I may have messed up here.....

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Wreckless

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I’m new on here but would value some advice from you guys.

I am in the process of gathering together parts for my 440 but I think I may have goofed in my parts choices in so far as the compression may be through the roof, and I hope you can put me right.

I have so far, a Crane 689521 cam, grind number HR-222/339, Trickflow 240 heads (78cc chambers), a set of SRP 231521 pistons that are -6cc with 1.865 compression height, bore 4.350 & stroke 4.150. Crank and rods are all Molnar items (440-4150MC6F & DH6760VTB8A respectively).

The block has not been machined yet so I dont know what effect decking etc will have on things.

How well do you think the above will work together? Someone advised that I need to ‘bleed off some compression’ with a hairier cam, but I don’t really know what that even means! I was going to use 1:5 rockers, but perhaps 1:6 would accomplish this bleed effect?

If relevant, I am going to run the 600hp Fitech on a Performer manifold (No room for anything taller).

All advice gratefully received!
 
Wreckless said:
I’m new on here but would value some advice from you guys.

I am in the process of gathering together parts for my 440 but I think I may have goofed in my parts choices in so far as the compression may be through the roof, and I hope you can put me right.

I have so far, a Crane 689521 cam, grind number HR-222/339, Trickflow 240 heads (78cc chambers), a set of SRP 231521 pistons that are -6cc with 1.865 compression height, bore 4.350 & stroke 4.150. Crank and rods are all Molnar items (440-4150MC6F & DH6760VTB8A respectively).

The block has not been machined yet so I dont know what effect decking etc will have on things.

How well do you think the above will work together? Someone advised that I need to ‘bleed off some compression’ with a hairier cam, but I don’t really know what that even means! I was going to use 1:5 rockers, but perhaps 1:6 would accomplish this bleed effect?

If relevant, I am going to run the 600hp Fitech on a Performer manifold (No room for anything taller).

All advice gratefully received!
Click to expand...
I've not ran your numbers yet but are you trying to stay on pump gas? Another option would be to tune and run E85 which has a higher alcohol content and allows you to run slightly higher compression.

Also, if the block hasn't been decked yet, you don't have to go to a zero deck, just have the shop make it square/flat. Run a thicker head gasket . Those will help you loose compression a couple tenths of a point.
 
Wreckless said:
I’m new on here but would value some advice from you guys.

I am in the process of gathering together parts for my 440 but I think I may have goofed in my parts choices in so far as the compression may be through the roof, and I hope you can put me right.

I have so far, a Crane 689521 cam, grind number HR-222/339, Trickflow 240 heads (78cc chambers), a set of SRP 231521 pistons that are -6cc with 1.865 compression height, bore 4.350 & stroke 4.150. Crank and rods are all Molnar items (440-4150MC6F & DH6760VTB8A respectively).

The block has not been machined yet so I dont know what effect decking etc will have on things.

How well do you think the above will work together? Someone advised that I need to ‘bleed off some compression’ with a hairier cam, but I don’t really know what that even means! I was going to use 1:5 rockers, but perhaps 1:6 would accomplish this bleed effect?

If relevant, I am going to run the 600hp Fitech on a Performer manifold (No room for anything taller).

All advice gratefully received!
Click to expand...
assuming a deck clearanace of .06 and your piston combo, if you run a .040 thick compressed gasket, you compression ratio is 11.5:1

now bump that to a .098 thick gasket and it drops your compression ratio to 10.15:1 with the same deck clearance and pistons. I think your cam will be just fine, just use the deck clearance and gasket thickness to tune the CR where you want it now.
 
Do not panic yet, cam is kinda small on duration. Get conn. Rod length , block is around 10.73, run compression numbers
 
I am going to run premium pump fuel which is 99/100RON here in England, equivalent to your 93/94MON I think, plus an octane booster which will work out to about 97/98MON.
As regards thicker gaskets, does that not have a detrimental effect on quench? Am I right in thinking that in itself can cause pinking / detonation issues?

