Hell, it's only money!! Ask Mikey how much it cost him to figure this stuff out. Blown engine=big bucks when a valve hits a piston. JMO
Building a 383 stroker - Enter At Your Own Risk
- Thread starter Bucketman
- Start date
Hell, it's only money!! Ask Mikey how much it cost him to figure this stuff out. Blown engine=big bucks when a valve hits a piston. JMO
fletcherson
Well-Known Member
I had a 383 with iron heads and 10.5 - 1 compression. I had detonation issues. I finally was able to control it with a timing computer, but the performance suffered. Aluminum heads did help it. I will not make that mistake again, but I had some good components and built around them... It cost me in the long run.
Like I said, it's only money. Back in the day, I had a 460 Ford punched to a 502 and was a screamin' meme. Detonation was it's failure when a piston came through the block. I had it in a Lincoln Mark IV, tunnel ram and 1100 Holley carb. It would cost you $100.00 to see under the hood. Camaros and Mustangs didn't have a chance.
Let someone else that knows what they are doing build the motor for you and you will come out cheaper in my opinion.
Indycars
Well-Known Member
1.) Dished piston will not effect the quench distance, they are not dished all the way to the edge, only in the center.
2.) Yes, you got the right understanding, no you are in right field now !!!
http://www.probeindustries.com/Chevy_350_2_5cc_Flat_Top_FPS_Pistons_p/l2256f.htm
I wonder where we differ, because I get a completely different SCR and DCR that you do. I looked up the Probe Piston and the only things that matched your info and picture were the Probe L2256F pistons with a 2.5 cc valve relief .... what are you using???
For engine 1 & 2, the only change was IVC angle of 64° and 66°. Engine #2 has two changes, gasket thickness.041" to .051" and IVC angle of 68°. I have to say, I really don't like a quench distance of.051" even thou the both CR decreased. I believe you gave up as much as you gained. If you never go over 5500 RPM, then you can do as 2old2fast suggested and go lower to .035" for you quench distance.
I would verify my deck height with a straight edge and feeler gauges. Just make sure the straight edge is directly over the piston pin. You should be able to get close enough to verify what the machine was suppose to do. Besides not every block is the same.
BTW, what camshaft are you using and I mean give the part number or post the cam card with the specs
You can get the above calculator except for the Cranking Pressure at :
https://tbucketeers.com/threads/dynamic-static-compression-ratio-calculator.12683/
2old2fast
Active Member
Don't know if it makes a difference , but the above examples use a 3.48 stroke , the engine the op is building would have a 3.75 stroke... I can't speak to running 10.4 on 91 octane , but would think that because these little cars are so lightweight that you'd probably be o.k. FWIW , I'm running 10.4 w/aluminum heads on 93 w/ 36* total timing , all-in at 2200 RPM , never a problem , in fact the heads are off right now for new guides & , I'm happy to report , no sign of detonation after about 20 K miles.... kinda pissed about the guides !!
dave
dave
Bucketman
Member
That's right, it is only money, can't take it with you when you go. But, as far as having somebody else do my engine, that would take the fun out of it. I might as well just buy a running and titled T-bucket. I know it would be a lot easier but it wouldn't be "mine".
Hey Fletcherson, did the aluminum heads solve the problem or just help?
As Dave said this is a stroker engine, 3.750 stroke. Pistons -4cc. Does that give me a 68cc chamber? Intake valve close angle is 64 degrees. The camshaft is a comp cam XE274H, part #12-246-3. I do have a station in town that sells 93 octane gas so that might help.
Hey Fletcherson, did the aluminum heads solve the problem or just help?
1.) Dished piston will not effect the quench distance, they are not dished all the way to the edge, only in the center.
2.) Yes, you got the right understanding, no you are in right field now !!!
http://www.probeindustries.com/Chevy_350_2_5cc_Flat_Top_FPS_Pistons_p/l2256f.htm
View attachment 11025
I wonder where we differ, because I get a completely different SCR and DCR that you do. I looked up the Probe Piston and the only things that matched your info and picture were the Probe L2256F pistons with a 2.5 cc valve relief .... what are you using???
For engine 1 & 2, the only change was IVC angle of 64° and 66°. Engine #2 has two changes, gasket thickness.041" to .051" and IVC angle of 68°. I have to say, I really don't like a quench distance of.051" even thou the both CR decreased. I believe you gave up as much as you gained. If you never go over 5500 RPM, then you can do as 2old2fast suggested and go lower to .035" for you quench distance.
View attachment 11026
I would verify my deck height with a straight edge and feeler gauges. Just make sure the straight edge is directly over the piston pin. You should be able to get close enough to verify what the machine was suppose to do. Besides not every block is the same.
