Dynamic Compression Ratio issue
Thread Starter
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
I've read through this thread with great interest. I have very similar car, '80 L48, but with flat top pistons. Have done much of the same research on replacing heads and cams but came up with slightly different result. Why didn't you select a larger head, 2.02/1.60 ports since you have the exhaust capacity? The cost over the smaller 1.94/1.50 heads is minimal. Or, does the Vortec head give "good enough" flow for the total set up?
Since I'm "waiting on funds"
I look forward to your results.
Good luck.
Since I'm "waiting on funds"
I look forward to your results.Good luck.
The Edelbrock 60797 E-tec heads have a 64 cc combustion chamber, 1.94/1.55 valves, and flow 64in/54ex @.100 lift, 130/104@.200, 186/140@.300, 220/169@.400, 223/183@.500, and 238/190@.600
The Edelbrock 60759 heads have a 70 cc combustion chamber, xxxxxx2.02/1.60 valves, and flow 73in/61ex @.100 lift, 140/108@.200, 200/144@.300, 238/163@.400, 244/175@.500, and 244/183@.600
As you can see, the flow numbers are pretty close, especially on the exhaust side, which is actually a tad bit higher flow on the E-tecs above .400 lift. With a 268H cam, it won't ever see even close to .500 lift, but even still, the heads flow pretty close, even with the smaller valves on the E-tecs. The combustion chamber design is very similar, if not identicle, to the chevy vortec heads, which imparts a "swirl" to the intake charge, atomizing it more thoroughly, allowing more efficient combustion. It also allows peak power to be made with less spark advance, allowing more compression to be run. Some people here on the forum had to beat me over the head with it for awhile,
but I finally saw that it makes alot of sense.Scott
Thread Starter
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
In general I'm pretty happy with the setup, but I honestly haven't had enough time to really work out all the kinks.
In addition to the above, my setup includes a Hayes 15lb Aluminum flywheel. Tranny is the optional close ratio Super T-10 4-speed and the rear is a 3.70. Carb is the original quadrajet.
Car sounds awesome at idle. The quick ramp on the comp cams 268h gives it a very nice sound in my opinion. Off the line it pulls strong all the way through 5500 (which is what you would expect), but I think there are a few things leaving HP on the table that I need to go back and fix....
The heads: My heads are very well worked 041 castings. They are fully ported and polished, have 2.05 and 1.6 valves with the chambers opened up around the intake to eliminate intake valve shrouding, have Ferrea 5000 neck-down valves and com roller-tip rockers. My local racing shop did a great job with them and the work is very high quality. Problem is they just can't match even the cheapest vortecs you can buy today, and that's just reality. I know I'm leaving a good deal of power on the table here.
The Exhaust: I wanted to go with something stock looking (kind of a theme), so I decided to get some repro 65 fuelie rams horns with the 2.5" dump (std Rams horns are 2" dump). I then used the front pipes from the 65 fuelie and the mid pipes from the 73 big block to create a true 2.5" all the way back to the muffler. A couple of problems here; the repro castings are terrible. Even after grinding them out to port match them to a fel-pro 1404 gasket (and the exhaust ports), I could just tell they weren't going to flow very well. If I had to do it over again, I would probably go with shorty headers, probably McJacks and the Pypes system from the headers/crossmember back. The difference in what I spent and this system would really only be about $600, but I was doing so much that I just couldn't do it. I love the sound, but like another poster said, an engine is an air pump, and mine could be more efficient.
If your open to some lessons learned, here's some free advice....
Cooling: Don't just concentrate on your power side, take a good hard look at your cooling system as well. Your new motor will make more heat than your old one, and the cooling system needs to be up to the task to help avoid detonation. The L-48 radiator has one less core than the L-82 radiator (atleast it did in 78), so you might want to think about replacing that as well. At the very least, pull the radiator and shroud and make sure it is all clean and undamaged. Replace the seals around the radiator to ensure you get good flow THROUGH the radiator, not around it. Get yourself a RobertShaw thermostat that has the bypass in it. I used a 180 degree model to lower the temp a bit from the 195 stock. The bypass hole will help eliminate air bubbles when filling the motor for startup. Most importantly, make sure your water pump is in good condition! I re-used my original water pump on my build as it felt just fine. The car had a vibration at around 70 that I thought was a driveline vibration that turned out to be the water pump. A Walker Stage II aluminum pump fixed the problem quite nicely. Check your fan clutch to make sure it is in proper working condition, it is a critical piece of the puzzle. If you need to replace it, look around on the web and by a real ACDELCO replacement.