Rod length by the way is 6.760”
 
Don't read anything into what you "think" the compression will be until you get your deck height.... It's a math equation and you need all the numbers....

JW
 
SLOPAR72 said:
Don't read anything into what you "think" the compression will be until you get your deck height.... It's a math equation and you need all the numbers....

JW
Click to expand...
This x1000^^
 
That's not a 440 anymore, but rather a 493, and with a 222 cam, suitable to be a tractor-puller. what are you going to install this into?
I read BB, A-body tech, but surely not a streeter
 
AJ/FormS said:
That's not a 440 anymore, but rather a 493, and with a 222 cam, suitable to be a tractor-puller. what are you going to install this into?
I read BB, A-body tech, but surely not a streeter
Click to expand...

Hmm. That’s why I’m worried! It is to be a road car, actually not a Mopar but a Jensen Interceptor.
 
Yeah, figure out the Compression ratio first... At 11:1 with that cam installed in the factory position (5 degrees advanced) dynamic compression should be about 8.4:1 and about 220 PSI, too high really for pump gas. IF you back it down and install it straight up you will be down to 8:1 dynamic and 200 PSI. This is still a bit on the edge, the tune will have to be really good. it should idle with 19" of vacuum though so nice and smooth. I was kind of in the same boat with my build (383 though, I had bought the one smaller cam). I ended up ordering a custom cam that should work better and still have the desired running characteristics I wanted, smooth, stock like idle and more power than stock. I ordered mine form Jones Cams.

Garth

PS the Jenson is super cool BTW...
 
dartgarth said:
Yeah, figure out the Compression ratio first... At 11:1 with that cam installed in the factory position (5 degrees advanced) dynamic compression should be about 8.4:1 and about 220 PSI, too high really for pump gas. IF you back it down and install it straight up you will be down to 8:1 dynamic and 200 PSI. This is still a bit on the edge, the tune will have to be really good. it should idle with 19" of vacuum though so nice and smooth. I was kind of in the same boat with my build (383 though, I had bought the one smaller cam). I ended up ordering a custom cam that should work better and still have the desired running characteristics I wanted, smooth, stock like idle and more power than stock. I ordered mine form Jones Cams.

Garth

PS the Jenson is super cool BTW...
Click to expand...

Garth,
This is the sort of tech that I struggle with! What’s the effect of having the cam straight up instead of advanced in the way the car will drive? Is this a way of ‘bleeding off’ compression as was mentioned to me by an engine builder over here? Your 383 was fitted to the mk2 interceptors and reckoned to be the engine to have!

The Jensen is bloody cool, but it tries my patience! Handbuilt cars......
 
I'll explain as best I can... Your cam is 284 degrees of duration (gross duration) so the intake valve starts to open 35 degrees of crankshaft rotation before TDC ( top dead centre), this is known as IVO (intake valve opening). Your Intake valve closes 69 degrees after BDC (bottom dead centre ) this is known as IVC on the cam card. So on the compression stroke the piston has already traveled 69 degrees of crankshaft rotation before it even starts to make compression. 35+180+69=284. Now your cam has a LSA (lobe sepperation angle) of 112 degrees, in other word the lobes are 112 degrees apart from centerline to centerline (most of the time this is also the max lift of the lobes, but this is not always the case with super fancy custom cams....) You cam, and most cams have "advance ground in" which means when installed @ 0 degrees they already advanced. In your case 5 degrees. So you subtract 5 from the intake 112 to get 107 and add 5 to exhaust 112 to get 117. If you are looking at the end of the cam and have the first to lobes lined up equally they are essentially rotating the cam 5 degrees for you. if you install the cam at true 0 you will be retarding it 5 degrees so the intake will open later at 30 degrees BTDC and close later at 74 degrees ATDC. 30+180+74=284. The engine therefore has less degrees of crankshaft rotation to build compression 180-69=111 degrees of crank rotation for the advanced setting vs 180-74= 106 degrees of crank rotation for the true 0 install. This is part of how you figure out dynamic compression. As for effects, typically advancing the cam helps with low end torque and retarding it increases top end power. There is lots more to it of course.... Some good reading here.

