BBC cam question up grade XR288HR
09-14-2017, 01:05 AM
#13
Charter Member # 55
Charter Member
Crane 731 will be good to about 5500 rpms on a 454. https://www.summitracing.com/parts/crn-168731
If you want more, go with a 741 or 525EFI cam https://www.summitracing.com/parts/crn-168741
If you want more, go with a 741 or 525EFI cam https://www.summitracing.com/parts/crn-168741
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09-14-2017, 06:07 AM
#16
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Lets say you had 3 cams. All were 236/244 duration, same lobe family, same lift, same 4* advance ground into them. Only difference, was their LSA's. The 114 may peak at 6000, the 112 at 5850, and the 110 at 5700 rpm.
The 110 LSA version of that cam, will have the most overlap. However, the 114 version, will have the latest closing intake valve.
The 110 LSA version of that cam, will have the most overlap. However, the 114 version, will have the latest closing intake valve.
09-14-2017, 06:10 AM
#17
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You can can call Lunati, they will grind you any of their cams on a Billet core. I wanna say the cost is around 400 for the billet stick with iron gear. Same for Howards, comp, etc. The profiles are in their systems, its just a matter of core selection. I personally would spend the few bucks more for the billet camshaft.
09-14-2017, 09:35 AM
#18
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Is duration related also to cubic inches when you looking at cam choices? I be read the advertisement in Summit/Jegs/Teague and they all have CID and CR ranges. I've noticed more duration seems to correlate larger CID to an extent. Cams are a black art to me so flame on
I spoke with Lunati the other day and that was their pick for my iron headed 565s. Called around a few others and similar specs lsa may differ between 112-114 and duration/lift moved a small amounts. All except Crane who recommended me to keep my 741 cams in the engines. I even spoke to a friend who had Bob M spec his top ends for his 540s years ago (afr heads, etc) and his cam specs were very close to all the recommendations I had received. Only real reason I'm looking as my engines run out of steam around 5k-5200 no matter how I prop the boat.
I spoke with Lunati the other day and that was their pick for my iron headed 565s. Called around a few others and similar specs lsa may differ between 112-114 and duration/lift moved a small amounts. All except Crane who recommended me to keep my 741 cams in the engines. I even spoke to a friend who had Bob M spec his top ends for his 540s years ago (afr heads, etc) and his cam specs were very close to all the recommendations I had received. Only real reason I'm looking as my engines run out of steam around 5k-5200 no matter how I prop the boat.
09-14-2017, 09:53 AM
#19
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Chris, duration is directly related to the rpm capability of the engine. It does not matter if it's 8:1 compression, or 10:1 , or 12:1. The engine needs xxx amount of duration to reach a specific engine speed
Cubic inch absolutely matters. Stroke change is the biggest difference , more so than bore size.
In my opinion, the 741/525efi cam, is simply too small for a 565ci. At least one that is trying to spin say, 5700-6000 range. Heck, mercury uses that cam in the 525efi. That's a 502ci that spins 5000-5400 range. Can't expect a 565 to make power higher than that , with same camshaft. We are pretty limited with valve lift in marine engines, so when lift is limited, duration is even further needed to reach the peak rpm goals.
The problem I've seen with cam companies , is often they are extremely conservative with duration. The water reversion class has been taught to them, and once they hear marine, immediately it's wide lobe separation and short durations. Most aren't familiar with fully jacketed tailpipe options, or say, a pair of 565s going in a 35 fountain or similar. Not every boat is a 30ft single engine deal that weighs 10k lbs.
On your builds Chris, i firmly believe a cam swap , the new parveys designed manifolds to replace the old gil style, and you'll see the engines wake up from 3500 to wot. They will be uncorked so to speak.
My cams are similar to the 525efi cam. With a blower on top, installed straight up, there were fizzing out at 6000ish. That's in a 468 with a blower. In an NA 565, not surprised they aren't pulling so well above 5200
Cubic inch absolutely matters. Stroke change is the biggest difference , more so than bore size.
In my opinion, the 741/525efi cam, is simply too small for a 565ci. At least one that is trying to spin say, 5700-6000 range. Heck, mercury uses that cam in the 525efi. That's a 502ci that spins 5000-5400 range. Can't expect a 565 to make power higher than that , with same camshaft. We are pretty limited with valve lift in marine engines, so when lift is limited, duration is even further needed to reach the peak rpm goals.
The problem I've seen with cam companies , is often they are extremely conservative with duration. The water reversion class has been taught to them, and once they hear marine, immediately it's wide lobe separation and short durations. Most aren't familiar with fully jacketed tailpipe options, or say, a pair of 565s going in a 35 fountain or similar. Not every boat is a 30ft single engine deal that weighs 10k lbs.
On your builds Chris, i firmly believe a cam swap , the new parveys designed manifolds to replace the old gil style, and you'll see the engines wake up from 3500 to wot. They will be uncorked so to speak.
My cams are similar to the 525efi cam. With a blower on top, installed straight up, there were fizzing out at 6000ish. That's in a 468 with a blower. In an NA 565, not surprised they aren't pulling so well above 5200
