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turbodave
dave cox

(11 posts)

Registered:
04/30/2018 03:00PM

Main British Car:


Prepping head for high lift cam - springs? Stem seals?
Posted by: turbodave
Date: April 30, 2018 03:04PM

Donor heads: standard 3.9 issue, standard valves (for now). Have a set of early SD1 heads with the machined (pre-sintered) valve caps I'll be using to get rid of the sintered stuff.

I'm going to be using a Crane 901171 F-248/3334-8, so need .533" lift at the valve per this: [powermechanics.com] (bottom of page 9)

I'm looking at my spring options. Stock spring pocket is measuring up at 1.236" OD x .843" ID and a installed height of around 1.55 at the moment.
Crane has suggested these springs as the only close option [www.cranecams.com] ... il&p=26305, but even these have an ID that is 1mm larger than the Rover spring pocket, and would need me to carve a much deeper pocket into the head (1/4" deeper). I'm also concerned about the extra radial movement of the spring at the cap.

I'm also looking at the stem seals. What do folks normally do here? it's not going to be that big of a deal to machine the stem seal location further down and knock the same amount off the top - I'm almost done making an angle-plate to put the valve guides vertical so i can machine the spring pockets (and guides) on the mill. It'll be a little time-consuming to do 16, but not difficult at all.

I of course am tempted to just jump on the UK piper springs; the VTSV8 - but would appreciate feedback on the longevity and reliability of these when used with a mechanical cam profile like the 248

Thanks!


roverman
Art Gertz
Winchester, CA.
(2895 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: roverman
Date: May 02, 2018 01:49PM

Crane should give spring seat pressure(min) ? You might consider a "beehive" as they usually have better working range and a lighter retainer. FWIW.


turbodave
dave cox

(11 posts)

Registered:
04/30/2018 03:00PM

Main British Car:


Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: turbodave
Date: May 02, 2018 05:15PM

Well, Crane recommended 99891-16 which is a dual, so would need different retainers and the pocket the spring sits in machining out completely to the guide. I was going to machine these deeper anyway, but this is even more - plus needs new retainers to match the duals.

Crane say I need 231lb at 490 lift, and 93lb closed, so that's looking like a pretty good match for the Comp Cams 979 if i wanted to be on the "light side"; maybe not using all the huge RPM potential of this cam, or the Compcams 980 if I did want to "go there" - while using a lot more spring force which is wasted energy and extra wear for that last little bit of RPM potential...

I know that the "beehive" melling VS1615 (formerly speed pro, formerly federal mogul) spring looks to be perfect, but that'll need new retainers....

That said, I don't know much about retainers generally - other than I know the post 1980 rover sintered retainers fall apart at high rpm, so I'll be using a set I've got on a set of older rover heads. Modern smaller / lighter retainers will allow for a lighter spring I'm guessing? How do I match a set of retainers to the collets / valves from my 3.9 engine? I see all kinds of materials offered for retainers; is any to be avoided?


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5544 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: May 03, 2018 10:49AM

I've heard SBC springs can be used but haven't tried that myself. If so there would be a huge variety. Smaller, lighter retainers let you use less spring pressure because of the decreased mass. Titanium is the hot lick but expensive.

Jim


mgb260
Jim Nichols
Sequim,WA
(1891 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 03, 2018 11:46AM

Yep, Z28 springs from Alex's Parts. Need longer valves though. Larger 2.3 Ford 4 cyl valves are about right length but need new seats. 1.74 IN, 1.5 EX.


MGBV8
Carl Floyd
Kingsport, TN
(3402 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: MGBV8
Date: May 03, 2018 07:41PM

SBC springs can be used in place of the stock springs for stock apps. I broke a spring on my 215 way back in 2001 in Sebring. Dan LaGrou said go to town & get a SBC spring. Got one at a machine shop & swapped it out. Did hot laps at Sebring the next day. In fact, it is still in there. :p

For big lift cams you may want more & certainly something that won't coil bind at max lift.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5544 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: May 03, 2018 07:51PM

So spring height is the issue with SBC springs? Wonder what the difference in installed height comes to? Depending on the wire used it could just raise the seated and open pressures a bit and still not bind. I could especially see that being the case with the beehive springs.

