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Joined
Feb 2, 2016
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Location
Alberta
My Car
71 Mustang 351C C6
Greatings, I was wondering who all has managed to run the Aussie heads on a 351c with flat top pistons and no detonation? It has a 270hr cam (willing to go to 284hr if the duration will help), EFI, performer intake, long tube headers, and am willing to run 94 octane with some booster. When I try and put in the specs I get anywhere between 8.4 an for 8.8 DCR depending on the head Cc, deck clearance, etc. This is just a weekend cruiser. 

Thank you

 
I've been known to build the odd one or two Cleveland with 302 Cleveland closed chamber heads. Actually I've built that combination many times in all forms from tow vehicles to street, street/strip to all out race engines from drags to circuit and even burnout engines. Flat tops, dish tops and even domes, stock stroke, increased stroke, decreased stroke, wet sump, dry sump and running on pump, avgas, LPG or even methanol, with all sorts of carb/s and intake set ups. In fact years ago the main staple of high performance Clevelands here in Australia were 2V cc headed engines as 4V heads were hard to get hold of and expensive, plus all the magazines back then were telling everybody that the 2V heads were heaps better, unless being an all out drag engine, lol. In fact I remember a magazine article over 25 years ago (would have it hidden in my junk somewhere) where they asked some of the best engine builders in the country about Cleveland builds. All but one said the 2V heads were the only way to go, the one that said 4V's is a very renowned Sprintcar and circuit engine builder and one I trusted his word back then, plus my old boss knew him as he use to build Sprintcar engines as well, back in NZ. We had a good formula for street, street/strip Cleveland builds from when I started as an apprentice in the late 80's and kept developing more power as time went on. There's still quite a few decent HP factory cast iron 2V headed engines running around over here in the high 600 to mid 700 HP naturally aspirated, but as aluminium heads become more affordable people are moving away from factory cast iron heads to the better flowing aluminium heads of CHI, AFD and Scott Cook (3V/ 4V style only on the SC) but there's those that still love seeing how far they can get with them.

As for detonation, well fuel plays only one part in the overall scheme of things. Tuning and things like spark plug heat ranges and ignition curves as well as getting you carb right is what helps with detonation. We have 98 Ron octane rated fuel over here which is roughly your 94 and there's plenty of 11:1 and even higher compression cast iron engines 2V engines running on it without detonation issues. There's a lot more 2V headed street engines over here than all the other heads combined. One of the main reasons are price, personally I've never paid more than $50 for a virgin pair of 302 2V heads, in fact I'll hunt down a complete virgin 302 Cleveland for $150-$200 as stock bore Cleveland blocks are getting harder to find. Another old trick was using 302C rods and Pistons to suit. I've personally never had a detonation issue with any Cleveland engine be it 2V or 4V open or closed chamber, get the tuning right and you should not have any problems. 

As for dynamic compression ratio, that's an interesting subject that seems to be getting more confusing than answers. I belong to another (small) forum which contains a lot of different engine people from a wide variety of back grounds (not just racing) which was formed as they wanted somewhere to discuss and share ideas without the "know alls" getting involved and having nothing constructive to say (no arguments which I love) In fact that site and this one are the only ones I really post up on as the other ones I look at are full of know alls, know F alls. I have actually had been thinking of DCR lately and a discussion had already started on that site when I went on for a look one night. Unfortunately I can not say too much about any of the discussions on that site (one of their stipulations) but one thing that did come from it that I can't see a problem with mentioning was, if DCR is the be all and end all on engines performing, than how did the muscle car engines back then manage to run without dramas. These were fairly high comp engines with smallish (by today's standards) camshafts and also where's the factory data on DCR's. There is none only static compression ratios. To be honest I'm still on the fence with it, but some of the discussion on it is very enlightening to say the least and has really got me thinking. One thing though was years ago building engines we never thought of DCR and knew what static comp you could get away with Super lead fuels (as we had it here until the end of 95) and what sort of cam it took to be suitable for the build. Look at cam catalogues and their cam recommendations state what static compression ratio is needed, not what DCR it's going to give you. Even when I fully understood what DCR is, I still bring it up on the high side or even over where it's not supposed to be suitable and have managed to have the engines run great without detonation issues. I'd really love to be able to post up what's been discussed on there, but I like being on there too much to loose it, plus the bloke that nominated me to be on there would really be pissed at me.     