Cam installation and Break-in: So much has been written on this subject and the fact that modern oils have less zinc and other additives that I won't go into it here. Needless to say I was petrified of wiping a lobe during break-in. A small bit of insurance that I had done was to send the cam and springs to High Performance Coatings in Whitsett, NC to have their anti-friction coating applied. Had the cam done to help with break-in and the springs to help them stay cool and extend their lifespan. Don't know if I overdid it, but everything is still working well 1100 miles later.
I hope I answered your question. Sorry about rambling on about the other aspects, feel free to discard the information you don't need, but having done the exact same thing you are now doing, I hope I've helped you avoid some potential missteps.
You will enjoy the build.
-Fred
In addition to the above, my setup includes a Hayes 15lb Aluminum flywheel. Tranny is the optional close ratio Super T-10 4-speed and the rear is a 3.70. Carb is the original quadrajet.
Car sounds awesome at idle. The quick ramp on the comp cams 268h gives it a very nice sound in my opinion. Off the line it pulls strong all the way through 5500 (which is what you would expect), but I think there are a few things leaving HP on the table that I need to go back and fix....
The heads: My heads are very well worked 041 castings. They are fully ported and polished, have 2.05 and 1.6 valves with the chambers opened up around the intake to eliminate intake valve shrouding, have Ferrea 5000 neck-down valves and com roller-tip rockers. My local racing shop did a great job with them and the work is very high quality. Problem is they just can't match even the cheapest vortecs you can buy today, and that's just reality. I know I'm leaving a good deal of power on the table here.
The Exhaust: I wanted to go with something stock looking (kind of a theme), so I decided to get some repro 65 fuelie rams horns with the 2.5" dump (std Rams horns are 2" dump). I then used the front pipes from the 65 fuelie and the mid pipes from the 73 big block to create a true 2.5" all the way back to the muffler. A couple of problems here; the repro castings are terrible. Even after grinding them out to port match them to a fel-pro 1404 gasket (and the exhaust ports), I could just tell they weren't going to flow very well. If I had to do it over again, I would probably go with shorty headers, probably McJacks and the Pypes system from the headers/crossmember back. The difference in what I spent and this system would really only be about $600, but I was doing so much that I just couldn't do it. I love the sound, but like another poster said, an engine is an air pump, and mine could be more efficient.
If your open to some lessons learned, here's some free advice....
Cooling: Don't just concentrate on your power side, take a good hard look at your cooling system as well. Your new motor will make more heat than your old one, and the cooling system needs to be up to the task to help avoid detonation. The L-48 radiator has one less core than the L-82 radiator (atleast it did in 78), so you might want to think about replacing that as well. At the very least, pull the radiator and shroud and make sure it is all clean and undamaged. Replace the seals around the radiator to ensure you get good flow THROUGH the radiator, not around it. Get yourself a RobertShaw thermostat that has the bypass in it. I used a 180 degree model to lower the temp a bit from the 195 stock. The bypass hole will help eliminate air bubbles when filling the motor for startup. Most importantly, make sure your water pump is in good condition! I re-used my original water pump on my build as it felt just fine. The car had a vibration at around 70 that I thought was a driveline vibration that turned out to be the water pump. A Walker Stage II aluminum pump fixed the problem quite nicely. Check your fan clutch to make sure it is in proper working condition, it is a critical piece of the puzzle. If you need to replace it, look around on the web and by a real ACDELCO replacement.
