milling heads for comp ratio increase

[j par]

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).

Yes I understand liking a nicely tuned economical daily driver. Again like my wife 66 Barracuda. the previous owner had put dual exhaust on it and I put the four barrel and a LB4D. It wasn't economical by today's standards and it was a fun little Cruiser I guess. Here's my full $0.02 on these motors. They all take up the same amount of space under the hood from 273 to 360. They are all basically the same motor and take the same basic parts. I put absolutely no value into a forged crank as opposed to a cast as I've never seen either one of them broken. Unless someone has done something extremely stupid or in a few cases some of those Eagle 4-inch cranks. They probably stopped making them not only because of expense that because they weren't necessary. Especially anything near a stock application. I'm not trying to suggest that you build a drag motor by the way I'm just trying to get the best bang for the bucks. Sometimes people will say even a big block in a truck gets better gas mileage because it doesn't have to work as hard for the same amount of gas?

 

[70Hardtop]

Yes I understand liking a nicely tuned ...

Yes That is true, I agree with all of it, except the forged vs cast - just me though...however without knowing very much at all I could say pretty certainly that a cast Mopar crank is going to be a better crank than an equivalent Chev one. And I have seen a broken cast crank - it was in a 318-3, which is the truck motor, cracked right in half but not fully in two pieces, but enough so that it had twisted slightly) and looked a bit strange when you looked at it in the engine. I know that the truck engines were supposed to all have forged cranks but this was a cast crank, so may have been swapped at some time through its life. Have no idea of the history of that engine or what vehicle it was in, may have been a truck or passenger car.

But back to the main idea... If I was in your area or similar place Stateside, no doubt I would change my options in line with what was readily available.

Still on cranks, I love this forum because in another thread it described the differences between a 273-318 forged crank and a 340 one. I had always wondered about that and even though I had noticed the drilled areas, neither me nor my Mopar mechanic at the time associated that with the heavier 340 rods.

 

[B3422w5]

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.

Headers are just 1 5/8 Dougs D453 units. Small tube. Original cam was Comp Magnum unit( a dog)
Gears havent changed, they are 4.10 with a 28 inch tire. Heads were checked and corrected stock units originally. Local friend( who is mighty handy) lightly ported the heads one evening after supper while he was on vacation, spent about 4 hours on them total. Then took them to local machine shop for new valve job and reassembly.
Yes, convertor is 4500 flash. It needs to be about 5200 and looser for the way the combo is currently. Wasnt right for how it was either.
I am swapping to a 904, and new convertor which i had setup to where i think it should be. Hoping it picks up significantly.
So from 12.17 to 11.26 so far, hoping for 10’s

 

[70Hardtop]

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.

Yes that is certainly the best idea. And just yesterday I found that the milling costs would be prohibitive. So that plan has been buried unfortunately. If I could get it done for under $300 I would do it but when taking the milling of the intake side into consideration it really doubles the cost. In my small city, it is all rather limited what we have available and here, it is almost unheard of to mill the intake side of the head (which to me is just common sense). The standard practice is to plane down the intake to fit. Easier for them they say, as it is easier to set up on their jigs and most jobs would be aluminium too. Other options to increase CR are a 0.020 copper head gasket in addition with new flat head valves (stainless). Compared to the OEM tulip shaped vale head. Over $700. Or use the money for a port job. Which I will start making enquiries about this week. I have a die grinder and some experience with port matching but that's all, not sure if I would be confident in tackling the runners and comb chambers and needing to get all even CC volumes. I have done reading about the methods and where to use the die grinder, but in practice, it's a different story. Even if I put on Edelbrock RPM heads, those CC are 63, which would reduce the CR even more.

 

[nm9stheham]

I'll apologize if I have missed this, but I don't have a clear picture of what heads you actually have. Where are you getting the info that the heads are/were 60 cc's? If you are reading that off of a lot of sites, they spec out the NHRA minimums, not actual factory cc's.

The only stock 273 heads with nearly that small a chamber are those with closed chambers. But what I see here are the milling numbers you need for removing so many cc's from OPEN chamber heads.

And what pistons? Are they flat or do they have a mild dome on them? If we don't look into all of this, I fear you are waay off in your assessment of CR.

