Camshaft for quad twin Webers/Dellorto's
Hi there
I am from The Netherlands and new to the British V8 community, but have seen the various posts of Dan Jones on the availability and types of camshaft for the Rover/Buick V8 engine as well as articles of David Vizard on cam basics. At prensent I am running a Crane 256 solid cam (256/266 @ 0.050"- advertised 292/302, LSA 108, lift 0.546/0.564" on a Wildcat Rover V8 with 352 CID (5.8 ltrs) with Wildcat cylinderheads (inlet valve 1.85" and outlet valve 1.55") quadrupple Dellorto DRLA48 (almost identical to Weber IDF48) on single independent inlet stacks. Engine is capable of 7000rpm+ but is mainly running between 1000 and 4000 rpm when driving normally. The car only weights 2000 pounds or 1000kgs. I have to renew the Crane 256 as one of the lobes is gone, but I believe Crane is no longer producing this camshaft so will need a replacement and after reading the various posts it would be interesting to see if there would be a more suitable camshaft for this particular engine. According the Weber carb experts this setup should have a camshaft with a wide LSA (minimal 110 and preferable 112-114 LSA) and minimal overlap to avoid "reversion"...which are pulses from the exhaust stroke while the intake valve is still open, that have nowhere to go but up into the carburetor. This disturbs high rpm airflow and causes the engine to think it's too lean at high rpm’s. Without a plenum, the flow is pulsed backward up into the carburetors because there is noplace else for the reversion pulse to go. On the other hand you want to have to have high lift and short advertised duration to get power. I notied some interesting solid cams mentioned by Dan Jones (F286/F288/F290/F294) but the LSA was not mentioned. Maybe there are some interesting hydaulic cams as well which could fit, as the 6500 rpm or higher is only used when there is an occational Porsche to beat at the traffic lights. Are hydraulic cams lasting longer as they are less dependent on oil splash at lower rpm ? In any cash you don't have to check the valve lash when going hydraulic.... I have mailed Woody Cooper at the Wedgeshop as well to see his views on this setup Pleased to hear your views ! Cheers Rik |
roverman Art Gertz Winchester, CA. (3188 posts) Registered: 04/24/2009 11:02AM Main British Car: 74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L |
Re: Camshaft for quad twin Webers/Dellorto's
Rik, Welcome to Brithish V8, I hope Fred Key will chime in with build advice. Sounds like an expensive engine,that deserves the best in cam/ valvetrain choices. IMHO, your current flat tappet cam is limiting the potential of this build,(small base circle and too slow of ramp speeds). With 7k rpm as a max power limit, I suspect a strong hydralic roller cam, should meet your objectives. Woody should be a good source for this. Dyno max with "Dan Jones", would help refine the best combination, ie. type of hedders/sizes, perhaps "shear plates" under you carbs. or over the venturi stacks to reduce reversion at overlap. Anti reversion can be augmented at the exhaust ports, with proper port mismatch or "cones". It would help many of us, to hear the complete story of your enging build/ British car ? Good Luck, roverman.
