Dart 8.1 Gen 7 Iron Heads
08-29-2013 | 04:53 PM
#151
Platinum Member
Joined: Jul 2008
Posts: 931
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From: Little River SC
I completed a 496 with a Whipple 3.3 for an Eliminator cat deck boat.
Stock 8.1 block
4.375 crank
6.700 rods
4.255 bore with CP pistons 8.1 CR
Dart Iron heads 11/32 valves, recommended valve sizes from Dart spec sheet, reworked chambers of edges and humps, ended up with 114 cc chambers.
@ 4100 780 torque, 5800 765 hp with 5 # boost.
If you, use the recommended valve lengths and us the larger spring pocket, with the adjustable guide plates and the scorpion extreme rockers, all will fit under the stock valve covers. Just be careful; that valve job is not sunk or you would have to shorten valve tip length.
The only thing I do not care for is the 8.1 main bearings, the upper is a one off, the lower is the same as a BBC.
Crane makes a very nice double row timing chain, with billet top gear. Note; cam sensor must match as I have been told; but had no issue.
We have developed an issue with the crank reluctor wheel in which was resolved with a closer air gap on the pick-up, but now has returned. Pick-up is showing signs of a sharp edge on crank pick up, we are going to pull engine and crank, something has happened with reluctor. We are replacing crank with a 4340 from Scat, I am told by sales they are in production.
My customer and myself are very pleased with the outcome, out side of resolving the reluctor wheel issue.
Thanks, also to Dustin @ Whipple for his calibrations and help on this project.
Stock 8.1 block
4.375 crank
6.700 rods
4.255 bore with CP pistons 8.1 CR
Dart Iron heads 11/32 valves, recommended valve sizes from Dart spec sheet, reworked chambers of edges and humps, ended up with 114 cc chambers.
@ 4100 780 torque, 5800 765 hp with 5 # boost.
If you, use the recommended valve lengths and us the larger spring pocket, with the adjustable guide plates and the scorpion extreme rockers, all will fit under the stock valve covers. Just be careful; that valve job is not sunk or you would have to shorten valve tip length.
The only thing I do not care for is the 8.1 main bearings, the upper is a one off, the lower is the same as a BBC.
Crane makes a very nice double row timing chain, with billet top gear. Note; cam sensor must match as I have been told; but had no issue.
We have developed an issue with the crank reluctor wheel in which was resolved with a closer air gap on the pick-up, but now has returned. Pick-up is showing signs of a sharp edge on crank pick up, we are going to pull engine and crank, something has happened with reluctor. We are replacing crank with a 4340 from Scat, I am told by sales they are in production.
My customer and myself are very pleased with the outcome, out side of resolving the reluctor wheel issue.
Thanks, also to Dustin @ Whipple for his calibrations and help on this project.
09-01-2013 | 04:46 PM
#154
Gold Member
Joined: Jul 2008
Posts: 3,748
Likes: 869
From: Delray Beach, FL
Personally, I ran a dozen scenarios before I built mine. The Dart heads really arent a great combo once you consider that you can run a point or so more compression with aluminum heads. You can make more power so the $ investment makes sense. FWIW when I imploded a piston the head on that side didnt make it, the intake walls were too thin (they were CNC ported stock heads)
Rage do you sit and wait for 496 threads to come up? LOL I think you may have done more R&D than Raylar...
I am glad their are a few nutty professors still fooling with the combo. I am still a fan of the Raylar heads. A great combo would be their stroker crank and the Dart block with 4.5 bore(or more). Would be a great N/A fuel injected 572 cubic inch combo.
Rage do you sit and wait for 496 threads to come up? LOL I think you may have done more R&D than Raylar...
I am glad their are a few nutty professors still fooling with the combo. I am still a fan of the Raylar heads. A great combo would be their stroker crank and the Dart block with 4.5 bore(or more). Would be a great N/A fuel injected 572 cubic inch combo.
09-02-2013 | 01:59 PM
#155
Thread Starter
Gold Member
Joined: Sep 2005
Posts: 1,987
Likes: 0
From: Missouri
Yep, I am just a nutty lurker waiting for the odd 496 post.
If I were starting from scratch the Raylar heads and the Holley EFI would be at the top of my list. If I was really starting from scratch the bigger the ci the better but not with the 496 block. I am basically done with my engine. I am at the comfortable MPH limit of my hull. I do need to add a dedicated external crankcase oil cooler for extended WOT running and final prop dial in. If some thing comes along to improve the Raylar intake manifold flow that would be of interest since its MAP does drop at the higher rpms seemingly indicating it can not keep up with the heads/engine. Not likely though.
My interest regarding the Raylar heads is idle curiosity as to do the Raylar CNC Extreme heads get the additional cfm with or without bigger valves and if so what size. It is amazing to me the cfm the standard Raylar heads get from the stock 496 valve sizes of 2.19 intake and 1.72 exhaust. Another curiosity I have is what happened to the standard Raylar heads to get the increase in cfm from that posted originally on the Raylar web site. I have assumed the original heads were as cast and the later numbers were from CNC porting upgrade.