Jim



mgb260
Jim Nichols
Sequim,WA
(1891 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 03, 2018 08:46PM

Jim, Carl is right on early stock SBC springs fitting stock valves. The Z28 springs are slightly larger in diameter, so you have to open the spring pockets. I used steel spring cups and installed height of 1.72 for 100lbs closed and 300lbs @ .500 lift. About perfect for a performance cam. I mentioned the 2.3 valves as that is what I used. I just can't seem to leave anything stock! Plus you can't beat the price.

[www.alexsparts.com]


turbodave
dave cox

(11 posts)

Registered:
04/30/2018 03:00PM

Main British Car:


Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: turbodave
Date: May 04, 2018 09:35AM

Swapping out valves, and then seats, all sounds very expensive compared to simply getting the comp cams springs and lowering the seat height? These are very reasonably priced.

[www.summitracing.com]
[www.summitracing.com]

I've also been reading a lot more about the beehive springs and smaller retainers - comp cams has a very cool catalogue here:

[www.compcams.com]

The 26915 springs with the 1787 retainer seem to be an ideal combination - initial research suggests that the rover keepers are indeed 7 degree? Yes, the pocket in the head will need to be machined deeper, but that is easy compared to swapping out seats!


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5544 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: May 04, 2018 10:26AM

So if the early SBC springs work, what is wrong with getting a performance version of that spring and just using it as-is? There definitely were performance springs available that didn't require any machining at all back then, have those all gone away?

Jim


turbodave
dave cox

(11 posts)

Registered:
04/30/2018 03:00PM

Main British Car:


Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: turbodave
Date: May 04, 2018 11:29AM

If I read the above posts; the SBC springs not good enough for anything other than near stock?
I need .533" of spring movement...


mgb260
Jim Nichols
Sequim,WA
(1891 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 04, 2018 12:13PM

Yeah, but a hot cam with small stock valves are a bottleneck unless Turboed or Supercharged. You can do as Chris did with the 300 heads. They turned down the 3.4 Chevy V6 valves to 1.69IN and 1.39EX. Largest you can fit with stock seats. I don't know the max you can fit with the Rover heads but you could do something similar. The high lift is a waste when the flow levels out about .480.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5544 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: May 04, 2018 06:54PM

I ran a comp cams 268H with their springs and the engine would hit 7 grand. Not sure what the lift was but should have been close. There was no machining of the spring pockets required. I don't understand the fixation on oversized valve springs.

Jim



Edited 1 time(s). Last edit at 05/04/2018 06:56PM by BlownMGB-V8.


MGBV8
Carl Floyd
Kingsport, TN
(3402 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: MGBV8
Date: May 06, 2018 10:51AM

Probably wouldn't need to do anything with a moderate cam like the 268H. About .450 lift, less with stock rocker arms.

The Crower 502323 that gets used here is a .488 lift with real 1.6 rocker arms. Won't even get that with stock rockers.

I use Comp Cams springs for my big lift solid lift cam in my Camaro. Didn't want to deal with pulling the heads for spring pocket work, so I used their beehive springs. Except, way back then they were calling them conical springs.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5544 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: May 06, 2018 12:40PM

So wouldn't the cam maker usually list the springs they recommended to be used with their cam? I have seen catalogs say that valve guide trimming was required for more lift and for teflon seals but normally their listed springs do not require pocket work.

Cams for the SBB are available with lift up to .635" (350, the earlier engines are almost identical in design but the cams will not interchange due to lobe spacing.) The stock cams provided lift in the general vicinity of .400" with a 1.55 rocker ratio. Some were more, some were less. I think I've seen specs for around .425". So I'm not sure that an extra .100" of lift is really that much of a challenge. Incidentally I think that 268H stick I used had lift around .480". Maybe yours had less. The cam I'm running now in my 340 (300 aluminum heads) has just a tick under .500" lift and I'm not even sure the valve guides were machined. It is currently fitted with the springs from that old 268H cam, which work but not as well as I had hoped.

