241 Heads
04-05-2009, 05:24 PM
#1
241 Heads Ive got a set of 241's that I am going to install to replace my 853's. I would like to mill the head to increase compression. What would be the ideal cc to mill them too to maximize power with stock cam? And what length pushrod is needed due to the reduced height? I might have some mild porting done but nothing major. Im mainly looking for the increased compression and a little better flow for the added power.
04-05-2009, 07:09 PM
#2
If you aren't aware, the difference between 853 and 241 casting heads is negligible. If you elect to port them, spend you efforts on the valvejob and blending in the bowl area.
Increasing compression with the stock camshaft is somewhat of a risky proposition. While LS6 engines run more compression, they also run a larger cam as well. Each full point of compression is worth 3-4% increase in HP, or about 10HP on a stock LS1 making around 350HP. That and what you termed mild porting might add up to about 20HP at the most.
For most, the effort to get that gain is probably not worth it. Considering that you have the bolt-on's, you may be better off going with a camshaft, or doing the heads in conjunction with a cam.
Edit: see Post #23 & post #27 for my change of heart on the above.
Increasing compression with the stock camshaft is somewhat of a risky proposition. While LS6 engines run more compression, they also run a larger cam as well. Each full point of compression is worth 3-4% increase in HP, or about 10HP on a stock LS1 making around 350HP. That and what you termed mild porting might add up to about 20HP at the most.
For most, the effort to get that gain is probably not worth it. Considering that you have the bolt-on's, you may be better off going with a camshaft, or doing the heads in conjunction with a cam.
Edit: see Post #23 & post #27 for my change of heart on the above.
Last edited by hammertime; 04-24-2009 at 07:24 PM. Reason: I learned a few things since I first posted this
04-05-2009, 07:56 PM
#3
I dont think you will gain even 5hp going from 853s to 241s. If you do mill them you will raise your dynamic compression ratio with the stock cam so you may be required to run less timing. Having to buy shorter pushrods, installing the same flowing heads, milling the heads, and keeping the stock cam seems like one of the most counter productive expenditures. You would honestly gain atleast twice the HP by going with just a cam, leaving the 853s on, save $100 on gaskets, $50 on bolts, $80 to mill, $150 to port (cheeply) same cost of pushrods, and spend $200 on a nice set of springs and make a much larger gain imo. Even with a smaller cam you can remain emmissions legal and gain a large ammount of power.
04-05-2009, 08:21 PM
#4
Emission dont matter where im at. From using the search button, multiple reliable people stated a decent increase (10-15) would be recieved even without the milling or the port work. A cam is definitely an option. I was thinking about the 228R on a 112. But Im running a 150 wet kit so I was just looking for a small increase to add to the mix. A head swap is easy for me so no concern there. What would be the ideal mill top put on those heads with a small amount of port work to get them to work the best that they can?
04-05-2009, 08:29 PM
#5
I honestly wouldnt even waste the money unless you have lost a head gasket. The most you can probably bump your dynamic compression ratio is something like .010" just guessing with the stock cam but just that difference can be made up by running a cometec .040" head gasket instead of the stock GM .054" head gasket to raise compression. See there is static compression which is the compression that your pistons and heads make (i.e 10.1:1 stock with 67ccs) and the dynamic compression which is of the engine running which i believe ideal dynamic compression is something like 8.5:1 or something i think stock is like 8.4:1 i THINK. I know my dynamic compression is something like 7.9:1. the longer duration keeps the valves open longer thuse bleeding off some of the compression
You dont want to run a higher dynamic compression with the nitrous as you will already have to retard timing and retarding timing even further could causeyou to lose power or create unnecessary knock.
Why do a 'small' ammount of port work? Are you doing this yourself?
You dont want to run a higher dynamic compression with the nitrous as you will already have to retard timing and retarding timing even further could causeyou to lose power or create unnecessary knock.
Why do a 'small' ammount of port work? Are you doing this yourself?
04-05-2009, 09:10 PM
#6
I have a friend who builds motors for the local circle track and a few others. He has already built a few motors for me and he does great work and he is going to do the port work for me for nothing. We didnt plan to mess with the intake side too much just more on the exhaust to help it flow a bit. Clean up the heads and possible get a bit more compression out of it. That was the idea.
04-05-2009, 09:32 PM
#7
Has he ever built an LS motor? No offense to your friend intended, but if he's spent his life around SBC circle track engines, he may not be the best candidate to start working over a cathedral port head, free or otherwise.
There are a few how-to's out there on home porting LS heads. At the least, it may be a good idea to print them out or show your friend what needs to be done.
