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Old 11-04-2012, 03:27 PM
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edelbrock rpm performer heads 350 vs 383

Ok i bought a used set of rpm performer heads "hope I did good" and im looking to build a bottom end for my camaro would I be better off with a 350 instead of a 383 with those heads a little confused about the specs on the heads there marked 6073 on the outside and 6061 inside but i think there 70cc with 170 or 185cc intake i want a good cruiser, kinda hotish, like 400hp range low compression motor. I know its not going to be good on gas but i want it to be efficient for what it is so 350 or 383 pros cons on ether

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Old 11-04-2012, 03:45 PM
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Either will work fine with those heads. 383 will make a lot more power and low end grunt. But for gas milage a low compression 350 is best bet. But for power go 383 higher compression 9.5:1 with good cam will make 400 range with ease.
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Old 11-04-2012, 04:15 PM
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For mileage you want the highest compression you can run with whatever cam you're looking at- but you also need to use a cam with low duration (which lends itself to lower compression).

If I were in your shoes, with those heads and a 383 I would go with a 10:1 compression and a cam in the 215 range with all the lift you can get (hyd roller with 1.6 rockers).
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Old 11-04-2012, 06:40 PM
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the 383 and 350 will make the same amount of horse power of very close to it. The 383 will make the power at a lower rpm due to the longer stroke.Those heads can easily make more than 400 hp
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Old 11-04-2012, 09:19 PM
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I seem to remember those heads flowing about the same or maybe a little better than the Chevy L31 Vortecs, so yeah, I'd do a 383 just for the torque.
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Old 11-05-2012, 05:10 AM
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i was planing a 383 build but doing research on my heads alot of people are saying they are not enough for a 383 idk but like i sayed i want around 400hp but i dont want to go over board with it cause i do plan on driving this car alot gas mileage is not my most concern but i do want something i can drive
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Old 11-05-2012, 06:00 AM
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Quote:
Originally Posted by munchigan View Post
i was planing a 383 build but doing research on my heads alot of people are saying they are not enough for a 383 idk but like i sayed i want around 400hp but i dont want to go over board with it cause i do plan on driving this car alot gas mileage is not my most concern but i do want something i can drive
If you need to get a new crank then there is no reason to not go with a 383. If you're on a tight budget and can reuse your crank then a 350 can hit 400hp pretty easily with those heads.

