I have a 1969 327 block for rebuild. would it be more beneficial to put 350 heads, 76cc (1.94 intakes) vs 60cc heads with 1.74 intakes? if so, what can is the max I have the heads milled ?
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I have a 1969 327 block for rebuild. would it be more beneficial to put 350 heads, 76cc (1.94 intakes) vs 60cc heads with 1.74 intakes? if so, what can is the max I have the heads milled ?
Depends on what pistons you are running and how far below the deck surface they are.....
they're flattops with valve recesses flush with deck.
Not trying to be a smart ass, but with the information you provided at this point, the best answer anyone can give you is as Dave said...."depends". The small valve/small chamber heads will increase compression and the small valves will make better bottom end torque but run out of steam quickly above 3500-4000 RPM. The small chamber heads could potentially raise compression too high to run on pump gas. The bigger valve heads will breathe a lot better but the compression drop may make the engine a real pig.
I would start by figuring out what the compression ratio will actually be with various combinations. To do this properly you will need to know the actual volume of the combustion chambers. Do not go by what the factory advertises the chamber volume as these old heads they are usually anywhere from 2-6 CCs larger than claimed. It’s best to actually CC the chambers to find out…..and you will need to do each chamber, as they will vary within the same head. Although not as fancy as some, JEGS and Summit both sell economy CC kits that will suffice for doing this
http://www.summitracing.com/parts/po...1155/overview/
JEGS Economy Cylinder Head CC Kit - Free Shipping on All Orders @ JEGS
After that you will need to figure out the volume of the piston valve reliefs and if the edge of the piston is beveled what that volume is along with the volume based on how far down the piston is in the cylinder at TDC. Do not assume the pistons are flush with the deck. You will normally find they are a few thousands down in the bore. The way to find this is with a depth micrometer or in a pinch a straight edge and feeler guages.
Finally you will need to know the compressed thickness of the head gasket.
With those values in hand find a decent on line calculator and plug in the numbers to come up with the real static compression ratio. From that point you can play with different thickness head gaskets and milling (figure .007” per CC as a ball park figure for milling ) to fine tune the compression.
The final step would normally be taking the real static compression ratio and plug that along with proposed cam profile into an online calculator to determine dynamic compression.
Sometime in this process you will also need to determine what grade fuel you will want to feed this thing to determine what you target compression ratio should be based on how you want to use the engine.
The Second Option
Go eeny meeny miny mo, bolt a set of heads on and see what happens.
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By the time you prepare a set of used heads, you would be far ahead buying new. I used World Product S/R Torquer heads on a 327 some years ago, and they worked great.They a S/R (stock replacement) heads are made for 327's: 2.02 valves, 67cc chambers. Here is the link:
http://www.summitracing.com/parts/wr...60-1/overview/
Or you could go with a set of Chevy Vortec heads. They would also be a good choice, although you would need a Vortec intake manifold. You can't beat the price on these:
http://www.summitracing.com/parts/na...make/chevrolet
Lynn also has a good point, building a old set of heads properly is not a real cheap proposition.....although depending on what you have to pay for the old heads it might still be slightly cheaper to do old castings. That will depend on the labor rate of local machine shops and the quality of their work.
I did a pair of "60cc" Power Packs earlier this year. After cleaning, milling, hardened valve seats, new valves (I upgraded from 1.72 to 1.94s) deshrouding the intakes, milling, new springs, retainers and keepers the bill was around $700 not counting the cost of the heads to begin with.
The heads Lynn lists are probably still a bit better as they likely have bigger runners and the combustion may be a lot closer to the claimed volume than the heads I started with. (On the Power Packs I started with, after milling .015 off, the chambers still ran between 62-64 CCs).
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I measured 76cc on the heads +/- 2. I have an edelbrock manifold and carb that needs to get used so I'm kinda stuck with the 882's instead of buying a couple others that need a different intake. ile b using pump gas so maybe I should b building to the max compression that precludes pinging. ive heard 9/1 to over 10/1. is there a number I should target?
