|04-09-2012 05:13 PM|
I'm not sure why you are tryi.g so hard to build an engine that will deliver less than stock power.
If you build this engine its going to be extreemely mild, so much so the thrill of owning a muscle car won't be there. Get over only getting 15mpg's get a healthier cam, run flat top pistons and enjoy the damn thing. Yea you'll lose a mpg, but you'll enjoy it a hell. A lot more! A mild solid cam like I recomended with flat top pistons and camel humps will run fine on 87 octane as long as its tuned right. Throw in a 700r4 and torque converter from an s10 4.3L. The whole project will be a lot cheaper a lot more fun, and will actually sound and drive like a camaro.
Those tiny cams you're looking at are the last thing id put in a car that was meant to be fun. Maybe a work truck but not that camaro.
You're looking to spend a lot of money and your build will net you almost no power gain due to that tiny cam.
The worst part is that it'll sound like a stock half ton truck. Yea, that's real impressive.
|04-09-2012 04:38 PM|
I'm thinking if I decked the block 0.020 down to 9.005, with the same other parameters listed above and used a Gasket compressed to 0.038 that would given me a 0.002 piston to deck height and CR 8.933 or 9.404 depending on the two piston choices above.
Or how about keep the stock deck height of 9.025, find a gasket that compresses to 0.020 and a quench of 0.042 and a CR of 8.795 or 9.381 ?
As my usual disclaimer, I'm just playing with numbers, but eventually they will turn into something real.
|04-09-2012 03:40 PM|
Until I know exactly what measurements I have to deal with, I am practicing shopping for pistons based on the following assumptions:
Deck height 9.025 stock
Rod length 5.7 stock
Head combustion chamber volume 64cc
1.678 compression distance (this was all they had in the dished or valve relieved pistons at Summit)
0.018 gasket (based on achieving a 0.040 quench, not ideal but all they had)
I found the following Keith Black pistons on Summit's site:
With a 4.030 bore, and +13.00cc piston head volume
I get a 8.946 CR
With a 4.000 bore, and +7.00cc piston head volume
I get a 9.426 CR
Looks like there aren't that many choices out there. Back to my latest question. What Compression Ratios am I looking for? Is the 8.946 my best choice if I stay with the camelhumps or will the 9.426 work fine with the vortec heads?
What other sites can I choose pistons from?
|04-09-2012 02:40 PM|
As stated, quench is very very very important. Don't buy pistons until you calculate your compression distance.
Then you go to whatever place you want to buy your pistons and you'll see 327 pistons with different compression distances. Here you see them listed below left.
The key is to take a really really really accurate measurement from the crank journal to the top of the deck. Then you can compare piston heights from the catalog, and select a piston that is very close to zero deck height. Then you can select the latest and greatest sealing .039 thick (compressed) head gasket, which will give you perfect quench. You can also select a piston that is a little down in the hole (cylinder) and have your block decked to get zero deck height.
To throw fuel on the camshaft fire, you might want to try a solid lifter Comp Cams 12-674-4 xs256 if you don't mind adjusting valves. It's the smallest solid lifter they make. Once everthing breaks in and work hardens, you can get by adjusting them once a year This cam is only if you're going to use headers. Double check your heads will handle .477 valve lift, which they should. Solid lifter cams (in the same grind category of a hydrualic lifter) have a more aggressive ramp so you'll gain power across the board and rev out a little further. I believe the other cam you selected, however, is an excellent choice.
Last but not least, fuel mileage. I honestly doubt you can get better than 17-18 mpg regardless of cam or tranny selection. From six figure miles of experience, I can tell you that a perfectly carbureted and tuned '65 Impla SS w/stock 327, 3.31 gears, and a 1969 Delta 88 two door with 2.78 gears both get 16mpg on the highway, plus or minus a hair. So did all my buddy's parent's full-size, small block v-8 cars from the latter 60s. (Without running the AC.) There is just too much wind resistance. A camaro is a little lighter, but that front end doesn't look too aerodynamic to me. Today's cars are amazingly clean.
