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tips, technology, tools and techniques related to vehicle driveline components

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turbodave
dave cox

(101 posts)

Registered:
04/30/2018 03:00PM

Main British Car:
SD1

Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: turbodave
Date: May 07, 2018 04:28PM

Lots of great info here. Thanks everyone.

Appreciate the heads up on Rimmers; for $210 I just bought a set of big valves :-)
You really can't complain about that price for a whole set of oversized valves can you?

Appreciate the note on the 11-degree angle (I would have double-checked before purchasing) but found two references that said 7 degrees... I guess that the interwebs were wrong again!

This is not going to be a road engine - it'll only be used on the track.
Will be in 3.9 using vitesse plenum with welded and ported plenum base (instead of the trumpets) and aftermarket management.

This cam has been recommended to me by someone who has used it for many years in many 3.9 engines, but they also use every part of 7000 rpm. I was looking for keeping to a 6100 rpm redline, using the factory 3.9 pistons while I shake down the car, and get a feel for the drivability of the cam, but know this cam (with a suitable CR) will still be pulling very hard at my redline once dialled in. I was told i needed every bit of flow the heads could give me, but was going to keep them standard initially, but then realised the spring issue - and of course, have just bought some valves, so will instead get the heads up to snuff.
Jim, I'm curious what your "desktop dyno" says about timing for this cam? Also, that 10:1 seems a shade low static CR for a cam like this doesn't it?


turbodave
dave cox

(101 posts)

Registered:
04/30/2018 03:00PM

Main British Car:
SD1

Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: turbodave
Date: May 07, 2018 04:33PM

And as far as how much I can cut the seat pockets down - I've got a scrap pair of 3.9 heads I'm going to section to aid my porting exercise, and will also look at the area under the spring pocket. I can laser cut as many shims as i need to at work to bring it back, so once I've figured out what I think I need pocketwise, I'll probably go deeper and shim back, as that'll allow me to play with the loads more easily.


mgb260
Jim Nichols
Sequim,WA
(2241 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: mgb260
Date: May 07, 2018 04:37PM

Dave, I assumed street motor. Racing with good fuel more likely 11 to 12.5. I'll run the program with fuel injection and 12:1 compression on a 3.9. Cam has 5 degrees advance ground in when installed straight up. So with a 3 keyway timing set retarded 4 degrees will actually be 1 advanced. It will move up the powerband. Probably a little more HP @7000RPM and a little less Tq @ 5000RPM



Edited 1 time(s). Last edit at 05/07/2018 04:53PM by mgb260.


mgb260
Jim Nichols
Sequim,WA
(2241 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: mgb260
Date: May 07, 2018 04:48PM

Dave, Ran the program at 12:1 for 3.9 injected motor. 342HP@6500RPM, 307TQ@5000. 1000RPM idle @20 degrees initial timing, 34 total and 11.5 Vacuum. The fuel injection helps there. This is just a simulation and probably optimistic. I just ran it 4 degrees retarded(actually 1 degree advanced). 347HP@7000RPM, TQ stayed the same 307@5000. Recommended initial timing moved up to 24 degrees. Total stayed at 34.



Edited 2 time(s). Last edit at 05/07/2018 05:02PM by mgb260.


mgb260
Jim Nichols
Sequim,WA
(2241 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: mgb260
Date: May 07, 2018 05:09PM

Dave, Where are you at? If in Britain, do you know Perry Stephenson? Haven't heard from him in a while on this board or V8Owners.


turbodave
dave cox

(101 posts)

Registered:
04/30/2018 03:00PM

Main British Car:
SD1

Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: turbodave
Date: May 07, 2018 05:31PM

Appreciate the info Jim. Just so we're on the same page - when you say "good fuel" do you mean premium or something more? Premium is all I'll be running.

Also - maybe I'm slow on the uptake here - what do you mean by "installed straight up" on the cam timing?