With flat top pistons and 76cc chambers, you are looking at around 8:1 compression which is okay for an average driver. With 67 or 68cc chambers you would have about 9.3:1 compression, which would be much better for a performance application. However, static compression is not as good of a guide as dynamic compression which takes in your cam specs, gasket thickness, etc.
if I build for 10:1 will the engine ping on unleaded gas? also, how much can I shave the heads b4 taking away too much head strength? btw, thank you all for the info. I really appreciate your time and expertise. Ron
I'm running 10.3 static and need 91/92 octane, preferably without ethanol because it will lose seven or eight octane points over a few weeks sitting idle. If I were building it today I'd be down in the 9 to one range shooting for 87 octane.Quote:
Originally Posted by ecreek
Please delete.
Looks to me like you just have an old 327 that you will freshen up a little bit and use for a daily driver. Nothing earth-shattering, just a motor.Quote:
Originally Posted by ecreek
None of the early iron heads will make any kind of power compared to the heads available to us today, so it really does not matter which heads you use, they're all junk. I might opt for the 882's simply because of the low static compression ratio they produce. As Lynn said, you'd be just over 8:1 static compression ratio. You never know what fuels will be available in the near future, so don't paint yourself into a corner with a high-compression ratio motor and then not be able to buy fuel for it tomorrow. There is nothing wrong with an 8:1 daily driver, but you will have to run a stock camshaft with it. Any hot-rod cam you bolt into the motor will want and need more than 8:1 static compression ratio.
Here's a tutorial I wrote for the wiki on another site. It explains the relationship between static compression ratio and the intake valve closing point @0.050" tappet lift. Cams must be matched to your combination. You cannot just reach out into thin air and grab any cam that you think looks good to you. You must build for it.
http://www.crankshaftcoalition.com/w..._compatibility
To answer your question about what static compression ratio to use with pump gas, generally use up to 9.5:1 with iron heads and up to 10.5:1 with aluminum heads. You can, however, use up to 15.0:1 static compression ratio with E85 fuel. Problem is that you have to use such a radical cam to support that SCR that usage on the street is very limited.
Use a cam something like this....
Crane Cams 114102 2010 Hydraulic Flat Tappet Camshaft and Lifter Kit Chevy 262-400 V8 57-87 RPM Range: 500-4000, Duration @.050": 184/194, Lift: 0.
I'm not saying you should use a Crane cam, I'm just showing you the cam timing you need to use with a low-compression motor. Use this cam timing to aid your search for the brand of cam you want. Be very careful about the quality of flat tappet lifters. There is some junk circulating out there, but if you buy a quality name brand like Crane or one of the other major cam makers like Iskenderian, Crower, CompCams, Lunati, etc., etc. and you buy their lifters with the cam, you should be OK. Alternately, toddle on down to your local Chevrolet dealer and belly up to the parts counter. Order a bone-stock cam and lifters for a 1980 Camaro 350 LM1/Z28. Those motors had an 8.2:1 static compression ratio and the cam designed for them will work well in your 8:1 motor. Again, buy cam and lifters together, from the same supplier.
Here's a tutorial that I wrote concerning using a flat tappet camshaft with the crankcase oils that are generally available off-the-shelf today. You must exercise extreme caution with them.
http://www.crankshaftcoalition.com/w...ips_and_tricks
Sidestep the nightmare of a flat tappet cam by moving up to a hydraulic roller cam or solid roller cam. You can get into a Howards cam and lifter retro-fit combo for about 600 bucks, that eliminates all the mumbo-jumbo in the tips and tricks article.
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again, thanks for the wealth of info. last question; How much can I mill the old heads b4 excessive iron taken off weakens them too much?
Most fellows will limit head surfacing to about 0.030" (thirty thousandths of an inch). On a small block Chevy head, each cut of about 0.006" (six thousandths of an inch) represents reducing the chamber volume by one cc.Quote:
Originally Posted by ecreek
If this were my build, I would limit cutting the heads to only the amount required to get a good, flat surface on the heads, like maybe 0.005" to 0.010". Do not cut the heads thinking that you will make a race motor. You won't.