You now know everything I think I know. Use this info at your own risk.
|04-09-2012 01:10 PM|
Looks like those Ebay pistons may not be the ones I want, even though the CR would be 9.19 with a .041 HG, the quench would be excessive at .066 (or .025 + .041). If I were to correct the quench by going with a thinner HG, then the CR would go up to 9.7. Is 9.7 too high?
Should I be looking for the same height pistons, but with a 11cc dish which would result in about a 9.139 compression ratio?
I'm starting to lean heavily on the idea of going with the Vortec heads from the get go, and I believe they also have the same 64cc combustion chambers, so I guess my question now, is what CR should I be aiming for? Is it the same for the camelhumps as with the Vortecs, or will the Vortecs hande a higher CR without detonation on regular gas?
Why would piston manufacturers market these particular pistons, How would I find the ones I really need?
I'm hoping the machine shop engine builder guy can advise me when he checks out my block and crank.
|04-08-2012 10:54 PM|
Different calculators and also different listings in catalogs, etc. will use negative numbers to represent both domes AND dishes, so you need to pay close attention to know how they're listing the volumes.
As for the estimated CR that you are seeing on that ebay listing, they're assuming the piston is 0.025" in the hole and a 0.041" HG is being used, w/a FT piston w/a 5cc dish, which is what they're saying w/the "+5cc"- in other words, the pistons add 5cc to the total volume. The calculator I linked to uses "-5" to represent a 5cc dish or valve relief volume.
If the quench was where it should be (~0.040"), the CR will be ~9.7:1.
|04-08-2012 04:26 PM|
Also any information on what it takes to connect up the linkage and electrical controls, I assume I would want to keep it very simple and avoid any computers such as the 700-R4 was commonly controlled by.
|04-08-2012 04:06 PM|
I'm planning to take the block and crank to the machine shop this Wednesday.
At this point I'm assuming a bore of 4.030, but should know for sure after the shop measures the existing out for me.
As for measuring all the volumes and heights:
I can probably measure the cc's in the heads myself.
How can I figure deck height or the distance from the top of the pistons to the deck, if I don't have any pistons yet to measure from? Since it is still a standard bore, could I assume at this point it has probably not been deck surfaced? Without measuring anything yet and assuming a 64cc head chamber, would these pistons be close to what I'm looking for? Here's an ebay link to some I've been watching:
Do they list enough specs on the Ebay ad to help me calculate the final static compression ratio, such as the compression distance of 1.675 and the dome volume of 5 which I think would actually be -5 as the dome would be considered negative, which in this case I think would include the flat top minus the valve reliefs. I'm guessing they must be assuming a standard gasket thickness when they estimate the compression ratios based on the head compression volumes.
If in the future (or now) if I decide to put on a set of Vortec heads, it looks to me like the Vortec chamber volumes are about the same as my 462 camelhumps, or maybe a little smaller as 62cc. I'm guessing the CR will be still be ok if I change out the heads later.
Keep theose comments coming. I'm getting a lot closer to knowing exactly what I want to do.
|04-08-2012 12:47 PM|
A few thoughts...
The target CR you have in mind is ideal for that cam. That said, to figure out what you need for pistons, you need to know a few things:
• Bore- is it 0.030" over or will it stay standard?
• What's the combustion chamber volume? This has to be measured to know whether the heads have been milled in the past, or if you have to mill them before using them.
• Piston deck clearance- this is how far down the hole the piston is at TDC. It can vary due to the block having been milled in the past, and due to manufacturing tolerances.
• Piston compression height (CH)- this is 1.675" for a stock piston and most "better" pistons. But there are pistons that are shorter from the pin to the piston deck; these are called "rebuilder" pistons and are made (usually) 0.020" shorter to account for the deck being milled to true them and to promote a good head gasket (HG) seal.