I see that you are going away from the milling idea. So much of this may be not useful to you anymore. But know that the 3% HP change versus 1 point in CR is quite misleading:
- That 3% number comes from a Wallace online calculator that makes oversimplying assumptions and looks at only one aspect of HP changes from CR, and so is not accurate to start with
- The number is ONLY for peak HP. It says nothing about HP and torque at lower RPM's. If you are road racing, rallying, or street cruising, then those lower RPM numbers are what are important, not the peak. BigBlock Mopar referred to this in post #38.

BTW, how are you using this vehicle?

 

[RustyRatRod]

Look dude, it;s not about us being happy with YOUR percentage approximations. I don't give a rat's butt. I'm just trying to tell you the truth. You know, keep you from being disappointed? You believe what you want, but milling half a pound off for 1 compression point is senseless, when some simple bowl blending can probably give you more power in comparison.

Sometimes I wish hot rod magazines never existed.

 

[B3422w5]

Like i said earlier, there is more to raising compression than raising compression.
With no other changes raising compression a full point and changing nothing else will net a modest gain both in horsepower and torque. This is fact. The amount of gain is debatable and influenced by several factors.
Where the bump in compression can really help is allowing other parts in the combination to be more effective, or allowing a bigger cam, as an example,to be used that could make more power because it might “like” the new compression ratio, and not like the old ratio.
Many things at work here, but bumping compression up in a lower compression motor is always going to be a positive step towards making more power. And milling heads is typically cheap. Cheaper than new pistons, etc. Just be aware after cutting the heads, you are kinda “ married” to them.
My own personal car benefited greatly from a bump in compression, just the throttle response and overally snappyness were notably different than they would have been had i just merely thrown the dual plane and mildly ported heads on it and otherwise left it alone. The extra compression allowed me to get away with a much more agressive camshaft it wouldnt otherwise have liked. Those modest changes resulted in a 10 mph difference at the track in the 1/4. And i say that as a veteran racer, who has raced forever.I made passes before and after. The compression bump was definately at the heart of those gains. Zero doubt about it.

 

[70Hardtop]

Look dude, it;s not about us being happy with YOUR percentage approximations. I don't give a rat's butt. I'm just trying to tell you the truth. You know, keep you from being disappointed? You believe what you want, but milling half a pound off for 1 compression point is senseless, when some simple bowl blending can probably give you more power in comparison.

Sometimes I wish hot rod magazines never existed.

You got yourself well named "just another dumbass" How true! - Long ago I made the decision to not read any of your posts due to the smart-arse (that's how WE spell it) and derisive nature of your comments (look up derisive if you don't know what that means), but I decided to read the last couple and if you had been paying any attention you would have seen that the post you wrote about "using milling money for head porting...", I gave a "like" to and said that was a good idea and was now considering it etc. But no, you have ignored the positive aspect and decided to go back and flog that dead horse again in a vitriolic way just for your own gratification or to make yourself look cool. I don't care if I get banned, you need to be told to shut your cake hole and grow some manners. And BTW, what sort of person would put a picture of a big busted female as their permanent icon on an automotive forum - what exactly is that supposed to mean?

 

[70Hardtop]

I'll apologize if I have missed this, but I don't have a clear picture of what heads you actually have. Where are you getting the info that the heads are/were 60 cc's? If you are reading that off of a lot of sites, they spec out the NHRA minimums, not actual factory cc's.

The only stock 273 heads with nearly that small a chamber are those with closed chambers. But what I see here are the milling numbers you need for removing so many cc's from OPEN chamber heads.

And what pistons? Are they flat or do they have a mild dome on them? If we don't look into all of this, I fear you are waay off in your assessment of CR.

I see that you are going away from the milling idea. So much of this may be not useful to you anymore. But know that the 3% HP change versus 1 point in CR is quite misleading:
- That 3% number comes from a Wallace online calculator that makes oversimplying assumptions and looks at only one aspect of HP changes from CR, and so is not accurate to start with
- The number is ONLY for peak HP. It says nothing about HP and torque at lower RPM's. If you are road racing, rallying, or street cruising, then those lower RPM numbers are what are important, not the peak. BigBlock Mopar referred to this in post #38. BTW, how are you using this vehicle?