BTW, what camshaft are you using and I mean give the part number or post the cam card with the specs
You can get the above calculator except for the Cranking Pressure at :
https://tbucketeers.com/threads/dynamic-static-compression-ratio-calculator.12683/
As Dave said this is a stroker engine, 3.750 stroke. Pistons -4cc. Does that give me a 68cc chamber? Intake valve close angle is 64 degrees. The camshaft is a comp cam XE274H, part #12-246-3. I do have a station in town that sells 93 octane gas so that might help.
fletcherson
Well-Known Member
The issue went away, but I changed the induction system also from a dual plane intake with a edelbrock 750 to port projection, so it's hard to be definitive about the heads being the total cure. I strongly believe they were the main issue. I only ever noticed it at low load, cruise in high gear, but it was persistent and rejecting, timing gad little effect. The timing computer did initially help it, but at a cost of performance. It ran best before the computer, etc... The end result with the pro jection, etc was awesome, but the price was double the initial build. I built the engine around some good heads and some other stuff that I had. If I would have just spent the time and cash in the beginning, it would have been fine without the other and a lot cheaper. Live and learn, right?That's right, it is only money, can't take it with you when you go. But, as far as having somebody else do my engine, that would take the fun out of it. I might as well just buy a running and titled T-bucket. I know it would be a lot easier but it wouldn't be "mine".
Hey Fletcherson, did the aluminum heads solve the problem or just help?
As Dave said this is a stroker engine, 3.750 stroke. Pistons -4cc. Does that give me a 68cc chamber? Intake valve close angle is 64 degrees. The camshaft is a comp cam XE274H, part #12-246-3. I do have a station in town that sells 93 octane gas so that might help.
Indycars
Well-Known Member
You are so right 2old2fast ......thanks!
That's why is important to post all the number to make a calculation, it definitely made a big difference in a CR calculation. From a DCR/SCR of 8.54/10.64 to 9.02/11.19.
I implore Bucketman to review every number in my posting for accuracy.
Looking at the first 3 engines, it's obvious that retarding the camshaft is not going to get you a CR that will run on 93 octane. According to your cam card installing cam Dot-to-Dot would be 3° advanced. And what if you are out of town and can only get 91 octane, that's all I can get in my locale.
The best solution would be to call Skip White and see if you can trade your pistons for some dished pistons will a 12cc to 15cc dish, 15cc being the best choice.
NOTE: The only trivial numbers in my calculation are line 7, 9 and 10, they can be left as is and not change the number a significant amount. Being the type of person I am, I had to include every possible volume in my Excel calculator.
That's why is important to post all the number to make a calculation, it definitely made a big difference in a CR calculation. From a DCR/SCR of 8.54/10.64 to 9.02/11.19.
I implore Bucketman to review every number in my posting for accuracy.
In your very first post, you said the chambers were 64cc. So I don't understand your question.
You don't want the gasket hanging into the bore and creating a hot spot that could cause pre-ignition. So yes I would use a gasket bore of 4.060 or maybe little bigger.
Looking at the first 3 engines, it's obvious that retarding the camshaft is not going to get you a CR that will run on 93 octane. According to your cam card installing cam Dot-to-Dot would be 3° advanced. And what if you are out of town and can only get 91 octane, that's all I can get in my locale.
The best solution would be to call Skip White and see if you can trade your pistons for some dished pistons will a 12cc to 15cc dish, 15cc being the best choice.
NOTE: The only trivial numbers in my calculation are line 7, 9 and 10, they can be left as is and not change the number a significant amount. Being the type of person I am, I had to include every possible volume in my Excel calculator.
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Bucketman
Member
So the two engines with 12cc and 15cc dished pistons are with the cam at 6 degrees advance? I see the IVCA at 64 degrees so I'm guessing that is the case. I called Skip White and left a message. They have been getting the worst weather in the world so I'm hoping they have someone there to call me back today. I talked to a guy there Sat. and he told me it would be a week and a half before it was ready to ship so maybe it's not to late to get the 15cc dish pistons. 9.9:1 is plenty of compression, don't know what I was thinking when I ordered the flat top pistons or if I was even thinking at all. . I need to be able to drive this on pump gas. Thanks guys, especially Indycars for showing me the chart he used to figure the CR's. I am from the show me state. lol
. I need to be able to drive this on pump gas. Thanks guys, especially Indycars for showing me the chart he used to figure the CR's. I am from the show me state. lol
Indycars
Well-Known Member
By my calculations when the cam is installed Dot-to-Dot, that is 3° advanced. Which also means the IVC angle is 64, just like in Engine #1. Same for Engine #4 and #5.
If you don't have Excel, then you can download "OpenOffice" for free and run Excel files from OpenOffice. That way you could play until your hearts content with the DCR/SCR calcs. For me, that's half the fun.
http://www.openoffice.org/
I have many, many Excel files for everything I do with an engine from documenting all the dimension/clearance values and another to make sure I checked everything and in what order to degreeing the camshaft to tracking the machine shop costs .... etc.
