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mgb260
Jim Nichols
Sequim,WA
(2465 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Max valve size for 4.0/4.6 heads?
Posted by: mgb260
Date: January 28, 2023 11:25AM

Jim, You may want 1.65 installed for .550 lift with .030 before coil bind. 1.6 only gives .530 before coil bind.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6470 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: Max valve size for 4.0/4.6 heads?
Posted by: BlownMGB-V8
Date: January 29, 2023 10:53AM

Yep you are right. I'm back to looking for .050" retainers. Any ideas on that? (or even .100" retainers for that matter)

Jim


mgb260
Jim Nichols
Sequim,WA
(2465 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Max valve size for 4.0/4.6 heads?
Posted by: mgb260
Date: January 29, 2023 11:15AM

Jim, just Chevy style for the single groove. The short Rover valves are the issue. The longer 75-76 Oddfire valve would work fine plus they are bigger, 1.62 IN and 1.42 EX. Would need 2 more IN and 2 more EX.

[taperformance.com]



Edited 2 time(s). Last edit at 01/29/2023 11:22AM by mgb260.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6470 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: Max valve size for 4.0/4.6 heads?
Posted by: BlownMGB-V8
Date: January 30, 2023 10:44AM

So, what is it, the retainers are not available in +.050", only the keepers are? So then I'd need to modify +.050" 7mm keepers by removing the locking ridge?

Just want to be sure what the plan is before I order the parts.

Jim


mgb260
Jim Nichols
Sequim,WA
(2465 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Max valve size for 4.0/4.6 heads?
Posted by: mgb260
Date: January 30, 2023 02:03PM

Jim, There are some double spring retainers that are +.050 but not beehive. most are 7 degrees too. Found this one .731 ID measurement:

[www.compcams.com]



Edited 3 time(s). Last edit at 01/30/2023 02:15PM by mgb260.


DiDueColpi
Fred Key
West coast - Canada
(1367 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: Max valve size for 4.0/4.6 heads?
Posted by: DiDueColpi
Date: January 30, 2023 06:57PM

Why not just machine the needed keeper groove into the valve stem and use the 7mm keepers.
Almost any lathe could do it in just a few minutes.
If you took the end of the valve stem down to 7mm you could put the keeper groove in a better position to accommodate your installed height.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6470 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: Max valve size for 4.0/4.6 heads?
Posted by: BlownMGB-V8
Date: February 01, 2023 11:58AM

I was wondering how using the 7mm keepers affects installed height? Stands to reason being for a smaller diameter valve that the taper of the 7mm keeper should be a smaller diameter than the taper of the OEM keeper and that would let the retainer sit higher on the valve stem. Has anyone looked at this? It could make it a whole lot easier to use the available beehive springs.

Jim



mgb260
Jim Nichols
Sequim,WA
(2465 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Max valve size for 4.0/4.6 heads?
Posted by: mgb260
Date: February 01, 2023 12:04PM

I think Dave was waiting on receiving them to experiment with.


DiDueColpi
Fred Key
West coast - Canada
(1367 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: Max valve size for 4.0/4.6 heads?
Posted by: DiDueColpi
Date: February 01, 2023 12:28PM

Pac carries beehive retainers to fit their 7mm keepers.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6470 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: Max valve size for 4.0/4.6 heads?
Posted by: BlownMGB-V8
Date: February 01, 2023 02:32PM

Yes but if the 7mm keepers are used with the 11/32" retainers like the CC 795's it would seem likely that they would sit lower in the retainer. How much lower is the question. We think if we can remove the projecting lock they will work with the large groove 11/32" valves. This would let us use a taller spring like (possibly) the 1276X.

Jim


turbodave
dave cox

(183 posts)

Registered:
04/30/2018 03:00PM

Main British Car:
SD1

Re: Max valve size for 4.0/4.6 heads?
Posted by: turbodave
Date: February 02, 2023 06:07AM

Well as an update I only just received the sample retainer snd locks yesterday, and still havenít received the spring. Fast shipping would appear to not be a PAC attribute. Iíll measure up tonight.

As regards modifying the valve stem, I donít have tooling to hold it in my shop lathe. May get away with the exhaust but canít put it in a 5c collet as they are only a 1Ē ish ID as I recall. Iíd really need to make some large soft jaws. If I hadnít already purchased these valves, and had them back cut and everything else for my heads, Iíd probably just be getting slightly longer valves and custom pushrods . I may still go that way if the machining of the locks becomes tedious - or if itís just going to be difficult to get adequate installed height.


turbodave
dave cox

(183 posts)

Registered:
04/30/2018 03:00PM

Main British Car:
SD1

Re: Max valve size for 4.0/4.6 heads?
Posted by: turbodave
Date: February 02, 2023 10:00PM

well, here is the results of the PAC-L8081 keepers and the Comp 795 retainers.

So, the Comp 795 is basically the same as the PAC-R310. The 792 is 2 thou smaller on the spring ID dia, and 10 thou larger on the major dia compared to the PAC-R310.
They both have an identical height from the top of the keepers (around a 7mm dia) to the top of the spring.
Basically, there is very little between them.