It comes down to budget and what you have. A 383 will have more torque BUT a well built 350 can easily provide the power you're wanting.
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Old 11-05-2012, 06:15 AM
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Quote:
Originally Posted by munchigan View Post
i was planing a 383 build but doing research on my heads alot of people are saying they are not enough for a 383 idk but like i sayed i want around 400hp but i dont want to go over board with it cause i do plan on driving this car alot gas mileage is not my most concern but i do want something i can drive
build the 383 it's be tamer,, meaning less of a tempermental beast..
it'll have more torque lower so you'll not get in the gas as much most of the time.. unless you are going fun runs..
will be easier on parts as the cam can be milder and still hit 400hp..
an honest 400 hp 355 is not a mild engine.. buy any means..
torque moves you, hp sells cars.
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Old 11-05-2012, 07:29 AM
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I can't say from experience, and perhaps I shouldn't say anything for that reason, but I'm going to through my two cents in anyway, and if anyone disagrees please correct me.
If I were you I'd start with a 87'-92' roller cam block and use the stock lifters/spider retainer for considerable cost savings. The stock type lifters/"dogbones"/spider retainer for roller blocks can be purchased in a kit for almost 1/2 the cost of retro-roller lifters alone(used in older blocks).
As far as the heads you have(I have the same) I would disassemble them and do some pocket porting/chamber blending/polishing. Mine had sharp edges where the valve seat inserts were cut, and seats installed too deep IMO, that might have caused hot spots for detonation. Get two used valves from the machine shop you plan to use, and insert into the chamber that your working on to prevent damage to the seats before grinding. I used a dremel with a flexible wand, and sanding rolls as I didn't have an air compressor for a die grinder. I'm sure most wouldn't recomment a dremel, takes alot of time and not the proffesional way to do the job, but I think it worked ok for me.
I'd then get the machine shop to check the valve guides to see if there ok before getting a valve job done. After the valve job have them milled just enough for clean-up of the deck for gasket sealing. Then cc the chambers and equalize them for consistant compresssion and CR calculation(mine measured an average of 72cc +/-.3 after all the work).
I'd also get some beehive springs/retainers/seat inserts to work with a roller cam. I used Comp Cams behives pn 26986-16 springs, pn 795-16
10*retainers, and pn 4694 spring cups, and all fit withouut maching the heads.
This is probably alot of over kill for a 400hp, low compression engine, but I would at least do the valve job, guides checked, springs checked, deck shaved, and cc'ed. Use the springs recommended by the manufacturer of the cam you use. The springs on mine were not spec'ed for a roller cam. Being that your talking about a low compression motor smoothing the chambers may not matter, but it wouldn't hurt and may be whats needed to equalize the chamber volumes. I can't guarantee it, but I'm bettting mine will support a 383 making 425-450hp. I'll have to wait and see if I lose the bet.
I'd also use a Scat crank and rods, for a six inch rod as you can get it internally balanced(with exception of flexplate if using a one piece rear main seal used in roller blocks). I don't like an unbalanced dampner on the crank snout as the front main bearing has enough of a load as it is with the accessory drives(alternator/pwr steering/ AC). I have heard some negative rumors lately about Scat cranks, but I bought mine directly from Scat awhile back, and it checked out good with my mics. I also got the Pro comp rods that have the ARP 7/16"cap screws that didn't require any clearancing on the block. I haven't checked cam clearance yet.
For lower compression I'd use a piston with a 12cc "d-cup" and a zero decked block with a head gasket of 0.039" thickness(Felpro pn 1010 has a preflattened copper ring for alum. heads) for a 0.039 squish/quench distance to ward off detonation. I can't guarantee that it would be able to run using 87 octane, but with 72cc chambers it comes to about 9.5:1 static CR, and with a Comp 270 roller cam the dynamic CR comes to about 7.8:1. According to Comp's camquest software it comes to 437hp and 480ftlbs torque.
Ignore the groves in the chamber pics. I'm using a flat top with 5cc valve reliefs and the CR comes to 10.2:1, so I'm trying to get every bit of detonation resistance I can. Don't know if they work anyways.
Just some things to think about!
FWIW
ssmonty
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Old 11-05-2012, 09:52 AM
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Never take a dremel to an aluminum head. Its too easy to trash the head. Also they are fine stock no need to mess with them unless your trying to make over 500 hp. Electric die grinder is what you need but not dremel you need low speed for aluminum heads. high rpm of dremel will eat into the head to fast. Air power is no good for alum heads either same issue and also stalls at low rpm.

@ssmonty that was a swirl device you removed. The air must spin around the valves and into the combustion chamber. that is why they leave the sharp edge around the seat pocket. you can clean it up but not take it out all together. Unless replacing it with a real full on pocket port job. Edelbrock did not cut major corners they just didnt pocket port the heads. You didnt either. Rule of thumb for aftermarket heads is only port them if you have too by class. Other than that buy the next size up. Once you max out your heads then maybe go back for the 10 hp the manuafacture left on the table.

@O/P leave your heads factory. Have the valves checked to see if they are seating up. other than that just leave them be. They can be ported and could use some work from the factory. But you will make 400hp without going to the trouble.
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Old 11-05-2012, 10:26 AM
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Hello Munchigan,

My 1977 Nova had a professionally built 383 with 60899 heads, mileage on longer drives was about 18 mpg, about what the original 350 got.
Engine had Comp 280H flat cam, dynoed at 430 Hp(5500rpm) 470 torque-nice engine, easy to start and drive. 60899 are 64cc straight plug RPM. I sold this engine and moved up to a 420 Dart. This car is a summer drive/cruise car, hasn't been to the drag strip. Engine was built and tuned for premium (91 octane) pump gas.

Here is a location to search your 6061 and 6073 heads:
Edelbrock.com

You have 4 digits as opposed to newer Edelbrock numbers of 5 digits, so your 6061 will be 60619 and 6073 will be 60739. You will see that both are 70cc, straight plug but 6073 is for solid flat tappet and hyd roller. You will have to do a bit of searching to find spring rates.

Hope this helps,
Regards,
Meldrum
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Old 11-05-2012, 03:01 PM
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Originally Posted by hcompton View Post
Never take a dremel to an aluminum head. Its too easy to trash the head. Also they are fine stock no need to mess with them unless your trying to make over 500 hp. Electric die grinder is what you need but not dremel you need low speed for aluminum heads. high rpm of dremel will eat into the head to fast. Air power is no good for alum heads either same issue and also stalls at low rpm.