If you are going to run a cam, .030 is about the max to remove. At roughly .006 per cc, that's 62 cc's after milling. You may need to mock everything up first and check PTV clearance, or be prepared to notch the pistons.
There are a few how-to's out there on home porting LS heads. At the least, it may be a good idea to print them out or show your friend what needs to be done.
If you are going to run a cam, .030 is about the max to remove. At roughly .006 per cc, that's 62 cc's after milling. You may need to mock everything up first and check PTV clearance, or be prepared to notch the pistons.
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04-06-2009, 08:11 PM
#8
Yes he has worked on plenty of LS1 motors. Why is it always sooo hard to get an answer to the simplist questions. Im not asking for advice on why im doing what im doing. I didnt ask on any techniques on porting or anything. I asked a simple question. When using a stock cam, what would be an ideal amount to mill the head to increase compression to get the most out of the heads in question? Its simple.
04-07-2009, 11:42 PM
#11
Yes he has worked on plenty of LS1 motors. Why is it always sooo hard to get an answer to the simplist questions. Im not asking for advice on why im doing what im doing. I didnt ask on any techniques on porting or anything. I asked a simple question. When using a stock cam, what would be an ideal amount to mill the head to increase compression to get the most out of the heads in question? Its simple.
04-08-2009, 08:52 PM
#13
How much remove is more about compromise than compression. Milling any head can reduce how much you flow at the peak. In other words, if you mill too much, any gains you get from the increased compression will be lost to the reduction in flow.
I can't tell you how much on a 241 head, that answer needs to come from an experienced head porter, and/or someone who has flowed 241 heads before and after milling. I do know from reading here that most heads .040 is the recommended max, and usually they are ported or aftermarket heads that flow more than stock. I answered conservatively at .030, because that last little bit could hurt you more than help you. Also worth noting, PTV clearance will not be an issue if you stick with the stock cam, but 228 and longer duration cams, depending on the ICL could put you rather close after milling and running a thin head gasket.
Glad to hear your friend has worked on LS1's. I've heard too many stories, including a local engine builder here, where a small block chevy circle track engine builder gets out of his comfort zone and does more harm than good. Especially on cylinder heads, too many go with the "bigger is better" approach, and that will hurt performance everywhere but the top end. Ok in a car geared to run 4000-7000 rpms twice every 30 seconds, not so good on a street driven car.
I should have taken you at face value when you stated "mild porting". Hope this helps!
I can't tell you how much on a 241 head, that answer needs to come from an experienced head porter, and/or someone who has flowed 241 heads before and after milling. I do know from reading here that most heads .040 is the recommended max, and usually they are ported or aftermarket heads that flow more than stock. I answered conservatively at .030, because that last little bit could hurt you more than help you. Also worth noting, PTV clearance will not be an issue if you stick with the stock cam, but 228 and longer duration cams, depending on the ICL could put you rather close after milling and running a thin head gasket.
Glad to hear your friend has worked on LS1's. I've heard too many stories, including a local engine builder here, where a small block chevy circle track engine builder gets out of his comfort zone and does more harm than good. Especially on cylinder heads, too many go with the "bigger is better" approach, and that will hurt performance everywhere but the top end. Ok in a car geared to run 4000-7000 rpms twice every 30 seconds, not so good on a street driven car.
I should have taken you at face value when you stated "mild porting". Hope this helps!
04-09-2009, 07:25 PM
#14
Thanks for the info. My car is an A4 and I do not want to shift any higher than 6200-6500 rpms. The porting is going to be very mild with a bit of polishing on the exhaust side. I run on the bottle so thats my main power adder. Im just looking to get a little extra by switching the heads to a set with a small bit of work. Ive thought a bit more into it and I might add a TR 224 cam with it.
04-11-2009, 02:06 PM
#15
as far as the 224 cam goes and milling. I ran 62cc heads with that cam and PTV was good. I also ran a stock head gasket. stock 241 is 67 so your talking 5 cc's removed. Its around .006 per cc so your talking roughly .030 thousandths removed from your head. That is what i know works. You can try milling more but i dont know how much. Are etching the pistons out of the question??
04-11-2009, 05:46 PM
#18
Okay lets turn this thread around a bit. I just picked up a VRX3 cam from a friend. What could I do to this set of 241's to get a bit more out of this cam. Is flycutting required? So heres what Im thinking, cam is a 226/228 .585/.588 114 LSA. Mill the heads .030 and use a .040 gasket as stated above? That combined with a small amount of polishing and porting.
04-11-2009, 06:02 PM
#19
well that completely changes everything lol. Thats a relatively large cam. u can run it with stock heads but im not so sure about milling. Etching is something u will probably have to do