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| Budget head and rockers https://slantsix.org/forum/viewtopic.php?t=33499 |
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| Author: | heckshemi [ Sun Jan 25, 2009 8:53 pm ] |
| Post subject: | Budget head and rockers |
I wanted an engine with a better flowing head and higher compression for power and economy but I want to spend as little as possible for machine work and parts seeing how I have very little money for engines and cars and such. I thought about intake valve to exhuast valve size ratio of the slant six and compared it to other engines and came to the conclusion that the slant six could use a much larger intake valve while retaining the stock exhaust valve. By only installing larger intake valve I cut my machining costs and parts needed. (Please share thoughts) So I installed 1.81" big block mopar exhaust valves on the intakes and extensive bowl porting on both the intake and exhuast ports. I left the runners and floors pretty much stock, just gasket matching. Had the head milled .100" and the deck milled for a 10.2 comp ratio. Enginebldr 340 springs and retainers and they even come with the single groove keepers needed for the new valves! Put it together and the pushrods were to long. A good time to try my cut and weld rockers rather than buy new pushrods. Plus the comp 264 cam I have has a little less lift than advertised. The stock rockers averaged about 1.47 ratio. Now they're about 1.58 after cutting about .070" and I was able to adjust for pushrod length. We'll see how they hold up, so far so good. My welding skills I would describe as average at best so they're not so pretty but I think they're strong enough. ![]()
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| Author: | terrylittlejohn [ Sun Jan 25, 2009 9:04 pm ] |
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i used a 360, 1.88 cut to 1.80, on my high compression engine with a 1.60 ex valve, i worked really good. nice looking pocket work on your head. |
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| Author: | Valleyant [ Mon Jan 26, 2009 5:05 am ] |
| Post subject: | |
Hi, Did you do this to a 170 slant 6? If so, would you use the same approach on a 225? Would like to hear how it responds to valve sizes you chose. Cool project! nico |
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| Author: | Dart270 [ Mon Jan 26, 2009 9:04 am ] |
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Nice work and nice pics! Some folks have also moved the Int valve over toward the exh and used a smaller exh valve to change the int/exh flow ratio. 1.80/1.40 or thereabouts without bore notches. Lou |
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| Author: | terrylittlejohn [ Mon Jan 26, 2009 9:11 am ] |
| Post subject: | |
it was a 225,i went from a .030 over bore with 318valves and 10.7/1 compression running 13.40et`s, then i went .060 over bore 360 valves and 11.4 compression running 12.80et`s,the 60ft times really pickup with the extra compression, 1.90`s to 1.70`s. |
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| Author: | Doc [ Mon Jan 26, 2009 12:51 pm ] |
| Post subject: | |
Be sure to check your spring pressures... the BB Mopar valves tipically use a taller spring and a 1.8 installed height. 340 springs are shorter. DD |
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| Author: | runvs_826 [ Mon Jan 26, 2009 4:39 pm ] |
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When/where is there benefits for the larger valves. I know that it's common practice no matter what engine you run. I've seen EngrBldrs valves commonly used for cam/compression/carb builds. I haven't seen such large valves, but I'm very interested now. Why did you go with a larger intake and same exhaust? What would be the benefit of one being larger over the other for N/A, super, turbo builds? Last, can you cut down exhaust valves? Sorry for all the questions at once, but I've been curious ever since I realised that 302 valves would work or a lot of chevy stock ones with some minor modifications. |
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| Author: | sandy in BC [ Mon Jan 26, 2009 6:28 pm ] |
| Post subject: | |
Depends on what you want to do and how you chose to get there. For me 1.72 intake and 1.50ex works...in conjunction with a split duration cam (280intake/270 ex) Mebbe Mr Hemi runs a long exhaust duration cam.......or mebbe big lift on the exhaust. ....I bet he isnt terbowed..... |
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| Author: | heckshemi [ Mon Jan 26, 2009 7:47 pm ] |
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I bought the valves directly from Ferrea in FL. Part #F5053 1.810" X 3/8" X .4910". I had to use shims to get the right spring height but it wasn't much. I made sure they didn't sink the valves down when they machined. I'm runnin a comp 264 cam just because that's what I had. My thought was the slant head needed more help on the intake side. This is just a high compression daily driver motor. |
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| Author: | wvenable [ Tue Jan 27, 2009 5:12 am ] |
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With a 10.2 comp ratio I assume premium is what you will put in the tank? What is the rule of thumb for pump gas? How much can you get away with? I know that with more overlap you can bring down static compression. Just curious, thanks! |
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| Author: | sandy in BC [ Tue Jan 27, 2009 7:07 am ] |
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There are 3 easy ways to measure compression. You refer to " ten to one"....that is static compression ratio. ,,,,a calculation based on cylinder volume BDC compared to volume at TDC.....mine is 9.5:1 you referred to overlap ....that is a component of dynamic compression ratio ,,,,a calculation based on static CR and valve timing.....mine is 8.48:1 another way is cylinder cranking pressure....mine is about 165/175lbs All these numbers work for me....today with todays 87 fuel on the right day....sometimes I spent a ton of time with several on-line calculators before I chose a cam for my already established CR. I chose a Dynamic CR I could live with on the street. Performance requires homework....or a ton of guess and try |
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| Author: | slantzilla [ Tue Jan 27, 2009 2:22 pm ] |
| Post subject: | |
My junk is at just about 11-1 static. It ran well on regular 87 back when I drove it on the street. It would pick up about a tenth on 93. It would slow down 2 tenths on 100. |
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| Author: | wvenable [ Tue Jan 27, 2009 5:31 pm ] |
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Sandy and Zilla thank you! If I was building a a Chevy ( been there -couple of smblks) or a 318 ( major sleeper) or a 440 (my personal fav) I think I would have fewer questions. Sure I had help. But........ I have learned more by screwing around with this six cylinder then all of the above. I enjoy the challenge. I am a teacher and I want to thank ALL of you for taking the time to teach me! |
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| Author: | runvs_826 [ Tue Jan 27, 2009 6:46 pm ] |
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+1 I'm planning on helping a friend with his 70 Firebird and building the engine over getting a Pep Boys rebuild. I've learned a ton from this site and continue to read and expirement hoping to try and give back too. |
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| Author: | slantzilla [ Tue Jan 27, 2009 6:46 pm ] |
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Your in deep poo if Sandy and I are teaching. At least my shop is closer to you than his is. |
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