Thanks for your post - Answer to the last question first - I might have already explained that previously - it is going into a 1970 ute (what you call a pickup) which is a daily driver and is also on the light side, 2750 pounds. And I don't race or overly heavy on the throttle constantly like some people. But I do have a bit of fun every so often.

CR, yes I do have the open chamber heads, as I will explain now. Well I got this info from several mopar sites that list the different casting numbers of the heads. I have seen a lot of differing information. Eg that Allpar site is very sloppy with info, I have seen around 4 errors or differing numbers in just the engine area.

Quote from Paul Pitcher Porting LA Cylinder Heads. "Production heads used on 64-65 LA engines have closed chambers 57-65cc in volume... with average closer to 64cc"

Table 1. Chrysler Small Block Cylinder Head Volumes (cc)

Casting Number Year Chamber Intake Port Exhaust Port
2465315/2658920 65-66 64.5 60 127
2843675 67-70 68 65 138

3418915 71-72 71 69 149
4027596 80-84 71 65 149
4323345 85-91 74 62 150
4323302 85-91 62 54 118


The table above has different numbers to the info I saw, which was that the early 64-65 273 had closed chamber heads and they are saying they had 57cc Comb chambers for a 9.2:1 CR. 1966 and 67 each had different casting numbers - not sure what type of head (maybe something to do with intake bolt hole angles), 1968-69 they went to the hydraulic cam and open chamber, also used on the 318, casting 2843675. Which is what I have and were 60cc (? That's what it said - must be wrong) and 8.8:1 . Because I was originally going to use a Felpro 318 head gasket I took off a couple of tenths of CR for that. My engine is just the standard 180hp 2BBL. So the pistons are the flat top (with valve reliefs). Yes I should work out the CR accurately for my engine and cc every Comb chamber. What is actual and what is written on sites can vary. I have to work out how to do that with what I have here at home, as I don't want to buy the kit. It shouldn't be too hard to do with some thought.

 

[nm9stheham]

If you have 675 heads, then count on around 68 cc's. Not 60 cc's; the NHRA minimum might be that, but the general factory chamber will be around 68 cc's.

Just know that the Mopar 'factroy' CR's are general optimistic by about 3/4 of a point over standard production. Your true stock CR is really around 8:1.

With your open chambers, the numbers given earlier about losing 1 cc for every .005 or .006 " shaved off is correct.

For street use, having better low end torque will be very much worth having; that is the point made by BigBlockMopar. Better torquer just driving around and better fuel economy. Getting the higher CR will be worth it. But, if the costs are too high for your budget, then going with the thin head gasket is most all you can do. The common thin gasket over here is the Mr Gasket 1121G. BTW, if you put in flat valves, you are going to lose about 2 cc's per chamber so that is not a big change in chamber size.

Does shaving the heads and intake to match cost a lot less? If it did, I would go that way. IMHO there is nothing 100% sacred about doing it one way or another. The shaving of the head on the intake side by 95% of what is taken off the bottom is just a way to not have to mill the intakes. If you don't mill the intake side of the head and then changed intakes later, then the new intake would have to be milled also. So that is why guys mill the intake side of the heads: to maintain easy future intake interchanging. But if you are going to keep the intake, then do it the easy, cheap way and move forward.

You mentioned Edelbrock heads. It would be an imporvement in CR over 675 heads, but the issue will be the valve size requiring the block to be notched. I tink you'll have the same problem with the Indy heads an their 62 cc chambers.

Have you looked into cams yet? There are some low duration high lift cams that would be worth your while in your use.

There is probably a combination of Silvolite Holden 253 pistons and long Eagle rods that can work with some machining, but I bet that would cost much more $$ so is probably not a good idea at all for your budget.

I wish we still had "ute's" over here; we had Ford Rancheors and Cheny El Camino's but they are gone from the market.

 

[66fs]

For a nice 273, you have all you need. The 273’s with the open chambered heads usually had pistons that were .020 higher in the bore. That pretty much puts them at 0 deck height. It typically takes a .040 cut to get to the NHRA minimum chamber cc’s. Usually machine shops charge the same for milling up to .020 of an inch. Then I’d cut the intake side of the head .019. If your shop can’t figure how to cut the intake side of the head, find another shop. If your valves and pistons seal, That is good enough. Use Felpro head gaskets and be done. You have the carb, intake, and cam. Just use good valvesprings, 340, and Viton valve seals while your in there. Add a windage tray and a double roller timing chain. Tune it, tune, tune it.

