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| xafalcon |
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If your local state law requires active EGR then go for heads that can support that, otherwise don't bother. Your cats should clean up your tailpipe emissions for any smog test you need to pass. I have no idea on what is required in Aussie. Over the ditch we have absolutely no emissions laws beside an excessive smoke law.
Maximum (static) compression depends on many things. The camshaft profile has the biggest single influence on what you can get away with. The longer the duration @ 050, the greater the static compression ratio can be before detonation becomes a problem. Next is that aluminium heads are generally good for 1 extra point over iron. Then comes the spark advance curve. Further down the list is intake efficiency (ram effect) and exhaust flow. If it was me I'd go for around 10.5:1 and run it on the lowest octane fuel that it can comfortably take without detonation while still running an optimal spark advance curve. Using a fuel with a higher octane rating than an engine needs only reduces power output. Fuel octane rating is roughly describing it's burn rate - high octane = slow burning, low octane = fast burning.
_________________ XA Faimont 351C, AU2 XR8 Manual 5.0, DA LTD 5.0, Mk1 Capri 5.0, 1995 Mustang 5.0, EF2 XR8 Manual, EF2 Fairmont Ghia 5.0, AU3 XR8 Auto, AU2 XR8 Auto, AU2 XR8 Manual Ute, TE Cortina 5.0 Manual, DU LTD 5.0 soon to be manual |
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| EBI347 |
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millard455 wrote: thanks to everyone for the replies, very much appreciated  well it looks like im going to use the 185cc competition heads. from what i have read the extra porting is of very good quality and the exhaust ports are raised slightly giving an average increase of about 10cfm across .200 - .600 valve lift range which is the area im aiming for and without loosing bottom end performance. i still have a few more questions if anyone can help out 1, should i be using the non emissions legal heads (no EGR) or the street ones? 2, what sort of compression ratio can i get away with on 98ron fuel? thanks heaps guys. dude honestly dont need egr support and dont get the heads with them as they mess with exhuast back pressure just run non egr heads but dummy up egr plate to a enginer or blue slip instector the egr just has to be in place and look like it works and as for your comp ratio you need to add up a few things like cam duration and so on but 98 ron is not real reliable at the pump so go a little conservative and stay under 11.1 to save your motor just incase u cant get pulp or have a bad batch of fuel 
_________________ MY CAR PLZ TAKE A LOOK forums/xtt909-update-t66227.html |
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| millard455 |
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combustion chamber volume?
hi all, what else apart from determining compression ratio should be factored in when choosing combustion chamber size? the heads im looking at (AFR185cc comp series) come with 58cc or 72cc chambers. thanks guys.
_________________ EL XR8 SERIES 2, 5SPD, HOT CHILLI RED, 200 ODD RWKW OF V8 FUN AND GAMES |
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| EBI347 |
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dude
58 cc if you are going n/a on a up to 347 with flat tops forgy's will net you around 11.1 if you are going boosted the 78cc will help bring down comp or if you are putting them on a 351 to 408 stroker.. which is what u want them for 363 but if you can give me your spec's can calculate comp for you i need 1 flycut in piston cc's.... should be available from piston manufacturer 2 thickness of head gasket or part number 3 58cc chambers in heads 4 piston deck height if you can... if not still can give u estimate 5 type of spark plug and part number these will give u only static compression you dynamic compression is the most important and will need \ 1 cam specs and partnumber 2 manaifold type and partnumber 3 size of valves and head port size
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| millard455 |
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thanks XTT909, ill try my best to get all the info.