• Quench distance- you want to be as close to 0.040" as you can. This promotes good combustion and lessens the need for octane. Some call a good quench figure "mechanical octane". You can get the 0.040" in several ways by juggling the HG thickness, piston CH and block deck height. That's one reason you have to start out knowing what you have in order to know what you need.
A stock block will be very close to 0.025" piston down the hole w/an unmilled block and a stock compression height piston. Combine that w/the stock steel shim HG (about 0.015" thick) and there you have your 0.040" quench distance. To use a steel shim HG requires the decks be freshly machined to help the HG to seal, and THAT is where the rebuilder type shorter pistons come into play. Starting to make sense?
So once these are all known and everything has been considered, the piston dish or dome volume can be determined. You may need a slight dish in this application. If this is the case once everything has been measured and considered, using an "inverted dome" type dish is the preferred type of piston. These are also called D-shaped dish pistons.
What you want to avoid doing is adding HG thickness to lower the CR. A thick gasket will give a wide quench distance, and that in turn increases the need for octane- so until the gasket gets WAY thick, there may be little help from a thicker HG (and an increases quench distance) when the need for octane is considered. For example, using a 0.041" compressed thickness HG on a stock, unmilled block and rebuilder pistons puts the quench distance at an unacceptable 0.086".
Another option is to use a flat top (FT) piston and a cam w/a little more duration @ 0.050" lift (like in the range of 212-216 degrees or so, depending on the exact static CR) in order to get an acceptable DCR, using readily available FT pistons instead of finding (and paying for) the right size inverted dome pistons. The chambers can also w be reworked to give more volume to lower the CR. Just remember that the more radical the cam is, the more torque converter stall you need and the less bottom end power you will have- which means a lower rear gear ratio or an OD tranny w/a short first gear ratio will be needed. It's all a balancing act.
Didn't mean to write a book, but this this is just the tip of the iceberg. Most of the info is derived from an outline that's being drawn up for a page in the Crankshft Coalition wiki.
|04-08-2012 09:15 AM|
I like the combination you listed in your last post.
That should give you a strong, mild running engine.
The only input I have is: I would reccommend going to a TH 200-4R overdrive transmission. You can even use the driveshaft without any modification. Simply move the crossmember back a few inches, and connect the lock-up torque converter through the brake light switch to take power away when the hit the brakes. Go to a 3.70:1 rear gear and you'll have snappy performance and cruise at highway speeds aith an engine RPM around 2000.
|04-07-2012 11:26 AM|
|ap72||Also, if you want a camaro that drives like a camaro you need a bigger cam. I would at least consider a mild solid cam, like the 401a2 cam. Run with 1.6 rockers and face oiling lifters. The 401a3 would be a good option too if you want more rumble at a slight loss of off idle power.|
|04-07-2012 11:23 AM|
|ap72||What fuel are you wanting to run? 87? If you insist on keeping those heads at least get them ported when you get them rebuilt.|
|04-07-2012 08:34 AM|
After much agonizing with different options, I've just about made up my mind on what I would like to do.
Pretty much my original proposal in my firrst post in this thread.
Going back to my original questions, what I'm really looking for is input on the details of my plan and what small items you would tweak.
9.15 compression pistons
462 camel hump heads
GM dual plane intake
Edlebrock 1406 600cfm carb.
Compcam 12-205-2 camshaft
One possible change I may consider if I find a good deal is to upgrade to some vortec heads and newer intake.
I don't want anymore input on why this is a generally bad plan or will be too expensive. This is what I want to do. If I wanted to be sensible with my money, I would have bought a Toyota Corolla and not a 67 Camaro. What I'm asking is help to fine tune or tweak this plan. Advice on:
Thank you guys for all your input so far.
|04-06-2012 06:18 PM|
|grandpa01||I might be temped to try the trans 1st with the 283. It's not ideal but a good start. I don't know if you'll be able to use OD much.|
|04-06-2012 06:12 PM|
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