Jim



Edited 2 time(s). Last edit at 05/06/2018 12:49PM by BlownMGB-V8.



minorv8
Jukka Harkola

(125 posts)

Registered:
04/08/2009 06:50AM

Main British Car:
Morris Minor Rover V8

Re: Prepping head for high lift cam - springs? Stem seals?
Posted by: minorv8
Date: May 07, 2018 01:49AM

Dave, I also thought that Rover keepers are 7 degree and bought a set of SBC valve retainers years ago. Big mistake. The Rover keepers are 11 degree. Comp Cams have a set of 11 degree retainers for 1,25" spring, part number 712-16.

Another thing to consider, how much material can you machine from the spring pocket and still have enough material left ?

With Rover heads and std length valves the springs (coil bind) will be an issue with high lift. Real Steel in UK used to sell a set but last time I checked they did not have them anymore.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5544 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: May 07, 2018 03:22AM

The old way of dealing with coil bind was a double spring, with a flat wound separator between them. Each spring used a smaller wire, so you could get higher total spring pressure and a shorter compressed height. Those springs should still be available.

Jim


mgb260
Jim Nichols
Sequim,WA
(1891 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 12:03PM

The LT1 springs at Alexs parts are good to .550 lift. If you are lowereing the seat, might as well go .030 wider. You asked about seals also. I always cut guides down for the Viton seals. Years ago I used the Perfect Circle Teflon seals on the intake valves and umbrella seals on the exhaust. Now I use the Viton on both. He also carries Beehive springs.

[www.alexsparts.com]

[www.alexsparts.com]



Edited 3 time(s). Last edit at 05/07/2018 03:52PM by mgb260.


mgb260
Jim Nichols
Sequim,WA
(1891 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 02:13PM

Dave, Rimmer Bros sell the largest Rover Valves for the stock seats. 41.4mm/1.629 IN, 35.5/1.397 EX. Do you know the length of the Rover Valves? The larger Ford 2.3 SOHC valves are 4.787 length. The 93-95 Camaro/Firebird 3.4 V6 valves Chris used were 4.705 IN and 4.736 EX. He had them cut down on a lathe from 1.718 IN and 1.425 EX to max size for the 300 head seats. 1.69 IN and 1.39 EX. He shimmed the rocker supports .2 to correct the geometry. Pushrods were Smith Bros .030 longer on EX. 350 lifters and pushrod oiling. You could do the same and turn the 3.4 V6 valves down to Rover max size. Do a 30 degree back cut also. He used Chevy Z28 springs. You could use the LT1 springs because of the higher lift. It would be a waste to use the small stock valves with that cam. Just my opinion.



Edited 2 time(s). Last edit at 05/07/2018 03:58PM by mgb260.


mgb260
Jim Nichols
Sequim,WA
(1891 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 03:32PM

Dave, You didn't say what short block you were using. 3.9/40 or 4.6? That cam is too big for the smaller displacement unless you plan drag racing, not very streetable. It would be usable in the 4.6. I did a Desktop Dyno simulation with my Performance Trends program. With the stock valve sizes I get 301HP@ 5500RPM, 315TQ@4500RPM. With the max size valves I get 347HP@ 6500RPM, 315TQ@5500RPM. 46HP gain but at higher RPM in the 4.6. I figured 10 to 1 compression. I used the Edelbrock Performer intake and 500cfm carb. For a street cam I don't go over 230 duration@.050 and .500 lift. You will have low vacuum at idle of around 8-9 and require around 18 initial spark timing. The cam has 5 degrees built in advance or it would be even worse.



Edited 3 time(s). Last edit at 05/08/2018 12:33AM by mgb260.
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