Finally, I left the UK many years ago; I'm not familiar with that name to be honest, but I was never really into the RV8 before I left that side of the pond, so wouldn't know anyway.


mgb260
Jim Nichols
Sequim,WA
(2241 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: mgb260
Date: May 07, 2018 05:56PM

Dave, On a typical aftermarket timing set there are 3 keyways. Some have 9. The 3 keyways correspond to 4 degrees advance, 0/straight up, and 4 degrees retarded. If you set up your cam at 0/straight up you are really 5 degrees advance because that is ground into the cam. So if you retard the timing 4 degrees you are still 1 degree advanced because of the 5 degrees advance ground into the cam. If you advance the cam you will lower the power curve, retard and you raise the power curve in RPM's. I figured the fuel as 91-93 Premium with added octane booster to 104. If you are just running premium limit your compression to 10.5. I figured you might be from the UK because you ordered those valves so quick. Perry frequented this site and is a Drag racer that had his MBGT into the 9's. I would not get rid of the trumpets but shorten them so the flare is flush with the bottom of the intake, it will help flow transition. Or you could use a sheetmetal intake like this for 444HP@7500RPM on my program. Similar to what Tim Lanocha uses in his TR7 race car.
custintakeQ.jpg



Edited 4 time(s). Last edit at 05/07/2018 06:18PM by mgb260.



turbodave
dave cox

(101 posts)

Registered:
04/30/2018 03:00PM

Main British Car:
SD1

Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: turbodave
Date: May 07, 2018 06:27PM

ahhh, my experience of cams in other engines is that the keyway is only a guide, and that only degree-ing in the cam, preferably using a vernier or 1-degree dowel adjustment is the preferred approach. I've not even looked at timing gear yet, so don't know what folks commonly use.

I got them ordered quick as I already had stuff in my cart with Rimmers...

I've had many conflicting opinions on the trumpets - the TVR guys are all over the place on opinions on them as well - but I've understood that building them back with weld to give a flush surface (sans trumpets), and then opening up the throats, plus blending to the inlet, is pretty much a known solution that works (sure it could be optimised more), but the stock dia trumpets being a little too small for a well ported head.



Edited 1 time(s). Last edit at 05/07/2018 06:28PM by turbodave.


mgb260
Jim Nichols
Sequim,WA
(2241 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: mgb260
Date: May 07, 2018 07:03PM

Dave, I still degree the cam to verify where it is, but using the keyways to put the power band where I want. You could remove the trumpets and mill a 45 degree transition to the port. Usually use the Buick V6 timing set. Have you done the recommended oiling mods? I would use the oil pump booster plate, T/A 60lb relief spring(or adjustable relief valve), larger 5/8"Buick V6 pickup and the T/A front cam bearing also. The clearance on the rod and main bearings is best at .0015 instead of .002 like Ford and Chevy.



Edited 1 time(s). Last edit at 05/07/2018 07:06PM by mgb260.


turbodave
dave cox

(101 posts)

Registered:
04/30/2018 03:00PM

Main British Car:
SD1

Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: turbodave
Date: May 08, 2018 10:09AM

I'm using the 94/95 "interim" front cover with the crank mounted pump, so hope to have little of the typical Rover V8 oiling issues. I will be making an adjustable pressure cap however.

I will be putting the restriction in the rocker feed (or going for full roller rockers).

Not sure what the T/A front cam bearing modification is? Can you advise? Thanks!


mgb260
Jim Nichols
Sequim,WA
(2241 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: mgb260
Date: May 08, 2018 11:37AM

The front cam bearing is grooved on the back side to move the oil feed hole to a better location to improve the oil wedge and reduce the load from the distributor and early oil pump. Years ago Phil Baker told me to lengthen the slots in the stock bearing from 1 to 3 o clock and 7 to 9 o clock installation for better oil distribution. There is also a front cover mod to put a squirt hole to the distributor gear.

[www.youtube.com]



Edited 1 time(s). Last edit at 05/08/2018 12:15PM by mgb260.


turbodave
dave cox

(101 posts)

Registered:
04/30/2018 03:00PM

Main British Car:
SD1

Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: turbodave
Date: May 08, 2018 01:51PM

ahhh, that's becuase the dizzy drive gear is also driving the oil pump?