So yeah, I've built hundreds of flat top piston with single valve relief, 2V cc headed Cleveland engines over the last near 30 years, of all types and detonation has never been a problem when everything is sorted. In saying that too, my 2V cc engines have never had an unmodified combustion chamber either, as they need some reworking to get the most out of them, but compression has still been at 10.5:1 minimum. Also they've all had some reworking in the intake throats as a minimum and on the bigger HP stuff the ports are also done, but don't increase the port size.  Intake vales are no bigger than a 2.070 and exhaust valves are standard 2V 1.65 with only the short side radius needing any work on the exhaust ports. Anything else I can help with, just ask or PM me.

 
Wow, thank you for the info! That's what I wanted to hear. I found a pair of heads here in Canada for a very reasonable price (considering North American prices) and I found a minor crack in one of my heads by a valve guide. I could just get it repaired but I hate the thought of repairing things, so I always make sure to improve while replacing. A 15-30hp bump in power would be perfect for the car. Aluminum heads up here are very pricey with the exchange rates currently. The problem is everywhere you hear both sides saying yes you can run it and no you cannot, I've been searching till my eyes hurt on finding an answer like you gave me. haha. I am planning on unshrouding the valves a little bit, and was hoping that would be enough to open up the CC a bit. I am not looking at making a ton of power as I limited myself with purchasing the 400hp fuel injection kit (which can seem to handle about 450hp). If need be I could richen up the AFR to help out also, but I'm not sure how much the EFI will affect

For newbies like me who haven't done much engine building it is nice to see a number range that can help decide what components to go with when considering DCR. Actually seeing a number at how the cam can help bleed off pressure. That being said, it looks like I could be anywhere between 10.5 and 11.2 CR depending on deck clearance and the actual CC of the heads.

I would appreciate any info you can give me on how much to unshroud the valves would be awesome.

Thank you.

 
Back when we had high compression factory hot rods we also had 100+ octane fuel available at most any service station. That all ended in the '70s, made life difficult for anyone who wanted to keep them running. Buying aviation fuel became popular, I knew guys that would go out to the airport with a few 55 gallon barrels in their pickups so they keep their cars running. Even low compression engines that were built for the new panther snot fuel had a lot of issues with pinging, partly (maybe mostly) due to the EPA compliant cam timing.

 
Back when we had high compression factory hot rods we also had 100+ octane fuel available at most any service station. That all ended in the '70s, made life difficult for anyone who wanted to keep them running. Buying aviation fuel became popular, I knew guys that would go out to the airport with a few 55 gallon barrels in their pickups so they keep their cars running. Even low compression engines that were built for the new panther snot fuel had a lot of issues with pinging, partly (maybe mostly) due to the EPA compliant cam timing.
And that is my concern. I have access to AV gas but don't want to be running it on a car that just gets driven around town on a sunny day. Please the lead would affect the O2 sensor.

 
I had my heads opened up to 60cc. I think stock they are around 58cc. I agree on not wanting to run aviation fuel. Do you have access to "race gas" at any local stations? We have one station in town that has it. 98 octane. It is a wee bit pricey (currently a little over $3.75/gal US). The line on Saturday morning during the summer is crazy though, like a car show at the gas station every weekend.

 
I had my heads opened up to 60cc. I think stock they are around 58cc. I agree on not wanting to run aviation fuel. Do you have access to "race gas" at any local stations? We have one station in town that has it. 98 octane. It is a wee bit pricey (currently a little over $3.75/gal US). The line on Saturday morning during the summer is crazy though, like a car show at the gas station every weekend.
I don't believe I have access to race gas.  Just 94 with 10% ethanol, and Toluene.

 
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Something else I should mention, not sure if it helps or hurts. I do not have vacuum advance set up. The distributor was set up knowing that the vacuum advance didn't work on it.

 
As for detonation, well fuel plays only one part in the overall scheme of things. Tuning and things like spark plug heat ranges and ignition curves as well as getting you carb right is what helps with detonation. We have 98 Ron octane rated fuel over here which is roughly your 94 and there's plenty of 11:1 and even higher compression cast iron engines 2V engines running on it without detonation issues. There's a lot more 2V headed street engines over here than all the other heads combined. One of the main reasons are price, personally I've never paid more than $50 for a virgin pair of 302 2V heads, in fact I'll hunt down a complete virgin 302 Cleveland for $150-$200 as stock bore Cleveland blocks are getting harder to find. Another old trick was using 302C rods and Pistons to suit. I've personally never had a detonation issue with any Cleveland engine be it 2V or 4V open or closed chamber, get the tuning right and you should not have any problems. 
I'm currently putting together an Aussie headed motor and am kind of clueless what to do with the timing since so much is changing from my 2v open setup. Are there any good resources to learn about tuning ignition? It has always been kind of a gray area for me, I would pretty much pick a number and back off if it broke up. I'm under the impression that the larger the chamber volume the more advance an engine will need to achieve a complete burn so I will be backing off a good amount.. I just don't know how much.