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DiDueColpi Fred Key West coast - Canada (1365 posts) Registered: 05/14/2010 03:06AM Main British Car: I really thought that I'd be an action figure by now! |
Re: Camshaft for quad twin Webers/Dellorto's
Hey Rik,
Welcome as well. We're going to need some more info before any meaningful recommendations can be made. As much info as you can, from velocity stack size, venturi size, intake volume, port flow, bore and stroke, rocker ratio, rod length, header and exhaust size to trans and diffy ratios. A realistic 7000 rpm limit on an engine like this will cause great difficulty pulling well from 1000 rpm. So a careful evaluation on your driving style can let someone recommend something that might be more suitable. I suspect that there is more useful performance to be had than your old cam was giving. Cheers Fred |
Re: Camshaft for quad twin Webers/Dellorto's
Hi Art & Fred,
Thanks for your answers and herewith some more info on the engine build (and car...) Wildcat Engineering V8 block (based on Rover V8) CID : 352 cubic inch (5.8 ltrs) bore 4.000” (wet T-liners) stroke 3.500” (forged steel crank) conrods 5.700” Wildcat Corrillo style EN24 - beam pistons 4.000” Keith Black 141 hypereutectic (1.490”) CR 11.5:1 Cylinderheads Wildcat stage I (designed by Ian Richardson of Wildcat Engineering, UK) cylinderhead inlet port 1.050" x 2.000" inlet valve 1.850" 47mm lift flow 0.185 106,00 0.277 150,60 0.360 185,70 0.462 216,00 0.540 231,00 0.647 237,60 cylinder outlet port 1.200" x 1.400" oulet valve 1.550" 39.5mm lift flow 0,155 72,90 0.232 107,60 0.310 153,00 0.388 191,50 0.465 191,50 0.542 191,50 Rockers 1:6 ratio Scorpion roller rockers Pushrods Crane hollow rods Valve springs Single with damper, clearance for lift of .564” about 0.05” between coils Sorry, no idea yet what the seat and open pressure is, but will check soon.... Exhaust Primery 1.600” diameter with each cylinder a length of about 7.000” inch Secondary 2.365” diameter, two pieces with each a length of 5 feet Fuel system & Ignition & oil system Carburettors 4 x 2 downdraft Dellorto DRLA 48 (identical to Weber IDF 48) with 45mm venturi's on single independent inlet runners (diameter 2.000" ported to exact 1.050" by 2.000") length about 3.5" each Ignition Mallory distributor (optical) with MSD 6AL and Accel supercoil Oilsystem Drysump with 3 stage Aviaid pump, oil cooler and accusump (6 quarts) Differential is Salisbury 3.54 Gearbox is a Borg Warner T5 WC, gear ratio is R 2.76 1st 2.95 2nd 1.94 3rd 1.34 4th 1.00 5th 0.80 This is all placed in a AC Cobra (British reproduction) with a weight of 2000 pounds (1000 kgs) and I own it now 20 years. Before the Wildcat engine I build and installed a tuned 4.6 RV8 crossbolted engine.and played arround with some other 4.6 RV8 engines, 4.5 RV8 engines and 3.5 RV8 engines. The car is mainly used on the road with RPM range during normal driving 1000-5000 rpm and some traffic light sprints up to 6500 rpm (crank and block are save to 7000 even 8000 rpm) Honestly, during normal driving engine is running between 1500 to 3500 rpm.... (2500 rpm cruising at higway @ 70 mph) so it seems more important to concentrate on the driving range then on topend horsepower. Racing days are over and its now more fun to pull in 3rd gear from 50 mph to 100mph to outrun some modern Porsches or other fast cars. Cheers Rik |
Dan Jones Dan Jones St. Louis, Missouri (280 posts) Registered: 07/21/2008 03:32PM Main British Car: 1980 Triumph TR8 3.5L Rover V8 |
Re: Camshaft for quad twin Webers/Dellorto's
> I have to renew the Crane 256 as one of the lobes is gone, but I believe Crane is no longer producing
> this camshaft so will need a replacement If you want to stick with the Crane 256, I happen to have a new one available that came in a group of parts I purchased a while ago. However, it sounds as if you are interested in perhaps moving the powerband down and running a hydraulic roller. If so, I can model the engine in Dynomation and run a cam optimization. Woody Cooper of the Wedge Shop has hydraulic roller lifters and cam cores available for the Rover V8 and I know the lobe limitations of those cam cores. BTW, we're getting ready to build and dyno test an engine with one of those hydraulic roller cams that I designed for a friend's MGB GT V8 project. > Are hydraulic cams lasting longer as they are less dependent on oil splash at lower rpm ? Hydraulic roller cams last much longer than flat tappet cams. The hydraulic roller cam cores are usually steel (though some HR cam cores are austemepred ductile iron) while flat tappet cam cores which are made of cast iron and the roller lifters roll rather than slide over the lobe so don't see the sliding friction. I have one engine with nearly a quarter of a million miles with a hydraulic roller cam. Dan Jones |
