the driveline, I just hold my nose and leave the room to find a place to puke.

You are going at the exact spot these guys want you to attack which is pour more money and technology into the engine. Don't get me wrong this will work; you can jack up the power till it overwhelms the installation losses. The problem is you have half a piece of information. From my reckoning by their formula to my experience you have an adjusted horsepower at the crank from 408 to 508. That's a huge spread and raises big questions in my mind as to whether the engine is down on power or whether that power is disappearing in the various installation losses. The installation is inclusive of ancillary drives such as the water pump, fan, alternator, power steering pump, possibly AC. Losses in the exhaust system. Losses in the torque converter, these can be significant as well as the transmission, drive shaft and rear end. Also the tires can eat a lot of power, especially when turning fast as they develop waves that move through the tire structure absorbing energy as they go.

So my opinion is that without a dyno run on an engine dyno, you're just pokin' at a pig while blindfolded.

Bogie
This is a great point if you're just chasing numbers for a dunk queen but I like chassis dunks for all these reasons. You're driving a car, not an engine. So a chassis dunk can be more effective for producing a powerful car. And as noted the trans, stall, exhaust, etc. all come into play and need to be given attention in your search for a powerful CAR.

An engine dyno will always give you higher numbers though if that's what you're after.
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Old 04-27-2013, 02:28 PM
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more cfm

Thank you all for your inputs.the weiand team G intake is the 7531 it will clear my set up as well the Victor jr and super victor jr will clear as well,the prts on the weiand are slightly bigger than both edelbrocks I mentioned,Weiand lists a powerband of 2800-7500rpm,both vicktor manifolds show 3500-8000rpm,and I do know of someone using the weiand with healthy results.
Mr Bogie Icould not care less about numbers as long as the motor is performing as well as it can but as I was shown on this site HP is a result of Torque,and I do see and feel the torque I beleive The car is being held back due lack of breathing and or fuel th A/F numbers were good and yes the carb has been tuned after the 6th pull with different fet size changes and bowl/air bleed adjustments where it is now gave the best results at the track and on the street from idle to 6500 rpm.
part and full throttle no hesitation and smooth transitions from both as well as plug reads,as for 'Them trying to suck money from me" the dyno sho itself did have few recomendations,first being reworking the heads for better flow,as for a valve size change yes it will have apositive impact on the motors ability to produce more HP,but the poting/bowl work should be done regardless,and since ican afford the valve work I will do it as well,it wont hurt,as for size 2.055 intake will be the minimum,but if I can fit 2.08or 2.10,that will depend on if i can put 1.65 exhaust in them as well,id rather go 2.055 and 1.65 than 2.08 and 1.6 or 2.10 and 1.6. Thnks again gents for the help .
If anyone has any other thoughts by all means I'm open to any and all advice.
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Old 04-27-2013, 03:08 PM
How fast is fast enough?
 
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Bigger valves are NOT always better. 2.02" should be just fine 2.05 is the largest I would consider and they may be too big.

A little porting would certainly help though. I'd focus on the port work, intake swap, and perhaps carb upgrades.

Another part to consider may be a better cam, it looks a little too big IMO, I could be wrong though.
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Old 04-27-2013, 05:14 PM
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more CFM

thanks a lot for your input AP. in regards to the card do you think I need more than 750 CFM as for the cam shaft I was looking at a single patt.ern 237 at 50 560 lift intake and exhaust or I might just go for a solid roller set up . the block is set up an.. again for the carbs I was thinking perhaps 850 CFM the however I don't know if I should go vacuum or double pump. it seems to run fine with the 750 double pump. very smooth and no stumbling hesitation at all, from: Idol to redline
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Old 04-27-2013, 07:38 PM
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you need to work out the problems first.First,WEIGH your car.My 1980 Z-28 came in at 3915#!!! I got it down to 3600, and 11.9s,took me a year.I think your car is 3-4 mph slower than should be.
The cam is not too big but it is hydraulic,solid is a little better. A single plane might make your car faster,

post your dyno graph including sfc numbers.
post an e.t. slip with all numbers.
tell us about the transmission specs
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Old 04-27-2013, 10:56 PM
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As for cars wait its 4000 pounds with driver and a full tank of gas, what formula is used in regards to the car's weight and the ET slip for the quarter mile.
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Old 04-29-2013, 10:28 AM
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As said the car weighs 4022 with me im it the tranny is a m_21 with 3:42rear I realize those last two factors are holding me back but the car has to be streetable. I'll get time slips and I know numbers posted the next day or two thanks guys
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Old 04-29-2013, 10:50 AM
How fast is fast enough?
 
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Originally Posted by sapsz28 View Post
thanks a lot for your input AP. in regards to the card do you think I need more than 750 CFM as for the cam shaft I was looking at a single patt.ern 237 at 50 560 lift intake and exhaust or I might just go for a solid roller set up . the block is set up an.. again for the carbs I was thinking perhaps 850 CFM the however I don't know if I should go vacuum or double pump. it seems to run fine with the 750 double pump. very smooth and no stumbling hesitation at all, from: Idol to redline
vacuum for the street, and DP for the track. A well tuned VS carb can perform VERY well though and if you want the best street manners it should not be overlooked.

For size- for peak power the bigger the better but you'll likely not be running at peak power much. I would get a well built carb that is done by a good shop and has excellent metering throughout the power band, in a multipurpose car consistent metering is more important than flow.

Or you can come into the light and just go EFI like all the manufacturers did 30 years ago.
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Old 04-30-2013, 10:50 AM
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This is a great point if you're just chasing numbers for a dunk queen but I like chassis dunks for all these reasons. You're driving a car, not an engine. So a chassis dunk can be more effective for producing a powerful car. And as noted the trans, stall, exhaust, etc. all come into play and need to be given attention in your search for a powerful CAR.

An engine dyno will always give you higher numbers though if that's what you're after.
Let me clairify why I want an engine dyno number, while I personally like big bragging numbers that's not what I'm looking for. The engine dyno tells you what the engine is capable of without the restriction of the installation. The chassis dyno tells you how much of what you put into the chassis actually makes to the ground. This tells me whether I need to look at the installation for power losses or the engine. Sometimes this is just a tuning problem, sometimes you have to rethink the installation. Most of the time some of each.

So to me it's all about collecting data and converting that data into useful information upon which actions can be taken to make changes. I find that going fast takes a lot of work. It may start with the engine but certainly doesn't end there and the hours of data collection and analysis can be tedious, a lot less than fun.

Bogie
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