Feel free to ask more questions, someone will know the answer!!!
fletcherson
Well-Known Member
Bucket man, it would be prudent to make sure you get the engine dialed in before building it even at the cost of shipping, whatever, so you can just enjoy your ride and not fight the preignition monster, don't set yourself up for a battle, you will have plenty of things to do. It's no fun to keep re curving the distributor, re jetting the carb, etc... On a otherwise great running engine due to preignition. Get the compression down to a reasonable number and let it live. You will not notice any performance loss over a point of squeeze in a tbucket. Jmo, not to be right, to help you be happy with your creation! I tried various fuel additives also, and I didn't have any real noticeable improvements, but it's pricey and a hassle. I'm sure there are some better alternatives. Also you are assuming the advertised octane numbers are accurate and putting yourself in a tight place at 93 octane, also what's the effect of the ethanol? If this is a tire burning cruiser, you don't need to push the envelope to achieve your goals here. It's easy to get carried away when conceiving these things, that's part of the fun. Just be realistic so it will make you proud. I have built toys for a while, and one of my trends (bad habits) is to try to get as much as I can from them, usually at the expense of going a little further than necessary. You know, if a little is good, a little more is better, right? Not always the case, I've learned. Lol.
Bucketman
Member
Thanks Fletcherson, I've decided to contact Skip White performance and see if they will exchange the flat top pistons for some 15cc dish pistons. I called and left a message today but I guess nobody was home. They said it wouldn't be ready to ship for a week and a half so hopefully they will do the swap for me. They have the exact same kit with the dish pistons so they shouldn't mind doing it as long as they haven't balanced the first kit. Even if it is balanced somebody else will be wanting it. Don't know if you saw the Excel Chart from Indycars but it has all the right information and with 15cc dish pistons it will give me 9.9:1 compression. That's more than enough for a street rod running on pump gas and I'm sure it will still smoke em if I put my foot into it. I bet it will be more satisfying to drive also.
Bucketman
Member
Now that sounds like fun! I'll make sure she takes along an extra pair of panties. LOL
Bucketman
Member
Good news. Skip White exchanged the pistons for 15cc dish. 9.9:1 SCR is plenty high for a street motor. With the aluminum heads I might even be able to burn 87 octane if I have too.
So with 64cc combustion chambers and 15cc dish piston wouldn't I have an effective combustion chamber of 79cc"s? Or is that not how it works? LOL,
@ Indycars, sort of what I was talking about when I ask this question. Thanks for all the help. Stan
So with 64cc combustion chambers and 15cc dish piston wouldn't I have an effective combustion chamber of 79cc"s? Or is that not how it works? LOL,
@ Indycars, sort of what I was talking about when I ask this question. Thanks for all the help. Stan
Indycars
Well-Known Member
I see now, yes you are right about adding the two numbers. In fact lines 6-11 are all about the total size of the combustion chamber, although some of those volumes are very small and trivial to the total size.
Ok what's next on your agenda for this motor??? I assume you will be checking all the clearances for the bearings, including crankshaft end play. It doesn't take expensive tools, just some patients and motivation to do it right. Machine shops make mistakes, just like everyone one else. But if you assemble the motor, it's your responsibility to make sure EVERYTHING is good. They should be glad to fix it if you catch it before you fire the motor.
To check clearances all you need is Plastigage and some feeler gauges, less than $20. When using Plastigage, there is a right way and a wrong way to use it, make sure you know the right way!
I have a Excel spreadsheet that would help with making sure that everything is checked and in the right sequence. I will try to post it today or tomorrow in the articles section of the website. I also have a scaled down version that can be printed for those that don't like computer files.
Below is a partial look at the spreadsheet:
Ok what's next on your agenda for this motor??? I assume you will be checking all the clearances for the bearings, including crankshaft end play. It doesn't take expensive tools, just some patients and motivation to do it right. Machine shops make mistakes, just like everyone one else. But if you assemble the motor, it's your responsibility to make sure EVERYTHING is good. They should be glad to fix it if you catch it before you fire the motor.
To check clearances all you need is Plastigage and some feeler gauges, less than $20. When using Plastigage, there is a right way and a wrong way to use it, make sure you know the right way!
I have a Excel spreadsheet that would help with making sure that everything is checked and in the right sequence. I will try to post it today or tomorrow in the articles section of the website. I also have a scaled down version that can be printed for those that don't like computer files.
Below is a partial look at the spreadsheet:
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fletcherson
Well-Known Member
Good news! That motor will be plenty strong and fun.
fletcherson
Well-Known Member
I love the feel of a standard tranny in a performance car! My 76 Ventura had a 455 4 speed and it would rip em loose in third no problem other than the clutches it consumed, lol. It put a smile on my face and scared away the Cameros and mustangs in the neiborhood.
Bucketman
Member
Yes I just got a set of 12 plastigauges for .001 to .003 in the mail today. Already have the feeler gauges. I've never used the plastiguages before but I watched a video of a guy doing it and making adjustments to the bearings with a scotch pad. Not to sure about that, but Skip White has bearings for undersize and oversize and a half size too. I guess that's .0005 under or over. I just printed out the chart. So I will go down the list and see what I can do.
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