Re: Camshaft for quad twin Webers/Dellorto's
Hey Dan,
Thanks for your reply and yes, after discussions with Woody it seems like a good idea to install a hydraulic roller camshaft and optimise the power band, as most of the actual driving is done in the 1000 to 5500 rpm with occational sprints to 6500 rpm so it does not make sense to install a cam for the 4000-7000 rpm range. I could run the Crane 256 at 800rpm idle and especially from 3000 it kept on going to 6800 rpm. So a bit more bottom power in the 1500 to 3500 rpm would be welcome. Thanks for the offer to run a roller cam through Dunomation, would appreciate if you could check what optimation could be gained with a proper roller cam for this engine. Valve springs installed have 110lbs @ 1.800"seat preasure and 325lbs @ 1.200" open, max lift 0.580" and pressure can be slightly adjusted (up/dpwn) by using different valve collets. What power figures are you expecting from the MGB V8 engine and is that the one with the Buick 300 heads ? So what roller did you put in, the 235/235@0.050" / LSA 110 / 0.565"/0.525"lift / OL 68 ? How is your driving experience with the roller cam, seems you feel a lot more torque and power availabe in the cruising rpm range. Thanks, Rik |
DiDueColpi Fred Key West coast - Canada (1365 posts) Registered: 05/14/2010 03:06AM Main British Car: I really thought that I'd be an action figure by now! |
Re: Camshaft for quad twin Webers/Dellorto's
So Rik,
I'm going to open pandora's box and suggest that a flat tappet cam might be the best choice for you. And here's why. Your head flow #s for the intake are acceptable but the exhaust is very poor. It stalls out @ .388" valve lift. So what you need is a cam that can open the exhaust valve very quickly to a fairly low lift, keep it there as long as possible and then close it quickly to help with your fuel standoff problems. A flat tappet cam has better early acceleration rates than a roller and in your case with such a low lift would be superior to the roller. To me something around 226-228' @ .050 intake and 234-236' @ .050 exhaust with a 110' lobe sep. would be close based on your set up. I would go back down to 1.5 to 1 rockers to take some of the flex and stress out of the valve train and put the lift @ the cam for the intake @ 0.340" and exhaust @ 0.270" That's going to be a bit of an oddball cam to grind but if you show your flow #'s to your cam grinder he'll understand what you are needing. That should buy you somewhere around 390 hp with a nice fat torque curve at about the same 390 ftlbs. It should pull hard from 1500 to 5500 rpm and rev easily to 6500. No matter what, with those exhaust ports, you are going to need some mighty long velocity stacks to contain the fuel stand off. Probably something in the six inch range. Anything shorter and the carbs become impossible to tune. Having said all that a roller with a few more degrees duration will get you close to the same power and will certainly last longer. But the cost is eye watering and a well maintained flat tappet should do 100k miles or so. Hope that helps some. Cheers Fred |
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roverman Art Gertz Winchester, CA. (3188 posts) Registered: 04/24/2009 11:02AM Main British Car: 74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L |
Re: Camshaft for quad twin Webers/Dellorto's
One Pandora, coming up. IMHO, The curent Crane cam failed after how many miles ? Don't use a flat tappet cam, to bandaid an exhaust port that needs attention. I suggest a read of the ported "Merlin" head, with a 1.50" exhaust valve. Some skilled flow bench developement will get the exhaust performing, as it should. I see no need for "Try-Y" headers, on your combination,(light weight,adequate gear ratios and torque/hp). You DO want a well placed balance pipe, between left/right banks.You might benefit more from a 1.6 rocker on exhaust, than intake. I suspect your valvetrain is quite stable, but a behive spring, might work well,(less rate rise over the nose,less harmonics and lighter retainer). Good Luck, roverman.
