383 build?

[Challenger340]

Tell that guy to cease and desist on those silvolite pistons..... YOU personally go order/buy a Burret/some solvent and CC the heads first so YOU know what they measure.
https://www.summitracing.com/parts/...MIo_bY3OyH8AIVlT2tBh3uaQgBEAQYASABEgJ9T_D_BwE

https://www.ebay.ca/itm/CYLINDER-HE...526930?hash=item48e7dae212:g:~RwAAOSwVVBe9eAX

just say'in....
with mopar engines especially and because so much of the 'published' data is incorrect....
there seems to be waaaaay too much of this..... 'the book says'..... 'the book says'..... 'the book says'.... coming from so-called machinists to cover their rears and you end up with garbage !

 

[SlinktRR]

I agree with challenger, measure everything especially combustion chambers. I used these pistons, icon840. This is for 4.15 stroke RB so not for your 383 but dished with pads and valve reliefs is the way to go with modern fuels and a closed chamber head. I wouldn't use flat tops with an iron head especially 915, this is not 1967 anymore the fuel has changed a lot. Not much more than the 2315.

https://www.summitracing.com/parts/uem-ic840-040

 

[BSB67]

I agree with challenger, measure everything especially combustion chambers. I used these pistons, icon840. This is for 4.15 stroke RB so not for your 383 but dished with pads and valve reliefs is the way to go with modern fuels and a closed chamber head. I wouldn't use flat tops with an iron head especially 915, this is not 1967 anymore the fuel has changed a lot. Not much more than the 2315.

You know that a 4.15 stroke 500" motor has no similarties to a 3.38" stroke 383 motor when it come to piston selection for a given head, right? Nothing.

If you put a dished piston in a 383, put a rope on it as you just created a boat anchor.

 

[SlinktRR]

I don't agree, the stroke doesn't matter. It's the compression ratio based on the cc of the head and the ability to build quench without detonating. The cam choice plays a big role in that. Iron 915 heads don't dissipate heat like an aluminum head I would be concerned about detonation with flat tops if they are coming close to zero deck, cam would have to be chosen well. Everything will have to be carefully selected to work together.

 

[1 Wild R/T]

YOU personally go order/buy a Burret/some solvent and CC the heads first so YOU know what they measure.

And in case you want to know how to CC your heads..

 

[1 Wild R/T]

I don't agree, the stroke doesn't matter. It's the compression ratio based on the cc of the head and the ability to build quench without detonating. The cam choice plays a big role in that. Iron 915 heads don't dissipate heat like an aluminum head I would be concerned about detonation with flat tops if they are coming close to zero deck, cam would have to be chosen well. Everything will have to be carefully selected to work together.

The stroke matters because with a short stroke it's hard to reduce the volume to raise the cylinder pressure... A dished piston will kill the potential to make power....

That's the reason I took closed chamber heads & milled .040 off of them....

 

[MarPar]

 

[SlinktRR]

D dish pistons like those icons are not the same as a full dish, you can still get quench at zero deck. They can also be customized to dial in the cc of the dish so you can get the exact CR you want. Flat tops are great like on austin's 383, but can you guarantee that it won't detonate with OP build using different components, or piston to valve contact? Maybe, but it will require some measurements and planning. Calculators are nice like this one:

https://uempistons.com/rt-4-calculators.html

This is where cam selection on measurements of the combo comes in. Target static and dynamic CR and cylinder pressure to minimize the possibility of detonation. It would suck to build a nice 10:1 motor and then have it ping all the time so much you have to mix race gas to go cruising around.

 

[PRHeads]

I wonder how all those Brand X guys seem to get by just fine with iron heads and good quench.

 

[Gary Stavely]

Thanks for all the replies and the differences of opinion.
I will forsure have the heads CC'd no questions asked as well as the block height checked, the motor has sat for a long time its the original motor for my 1967 coronet and was a 2bbl but I am changing to a 4bbl. My understanding is the 2bbl came with dished pistons hence the 9.2:1 compression ratio and the 4 bbl came with true flat tops hence the 10:1 compression ratio, I could be wrong there I have been before lol.
I know without actually measuring the book numbers are just numbers, but without measuring the 2315 pistons will put me .016 in the hole and around 9.7:1 CR according to the stock specs.
These 383 engines seemed to have changed a lot during the 66-71 time period and even the years before that, It's not going to be a problem switching pistons right now and my engine builder is a very knowledgeable and respected guy... I am not sure why he wanted to order the silvolites but I am thinking it was a quick decision as he is a busy fella and I am not to worried about it as long as I know they won't be in my engine...
The 1967 engine had a compression height of 1.908 and the 1968 was 1.934, the 2315's are 1.920 and measuring from the stock specs it puts me at .016 in the hole, I do realize these are just numbers until the measuring takes place but it puts me right in the ball park of where I want to be.
I apologize
.5×3.38+6.358+1.920=9.968
9.968 (comp height) -9.98 ( deck height) = .012 not .016 as I posted, hopefully these numbers will be close when we measure but I am not holding my breath lol.