 

[RustyRatRod]

You got yourself well named "just another dumbass" How true! - Long ago I made the decision to not read any of your posts due to the smart-arse (that's how WE spell it) and derisive nature of your comments (look up derisive if you don't know what that means), but I decided to read the last couple and if you had been paying any attention you would have seen that the post you wrote about "using milling money for head porting...", I gave a "like" to and said that was a good idea and was now considering it etc. But no, you have ignored the positive aspect and decided to go back and flog that dead horse again in a vitriolic way just for your own gratification or to make yourself look cool. I don't care if I get banned, you need to be told to shut your cake hole and grow some manners. And BTW, what sort of person would put a picture of a big busted female as their permanent icon on an automotive forum - what exactly is that supposed to mean?

Well then dont read my posts. I never insulted you, just told you that I really didnt care which way you go. So how bout this? Cram it up your butt.

 

[70Hardtop]

If you have 675 heads, then count on around 68 cc's. Not 60 cc's; the NHRA minimum might be that, but the general factory chamber will be around 68 cc's.

Just know that the Mopar 'factory' CR's are general optimistic... and Chevvy El Camino's but they are gone from the market.

Thanks for post, I read it twice. I didn't like hearing about the 'optimistic CR numbers' Oh dear, more woe. Some of the things you talked about I have already mentioned previously but to save you trawling through the whole thread again I will briefly mention again: The bottom end is all done so I won't be doing anything more on that. I did briefly look at the Holden pistons but they wouldn't fit with these light, full floating rods I had lying around (resized, stress relieved, weight matched and fitted with ARP bolts). I checked the piston height in the bore as 66fs mentioned and they are level with the deck. It is essentially a "re-ringer" with a few extras. The condition when pulled apart was so amazingly clean and obviously low miles, that's why I chose this path of rehone and reusing the pistons (new 273 pistons are hard to get and Egge ones were too expensive for this exercise). Yes I knew that the 2.02 valves in the Edelbrocks were too large for this capacity engine. As for cam, I already had a small solid grind on the shelf not doing anything, around 0.47 lift, and since I wanted this 273 to be a mech cam engine (which a 67 engine should have been), it was perfect. Mopar M1 dual plane with a 1" spacer, small ports on the heads will be port matched to that (not much to remove really).

Yes I looked at getting intake surfaces milled and it is cheaper, $550 compared to about $950, but after reading people's posts here about that I thought it would be a good idea to not touch a brand new intake but rather get all the milling done on the heads. Then I can swap intakes and not worry about altering it and then having an intake that will only fit that engine. I didn't want to be spending $1000 or more on these very average 318 heads, when I can see that Edelbrock complete bolt on ones are only a bit more than that! I suppose in this instance the old 273 with its small capacity is a little limited in what can be done these days (esp down under where old chrysler stuff is often very hard to source - eg closed chamber heads!). Anyway, I have just bought some stainless exhaust valves (single groove) super cheap, they were on special A$60 delivered, set of 8. They are 1.6", so maybe I could decide to put them in , and no great loss if I decide not to. I read that the larger exhaust valve can improve low down torque (from a Mopar head porter) but will have to research that a little more

As 66fs said, I have everything I need for a nice street 273. I could always get the heads milled to the maximum of 10thou, then wouldn't need to worry about the intake, and if I used a 0.021 copper gasket, should bring the comp up a bit more.

66fs - as for using a windage tray, I did think about it but more cost and I already have new ARP main bolts to use. It is not necessary for how I will be driving it, as a normal car mostly - as nm9stheham mentions, it is 90% about the torque and drive-ability factor. However it has a nice DRTC fitted now.