Edited 1 time(s). Last edit at 10/25/2013 11:29AM by roverman. |
Re: Camshaft for quad twin Webers/Dellorto's
Thanks for the input and Pandora's insight, I will recheck the original data flow sheet to see if I made some errors in the exhaust numbers as it is indeed strange that the numbers are staying the same after 0.388" lift.
However, the actual exhaust flow of 191 CFM at 0.542" is better than elsewhere quoted for RV8, Merlin F85 heads or Buick 300 (@ 154 CFM at 0.550") and are flowing 80% of the inlet side being 231 CFM. Sofar I have not seen Rover/Buick ort other heads with better flow rates for this engine.... With the 256/266 Crane and LSA 109 I had no problems with the short intakes and the quad carburettors even at higer rpm's, engine responded very vast on the throttle which was very much different then the tuned 4.6 engine with the same type of carburettors (IDF 44). Balance pipe can be done, large velocity stacks are not an option as they have to stay under the bonnet. Rules here are a bit different than in the US.... Cheers Rik |
DiDueColpi Fred Key West coast - Canada (1365 posts) Registered: 05/14/2010 03:06AM Main British Car: I really thought that I'd be an action figure by now! |
Re: Camshaft for quad twin Webers/Dellorto's
Hey Art,
I'm assuming that nothing is going to be done to the heads as this was advertized as a camswap. A flat tappet cam, can and will, live a long healthy life if the proper clean oil is used. Spring rates can stay down as the lifters are much lighter, reducing the movement of a very flexible valve train Throw a dial indicator on the rocker shaft some day. And watch it wander around like a drunken sailor, even with the stock springs. The lower ratio rockers are recommended because a higher ratio just isn't warranted with such a low lift/ flow port. The higher ratio rockers just give you lift that can't be utilized. They also magnify any unwanted valve train movement, costing you power. Getting a cam ground that doesn't need the crutch of a high ratio rocker will make you happier in the long run. Of course getting the exhaust port up to speed would be ideal but I'm not sure that thats in the cards right now. Anyway trhat's one mans opinion. Cheers Fred |
roverman Art Gertz Winchester, CA. (3188 posts) Registered: 04/24/2009 11:02AM Main British Car: 74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L |
Re: Camshaft for quad twin Webers/Dellorto's
Rik, Crane #256 being mechanical, lifters lifters with an EDM hole of approx. .020", at/near center of face, add much better longevity, 2 cents. Should you close up the hot valve lash, say .005", on int./exh.,only as a test, AND the motor looses slight amount of power, I would suspect overlap is a problem. Cheers, roverman.
Edited 1 time(s). Last edit at 10/25/2013 05:58PM by roverman. |
Re: Camshaft for quad twin Webers/Dellorto's
Scorpion roller rockers are stud mounted, same style as SBC heads, so no rockershaft mounted.
Didn't plan to get the heads of, just a cam swop and see if it is worthwile to change the cam specs. When heads would be maximum ported flow figures of 265 cbf inlet and 215 cfm outlet could be achieved. Wasn't planing to race again so will keep the heads 'as is' for the moment. On the 256 I did use the EDM lifters from Ferrea... Question was, would this carb setup benefit from wider LSA and less overlap, any experience ? Cheers Rik |
DiDueColpi Fred Key West coast - Canada (1365 posts) Registered: 05/14/2010 03:06AM Main British Car: I really thought that I'd be an action figure by now! |
Re: Camshaft for quad twin Webers/Dellorto's
The short answer is yes.
If you can't contain the fuel standoff then taking some of the duration out will help with your combo. I think the most obvious indicator of this is Dan. He's a pretty smart cookie, and if he's not using that cam then probably you shouldn't either. Cheers Fred |
Re: Camshaft for quad twin Webers/Dellorto's
Thanks Fred, will see if Dan can assist with his Dynomation for better duration and lift.