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Ditto what Tech said - just get a nice square surface. Milling heads has introduced a lot more problems than it has solved. All things equal, you're better off going with a thinner head gasket.
btw, the head gasket I hav miked at .052. how far will it crush when the head is torqued down?
They're generally sold stating "compressed thickness" on the package. I would think that the amount of crush is going to vary based on composition, but don't go by my thoughts on this one....
As Roger stated - gaskets are typically sold with their compressed thickness listed on the packaging. .052 is a thick gasket - stock SBC is typically .041.
In my opinion, in a rebuild situation, the head gasket should be selected after the piston to deck clearance has been determined. Ideally the quench should be in the .039 to .045 range. For example, if you have your block decked and squared and the pistons measure .010 from the deck at top dead center and you used a .030 gasket you would be at .040" quench, which in my opinion is near perfect if you’ve built everything else correctly.
I just found some 14014416 heads off a 305. they're 58cc according to chevy casting #'s url. I calculate 10.86 compr ratio if I use a gasket that crushes to .043 and a .010"' deck clearance. the vales r 1.84 intake. am I headed for trouble with pump gas?
IMO yep. You might get away with 10.86 and premium ethanol blend with aluminum heads, but I'd say iron heads are going to be detonating if you push the timing.
is it possible to adjust the timing to prevent detonation. if so, how much do I "lose" by way of performance?
No, you cannot adjust yourself out of a bad choice. Forget those heads.
I don't understand why you're being so hard-headed about this static compression ratio thing. Max 9.5 for iron heads. Max 10.5 for aluminum heads. Each point only allows the motor to make 4% more power, so taking a 300 horsepower 9:1 motor to 10:1 will make an additional 12 horsepower. That's it. That's the awful truth. Keep your street motor at 9.5 or less for pump gas and iron heads.Quote:
Originally Posted by ecreek
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its what I have available. and I wanted valves larger than 1.72. ide reaaly like 68-70cc chambers with 1.84 intakes (to accommodate the edelbrock manifold and 4V carb). that gets me in the low to mid range 9's CR. ide setl for any % increase in HP if it doesn't lead to detonation. do u know of any cast irons that fit this bill?
Stop! Save your money. Then buy a set of new Vortec heads and intake. It's better to wait and do it right the first time. It costs a lot more to do it wrong and have to fix it again later.
You want budget friendly? Here: Chevy SBC 350 190cc 64cc Straight Complete Aluminum Cylinder Heads 600 Lift | eBay They are not AFR's but better than fooling with old iron heads and they will work with the intake you have,stick a duplicate of the L79 cam in it and claim 365 HP.
I can find an 4V intake easy enough but don't know which head casting #'s I should be looking at. n e thots on this?
The reason you're finding old, "high performance" iron heads so easy is that very few people want them any more unless they're building some period perfect, numbers matching car. Several guys have pointed out that you're going to spend as much or more buying a set of old iron heads and then having them done right than you'd spend on a new set - go back and read Mike's Post #6 again and think about what he's saying. Now the guys selling will be telling you just the opposite, how much better their old double hump heads are than the new stuff, but that's bogus. I wouldn't invest the money in an old, unknown set of iron heads but it's your money.
Ain't it the truth, Roger? Those old cast iron production heads are only good for ballast. The technology that was used to produce them is 40-50 years old.Quote:
Originally Posted by rspears
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no, I meant vortec head casting #'s are what I don't kno what to look for. I found the vortec intakes for carbueration easily enuf but don't kno which vortec heads to buy for my old 327. will they all fit? or should I b looking for a certain casting # (#'s) suitable for what I need (pump gas) without getting too much compression. a casting # or 3 would help me head in the right direction (no pun intended).
Lynn gave you a link for the Vortec heads from Summit back in post #5 and clarified that you'll need the Vortec intake for them to work. As for "...will they all fit?", I'll leave that to the Chevy guys that have kept up with all of the details through the years.Quote:
Originally Posted by ecreek
First off I’m not trying to get into a pi$$ing contest with this post, but I do have a couple of pointed questions.