@ssmonty that was a swirl device you removed. The air must spin around the valves and into the combustion chamber. that is why they leave the sharp edge around the seat pocket. you can clean it up but not take it out all together. Unless replacing it with a real full on pocket port job. Edelbrock did not cut major corners they just didnt pocket port the heads. You didnt either. Rule of thumb for aftermarket heads is only port them if you have too by class. Other than that buy the next size up. Once you max out your heads then maybe go back for the 10 hp the manuafacture left on the table.

@O/P leave your heads factory. Have the valves checked to see if they are seating up. other than that just leave them be. They can be ported and could use some work from the factory. But you will make 400hp without going to the trouble.
HCOMPTON,
The ridges around the valve seat inserts were not swirl devices. Some chambers on the head had them and some didn't. It was left from the machine operation at the factory to install the seats. I believe a machine operation be it by CNC, or manual mill, or something else was used to cut the bore to the same depth for each chamber relative to the table height of the machine. However each chambers casting depth wasn't consistant thus the ridge on some chambers and not on others.
If your refering to a vane downstream of the valve guide, there wasn't one on these heads. I did reduce the diameter of the guide bosses to reduce air flow restriction although it won't make that much of a difference, similar to the reduced valve stem diameter of the Manley "Pro Flow" valves I installed. I figure every little bit helps as far as beating the next guy.
If your refering to a swirl vane in the chamber such as a raised boss around the spark plug location, there wasn't one in my heads.
As far as a "Rule of thumb for aftermarket heads is only port them if you have too by class" thats the first time I've heard of that. I have heard of no porting allowed in certain classes. As far as I'm concerned I had the spare time and the will to try to make them better than stock before I installed them on an engine vrs removing them to do the same later.
Just MHO.
To each his own,
ssmonty
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Old 11-05-2012, 03:43 PM
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Originally Posted by ssmonty View Post
HCOMPTON,
The ridges around the valve seat inserts were not swirl devices. Some chambers on the head had them and some didn't. It was left from the machine operation at the factory to install the seats. I believe a machine operation be it by CNC, or manual mill, or something else was used to cut the bore to the same depth for each chamber relative to the table height of the machine. However each chambers casting depth wasn't consistant thus the ridge on some chambers and not on others.
If your refering to a vane downstream of the valve guide, there wasn't one on these heads. I did reduce the diameter of the guide bosses to reduce air flow restriction although it won't make that much of a difference, similar to the reduced valve stem diameter of the Manley "Pro Flow" valves I installed. I figure every little bit helps as far as beating the next guy.
If your refering to a swirl vane in the chamber such as a raised boss around the spark plug location, there wasn't one in my heads.
As far as a "Rule of thumb for aftermarket heads is only port them if you have too by class" thats the first time I've heard of that. I have heard of no porting allowed in certain classes. As far as I'm concerned I had the spare time and the will to try to make them better than stock before I installed them on an engine vrs removing them to do the same later.
Just MHO.
To each his own,
ssmonty
Some types of racing require stock or limited port volume. In that case specail concerns need to be address as everyone else has done the same. For racing go for broke.

Lip around seat from steal to alum needs to be cleaned up but can have little effect if seats were installed correctly.

Yes they cnc the heads but do not cnc port the heads its just part of the manufactuing process. Cnc porting cost extra.

The reason not to port aftermarket heads is they do produce the numbers unmolisted. If you have an issue with the head you cant send it back if its cut. Also if you need more flow just buy a head that is desgined to flow more. Get 210cc heads or 234cc heads. Dont buy the smallest port head and try to make it bigger its not that simple. Cutting the heads will most likely end with less flow. Many engine builders are looking to add metal to the heads. Just removing metal wil not increase flow. Also on stock heads there are many reasons to remove a little metal to clean them up. Casting marks and bumps that can be removed to make more power. On after market heads they cast them with good ports so its not likey there is any power to be had with easy port work. If so they would do ot before they ship it out.