 

[famous bob]

Thanks for post, I read it twice. I didn't like hearing about the 'optimistic CR numbers' Oh dear, more woe. Some of the things you talked about I have already mentioned previously but to save you trawling through the whole thread again I will briefly mention again: The bottom end is all done so I won't be doing anything more on that. I did briefly look at the Holden pistons but they wouldn't fit with these light, full floating rods I had lying around (resized, stress relieved, weight matched and fitted with ARP bolts). I checked the piston height in the bore as 66fs mentioned and they are level with the deck. It is essentially a "re-ringer" with a few extras. The condition when pulled apart was so amazingly clean and obviously low miles, that's why I chose this path of rehone and reusing the pistons (new 273 pistons are hard to get and Egge ones were too expensive for this exercise). Yes I knew that the 2.02 valves in the Edelbrocks were too large for this capacity engine. As for cam, I already had a small solid grind on the shelf not doing anything, around 0.47 lift, and since I wanted this 273 to be a mech cam engine (which a 67 engine should have been), it was perfect. Mopar M1 dual plane with a 1" spacer, small ports on the heads will be port matched to that (not much to remove really).

Yes I looked at getting intake surfaces milled and it is cheaper, $550 compared to about $950, but after reading people's posts here about that I thought it would be a good idea to not touch a brand new intake but rather get all the milling done on the heads. Then I can swap intakes and not worry about altering it and then having an intake that will only fit that engine. I didn't want to be spending $1000 or more on these very average 318 heads, when I can see that Edelbrock complete bolt on ones are only a bit more than that! I suppose in this instance the old 273 with its small capacity is a little limited in what can be done these days (esp down under where old chrysler stuff is often very hard to source - eg closed chamber heads!). Anyway, I have just bought some stainless exhaust valves (single groove) super cheap, they were on special A$60 delivered, set of 8. They are 1.6", so maybe I could decide to put them in , and no great loss if I decide not to. I read that the larger exhaust valve can improve low down torque (from a Mopar head porter) but will have to research that a little more

As 66fs said, I have everything I need for a nice street 273. I could always get the heads milled to the maximum of 10thou, then wouldn't need to worry about the intake, and if I used a 0.021 copper gasket, should bring the comp up a bit more.

66fs - as for using a windage tray, I did think about it but more cost and I already have new ARP main bolts to use. It is not necessary for how I will be driving it, as a normal car mostly - as nm9stheham mentions, it is 90% about the torque and drive-ability factor. However it has a nice DRTC fitted now.

Well then dont read my posts. I never insulted you, just told you that I really didnt care which way you go. So how bout this? Cram it up your butt.

Dang I love this place !!

 

[nm9stheham]

OK, OP, very good summary. Looks like you did some homework on this before. Glad to hear the piston height are indeed level with the deck; that is a lot better than a stock 318! The small displacement of the 273 makes small changes in chambers, etc. a lot more critical to static CR.

I ran your number through with 68 cc chambers, .028" head gasket, and about 4 cc's volume in the piston eyebrows and down to the top ring, and come up with 8.17 static CR.

As for the milling, several folks here have reported that they can mill up to around .030" off the bottom of the heads and not have to mill the intakes and things still line up. So assuming you did that, that would would cut around 5 cc's from the chambers. I'll guess that the flat-faced exhaust valves will save around 1 cc, and if you did that, shaved the heads .030", and found/used a .021" head gasket, then your Static CR would be up a bit over 8.9. That is a pretty good increase for those small changes, and that will definitely show up positively in street performance.

I am now curious about your cam duration specs. Being solid with .470 lift, it might be of pretty long duration and that can become a low rpm torque killer.

 

[Wyrmrider]

I sorta skimmed through these threads so...
Are these the oem heads and has this motor been built B 4?
in any case B 4 you mill
cc both heads at both ends
your head miller can then set up to even up the cc's for all 4 end chambers
so you do have open chambers? too bad no quench
you already have adj rockers and solid cam is ok with you?
you can blend your bowls yourself
B sure your guides are in good shape- I use K line inserts with the inside knurl to hold some oil and use Viton seals
If you are going to higher than stock lift B sure to check retainer (keeper) to seal clearance B 4you take your heads apart
I'll try and read this thread later
AFB or AVS good choice for your motor
of course all the 318/ 360 comments apply
you can get HP based on heads and rpm
but you get it at a lower rpm with a bigger motor

 

[70Hardtop]

OK, OP, very good summary. Looks like you did some homework on this before. Glad to hear the piston height are indeed level with the deck; that is a lot better than a stock 318! The small displacement of the 273 makes small changes in chambers, etc. a lot more critical to static CR.