Valve Timing Events and the Order of Importance - Engine Builder Magazine

Lots of things go into choosing a cam. Engine specs are just part of it. Weight of the car, rear end ratio, tire size, transmission, torque converter, all play a roll. Also of course the expected outcome, how much power do you want? and when? do you want a smooth idle and vacuum for power brakes or accessories? Is a little rump at idle good? is a lots better?

I built my engine around having a smooth, stock like idle while maximizing power within those parameters, I could run a much bigger cam but I don't want to, some people would have for sure.
 
dartgarth said:
I'll explain as best I can... Your cam is 284 degrees of duration (gross duration) so the intake valve starts to open 35 degrees of crankshaft rotation before TDC ( top dead centre), this is known as IVO (intake valve opening). Your Intake valve closes 69 degrees after BDC (bottom dead centre ) this is known as IVC on the cam card. So on the compression stroke the piston has already traveled 69 degrees of crankshaft rotation before it even starts to make compression. 35+180+69=284. Now your cam has a LSA (lobe sepperation angle) of 112 degrees, in other word the lobes are 112 degrees apart from centerline to centerline (most of the time this is also the max lift of the lobes, but this is not always the case with super fancy custom cams....) You cam, and most cams have "advance ground in" which means when installed @ 0 degrees they already advanced. In your case 5 degrees. So you subtract 5 from the intake 112 to get 107 and add 5 to exhaust 112 to get 117. If you are looking at the end of the cam and have the first to lobes lined up equally they are essentially rotating the cam 5 degrees for you. if you install the cam at true 0 you will be retarding it 5 degrees so the intake will open later at 30 degrees BTDC and close later at 74 degrees ATDC. 30+180+74=284. The engine therefore has less degrees of crankshaft rotation to build compression 180-69=111 degrees of crank rotation for the advanced setting vs 180-74= 106 degrees of crank rotation for the true 0 install. This is part of how you figure out dynamic compression. As for effects, typically advancing the cam helps with low end torque and retarding it increases top end power. There is lots more to it of course.... Some good reading here.

Valve Timing Events and the Order of Importance - Engine Builder Magazine

Lots of things go into choosing a cam. Engine specs are just part of it. Weight of the car, rear end ratio, tire size, transmission, torque converter, all play a roll. Also of course the expected outcome, how much power do you want? and when? do you want a smooth idle and vacuum for power brakes or accessories? Is a little rump at idle good? is a lots better?

I built my engine around having a smooth, stock like idle while maximizing power within those parameters, I could run a much bigger cam but I don't want to, some people would have for sure.
Click to expand...
Garth,
That’s a hugely helpful description, thank you for that and the link too. I really was wanting what you described with your engine, i.e. smooth idle and lots of vacuum plus plenty of grunt.
 
Get all the numbers and figure out the compression, ( I can help you with that too), then we can see how that cam will work or find one that will work better for you.

Garth
 
Garth,

At last the bare block is with the builder! He has measured all the clearances, crack tested and sonic tested everything and declared it sound. As soon as I know all the final numbers I will post again.

One thing that came up and slightly surprised me was, even though we’re going from main cap bolts to studs, that after measuring everything no line hone is needed.
Everything I’ve read says that honing is required after converting to studs, but I guess if everything’s torqued up and all the holes are still concentric then all is well? Does that sound right?
The studs came as part of a Hughes girdle kit which he is not keen on using! Not sure I completely get his reluctance, but I’ve posted about that here:
Hughes main stud girdle - yes or no
I’d welcome your thoughts!
 