Swirl devices are on the port roof and split by the guides. Depending on which way the air swirls around the valve. Ypu have both side cut the same and it does not flow that way it flows around the valve.
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Old 11-06-2012, 10:14 AM
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Hcompton,
"Yes they cnc the heads but do not cnc port the heads its just part of the manufactuing process. Cnc porting cost extra." No BS? They don't CNC port the head for free? Wow, I never would have though they would charge extra for time spent on a $250,000 5-axis machine. By the way, I never said anything about CNC porting.
"Also if you need more flow just buy a head that is desgined to flow more."
Just give him the money.
The op said he had a set of heads allready and that he was concerned that they may not be enough for a 383. I was trying the show him that they could be improved somewhat with a little work. I wasn't trying to tell him to do all I did, just some of many options he had to make them better.
"The reason not to port aftermarket heads is they do produce the numbers unmolisted. If you have an issue with the head you cant send it back if its cut. Get 210cc heads or 234cc heads."
Am I the only one that has tried to clean-up an aftermarket head? Do you think they'll take back the op's used heads if he does'nt grind on them? Maybe the op doesn't want to lose low end throtle response and torque by giong to a larger port head. He only said he wanted it "kinda hotish". I think he would be happy with a 383 with the Edel. heads he has, and I think he a would like them even more with a little work done.
Funny, your the one I see telling others to follow write-ups in Hot Rod magazine for engine builds. Don't I see Hot Rod doing articles on DIY porting now and then too?
Like I said, most wouldn't reccomend a dremel and I didn't have an air compressor. I also thought I could do what I wanted with a $30 rotary set I saw at Advance Auto vrs buying a $150 Milwaulkee grinder and $50 worth of bits for a one time job. You don't think an electric grinder can remove material very fast???? I still think a dremel style tool with a wand, and keeping it moving back and forth without letting it stay still for any length of time, with a sanding roll/cartridge just below the seat insert, and around the chamber, and the short side radius would do a decent job of bowl clean-up/ chamber polishing for the DIYer.
ssmonty
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Old 11-06-2012, 10:45 AM
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Quote:
Originally Posted by ssmonty View Post
Hcompton,
"Yes they cnc the heads but do not cnc port the heads its just part of the manufactuing process. Cnc porting cost extra." No BS? They don't CNC port the head for free? Wow, I never would have though they would charge extra for time spent on a $250,000 5-axis machine. By the way, I never said anything about CNC porting.
"Also if you need more flow just buy a head that is desgined to flow more."
Just give him the money.
The op said he had a set of heads allready and that he was concerned that they may not be enough for a 383. I was trying the show him that they could be improved somewhat with a little work. I wasn't trying to tell him to do all I did, just some of many options he had to make them better.
"The reason not to port aftermarket heads is they do produce the numbers unmolisted. If you have an issue with the head you cant send it back if its cut. Get 210cc heads or 234cc heads."
Am I the only one that has tried to clean-up an aftermarket head? Do you think they'll take back the op's used heads if he does'nt grind on them? Maybe the op doesn't want to lose low end throtle response and torque by giong to a larger port head. He only said he wanted it "kinda hotish". I think he would be happy with a 383 with the Edel. heads he has, and I think he a would like them even more with a little work done.
Funny, your the one I see telling others to follow write-ups in Hot Rod magazine for engine builds. Don't I see Hot Rod doing articles on DIY porting now and then too?
Like I said, most wouldn't reccomend a dremel and I didn't have an air compressor. I also thought I could do what I wanted with a $30 rotary set I saw at Advance Auto vrs buying a $150 Milwaulkee grinder and $50 worth of bits for a one time job. You don't think an electric grinder can remove material very fast???? I still think a dremel style tool with a wand, and keeping it moving back and forth without letting it stay still for any length of time, with a sanding roll/cartridge just below the seat insert, and around the chamber, and the short side radius would do a decent job of bowl clean-up/ chamber polishing for the DIYer.
ssmonty
Not trying to argue with ya. But you dont move the bit back and forth when porting. You cut for right to left against the rotation of the bit. Sanding rolls are for cast iron heads, use a home made flapper for aluminum heads. Ask at local machine shop they can show you how it works. Home made flapper is 1/4 inch tool steel rod with slit cut in top for sand paper. just one 3 inch x 1 inch strip folded over to fit inside the bit. It will cut fast and clean with no bumps and leave your port floors dead flat. Sanding rolls will leave bumps and dips in the port floor. use cross cut carbides for any metal reshaping.

Electric die grinders are more powerful than air. They have better tq that gives better control. Not just whacking it back and forth a bunch of times.

The OP has heads that are fine for 383 no need to take a first run at porting with an expensive set of heads. They will make big power without anything being done to them. Why take the risk of bad port work on 1500 heads when they will do the job bone stock. So kinda hotish = stock edlebrock heads. Right?
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