5-8% is totally off the map. Ain't happenin. Do what you want. It's your money. But I am shootin you straight. You "heard" wrong.
milling heads for comp ratio increase
- Thread starter 70Hardtop
- Start date
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5-8% is totally off the map. Ain't happenin. Do what you want. It's your money. But I am shootin you straight. You "heard" wrong.
j par
Well-hung Member
Through a dingle ball hone in one of those three forties and a cheap rebuild kit and be light years ahead?
That's fine J Par, I know where you are thinking... in our game there is no substitute for cubic inches. Aussies think exactly the same way and the 360 engines are very sought after. You are right, a 318 or 360 will fit into the same place and make more power for less hassle - that is, IF I had those choices available. My 318 is now sitting in my blue 1970 Hardtop (aka 69 Dart body). Personally, I like the idea of a solid cam 273 and it is going into a daily driver. So fuel consumption is also a consideration. This car is very light, a 1970 Valiant ute, as we say, (short for utility) or in your terminology - pickup. See photos. The B3 Blue one is closer to how mine will be after a paint job. I actually bought this car with a 360 in it. But sold just the engine for exactly the same price as I bought the whole car for! Also these model Valiants never got the 360 and the trans tunnel is too small for the TF727, without mods. Mine had a 904 and it was burnt out from the 360. The rear axle is also only a Borg Warner 6 cylinder unit, so that's another thing to consider for using a small V8.
BTW, Fifty bucks for a good running 318 must have been the bargain of the year!
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j par
Well-hung Member
I understand about making do with what you have completely. I can assure you that 904 didn't burn out just because it was behind a 360. Too many people on here with good drag racing results with the minimal of modifications. That 904 burn out because it was time for it. The only time I've ever wanted a 727 is in my truck consequently that's the only one I have right now. I built a nice 904 Last Summer that I drag race behind that 318 with the 360 heads I was talking about. Keep making do with what you have for sure but if you ever want to see any real power or anything that will light your world on fire it ain't going to be in that 273 unless you put a power Adder on it. And again by that time the money spent elsewhere will get you bigger smiles. Oh yeah I should probably shoot you a picture of that 318 with the 360 heads? The $50 318 motor with the 360 junkyard heads that I lapped the valves Myself by hand and had milled?
For my wife...
Yep, you sure wouldn't miss that motor in the dark! Good idea keeping the water pump natural colour, I also like to do that, and I also keep the timing cover natural, in some cases I have even polished that. Well the 904 was trashed whoever had the car before me, probably misuse or running with not enough oil, or overheated by towing, something like that, not sure what was done while driving, but it did damage to it. I wouldn't fully agree with you on the 273 not lighting up my world - true if we are taking cost into consideration I suppose, that's true with most small capacity engines, but if someone with knowledge and money (and plenty of equipment) put their mind to it, I'm sure that a 273 could be made to crank out some big numbers which would put a smile on the driver's face. To prove that point, there was a group of keen guys here in Oz about 10 years ago who wanted to prove how strong a Holden 308 engine (Aust division of GM ) could actually be. With extensive work they managed to extract a record 2000 HP out of a 308 block. Sure, they would have done everything humanly possible to it, and probably cracked a few in the process, but just goes to show what could be done. I'm sure a similar result could be had with an LA block also. If a 273 was resin filled, critically machined and every aspect of the engine scrutinised and blue printed, big dollar ignition etc, with a huge solid roller cam and fully worked heads, I'm sure that mid 400s HP would be possible without stroking or aluminium heads.
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Marcohotrod
Well-Known Member
cutting about .050" will increase compression ratio about 1 as has been said. good for about 3-4% more power and torque. refaced lifters sounds very old school and questionable. refaced flat or convex? refaced a little or beyond the hardened surface? will your copper gaskets be in the correct hardness range ?
BigBlockMopar
BigBlockMember
70Hardtop,
are use going to use 'normal' FelPro headgaskets (.039/.041"), or the thinner (.028") MrGasket ones?
are use going to use 'normal' FelPro headgaskets (.039/.041"), or the thinner (.028") MrGasket ones?
Marcohotrod
Well-Known Member
some shops charge more to cut more. research head gaskets-go thin and different brands have different bore sizes. like some felpro are 4.180", and some like McCord or Victor are 4.060"
MHR, Good point about the lifters, I may just buy new ones (solids), they range in price from A$140 (Mexican made Elgin 'dumbbell' OEM style) to $345 for Crower.