Rather than use what you have for a deck height as measured, just calculate off the 10.720 blueprint height and have the builder square deck it to there.
IMO you have the wrong pistons. Source a set that has a big dish, then set the quench at less than .040 via the gasket choice. There's no reason you have to have a static anywhere over 9.5:1 for this build. Build it to run on your low grade - you'll enjoy the final product more and not have to dick with the tune to make it work.
 
Personally I would line hone, just to make sure. Usually when changing to studs or even APR rod bolts it is wise to machine everything up true. This is especially true if the new bolt/stud is torqued to a higher spec (APR rod bolts). On the girdle, I don't think it's necessary, but you have it and it definitely will not hurt to put it in.

Garth
 
[QUOTE="moper, post: 1972126498, member: 521"%]
IMO you have the wrong pistons. Source a set that has a big dish, then set the quench at less than .040 . There's no reason you have to have a static anywhere over 9.5:1 for this build. Build it to run on your low grade - you'll enjoy the final product more and not have to dick with the tune to make it work.[/QUOTE]

As I’m using aluminium closed chamber heads (Trickflow 240’s), does this mean I get the builder to work to 10.5:1 static due to what I understand to be the one point of compression difference between iron and al heads? Otherwise I will essentially be no better off than the standard 8ish to 1 won’t I?
 
Material does not change mechanical compression ratios. You can ignore the "subtract one compression point for aluminum". While there are some thermal differences with running aluminum the effect is less dramatic than that. For purposes of camshaft choice use the calculated static compression ratio. The TF240s have a 78cc chamber according to what I've read (full disclosure - I haven't held a set personally). The problem is the flat top pistons with only 6ccs of valve relief and using the KB calculator that yields a static ratio of 11.8:1. Too high IMO and not needed for your intended use. What you need is SRP p/n 345809. Those are a 24cc dish and would give you 10:1 with the same Felpro 1009 gasket.

Edit - you're building an RB based stroker. You will not be disappointed. This adjustment simply makes the end result easier to live with.
 
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Thanks Moper,
That’s cleared up my misunderstanding. I was just concerned that the motor would be a bit flat (Relatively speaking...!). Luckily, my Crane 689521 cam is apparently a good choice for my application according to my engine builder, with more appropriate pistons. If he agrees, then those -24 SRP would be my first choice, seem like a better (cheaper....) bet than a custom set he was pushing me towards!
 
I normally use the 20-24cc dished pistons in my builds. I have the mains honed, and the decks square-decked to give me a piston up out of the deck by .005". I use the chamber size to set the static ratio and that can vary by intended use. The idea is to get the pistons within .035" if the head with the 1009 gasket with the static I want. That's how I do it - but others go about it differently. I love the cam choice. I've used the HR LA version before, and the B/RB flat tappet hydraulic version at least 5-6 times.
 
A quick update on progress, and a belated thank you for everyone’s valuable advice!
We have arrived at a final spec, with -24cc pistons, of 9.7:1 compression which will run nicely on our pump fuel over here. The engine is not quite ready for the dyno, but the figures show 590hp and similar torque, I think max rpms won’t be much different to standard.

6AF22AA7-5965-4F6D-80BF-C54C52CA73C3.jpeg
B484EAFE-B46C-49B3-8051-FAB24FFC02EB.jpeg


I do have one issue that I’d love some input on, and that concerns the head gaskets, or more specifically the three little horizontal slots in them.
Now, in the Jensen the engine is a VERY tight fit with pretty much no room around it in the engine bay, consequently they are notorious for overheating in traffic, of which there is a lot in our crowded little island! A lot of guys open up these slots from the current .720 x .118 to the old ‘pre-emissions’ spec of .940 x .455. See below:
FF6028D4-0E11-473A-BC0B-BDCA1BED0694.jpeg

D9EA14A4-9019-4B2C-80B3-E9155800970D.jpeg

Should I ask my builder to carry out this mod, or at least order custom gaskets with the larger slot size?
It’s a bit of a bugger, because he’s fitted the heads, but better to get this sorted now rather than when the motor is back in the car!
 
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