If my current heads need to be replaced at some point, they have some issues, since I am cheap I will likely want to replace just the bare head and reuse all valve train components except maybe push rods if the lengths needed changes. There in my continued interest in the Dart heads as an option to another set of the ported HP3 heads. The Darts would need to be ported to the bigger intake valves as well. One of my risks with the Darts is that more ECU fuel table work could be required which I would like to avoid for the PCM555. Also my bed rock requirement of 87 octane comes into play.
The report herein from Crayolacrazy that the Dart heads with the same bigger valves as his Tyler Crocket CNC'd heads required an additional half pound of boost to make the same ~810HP is disconcerting. Of course the T Crocket heads were ported and the Darts were not and he is running 0.621 lift and I am not quite 0.6. Some flow numbers I got from Tyler many years ago on his ported heads were a little lower than mine. I would sure like to get flow numbers from Crayolacrazy on his Dart heads if available.
How are those HO600's working for you?
OK back to lurking.
If I were starting from scratch the Raylar heads and the Holley EFI would be at the top of my list. If I was really starting from scratch the bigger the ci the better but not with the 496 block. I am basically done with my engine. I am at the comfortable MPH limit of my hull. I do need to add a dedicated external crankcase oil cooler for extended WOT running and final prop dial in. If some thing comes along to improve the Raylar intake manifold flow that would be of interest since its MAP does drop at the higher rpms seemingly indicating it can not keep up with the heads/engine. Not likely though.
My interest regarding the Raylar heads is idle curiosity as to do the Raylar CNC Extreme heads get the additional cfm with or without bigger valves and if so what size. It is amazing to me the cfm the standard Raylar heads get from the stock 496 valve sizes of 2.19 intake and 1.72 exhaust. Another curiosity I have is what happened to the standard Raylar heads to get the increase in cfm from that posted originally on the Raylar web site. I have assumed the original heads were as cast and the later numbers were from CNC porting upgrade.
If my current heads need to be replaced at some point, they have some issues, since I am cheap I will likely want to replace just the bare head and reuse all valve train components except maybe push rods if the lengths needed changes. There in my continued interest in the Dart heads as an option to another set of the ported HP3 heads. The Darts would need to be ported to the bigger intake valves as well. One of my risks with the Darts is that more ECU fuel table work could be required which I would like to avoid for the PCM555. Also my bed rock requirement of 87 octane comes into play.
The report herein from Crayolacrazy that the Dart heads with the same bigger valves as his Tyler Crocket CNC'd heads required an additional half pound of boost to make the same ~810HP is disconcerting. Of course the T Crocket heads were ported and the Darts were not and he is running 0.621 lift and I am not quite 0.6. Some flow numbers I got from Tyler many years ago on his ported heads were a little lower than mine. I would sure like to get flow numbers from Crayolacrazy on his Dart heads if available.
How are those HO600's working for you?
OK back to lurking.
Last edited by Rage; 09-02-2013 at 02:13 PM.
09-02-2013 | 03:11 PM
#156
Gold Member
Joined: Jul 2008
Posts: 3,748
Likes: 869
From: Delray Beach, FL
They are good! I have a few things "i wish" I would have done. Wish I stroked them, Wish I used Dart blocks with bigger bores, Wish I used tubular style exhaust and the final, I wish I had IMCO SCX's! Otherwise they have been turn key and never had an issue. I have drive issues at times... I rarely even run them at WOT and already have about 100 hours on them.
Your 87 octane brings up another question. I have never had an issue and feel like I short changed myself on compression. I should have wiped .030 off the heads when I had the chance. Also, I think Raylar has yet another cam the BP-209, I wouldnt mind trying it as well.
Do you think you are close to a detonation issue with your compression?
Your 87 octane brings up another question. I have never had an issue and feel like I short changed myself on compression. I should have wiped .030 off the heads when I had the chance. Also, I think Raylar has yet another cam the BP-209, I wouldnt mind trying it as well.
Do you think you are close to a detonation issue with your compression?
09-02-2013 | 09:21 PM
#157
Thread Starter
Gold Member
Joined: Sep 2005
Posts: 1,987
Likes: 0
From: Missouri
Sounds like you know exactly what you are going to do for your next engine upgrade.
No, I do not think so. That is because I copied the HP3 Gen II race engine specification to the letter. It was designed to run 100 hours WOT w/o failure on 87 octane. I still wish my PCM555 ECU reported detonation events like the GM MEFI ECU does. I have had the heads off a number of times and zero evidence of any detonation as well. The cylinder compression is a low 150 psi. The stock 496 is 175 psi.
All you probably already know, but there is published data that shows relationship between dynamic compression vs octane vs detonation. You could crunch your engine numbers with and w/o that 0.030" head mill and see for yourself theoretically at least how close you are to detonation.