I watched he guy do the lifters, he knew what he was doing, he hardly took any off, just the absolute minimum to get the curve and of course done with a slight convex shape. The reason I was considering using them (they are the dumbbell type) was only because the cam is not new either.
I don't know about the copper hardness, I know that when copper is worked, it changes hardness and should be annealed. I will have to do more research on that. The metal supplier says he has supplied lots of these sheets to vintage car guys. There is also a place in the States that makes them for you (out of copper if you want, or steel) but nearly $200 last time I checked.
Hi BBM, I would probably use the thinner ones, but I would like to know how much effect the larger bore would have on CR and also if any effect as a carbon pit that would stay red hot during operation. I have read a few people's experiences about this and some say it has no effect, others can notice something.
I would use all of the milling for compression money to put towards a good head port job. You will come out way ahead of the added compression, IMO.
famous bob
mopar misfit
^^^^^^^^
I agree ----------
BigBlockMopar
BigBlockMember
The KB silvolite site has a CR calculator online, as well as other sites where you enter all the specs to find out a gasket bore’s influence on CR.
Compression builds torque which means low rpm power.
The fact it hardly shows up at dynographs is because dyno’s start measuring at 2-3000 rpm, while rpm range of most regular part-throttle driving is in the 600 to 2500 rpm range.
When you start out with a low ‘smogger’ cr ratio, I would say try to get the cr up to ‘modern’ levels.
Especially if the local fuel type allows it.
Compression builds torque which means low rpm power.
The fact it hardly shows up at dynographs is because dyno’s start measuring at 2-3000 rpm, while rpm range of most regular part-throttle driving is in the 600 to 2500 rpm range.
When you start out with a low ‘smogger’ cr ratio, I would say try to get the cr up to ‘modern’ levels.
Especially if the local fuel type allows it.
B3422w5
Well-Known Member
You will take some heat for the 5-8% comment regards power, but sometimes the overall flavor of the combination changes by having more compression, and that allowing things to work better and make more power.
My current car/ combination is a perfect example. Stock 360, pistons 028 in the hole, 50 thou head gasket, comp 292 cam, stock eddie heads..... single plane Mopar intake..... car ran 12.17 best with 4.10 gear and 8 inch 4500 flash convertor.
Replaced cam to 260/264 Howards cam( similar lift), dual plane intake, took heads off, had them mildly ported, setup up with new springs, etc, for new cam, milled them to 57cc( about 45 thou) and reinstalled with 28 thou head gasket. No other changes.... cam, intake, mildly port heads, mill for compression, thinner head gasket...... car ran 11.26
This in spite of the fact the cam i installed i am aware is probably one step too big for what i have( i was in a hurry and it was on the shelf when i made these changes)....... a bandaid would be more convertor and maybe gear, convertor change is in the works as we speak
So here we have a decent bump in compression allowing a motor to be able to make more power( lots more) with just a couple easy changes. I suspect this thing will get in the 10’s yet, its gonna love the convertor swap with that big cam
You really need to find Jim Laroy's thread about the 440 he did dyno pulls on that was under 8:1. I think it was like 7.4 and then he put closed chamber heads on and made it like 7.7. It made ridiculous power for such a low compression engine. It's all in the heads, man, but go the direction you want.
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j par
Well-hung Member
Yes I understand that in this day and age with money almost anything can be done what I was trying to say is with the same amount of money that you're putting into this 273 you would be the Power ahead doing something bigger. For instance...
Dodge / Mopar 360 long block
j par
Well-hung Member
Now if I was to go buy that for $100 and run a dingle ball hone through it and slap it all together with a $100 Summit and lifter/cam and $100 rebuild kit it would probably have way more torque and horsepower then almost anything you can do with that 273 on three times the budget.
j par
Well-hung Member
What you mean more horsepower for Less?But what fun would that be?
Yep. It isn't about cheap horsepower. It's all about the underdog. I get waxed regularly by late model pick up trucks but boy do I have fun.
j par
Well-hung Member
It's not all about the horsepower and winning every race for me either but I'm always running a tight budget and looking for the best bang for my buck.