 
For what its worth, I recently rebuilt my 2v (.030 over bore) and swapped the 2v open chamber heads with a set of Aussie closed chamber 2v heads unmodified (I have read the Aussie heads are typically between 56 and 59cc). I installed a set of 18cc dished pistons from DSS Racing to help with compression with a stock crank. A somewhat mild cam from Howards. Want a smooth idle and need good vacuum for the A/C, EGR, Auto Trans, etc. I used an Edelbrock performer 4v intake for a 351C 2v and a late model Ford 4300A square bore Carb. I had the carb and a EGR plate for years and wanted to keep as much of a stock look as possible.

The Howards CAM and Springs 231031-10 Hydraulic Flat Tappet 1600 to 5000 Camshaft and springs Lift: .496 / .496, Duration @ .050: 213 / 213, Centerline: 106, Fair idle, Good low to mid-range torque.

All that said, I am using on 91 Octane. I am still playing with the setup and have not had the car on the street much...yet. So far the timing seems best at 16 BTC and my CR and DCR are estimated at: 9.67 and 8.03 with no issues. I used 57cc for the Aussie head volume.

 
Unfortunately, like every other performance engine built, there is no set tune for a 2Vcc headed Cleveland engine either. It's all about finding that sweet spot that actually works for your engine. They still like plenty of initial timing I've found, around the 12-16* mark and while some engines may want 34-36* or even more total advance, others may want 28-32* total advance, usually all done by 2800-3200 RPM. Same with plugs some like the standard heat range plugs while other engines want them colder and with the ignition set up use a distributor and coil that throws out decent spark and use good quality leads with as little as possible resistance. Also a carb around the 750 CFM in whatever style you want, vac sec or DP works fine for any decent 2V engine, but have had some decent success years back with 700 DP Holley. Also stick with a dual plane like the performer or even the air gap unless you intend on really spinning the engine, but I get the feeling we're talking about street engines here and even if some strip work is intended, stick with the air gap.  

To answer the vacuum advance question, I don't find them necessary, but it depends on the owners driving requirements to whether I use one or not. For high performance engines I never use distributors with vacuum advance for obvious reasons like locking out the distributor and running  convertors with high stall  speeds. As for timing curves and tuning of the ignition set up, it's all trial and error doing it yourself, but I like to start with 12* initial and keep the standard extra 20* of mechanical advance for a total of 32*. If no pre ignition then simply step up the timing and if you do have some pinging then try a colder plug by one or even two heat ranges first, this is the reason I use cheap spark plugs for this process instead of forking out more than I have too, to find the heat range I'm after before buying the good spark plugs. With the carb stay with the factory settings or if you have a good running carb stick with it and change nothing as this gives you a base to work with, but work one thing at a time, either timing (firstly) then carb (unless it's extremely lean) to find that sweet spot as changing too many things at once will not show you what's working better to give you the best outcome. But make sure the distributor is in good working order first without any excessive play in the shaft and things like the rotor and cap are in good order and same with the coil, make sure it throws out a good strong purple/blue spark and not a weak yellow/orange spark as any tuning will be useless with problems here.  

As for chamber work it's not so much opening up the chambers, but blending and radiusing what's there that gives the best results, in fact one little mod was found to not pick up anything on a bench, but at the track it did. I'll need to dig out a 2Vcc head and show what needs to be done how and where as trying to describe it would cause confusion. Remember the 2Vcc head was never designed as a performance part, but rather just a bread and butter 302 2 barrel (4barrel from mid76) engine thats chambers was just designed for achieving 9:1 compression in them. The best thing to help with valve shrouding is to keep the valve at, or as close as possible to standard sizes, another thing we found over the years. We knew from the start a 4V intake was too big for a 2V (even 4V) head so cut them down to 2.12 then 2.1 for quite a while as it worked very well, but when we stepped down again to a 2.07 we found even better gains. We tried the standard 2.05 valve and worked quite well too, but the 2.07 intakes were more easily available back then. We also used a 4V exhaust valve as it was common knowledge that and short side radius work was all that was needed for the exhaust. It was the same time when 2.1 intakes and 4V exhuast valves had a shortage, so with the 2.07 intake valve we tried a 2V exhaust valve. That showed everything was fine with a better intake to exhaust bias, so we just kept using 2V sized exhaust valves after that.   

Anyway all, sorry but I'm absolutely buggered from the last two days of work and starting to doze off, so I'll get back to it tomorrow and hope whatever I've written this evening makes sense. If not let me know and I'll get back to it tomorrow.   

Thanks

 
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