First off have you really measured anything or are you going off information you got off various web sites to get your information from? The reason I’m asking is you reply to the question on the real chamber volume of the 76cc heads you were looking at….. “I measured 76cc on the heads +/- 2” . I’ll admit I haven’t seen everything but on all the unmilled OE Chevy heads I have CCed over the years have always been AT LEAST 2 to 6 CCs (or more) larger than the factory claimed.
Most flat top pistons also have valve reliefs cut into them and in some cases have a bevel around the outer edge…..have you measured or gotten that volume form the piston manufacture?
Have you measured how far down in the cylinder the piston actually is at TDC or are you just assuming it’s a 0 deck height? If the piston is down that volume also needs to be included in your calculations.
If you haven’t gone to the trouble of actually taking these measurements chances are your calculations for static compression you’ve figured is going to be on the high side……which is actually good news for you. Not taking the measurements reduces you to just taking a SWAG at where you will be.
Push come to shove you can get head gaskets in various thicknesses to drop the compression. We’re currently planning on .085 compressed thickness gaskets on a numbers matching DZ 302 to get compression down a streetable level.
The same would hold true for the 327 your building (assuming your real static compression ratio is what you claim). The thicker gaskets usually play hell with the quench and will drop potential power but at least the car will be drivable. Now of course you have to figure an additional $200 for the gaskets in addition to what you pay for the heads and having them rebuilt. So in the end what have you really saved by using OE heads?
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Maybe this will help:
The L31 Vortec comes in two different casting numbers, 10239906 (#906) or 12558062 (#062). Originally, the stock #906 casting head was available in two versions. One version had an Inconel exhaust seat with single angle valve grind and was available on 1 ton trucks. The other version was the traditional three angle valve grind. Other than that, the #906 is the same as the #062 head. GM Performance Parts Bowtie Vortecs are offered in “small port” (#25534351), which has 185cc intake ports/65cc exhaust ports, or the “large port” (#25534445), which features 225cc intake ports/77cc exhaust ports. (You don't want the large port heads for a 327.) Both GM factory and GM Performance Parts Vortecs come with 1.94 intake/1.50 exhaust valves. According to the engineers at GM, “Stepping them up to 2.02 valves doesn’t help them any, so it’s not recommended. The port was designed to match the 1.94 valves. With the Vortec flow velocity, you need less spark advance to make power which is a clear indication of a more efficient burn.” Maximum valve lift on Vortec cylinder heads is .460″ to .480″. This range is due to production line machining and casting variance. It is highly recommended to check for clearance on anything over .460″ lift. Vortec heads require a Vortec style 8 bolt intake.
as to Mike P's response I thot that my decision to go with vortecs rendered all ref to cast irons moot. given that, I appreciate rumrum's info on 906's n 062's. that's what I needed to start looking in the right direction. of course I am grateful for all the excellent info rendered by all rspondents. I mention again that ime not looking for a super hi perf engine, just a pump gas runner with compression that precludes detonation burning such.
“…..as to Mike P's response I thot that my decision to go with vortecs rendered all ref to cast irons moot……”
Again, I’m not trying to get into a wizzing contest about this. The main point I’m trying to make is that to really know what your static compression ratio is going to be will require that you actually measure things.
Advertised specifications for things like chamber volume, compression height etc are often on the optimistic side and this holds true on whether the parts are OE or aftermarket.
Here is a link to an article on Vortec heads that in general you might find interesting.
Vortec Cylinder Heads
One quote you might want to take away from it however is this one.
“……While they are 'advertised' with a 64 CC chamber they can vary from 64-68 CC's in production.......”
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Mike, this is erroneous information according to John Erb, chief engineer at Keith Black pistons. He says that a motor will detonate worse with a wider squish and lower static compression ratio than it will with a tighter squish and higher static compression ratio. Squish trumps SCR.Quote:
Originally Posted by Mike P
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how and where would I order a head gasket of a specific thickness, give or take?