I follow you. I could have put something bigger in my 66 for half the price or less. But like I said, what fun would that be. I could'a/ should'a pulled the original 273 out and sat it in the corner and put a 340/360 in. I wanted to build the original engine. That was fun for me even though it wasn't the cheapest option.
thanks for well written post, I love reading about these real life experiences! Obviously people here are not happy with those numbers I gave - I'm not defending myself, just recounting what I read; it's not from my experience, nor am I laying that down as law, and possibly taken alone, they are out of context. Yes, even with my limited experience I can see that over 5% power increase would be hard to get from just a one point CR increase alone. But lets look at the big picture, these are percentages, not HP numbers. So in a low horsepower stock engine (whatever that is, not necessarily Mopar or even a V8, or maybe not even a car engine), perhaps it IS possible to get 5 or more PERCENT increase in power/torque from that CR increase. But talking Mopar A engines, it probably does apply.
B3422w5 It's a well written post because you have put in writing from a more balanced perspective; CR increase as part of a combination of changes that work better together. That's probably what I also should have said (well I think I did mention it somewhere) that with my 273 engine, obviously I am doing more than just that one thing of increasing comp.! I am using a bigger than stock solid cam (approx 0.47), heavier springs /w dampers, M1 high rise dual plane (port matched to heads), small 4 BBL carb, headers with twin exhaust, and also a 2600 stall in a shift kitted 904. Plus upgraded ignition. So all considered, it's important that I get the CR up from approx 8.5:1. Even 9.7 or 9.8:1 maybe. We have 98 octane fuel here and as I mentioned will be running a fuel additive as the valves seats are not induction hardened.
B3422w5, that performance from that 360 is incredible, almost a flat 12 from just those few changes. The gearing and heads would be the biggest factor (and I assume big port headers and 2.5" system?) but did you bolt them straight on from the box, or check all the valves and seats for sealing etc? Also the 292 cam, was that a Comp Magnum or Purple shaft? They recommend 3000-3600 stall for those cams. So when you say "more converter" do you mean less stall? As 4500 is pretty dam high. And incredible to see almost a whole second faster with the extra work done.
Yes I know exactly what you are saying and it all makes great sense. However not only do most of us here not have those great opportunities (as I said, 360s are very sought after here, and getting very rare too, we only got that engine for a few years in a few models. We just don't have the numbers that you do) but especially in my city, which is very limited compared to Sydney Melbourne Brisbane (all East coast). Also, I don't WANT a 360 or 318. I had both of those, as I said, I sold the 360 because it was too big for what I wanted and I got all my money back so basically got the car for free minus the engine. The 318 I had went into another vehicle. The 340s are both earmarked for my E bodies. I had the 273 lying around and want to use THAT one as an economical daily driver. And in any case, it hasn't cost me a heap, and i had some parts lying around that suited that engine well. Also I have never had a 273 and now I will have one. It's not the ultimate power I want or need (have more Mopars for that). I just want a nicely improved economical 273 for my ute. Hope you understand.
As an example of the differences in prices, about 11 years ago I bought a complete and running (but unknown condition) 360. Came out of some imported US car. Had all the fruit: ignition, alternator and Holley carb. I paid $2000 which was a very good price at the time! And this was 11 years ago. I was lucky, all except one bore had very good compression, that turned out to be a burnt valve which I replaced. New head gasket, Sig Erson 290 Cam and better springs, new DRTC, single plane Weiand and a TQ plus headers and twin system and that engine in my Challenger was a great engine - I took it up to 130mph and it was still accelerating (the 2.6 diff helped there).
That's my thinking too TMM. I have other Mopars for the tyre (Aust spelling!) shredding if I want. See my last post...it's all about doing up a nice little underdog. In my biased opinion, the 273 in 4bbl 275hp form is the second best small block in the world. And we all know what the best one is. The factory got over 1hp per Cu In with a few simple changes and the 273 is inherently such a revvy engine, and espec in the 1967 and lower, mech cam form which is what I will have with forged crank, light full floating rods, for me it is a bit more special and as they are very rare now down here, another reason.
BTW, to J Par - even those cheap parts from Summit that you mentioned, still equates to around or over A$500 by the time I get them with exchange rates and shipping and fees. PLUS, I just couldn't do a slap together job like that - I just couldn't do it, if it was all apart, even if I reused the pistons with new rings, I would have to put in new bearings and new DRTC as a minimum, really would also need better springs with any reasonable cam. New oil pump, cheap insurance but still adds to the cost, So all up, and with buying the hone (as I don't have one), I would still be looking at well over grand. (all this is assumed if I could get a complete 360 for $100)
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