1, http://www.jepistons.com/Catalogs/Autom ... _bore.aspx part no- 232475 6.5cc dome 2, AFR recomend fel-pro 1011-1 3, AFR heads come with 58cc or 72cc, im looking at AFR1383 4, is that what JE call comp ht? 1.100? 5, AFR recomend autolite 3924 cam, http://www.compcams.com/Cam_Specs/CamDe ... =1068&sb=2 manifold, unsure on this but was looking at TRICK FLOW track heat TFS-51511002 or R series TFS-51511003 with 75mm upper heads, AFR1383 2.020 intake 1.600 exhaust 70cc exhaust ports i hope thats everything. thanks very much for this XTT909
_________________ EL XR8 SERIES 2, 5SPD, HOT CHILLI RED, 200 ODD RWKW OF V8 FUN AND GAMES |
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| EBI347 |
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DUDE U WANT TRICKFLW BOX R TO SUIT 351 WINDSOR
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| TerroristGHIA |
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I DO
Brett
_________________ The Terrorist ED Retired due to RUST. |
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| Steady ED |
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millard455 wrote: thanks XTT909, ill try my best to get all the info. 1, http://www.jepistons.com/Catalogs/Autom ... _bore.aspx part no- 232475 6.5cc dome 2, AFR recomend fel-pro 1011-1 3, AFR heads come with 58cc or 72cc, im looking at AFR1383 4, is that what JE call comp ht? 1.100? 5, AFR recomend autolite 3924 deck height is where the piston sits in relation to the deck. eg. .010" down the bore is pretty common... or you have the block decked to bring it to zero... going roughly off what you've got there, using the 58cc chambers will get you 12.9:1, 72cc 10.7:1... thats using .040" for compressed gasket thickness, and piston to deck at .010" down.
_________________ ED XR8 Sprint - S-Trim, V500, 249rwkw |
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| xcabbi |
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That's a massive change in compression
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| MICKYYYY |
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Hey bud the 363ci dyno graph i tried to get my hands has now changed to solid roller and dosent have old dyno sheet. I do know these guys have built 363ci with AFR 205cc heads and hyrolic roller cam engine that made the same hp so give them a call and see if u can get it from them.
http://www.highperformanceworld.com.au/
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| Steady ED |
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heres the comp calc i was using if anyones interested/wondering how i came up with that...
http://www.csgnetwork.com/compcalc.html
_________________ ED XR8 Sprint - S-Trim, V500, 249rwkw |
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| millard455 |
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Steady ED wrote: heres the comp calc i was using if anyones interested/wondering how i came up with that... http://www.csgnetwork.com/compcalc.html thats the same one i had a play with and funny enough even though i wasnt sure on the last question i got prety much the same result  would i be better of looking for another piston with more dish and use the 58cc chambers or stick with what im already looking at- 6.5cc piston 72cc chambers and cop ratio roughly 10.7:1? i ask this because most of the combos ive found to compare seem to stay with the 58cc chambers thanks guys.
_________________ EL XR8 SERIES 2, 5SPD, HOT CHILLI RED, 200 ODD RWKW OF V8 FUN AND GAMES |
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| xafalcon |
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I'd go with a bigger chamber. Gives you room to machine in the future if you want/need to. Easier to make a large chamber smaller, than a small chamber larger. Others may have a completely different opinion though....
_________________ XA Faimont 351C, AU2 XR8 Manual 5.0, DA LTD 5.0, Mk1 Capri 5.0, 1995 Mustang 5.0, EF2 XR8 Manual, EF2 Fairmont Ghia 5.0, AU3 XR8 Auto, AU2 XR8 Auto, AU2 XR8 Manual Ute, TE Cortina 5.0 Manual, DU LTD 5.0 soon to be manual |
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| MICKYYYY |
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people usually go smaller chamber so if they want to go boosted later they can just change the heads and away they go again and also sealing is apparently better with smaller chamber.
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| xcabbi |
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xafalcon wrote: I'd go with a bigger chamber. Gives you room to machine in the future if you want/need to. Easier to make a large chamber smaller, than a small chamber larger. Others may have a completely different opinion though.... Im guessing your method of decreasing combustion chamber volume involes shaving the head and/or decking the block. All fine and dandy if you have suitable piston to valve clearances. If not then its better to get the small chamber heads and open them up. |
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