When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Theoretical and Street RacingUse this board to ask questions about street racing, discuss your street races, and "who would win?" questions. Keep it safe.
Not yet. Have to sit down and figure out the math for the Intake Closing Event and plop it in Wallace Racing's Calculator. Hoping for no more than 8.5:1, but would like to have it around 8:1.
If you haven't already, check out this paper on dynamic compression. Then download THAT calculator. It makes easy math out of the cam and engine specs. http://cochise.uia.net/pkelley2/DynamicCR.html
If you haven't already, check out this paper on dynamic compression. Then download THAT calculator. It makes easy math out of the cam and engine specs. http://cochise.uia.net/pkelley2/DynamicCR.html
Thanks a bunch skinny. The Wallace Racing one was very similar. Maybe a touch less. Best numbers I feel I can come up with is a 10.4:1 Static Compression, 8.5:1 Dynamic with .043 quench. If you think I need to sacrifice my DC more I can always use a thicker gasket. The one I used in the calculator is a 4.060 bore with a .021 squish. Thats using the Intake Closing Event (67* ABDC)with the XR270HR Cam.
Last edited by usmechanix; 02-03-2016 at 01:44 PM.
Reason: forgot to include the angle
What I like about the Kelly calculator is that you can use advertised cam specs and it will calculate the IC event (which should be verified) as well as head gasket dimensions, valve relief, etc. It leaves little to chance or guessing.
What did you use for your piston below deck value? Valve relief volume?
used a below deck height value of .022 since the block hasn't been decked, and a compression height of 1.678 on the pistons, the valve relief volume is listed as either .100 inches or -.5cc.
It would be wise to actually measure the piston to deck clearance. .022" is optimistic for an unmachined block. Don't be surprised at numbers in the .026-.036" range in the same engine. That'll make a noticeable difference in your SCR/DCR.
It would be wise to actually measure the piston to deck clearance. .022" is optimistic for an unmachined block. Don't be surprised at numbers in the .026-.036" range in the same engine. That'll make a noticeable difference in your SCR/DCR.
Okay cool. when I put the Rotating Assembly in. Where do I measure to from the deck? Any flat part of the piston to the deck height?
I'm just messing with the numbers in the Calculator. Even If I open up the deck clearance to .035 my SC/DC still sits around 10:1 and 8.2:1 with the same squish of .021(I haven't bought my Head Gaskets yet just using this as a number). The quench however opens up to .056... How much of a downer is that going to be? I've been told that SBC like around .040?
So of course Herbert gets back to me on Facebook no less. Thinking I'm going to end up with their CH4 grind. 220/225 dur at .50 .510/.510 lift. is the 112 LSA going to Screw me over if they won't make one in a 110? or do I need to pick one with a different Intake Centerline.
The advertised duration is 275/280 from their website.
The LSA is 112.
All we lack is the Intake Centre Line (ICL). That is something that is ground into the camshaft along with the LSA.
I'll work with this and try a few iterations so you can see where this might be going. The missing flow data on the heads is a drag too.
I've been told I can return the cam I have for whatever Herbert Hydraulic Offering that they have. I think that the CH4 is the way to go as long as I use 1.6 ratio rocker arms. They also said that I may choose whatever LSA and Centerline I like. I was thinking about a 108 LSA with a 106 Centerline.
The following is misleading in that the head flow data isn't truthful. With no value below .400", the cfm for a ported Vortec head are substituted. That your heads flow that well down low is very unlikely. Anyway...
Herbert cam installed in a 331 SBC. Herbert heads (see above), small tube headers with mufflers. 9.9:1 SCR. 7.5:1 DCR. Description is Herbert.
I've put that up against my 355 with 180cc heads and a more or less XR276HR. Description 9.9 2nd revision.
See your peak hp is 6000-6500. Whether that happens with that cam is debatable. The heads would support it though.
Also attached is a Herbert headed and cammed 331 with 10.39:1 SCR and 8:1 DCR. Description Herbert 10.39. It's against the lower compression version. More compression equals more torque everywhere. A shorter cam will get you more torque down low but the upper end tends to suffer as you run out of lungs (cam duration).
SCR and DCR charts are included with some values I guessed at and some based on what you've got.