I ran your number through with 68 cc chambers, .028" head gasket, and about 4 cc's volume in the piston eyebrows and down to the top ring, and come up with 8.17 static CR.

As for the milling, several folks here have reported that they can mill up to around .030" off the bottom of the heads and not have to mill the intakes and things still line up. So assuming you did that, that would would cut around 5 cc's from the chambers. I'll guess that the flat-faced exhaust valves will save around 1 cc, and if you did that, shaved the heads .030", and found/used a .021" head gasket, then your Static CR would be up a bit over 8.9. That is a pretty good increase for those small changes, and that will definitely show up positively in street performance.

I am now curious about your cam duration specs. Being solid with .470 lift, it might be of pretty long duration and that can become a low rpm torque killer.

Thank you heaps for working out the static CR. I was actually going to get an accurate CC on each one first before I put the numbers in myself. But that has given me a good idea - but pretty low isn't it! . I have looked at youtube and there are plenty of videos showing how to do the measurements for cc.

But that is good news about the 30thou milling amount - it seems a lot compared to what is recommended! I can easily do a dummy assemble of heads and intake and check how much room I have to play with and how the bolt holes line up. Maybe first with a 40thou Felpro and then with no gasket and look at how it changes etc. If I can take 30 thou off, that is a very good start. If it is tight and almost there, I don't see why I can't run a rat-tail file through the intake holes to facilitate lining up.

You may be right about the cam - here attached are the specs. It is an 'Ol Skool Schneider cam, valve lift 0.48, 290 duration and look at the lobe separation - only 107. So this cam may be a little rough idle and perhaps more suited to a hotter 340, but it's the only one I have and I don't see why it couldn't be made to work pretty well. Schneider didn't give me the RPM range but at a guess I would say 1800-6200, Does that sound close? (just a guess) I am running a 2500 stall so that will help -final drive is 3.23 and as I mentioned, it is a light-ish vehicle around 2750pounds

 

[70Hardtop]

I sorta skimmed through these threads so...

Thanks for your contribution... To suit your post I have answered each line:

Are these the oem heads and has this motor been built B 4? Engine had never been rebuilt as far as I could see, however it had an old DRTC fitted and a hyd cam which didn't arrive until 68 according to what I read, and mine is a 1967 engine, so perhaps the cam had been swapped at some point. Yes they are just the average 318 heads xxx675 casting
in any case B 4 you mill, cc both heads at both ends, your head miller can then set up to even up the cc's for all 4 end chambers. I don't know much about that, I still need to check all the cc's yet.
So you do have open chambers? too bad no quench Yes open chamber, closed chamber ones from an earlier 273 would be very nice!
You already have adj rockers and solid cam is ok with you? Not sure what you mean. Yes OEM 273 adj rockers. Cam specs given in previous post, and my thoughts also
you can blend your bowls yourself I was thinking of doing some very light work on them but doing too much will eat into the already low CR. I am port matching the intake -heads
B sure your guides are in good shape- I use K line inserts with the inside knurl to hold some oil and use Viton seals Guides have all been checked and done where required (K-liners). But exhaust guides will have to be redone when I install the bigger 1.6 stainless valves.
If you are going to higher than stock lift B sure to check retainer (keeper) to seal clearance B 4you take your heads apart Yes good idea!
I'll try and read this thread later
AFB or AVS good choice for your motor I hope so too
of course all the 318/ 360 comments apply
you can get HP based on heads and rpm
but you get it at a lower rpm with a bigger motor True... NCS4CI (no cheap substitute for cubic inches).

 

[Abodybomber]

Thank you heaps for working out the static CR. I was actually going to get an accurate CC on each one first before I put the numbers in myself. But that has given me a good idea - but pretty low isn't it! . I have looked at youtube and there are plenty of videos showing how to do the measurements for cc.

But that is good news about the 30thou milling amount - it seems a lot compared to what is recommended! I can easily do a dummy assemble of heads and intake and check how much room I have to play with and how the bolt holes line up. Maybe first with a 40thou Felpro and then with no gasket and look at how it changes etc. If I can take 30 thou off, that is a very good start. If it is tight and almost there, I don't see why I can't run a rat-tail file through the intake holes to facilitate lining up.