Summit is one place - http://www.summitracing.com/search/p...e/head-gasketsQuote:
Originally Posted by ecreek
or JEGS is another. You can also go to your local NAPA store and get some selection, but perhaps not the more exotics.
wow I dint realize head gaskets could b so expensive. but thanks for the info. summit is well organized in presenting the variety of gaskets. Rock auto wasn't as definitive and cost me a lot of time searching. Jegs was ok but summit was way betr.
ON the heads ..the 906 heads hold up better if looking for a used vtec head the stock spring pad limits the springs to what can used i cut this to a smaller seal od and open up the spring cup no deeper or bigger on spring id i do cut back second inner step on head. it could cost $700 when all said in done for machine work to a old head casting or a newer 906 used , set of RHS are about $100 more loaded and gone this way on some and iron ealges as well as the older intake will seal up fine on port runner so any intake will fit . head s i listed are a copy of Gm vtec but a much thicker head and a intake head runner of 170 cc same as gm why wast good money on Gm casting ? seen more busted then good? so you have that in the back of your mind ? well i would long with the piss poor deck finish even if new better go to the machine shop and check deck finish o have many time cut a chevy head cast past .004 just to get to the bottom of the wave finish on the deck of the Gm head and seen were the are much like a saw tooth and work on the head gasket fire ring on cc heads never taken any had for granted . many years ago i never did this build the engine if you needed you used better gas but times have changed i CC every head on evey s engine. i build i CC them on the mill to find out were there are at many times there tell tail signs to tell if a casting been heavily milled . if the cc of the pistons is listed on a fully machine piston top i may check one piston. some custom made race stuff can be much harder to check . if i have or re working a piston i use volume sleeves were i check them for cc. i start at first ring up as there is some volume here. as the top of piston to bottom oil rail is about 030 smaller then piston bore size . if piston are not fine but the only thing i can get or customer will not pay or a time deal . for customs then i may move the chamber CC or head gasket to work . if off a cc one way or another will not matter on some builds .this way works very well to is if reworking a piston is to know the gram of pistons and cc with out wrist pin or with how ever its easier for me with out pin. then cut to weight=ccs works out to be about 2.7 grams =1cc . on a fully stock or cast dome finish tops of pitons if i am getting real close to what i feel may not run good on so/so gas i check it . stock stuff i do not spend as much time as on the race stuff. well thats not to say do not know were i want the CR . i know were i want the deck on the block and what head gasket before i start any machine up to make a cut . less there some bad twisted or low spots or need a deeper valve fly cut i stay to the build plan . i am going to know what head gasket size and cc they are.i seen many gaskets out there for stock rebuild head gaskets as much as 060 thick i stay way from cheap head gaskets . the steel plate MLS or a steel fire ring plate teflon/fiber/grafoil facing will not move on the thickness much they may be lested as .041 thick you many seen after used to 002. less. ON Cams ..i would not use a flat lifter less bone shock build. even so i would have hard time buying a Gm cam . many builds i gone to retofit roller. after i go threw all the list of things they must do for a good brake in with a hyd flat lifter cam and tell them i just can not help them if they wipe it and cam company may not help them the roller cam starts sounding good to them and if i build there engine i sell the cam lifters at cost .i do not add any more time on the build if i were to put a flat lifter cam in there engine .so i do not have to hear they wiped a cam .Gm cam and lifers sound good and have a good track record .but still can fail... so then your going to ask for help ? never tired it but would think you may get the brush off at the parts counter . so if i was going to put a flat lifter cam in any thing i would buy a horwards even if it was a bone stock mild RV cam as there max 5 year certified no fault warranty is the ony way to go i did not say much about the flat soild cams as i still used them and feel that a few small steps in prep on lifter and the EDM lifter is a good way to go but hardly use much solids most guys do not want to spend the time adjusting lifters . so most all mild stuff will see a hyd roller cam the after that a go solid roller cam setup.. Well this is how i build them and just glossd over some things other may build them different so far it,s world very good for me