Remember this is for comparisons sake and not necessarily the number you will get. Personally I can't see the Herbert cam peaking at 6000 rpm ( 220 @ .050" ) and making 430 hp. But the heads help up top compared to my 180cc. The Herbert cam and my 274 are similar. As is the 276. It looks to me that if you could support turning 7500 rpm, then put as much air through your heads as they can deliver and make your power that. Lots of air. Lots of engine speed.
So my general assessment for a good street engine is to build torque. It's a little tougher with smaller cubes. Tougher still because I'm thinking your heads don't do well at low lift and will hurt efficient cylinder filling. Keep the compression up, the duration shorter and work towards building low speed torque that way. Hopefully the Herbert heads aren't terrible below .300". That part is throwing darts.
So the short answer is that the Herbert Cam would work and dare I say work well given the other parameters of my engine. The only question is how well given that the flow data below .400 is missing. Would you mind plugging in my data with the Herbert Cam? If I have Herbert do a 108 LSA 106 Intake Centerline .275/280 Duration 220/225 at .50. The Intake Closing event I came up with is 63.5. how do you screenshot windows? I'm using .030 Deck Clearance to air on the side of caution that it is in fact taller. I was just planning on adjusting the gasket thickness accordingly to reach as close to possible the 8.2:1 desired DR. The only problem at that point is figuring out the quench issue.
4.04 Bore.................................4.040 Bore
3.25 Stroke..............................2.538 Dynamic Stroke
64cc Combustion Chamber...........64cc Combustion Chamber
.021 Head Gasket Thickness....... .021 Head Gasket Thickness
4.06 Gasket Diameter.................4.06 Gasket Diameter
.030 Deck Clearance................. .030 Deck Clearance
.5cc Dome Piston..................... .5cc Dome Piston
I actually ran that test earlier. And surprisingly (or maybe not) the tighter LSA didn't impact the curves much at all. Maybe past 7000 rpm.
Which I won't be doing anyhow lol. But it's nice to see some theoretical power numbers. I gonna guess a bit lower with the unknown flow numbers but it still looks good to me
I think really what's happening here is that you're rpm limited in a mechanical sense before you might be if you took those heads to their limit. It's seems (and I've heard it said) that they extend the range of the cam because they flow well up top. That said, like I said earlier, if you could get to 7500 rpm...
So, since you can't, build accordingly. Short cam. Maximize compression pressure at low rpm. Hope the heads are good enough. Interestingly, that broader LSA (112) takes some of the overlap out of the equation. That'll have some benefit in the driveability part of things with your carb setup. Lots of idle vacuum I would think and a good strong carb signal.
Do not adjust head gaskets to fit a target DCR... Fix the quench height, and adjust the cam to hit the target DCR.
The .038" to .045" quench is key to detonation resistance, and higher VE%. It will ping more with a wide quench and lower DCR than you will with tight quench and higher DCR.
Adjust cam timing to hit a target DCR, you can advance/retard cam at the lower timing chain gear keyway or at the upper cam gear dowel pin (with offset bushings)
Do not adjust head gaskets to fit a target DCR... Fix the quench height, and adjust the cam to hit the target DCR.
The .038" to .045" quench is key to detonation resistance, and higher VE%. It will ping more with a wide quench and lower DCR than you will with tight quench and higher DCR.
Adjust cam timing to hit a target DCR, you can advance/retard cam at the lower timing chain gear keyway or at the upper cam gear dowel pin (with offset bushings)
I was adjusting gasket thickness to achieve the desired quench height and then adjusting the intake valve event to achieve the DCR I posted is that not okay? I believe I'm reading use the 112 LSA grind as is and find a way to degree the cam in a way that maximizes DCR and sticks quench squarely around .035-.040 right? Just use a regular gasket? As far as being mechanically limited in rpm I don't know if I am or not... retrofit hyd. roller lifters I've read tend to be heavy and don't survive long after 6000rpm, unless someone can convince me otherwise I wouldn't feel comfortable pushing them past 6500.
Last edited by usmechanix; 02-04-2016 at 06:07 AM.
At this point I would think that you're waiting on an assembled shortblock. From there you can measure the deck and select a head gasket that will get you to your target quench(.040" for example). See where your compression ratio ends up. Unless you want further machining that's about all the flexibility you get. Chances are the cam you have will fit well enough.