 

[Challenger340]

Thanks for all the replies and the differences of opinion.
I will forsure have the heads CC'd no questions asked as well as the block height checked, the motor has sat for a long time its the original motor for my 1967 coronet and was a 2bbl but I am changing to a 4bbl. My understanding is the 2bbl came with dished pistons hence the 9.2:1 compression ratio and the 4 bbl came with true flat tops hence the 10:1 compression ratio, I could be wrong there I have been before lol.
I know without actually measuring the book numbers are just numbers, but without measuring the 2315 pistons will put me .016 in the hole and around 9.7:1 CR according to the stock specs.
These 383 engines seemed to have changed a lot during the 66-71 time period and even the years before that, It's not going to be a problem switching pistons right now and my engine builder is a very knowledgeable and respected guy... I am not sure why he wanted to order the silvolites but I am thinking it was a quick decision as he is a busy fella and I am not to worried about it as long as I know they won't be in my engine...
The 1967 engine had a compression height of 1.908 and the 1968 was 1.934, the 2315's are 1.920 and measuring from the stock specs it puts me at .016 in the hole, I do realize these are just numbers until the measuring takes place but it puts me right in the ball park of where I want to be.
I apologize
.5×3.38+6.358+1.920=9.968
9.968 (comp height) -9.98 ( deck height) = .012 not .016 as I posted, hopefully these numbers will be close when we measure but I am not holding my breath lol.

On a .030" over 383
The ONLY way you are getting anywhere close to 9.7:1 with the 2315's @ .012" down hole from the deck at TDC is if.....
and
assuming whatever Composition style Head gasket you use is around 10 CC's....
your 915 Cylinder Heads CC at 78 CC's

And again, IMO....it is in your best interest to CC the Heads yourself so you know ? rather than "getting them CC'd".... especially if it's being done by the same "very knowledgeable and respected guy" who was ordering you the Silvolites at 1.848" Compression Distance for your 383 Mopar Engine when you asked for a high 9's:1 originally ?
Being 'busy' is no excuse for not finding you the parts conducive to what you were asking for ?

Sounds like more than a few of us here..... have invested more time doing the Math for your build than he did ?

Remember also... to pass along to your 'very knowledgable and respected guy'
that when calculating the CR's of the factory BB Mopar Engines.... they utilized a Steel Shim style Head Gasket(.022" thick) that came in around 5CC's volume for calc purposes
whereas...
you will probably be using a Composition style Head Gasket (mostly around .040" thick) that come in around 10 CC's for calc purposes
and
depending 'where' you are in the CR range can LOWER your CR up to a 1/2 point using the Composition Gskts.

 

[Challenger340]

I had the block decked .020 which actually brought me to .002/.003 out of the hole. Head gaskets are just standard .039 Felpros. The cam is the Hyd roller below, I use solid roller lifters and Harland sharp rockers with lash around .005 cold. I do not have the measurements you are asking for as this cam change was done on a running motor without pulling the heads, I do however have a video from the borescope somewhere, I’ve shared it on here before. Cam is installed “strait up”. It’s the cams with lots of duration and a late exhaust valve closure that will cause the first interference problem, piston don’t care how far the valve opens so long as it gets out of the way before the piston gets there.

View attachment 1098624

I think you are doing very well... and obviously haven't experienced any Piston to Valve issues.
Did you check the Piston to Valve Clrc with the 224/230 @ 050 Roller Cam ?
I'm thinking your Composition Head Gskt (+.020") and small duration Cam/Valve Heights after rebuild may be helping keep things away from each other ?

We've made 444 Ft Lbs with 430 HP on the Engine Dyno on a 383 using 906 Irons and just the Comp XE274H Flat Tappet Cam at 224/230 also, probably similar power to yours, albeit NON-Roller

 

[Gary Stavely]

On a .030" over 383
The ONLY way you are getting anywhere close to 9.7:1 with the 2315's @ .012" down hole from the deck at TDC is if.....
and
assuming whatever Composition style Head gasket you use is around 10 CC's....
your 915 Cylinder Heads CC at 78 CC's

And again, IMO....it is in your best interest to CC the Heads yourself so you know ? rather than "getting them CC'd".... especially if it's being done by the same "very knowledgeable and respected guy" who was ordering you the Silvolites at 1.848" Compression Distance for your 383 Mopar Engine when you asked for a high 9's:1 originally ?
Being 'busy' is no excuse for not finding you the parts conducive to what you were asking for ?