I checked the exhaust figures on the actual flow data sheet and I placed the wrong figures in my excel sheet : Lift flow 0,077 38,7 0,155 63,08 0.232 92,7 0.310 123,8 0.388 170,68 0.465 180,05 0.542 191,50 At least flow is increasing with lift.... Brgds Rik |
Dan Jones Dan Jones St. Louis, Missouri (280 posts) Registered: 07/21/2008 03:32PM Main British Car: 1980 Triumph TR8 3.5L Rover V8 |
Re: Camshaft for quad twin Webers/Dellorto's
> At least flow is increasing with lift....
High lift exhaust flow is not as important as one might think. The exhaust port sees cylinder pressure and blows down early in the valve lift cycle. That's the reason why exhaust valves are smaller than intake valves. The intake valves only see atmospheric pressure (in normally aspirated engines) so need a larger valve. Also, the larger the valve, the higher the lift at which peak flow is reached. Exhaust valves also don't need to accelerate as fast as intake valves. Though it wasn't on a Buick/Rover V8, we've tested running rocker ratios on the dyno and found shorter exhaust ratios make better average power. I suspect that does vary depending upon the application, though Vizard says its a trend he's seen with most cylinder heads. Rik, I'm working on a cam optimization now. Dan Jones |
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Re: Camshaft for quad twin Webers/Dellorto's
Thanks Dan, I am in contact with Woody @ the Wedgeshop to see if present valve springs and pushrods can be used with the rollercam
Valve seat spring pressure is now 110 lbs @ 1.800" (installed height on the heads is also 1.800") and over the nose pressure is 325 lbs @ 1.200" Valve spring rating can increased when using different type valve keepers. If you need more data then let me know. Cheers Rik |
Dan Jones Dan Jones St. Louis, Missouri (280 posts) Registered: 07/21/2008 03:32PM Main British Car: 1980 Triumph TR8 3.5L Rover V8 |
Re: Camshaft for quad twin Webers/Dellorto's
> I am in contact with Woody @ the Wedgeshop to see if present valve springs and pushrods can
> be used with the rollercam The pushrods will be too long as the roller lifters are taller (due to the roller wheel diameter). > Valve seat spring pressure is now 110 lbs @ 1.800" (installed height on the heads is > also 1.800") and over the nose pressure is 325 lbs @ 1.200". Valve spring rating can > increased when using different type valve keepers. Your intake valve size is close to my 1.9" diameter AFR heads (for Ford 5.0L V8). Those run 130 lbs on the seat for standard hydraulic roller lobes. > If you need more data then let me know. I made a guess at the total induction runner length. Basically what I need is the distance from the intake valve to the bell mouth of carb or stack. I've measured the distance from the intake valve to intake manifold for stock Rover and TA Performance Rover heads so can make an educated guess but I'll need the intake runner length and the carb and stack length. Dan Jones |
roverman Art Gertz Winchester, CA. (3188 posts) Registered: 04/24/2009 11:02AM Main British Car: 74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L |
Re: Camshaft for quad twin Webers/Dellorto's
Let's remember, one can increase seat/max lift pressure with "shims" under the springs. MUST follow required coil bind clearance, as suggested by manufacturer. "Beehive" springs want to be close to coil bind, for best results. Good Luck, roverman.
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Dan Jones Dan Jones St. Louis, Missouri (280 posts) Registered: 07/21/2008 03:32PM Main British Car: 1980 Triumph TR8 3.5L Rover V8 |
Re: Camshaft for quad twin Webers/Dellorto's
Rik,
Modeled your engine and ran it through the Dynomation cam optimization program. The first cut at a custom hydraulic roller returned: 290/296 degrees seat duration 0.560"/0.520" lift 111 degrees LSA installed on 107 ICL 2.57 ramp rate This cam has 71 degrees overlap versus 81 degrees for the solid flat tappet Crane F246. The HR makes similar peak power at around 500 RPM less and about 25 ft-lbs more at 2000 RPM. Send me a private message with your email address and I'll email your the results with the comparison plots. I'm headed out of town for a few days so it may be next week before I can get to it. Dan Jones |