You may be right about the cam - here attached are the specs. It is an 'Ol Skool Schneider cam, valve lift 0.48, 290 duration and look at the lobe separation - only 107. So this cam may be a little rough idle and perhaps more suited to a hotter 340, but it's the only one I have and I don't see why it couldn't be made to work pretty well. Schneider didn't give me the RPM range but at a guess I would say 1800-6200, Does that sound close? (just a guess) I am running a 2500 stall so that will help -final drive is 3.23 and as I mentioned, it is a light-ish vehicle around 2750poundsView attachment 1715169770

It's not a bad cam choice, tuning it in ,will be an effort. Solids do have higher vacuum, and more torque than similar hydraulic cam grinds.
Initial and total timing at 3000 crankshaft rpm , pay attention the the idle speed ,and the transfer slots , ARE THE KEYS ,HERE. ...

 

[70Hardtop]

It's not a bad cam choice, tuning it in ,will be an effort. Solids do have higher vacuum, and more torque than similar hydraulic cam grinds....

That's good to know! Hope it's true with this one, the 275hp factory offering had a 0.50 lift and was a mechanical setup. So I don't think this Schneider is too far removed, maybe in duration and lobe separation it would be a little more radical. I'm thinking the factory one would be in the vicinity of 262 duration and 110 deg sep.

 

[Abodybomber]

That's good to know! Hope it's true with this one, the 275hp factory offering had a 0.50 lift and was a mechanical setup. So I don't think this Schneider is too far removed, maybe in duration and lobe separation it would be a little more radical. I'm thinking the factory one would be in the vicinity of 262 duration and 110 deg sep.

You have to be PATIENT AND PERFECT, to make it work....

 

[70Hardtop]

You have to be PATIENT AND PERFECT, to make it work....

mmm, well I am the first one...

 

[nm9stheham]

I put you cam specs in a calculator and worked out what is called DCR.. dynamic compression ratio. It is an indicator of low end torque. The DCR works out to the range of 7.1 or 7.2 depending on exactly what advertised duration one assumes based on the slow ramps on this cam. That is not much different than a stock 318.

No, I don't think this will be a good cam down to 1800 RPM. More likely 2800-3000 RPM. So for me, this would be too big on duration for a good street cam; I think it will be a little bit doggie when you first move out, regardless of how well it is tuned. Not awful with your lightweight ute, but it won't light up the tires when you first push on the throttle. And fuel mileage will be poor with the small LSA.

 

[70Hardtop]

I put you cam specs in a calculator and worked out what is called DCR.. dynamic compression ratio. It is an indicator of low end torque. The DCR works out to the range of 7.1 or 7.2 depending on exactly what advertised duration one assumes based on the slow ramps on this cam. That is not much different than a stock 318.

No, I don't think this will be a good cam down to 1800 RPM. More likely 2800-3000 RPM. So for me, this would be too big on duration for a good street cam; I think it will be a little bit doggie when you first move out, regardless of how well it is tuned. Not awful with your lightweight ute, but it won't light up the tires when you first push on the throttle. And fuel mileage will be poor with the small LSA.

hell, the prognosis is not looking good. Thanks for doing that calculation. I did think the specs looked a bit radical, more suited to a torquey 360 I would assume. I have a set of Rhoads lifters, the latest type, V-Pro, I wonder how they would improve things...I have done a lot of reading and seen reviews from many users and they are supposed to work well in cases like this, improving low down torque on engines with bigger cams by reducing the lift at low rpms, but bringing it all back at around 3000-3500rpm. A primitive form of variable timing. Duration is the length of time in degrees the valves stay open, and these lifters won't change the duration but they will reduce the amount that the valves will open in the critical lower ranges. They might be worth a try and these ones need to be used with adjustable rocker gear as well.

 

[nm9stheham]

Yes that is the idead behind them and they have been out since the late 60's or early 70's and do what you say. I would surely put those in for this cam in that small engine.

BTW, when I ran the DCR numbers, I dropped the duration from 290 to 280 degrees to try to somewhat compensate for the slow ramps and get to an 'effective' DCR. So I already tried to compensate things.

But if it were me, I'd go for a different cam. My racing discipline is rally, and a real, wide torque band is critical for that, not peak HP. (That, or a 6 speed transmission!) That same approach works on for a perky street engine.