Cam installation and Break-in: So much has been written on this subject and the fact that modern oils have less zinc and other additives that I won't go into it here. Needless to say I was petrified of wiping a lobe during break-in. A small bit of insurance that I had done was to send the cam and springs to High Performance Coatings in Whitsett, NC to have their anti-friction coating applied. Had the cam done to help with break-in and the springs to help them stay cool and extend their lifespan. Don't know if I overdid it, but everything is still working well 1100 miles later.
I hope I answered your question. Sorry about rambling on about the other aspects, feel free to discard the information you don't need, but having done the exact same thing you are now doing, I hope I've helped you avoid some potential missteps.
You will enjoy the build.
-Fred
Yeah, my car has a stock th-350, (wanna go to a 200-4r someday)stock converter, 3.08 rear, so I'm concerned with having enough low end grunt.
I wrote in an earlier post that since the radiator has to be removed to install the cam, I am planning on replacing it with an aluminum one. If money gets tight, I might consider what you have told me about the L82 rad being better than L48, but either way, some sort of radiator upgrade will take place.
I am looking into the pro plasma nitriding process Comp Cams has, might be some good insurance, as I too am paranoid about smoking the cam at breakin. I would just be sooooo bummed.......Anybody know anything about this process?
Scott
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Burning Brakes
Joined: Nov 2004
Posts: 1,193
Likes: 176
From: Hillsborough NC
Hi Fred! Glad your happy with your build.
If the porting work is as nice as you say your not giving up anything. Everybody always says the Old 1960's early 70's heads are just not on a par with the modern heads. I worked in a high performance machine shop in the 70's. These were all we had. Used to have 10 second cars running these. It's true the chamber design is different getting them to flow well is an art and a lot of hard work.
Scroll down and look here at the Chevy '461X C/ED Ported Meaux Racing Heads.
http://users.erols.com/srweiss/tablehdc.htm#Chevy
The 461 X was a early 60"s fuelly head. Stock GM. You can port these big time. They are a very similar design to your 041 heads with a few minor differences. The accessory bolt holes are added and the temperature sending unit hole is different. The Ported 461X flows 282 on the intake side and 253 on the exhaust side with a 89.7% I/E ratio. Those numbers blow the vortec's out of the water. They even beat out the New AFR 227's on exhaust flow. Too bad you didn't check your flow numbers on a flow bench before you installed them. Probably would have suprised you.
If the porting work is as nice as you say your not giving up anything. Everybody always says the Old 1960's early 70's heads are just not on a par with the modern heads. I worked in a high performance machine shop in the 70's. These were all we had. Used to have 10 second cars running these. It's true the chamber design is different getting them to flow well is an art and a lot of hard work.
Scroll down and look here at the Chevy '461X C/ED Ported Meaux Racing Heads.
http://users.erols.com/srweiss/tablehdc.htm#Chevy
The 461 X was a early 60"s fuelly head. Stock GM. You can port these big time. They are a very similar design to your 041 heads with a few minor differences. The accessory bolt holes are added and the temperature sending unit hole is different. The Ported 461X flows 282 on the intake side and 253 on the exhaust side with a 89.7% I/E ratio. Those numbers blow the vortec's out of the water. They even beat out the New AFR 227's on exhaust flow. Too bad you didn't check your flow numbers on a flow bench before you installed them. Probably would have suprised you.
Good information on the heads. I think I'm going to start with getting rid of the chinese manifolds and get a nice set of coated flotech or hedmann elites for the car. Maybe the heads really do flow well, but I'll never find out with those manifolds....
Funny story on the heads which you in particular will appreciate... The guy I bought them from on Craigslist was getting rid of them so he could put on a nice set of aluminum ProComp heads
I was polite and wished him well. Later, I figured that was fitting penence for selling me heads that needed so much work.
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
Funny story on the heads which you in particular will appreciate... The guy I bought them from on Craigslist was getting rid of them so he could put on a nice set of aluminum ProComp heads I was polite and wished him well. Later, I figured that was fitting penence for selling me heads that needed so much work.
I was polite and wished him well. Later, I figured that was fitting penence for selling me heads that needed so much work.
He got a great deal on those pretty aluminum heads. Yours probably flow better.