I won't need any of that as the dizzy gear turns only the dizzy shaft.

I always like to maximize the oiling of all journal bearings by chamfering and smoothing as needed, so will take a look at the cam shells as well.

I understand that the later crank driven pumps are night and day better at moving oil than the gear driven pumps and can run higher pressures without the issues of higher pressures on the gear-driven pumps. The only downside is they are a swine to prime (i know that from experience with a 4.6 disco motor i rebuilt previously.


kennedyrd
Chris Wong

(2 posts)

Registered:
06/01/2022 06:24AM

Main British Car:


Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: kennedyrd
Date: June 01, 2022 06:55AM

Hi there, sorry for being so late to the party, but I wondered if you ever got this engine going? I was searching for data on suitable valve springs to use in my 3.9 litre Rover (sleeved 3.5) which uses a Crane F248 profile. The motor sounds very similar to what you describe, and I am experiencing valve bounce above 7000 rpm. I ran it to 7800 on the dyno to see if it would take it, but you could hear the valve thrash, and the power curve falls off a cliff over 6700 where it eventually made 357hp. I have the limiter set to 7200 rpm. It is used in a TR7 circuit car.

Other mods include custom made Wiseco pistons, as I used longer 6" SB Chev (Chinese Manley replica) steel rods that then required a rebalance as it was so heavy. I had a girdle made for the crankshaft, as I was expecting really high revs, like over 8000. Was pleased with the HP, but not the low revs. The problem is valve bounce, so I am interested if you guys got a beehive setup to work? I think my valves are heavy, as I used cut down Ferrea valves for a SBC as well. It uses Yella Terra roller rockers with custom pushrods and custom composite head gaskets to arrive at 10.8:1 compression on flow tested self ported heads. Likewise the exhaust system was self fabricated to run forward like a TVR. This was necessitated due to insufficient room beside the engine which had been shifted rearwards as well as having some space taken from the dry sump pump.

Induction is from a modified annular booster 650 double pumper Holley on a Denco engineering single plane manifold. The heads were self ported and tested on a flow bench at the same place.

It is road legal here in NZ, but only with a special permit. It is perfectly drivable, but there is drivetrain snatch if trying to drive in traffic. I would not consider it a pleasant daily driver with the F248, but fine as a special occassion car. Idle is a lopey 900rpm once warmed up.

Is your motor similar? Does it rev higher without valve thrash, and if so what springs and retainers did you end up using? Did they require the spring seats to be cut lower, and if so by how much? I am stripping the engine and would like to address the valve spring issue while it is apart. Thanks for any info you guys may have gleaned since this post was started.


mgb260
Jim Nichols
Sequim,WA
(2241 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: mgb260
Date: June 01, 2022 10:38AM

Chris, Chevy Z28 springs are commonly used but good to only 6500 RPM. There are some aftermarket Beehive springs that may work. I'll try to find a link.


mgb260
Jim Nichols
Sequim,WA
(2241 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: mgb260
Date: June 01, 2022 10:48AM

These LS Beehive springs may work for you if you open up the spring pocket and cut down the valve guide:



[www.alexsparts.com]



BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6218 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: BlownMGB-V8
Date: June 02, 2022 10:15AM

I used a Ford beehive. Something to remember though, they work their best when near coil bind at fully open.

Jim


kennedyrd
Chris Wong

(2 posts)

Registered:
06/01/2022 06:24AM

Main British Car:


Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: kennedyrd
Date: June 04, 2022 01:58AM

Thanks so much guys! LS spring kit sounds easiest as think we used SBC retainers if they are the same?

Also here is a picture of the motor. I must also apologise for stating it used a Denco engineering manifold. It in fact uses Harcourt manifold and rocker covers. They are NZ made, and they used to make a beautiful bearing girdle. Unfortunately it was no longer available when my motor was built.

TR8 motor small file.jpg



Edited 1 time(s). Last edit at 06/04/2022 07:54AM by kennedyrd.
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