As for lifters, I chose to go with one of the short travel types. Only because I was having trouble with Comps standard lifter. Usable RPM for me was extended to 7000. Then again I've got very light valve springs (bee hive).
Don't forget to run a 1.6 rocker with that Herbert cam. Give those heads all the lift you can.
Sounds good Skinny I will update you when I get to that point. I got the Bare Block back along with the crank and pistons/con rods. Just waiting on Bearings. Have to file my ring end gaps too.
As other have said - cam and heads are too large for a 327.
As you already have limited low end in a motor this size - you want to maximize the low end power by using smaller cc heads (that still flow well), a smaller roller cam (has more lift at the same duration than a non-roller) and a dual plane intake (can be a high rise).
It isn't hard to build a 350 that makes 400hp and 425TQ, 327 being shorter stroke should still put out 350 to 375hp and have great low end and be very streetable with a street stall converter and lowish gears.
At this point I would think that you're waiting on an assembled shortblock. From there you can measure the deck and select a head gasket that will get you to your target quench(.040" for example). See where your compression ratio ends up. Unless you want further machining that's about all the flexibility you get. Chances are the cam you have will fit well enough.
As for lifters, I chose to go with one of the short travel types. Only because I was having trouble with Comps standard lifter. Usable RPM for me was extended to 7000. Then again I've got very light valve springs (bee hive).
Don't forget to run a 1.6 rocker with that Herbert cam. Give those heads all the lift you can.
Hey Skinny. I was finally able to put everything together. I was also able to dig through Stan Weiss's info and find Head Data that matches what Herbert had listed EXACTLY!!! so you can do with that what you will... Anyways.
The Data Herbert Lists as flow data for their head matches the Flow Data I found for a Pro Comp Head oddly enough.
Piston to Deck Clearance is as follows.
Bank 1 Min. .012 Max. .016
Bank 2 Min. .021 Max. .025
Now I no they're significantly different, but at least there is some consistency front to back though not necessarily in that order. I think as opposed to tear it all apart again I'm going to equalize it with the Head Gaskets which I can get both in a 4.1 inch bore with a .016 and .026 squish respectively. Bringing my quench .042 on Bank 1 and .041 on Bank 2. Using Kelleys Calculator I'm coming up with 8.5 and change on both Banks for DCR. That seems a bit high for Pump Gas, I will leave it up to y'all to see what the community consensus is.
Here's the rest of the Data again just to bring everyone up to speed without reading for Days.
Camshaft Information
Static CR Bank 1
Static CR Bank 2
Dynamic CR Bank 1
Dynamic CR Bank 2
Thanks again for putting up with all my nonsense. I just want to make sure I'm doing this right. Thanks for reading and all the help.
10 thousandths between left and right? Seems to me that the machine shop may have missed something. Or your measurements are off. Personally, I wouldn't go the different head gasket route to compensate. But that's just my take on it. Now for what it's worth, I've worked with blocks that were 10 thou out between cylinders. It makes getting to a precise value for something like quench very difficult. I went for the tightest cylinder regarding p/v clearance, compression ratio, quench, etc. Interestingly, it was those cylinders that experienced the most wear on the rod journal bearing.
10 thousandths between left and right? Seems to me that the machine shop may have missed something. Or your measurements are off. Personally, I wouldn't go the different head gasket route to compensate. But that's just my take on it. Now for what it's worth, I've worked with blocks that were 10 thou out between cylinders. It makes getting to a precise value for something like quench very difficult. I went for the tightest cylinder regarding p/v clearance, compression ratio, quench, etc. Interestingly, it was those cylinders that experienced the most wear on the rod journal bearing.
Well to be honest there really was no other block prep done besides a hone and replacing the cam bearings. My machinist is "old school" and "doesn't worry about that sort of thing". However I have seen him build some terrific running engines. I did take the painstaking effort however to use a dial gauge on top of each piston to make sure it was at TDC and then used a flat edge used to check deck straightness across each pistons center and feeler gauges to measure the piston/deck clearance. So I'm actually pretty proud of only having 4 thou front to back. I certainly understand your point of view. I do know that every little bit helps when it comes to this sort of thing. I guess my question is if the point is to make every cylinder as equal as possible, why can't I use head gaskets at this point? What's the harm? I'm not trying to argue here I'm honestly asking because I don't know. I know I can spend a crap ton of coin on this thing to make it straight as an arrow but is it really going to be worth it in the long haul? Are we talking 5-10 hp for another several hundred dollars? That seems silly. Also what do you think about those flow numbers for those Pro Comp heads and DCR figures? Do you think that the DCR is safe given the small dome with aluminum heads or will I need to retard the cam timing 4 degrees to drop that to say 8.2 ish? Would you mind tossing all that info in your Dyno Software again? I feel like I'm starting to seem needy so if I'm in any way starting to be frustrating for you please feel free to tell me. I sincerely appreciate all the help.