The PAC-L8081 are listed as a +.050" height. I wish I'd have also got a few of the PAC-L8080 but for some reason didn't....
The L8081 are shown as a +.050" height, and the L8080 are +.100"
Based on the drawing below, this would put the Comp 795 / PAC-R310 at basically the same height as the stock retainer.

So that may be of some help.

I really can see the benefit of the longer valves now..... An extra 1/8" would be night and day in solving many of these issues.
10_deg_options.png



Edited 1 time(s). Last edit at 02/02/2023 10:02PM by turbodave.


mgb260
Jim Nichols
Sequim,WA
(2465 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Max valve size for 4.0/4.6 heads?
Posted by: mgb260
Date: February 02, 2023 11:15PM

Dave, You drilled out the ridge in the keeper so it fit the same as stock? The + .050 or + .100 would only make a difference if you grooved the valve?


turbodave
dave cox

(183 posts)

Registered:
04/30/2018 03:00PM

Main British Car:
SD1

Re: Max valve size for 4.0/4.6 heads?
Posted by: turbodave
Date: February 03, 2023 06:22AM

Ugh, yep. Thatís what happens if youíre tired and try to get something out without thinking properly!!!!

Youíre absolutely right, I got myself mixed up. That only refers to the keeper groove positions in the keeper, so ignore all the stuff about trying different keepers.
The important reference is the dimension showing how much lower this ends up compared to the stock setup. Itís not greatÖ..
I think Iím back to modifying the retainer to 11 degrees.

Still need to figure out a spring pocket cutter mindÖ. The Comp 4716 is 1.320 x 0.630. That would allow me to grind the ID out to ,720 and the OD down to whatever.



Edited 1 time(s). Last edit at 02/03/2023 10:24AM by turbodave.


turbodave
dave cox

(183 posts)

Registered:
04/30/2018 03:00PM

Main British Car:
SD1

Re: Max valve size for 4.0/4.6 heads?
Posted by: turbodave
Date: February 03, 2023 09:05AM

This overlay shows the difference - basically the 11-deg Rover keepers are smaller on the taper dia than the 10 deg keepers.

KEEPER_OVERLAY.jpg



BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6470 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: Max valve size for 4.0/4.6 heads?
Posted by: BlownMGB-V8
Date: February 03, 2023 09:28AM

Well I didn't expect that. Going the wrong way isn't it? OK well my pieces of carbide came in, it looks like making the reamer is in my future. Might as well order the retainers I guess. Honestly though it'll be less fiddly to ream the retainers than the keepers. At least that's a pretty simple lathe or drill press operation once the reamer is made. You could single point it in the lathe as well of course and that would be an easier setup once the right tool is in hand, but overall a slower operation. Might be possible to cut deeper to get more on the spring height also. Provided there is enough wall thickness this sounds like the way to go.

Jim



Edited 1 time(s). Last edit at 02/03/2023 09:31AM by BlownMGB-V8.


turbodave
dave cox

(183 posts)

Registered:
04/30/2018 03:00PM

Main British Car:
SD1

Re: Max valve size for 4.0/4.6 heads?
Posted by: turbodave
Date: February 03, 2023 11:07AM

Jim B: Agreed.

I'm personally back to looking at the Comp 26981 spring. While the install height is not quite as favorable as the PAC 1231X the base of the spring matches the seat pocket cutter I already have....

Plus modifying the Comp 795 to 11 degrees means I need only dig out 70-80 thou from the seat pocket.

As regards your concern about wall thickness, scroll back to page 8 and look at the post from January 23, 2023 10:34AM. I have detail on the reduced wall thickness and percentage reduction on cross-sectional area.

Are you going to set an indicator stop on your machine so they machine to the right height?

I'm probably just going to take my machine shop up on their offer to stand and operate the Haas lathe and knock all mine out. I'll also knock the top ridge off like in this image. I can just as easily do a set for you if you are interested?

comp_795_5.png



Edited 1 time(s). Last edit at 02/03/2023 11:08AM by turbodave.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6470 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: Max valve size for 4.0/4.6 heads?
Posted by: BlownMGB-V8
Date: February 03, 2023 11:18AM

Dave, depends on the cost but yeah why not? I don't see any need to machine the top of the retainer though. It's below the valve tip and the roller is below the body of the rockers so there's no way they are ever going to make contact.

Jim


mgb260
Jim Nichols
Sequim,WA
(2465 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Max valve size for 4.0/4.6 heads?
Posted by: mgb260
Date: February 03, 2023 11:23AM

I've read you want .050 rocker to retainer clearance. Everything moves around after 7000RPM.


mgb260
Jim Nichols
Sequim,WA
(2465 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Max valve size for 4.0/4.6 heads?
Posted by: mgb260
Date: February 03, 2023 11:32AM

Comp Cams Beehive specs:

[www.amazon.com]

Bottom of page 26918 would work for Jim at 1.65 height.



Edited 1 time(s). Last edit at 02/03/2023 11:34AM by mgb260.
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