No, I do not think so. That is because I copied the HP3 Gen II race engine specification to the letter. It was designed to run 100 hours WOT w/o failure on 87 octane. I still wish my PCM555 ECU reported detonation events like the GM MEFI ECU does. I have had the heads off a number of times and zero evidence of any detonation as well. The cylinder compression is a low 150 psi. The stock 496 is 175 psi.
All you probably already know, but there is published data that shows relationship between dynamic compression vs octane vs detonation. You could crunch your engine numbers with and w/o that 0.030" head mill and see for yourself theoretically at least how close you are to detonation.
Last edited by Rage; 09-03-2013 at 10:23 AM.
09-03-2013 | 01:34 PM
#158
Registered
Joined: Jan 2004
Posts: 2,777
Likes: 12
From: San Diego, California
I was going to post the cylinder head flow numbers, but Hog beat me to it!
The Dart cylinder heads are a great solution for people limited by their racing class to cast iron heads or for those working on a budget. They weigh a ton and you can't throw boost at em, but if you're running NA and you want more power - they are a solid solution.
If you're planning to put a cam in your boat on stock heads or dart's iron heads, we recommend running a high lift spring kit like the one on our camshaft / valvetrain page:
http://www.raylarengineering.com/cam...alvetrain.html
Speaking of cams - yes we do have a few more we offer now! The BP-209 Kieth mentioned is our all-out race or stroker camshaft. Its part of our high lift series of cams, which require our forged flycut pistons and works particularly well in all-out stroker applications and 4.5 bore blocks. The two other new cams are more for street use - a low boost / low lift turbo cam for stock pistons and a high boost / high lift turbo cam for applications running our forged components.
Our heads use 2.19 / 1.72 valves with 11/32 valve stems for additional air flow in our Big Power aluminum cylinder heads. More information on our heads can be found here: http://www.raylarengineering.com/cylinder_head.html
If you are looking for 496 marine specific information, we now have a couple pages geared in that direction as well:
Build your own Raylar HO motor:
http://www.raylarengineering.com/packages.html
Marine Engine Kits:
http://www.raylarengineering.com/496...nce-parts.html
We are making a serious effort to be as transparent as possible with our new web site. If you have any questions, I will try to answer them here as well as on the new web site for future power boat enthusiasts.
The Dart cylinder heads are a great solution for people limited by their racing class to cast iron heads or for those working on a budget. They weigh a ton and you can't throw boost at em, but if you're running NA and you want more power - they are a solid solution.
If you're planning to put a cam in your boat on stock heads or dart's iron heads, we recommend running a high lift spring kit like the one on our camshaft / valvetrain page:
http://www.raylarengineering.com/cam...alvetrain.html
Speaking of cams - yes we do have a few more we offer now! The BP-209 Kieth mentioned is our all-out race or stroker camshaft. Its part of our high lift series of cams, which require our forged flycut pistons and works particularly well in all-out stroker applications and 4.5 bore blocks. The two other new cams are more for street use - a low boost / low lift turbo cam for stock pistons and a high boost / high lift turbo cam for applications running our forged components.
Our heads use 2.19 / 1.72 valves with 11/32 valve stems for additional air flow in our Big Power aluminum cylinder heads. More information on our heads can be found here: http://www.raylarengineering.com/cylinder_head.html
If you are looking for 496 marine specific information, we now have a couple pages geared in that direction as well:
Build your own Raylar HO motor:
http://www.raylarengineering.com/packages.html
Marine Engine Kits:
http://www.raylarengineering.com/496...nce-parts.html
We are making a serious effort to be as transparent as possible with our new web site. If you have any questions, I will try to answer them here as well as on the new web site for future power boat enthusiasts.
Last edited by Raylar; 09-03-2013 at 02:13 PM.
09-03-2013 | 04:19 PM
#159
Thread Starter
Gold Member
Joined: Sep 2005
Posts: 1,987
Likes: 0
From: Missouri
Thank you Larry. Your helpful tone, rather than the somewhat combative tone of years past, is truly refreshing and much appreciated!
I have your complete forged stroker kit and Cool Cap intake manifold on my engine and am very satisfied with their performance.
Just to confirm, both the Raylar aluminum CNC Extreme heads and the standard Raylar aluminum Heads use the same 2.19 intake and 1.72 exhaust valves?
I have your complete forged stroker kit and Cool Cap intake manifold on my engine and am very satisfied with their performance.
Just to confirm, both the Raylar aluminum CNC Extreme heads and the standard Raylar aluminum Heads use the same 2.19 intake and 1.72 exhaust valves?
09-03-2013 | 06:32 PM
#160
Registered
Joined: Jan 2003
Posts: 853
Likes: 0
From: Pgh. Pa.
no. one you cant get Tylers heads any more thats why I bought darts bear heads they are available ,I would love to own raylars heads bear ill put my own valves in them. butt.If i make any more power ILL need drives . also pcm 555 game .Im running 8.5 lbs boost.
Last edited by crayolacrazy; 09-03-2013 at 06:42 PM.