Last edited by usmechanix; 02-23-2016 at 10:15 AM.
I don't mind helping at all.
As for using two different head gaskets...I can't offer advice one way or the other. I will say that I understand that the shim gaskets (.015") are surface finish critical. If your block deck finish doesn't meet the requirements recommended by the manufacturer, gasket failure is possible. Others here have more experience with those gaskets than I do. (my personal preference is the Clevite/Victor Reinz 5746).
I'll crunch your numbers through my program and see how it shapes up. I will say that the difference in power output between 8 and 8.5 DCR wouldn't warrant going to extremes to achieve. The lower compression may well offer less tuning headaches.
Not yet. I'm still waiting for Herbert to get in touch with me about how much Im going to owe them after sending that massive cam and 1.5 rocker arms back. Exchanging the rockers for 1.6 comp roller rockers. Did you have something in mind? So you think that higher DCR is safe for pump gas?
I ran a couple of simulations and will try to post them tonight.
I will say the shorter stroke of the 327 pushes the rpm range of the 270 cam well past where I thought it would. It plateaus at 6000-6500 rpm. (keep in mind this is a computer simulation) but it's common knowledge that cubes and cam profiles are joined at the hip (so to speak).
As for an 8.5 DCR, I can't say how that would work with aluminum heads. I know it's not a good idea with iron heads. That said, I've learned to make my choice with less compression rather than more. Timing is far more important (especially with a real street car) and the small increases in compression in an attempt to maximize performance often don't pay off.
I don't believe for a second that your 331 will make that kind of power with a 270 cam. 440+ is a big number for a little engine. Still, it gives you an idea on how the power curve might look. It's interesting to see that the smaller cubes extend the rev range as the heads/cam have to feed that much less compared to a 350.
Anyway, there you go.
I don't believe for a second that your 331 will make that kind of power with a 270 cam. 440+ is a big number for a little engine. Still, it gives you an idea on how the power curve might look. It's interesting to see that the smaller cubes extend the rev range as the heads/cam have to feed that much less compared to a 350.
Anyway, there you go.
Wow! That does seem a little strange. Even if it's lower than that peak number it seems like the 400/400 watermark is entirely possible. I appreciate all the leg work on that
400 hp with enough rpm, yes. The torque you see is undoubtedly attributed to the higher compression. 8.5:1 running compression is pretty healthy for a street engine on pump gas.
Here's a look at your 331 with the 270 cam and Vortec heads. Those heads are a benchmark for me because I have a pretty good idea how much horsepower you can make with them and what to expect in the way of results from the drag strip and the highway.
400 hp with enough rpm, yes. The torque you see is undoubtedly attributed to the higher compression. 8.5:1 running compression is pretty healthy for a street engine on pump gas.
Here's a look at your 331 with the 270 cam and Vortec heads. Those heads are a benchmark for me because I have a pretty good idea how much horsepower you can make with them and what to expect in the way of results from the drag strip and the highway.
That's interesting. Even with the Vortec heads it's still a strong naturally aspirated small cube motor. I was really looking to pass the 375 mark of the old fueled motor. I pretty stoked with how much mmmf this thing will have. Gotta finish the Trans work and stuff a 3.42 behind and I think it will be a blast to drive
I would think that this engine would like all the gearing you can give it. It's going to need rpm to make power and you have to get to that rpm in a hurry. Not sure how your T5 is going to hold out but a T56 with the steep first gear would make your ride a lot of fun.
I would think that this engine would like all the gearing you can give it. It's going to need rpm to make power and you have to get to that rpm in a hurry. Not sure how your T5 is going to hold out but a T56 with the steep first gear would make your ride a blast.
It should take it. The gears I'm puttin in should be able to take up to 600 torque.
02-03-2016, 09:08 AM