Sounds like more than a few of us here..... have invested more time doing the Math for your build than he did ?

Remember also... to pass along to your 'very knowledgable and respected guy'
that when calculating the CR's of the factory BB Mopar Engines.... they utilized a Steel Shim style Head Gasket(.022" thick) that came in around 5CC's volume for calc purposes
whereas...
you will probably be using a Composition style Head Gasket (mostly around .040" thick) that come in around 10 CC's for calc purposes
and
depending 'where' you are in the CR range can LOWER your CR up to a 1/2 point using the Composition Gskts.

Thanks! Ya I just used a online calculator with a .040 gasket thickness and I believe I came up with 9.66:1. Don't worry those silvolites are not going in there and maybe doing the assembly myself is not a bad idea, that was my plan in the first place and I am capable its just not something I do every day.

 

[AustinGriggs]

I think you are doing very well... and obviously haven't experienced any Piston to Valve issues.
Did you check the Piston to Valve Clrc with the 224/230 @ 050 Roller Cam ?
I'm thinking your Composition Head Gskt (+.020") and small duration Cam/Valve Heights after rebuild may be helping keep things away from each other ?

We've made 444 Ft Lbs with 430 HP on the Engine Dyno on a 383 using 906 Irons and just the Comp XE274H Flat Tappet Cam at 224/230 also, probably similar power to yours, albeit NON-Roller
View attachment 1099417

I did check it, but with a borescope turning the motor over watching the events. There was never anything remotely close needing further investigation. So i sent it, alot. I do intend on having the heads off this summer before my #MoparVsBrandXstreetcarShowdown this fall in Alabama so Ill try to get some of the questions answered then. I already have the headgaskets in the closet for the job some Cometic .036 ones that arent hoola hoops around the 383 bores. Going to do some tweeks to the heads and put it back together. New converter and a 3.73 set, trying to get the car around the 7.60 range and 90mph and then... leave it there, it's a mule for my Ratty Muscle Cars races.
Good luck on putting this motor together, I look foward to seeing how it does.

 

[AustinGriggs]

I don't agree, the stroke doesn't matter. It's the compression ratio based on the cc of the head and the ability to build quench without detonating. The cam choice plays a big role in that. Iron 915 heads don't dissipate heat like an aluminum head I would be concerned about detonation with flat tops if they are coming close to zero deck, cam would have to be chosen well. Everything will have to be carefully selected to work together.

Your piston have a 23cc dish, with your monster stroke crank and a 78 cc head that equates to 9.65:1... pretty good. Now change nothing else but the crankshaft and a rod to get it to the top of the bore / or wrist pin location.... and you have an 8.05:1 compression pile of trash. How does stroke not matter?

 

[Gary Stavely]

Due to the unavailability of the 2315' s I think I am going to go with the icon 687, heads cc'd to 78cc. Pretty pumped, a bit more compression but I don't mind that one bit...

 

[AustinGriggs]

Due to the unavailability of the 2315' s I think I am going to go with the icon 687, heads cc'd to 78cc. Pretty pumped, a bit more compression but I don't mind that one bit...

I think if you go with those pistons you are going to wanna change more in your equation.
For starters the compression height is 1.912 which is .008 lower than the 2315s not bad but with the thin gaskets you are barely in the the territory of chasing quench with out having the block decked alittle. And with that bump up in compression it could use the help from a good quench distance. My calculations of your new combo on Diamonds calculator is 10.38 with a .022 gasket. That’s great for making power, but that mild cam and factory intake manifold you plan to use doesn’t compliment it well. If you went with a regular gasket you are way out of the quench chase where as you will likely be looking at detonation with the 40 degrees of timing you will be force to run to make happy to run ok.
By the way I checked Summit and EBay, they both have 2315s ready o ship. Just FYI

 

[gdrill]

 

[1 Wild R/T]

By the way I checked Summit and EBay, they both have 2315s ready o ship. Just FYI

Only 9 in stock better hurry Or is that 9 sets of 8 pistons...

https://www.summitracing.com/search...coronet/part-type/pistons?N=part-type:pistons

 

[Gary Stavely]

I need .040 I apologize if I didn't mention it, they have one set coming into Ohio in a month bur that date is not 100%