Engine and Transmission Tech

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

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BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5243 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: 4.5/4.9 Cadillac V8
Posted by: BlownMGB-V8
Date: July 09, 2017 11:59PM

What does the stock setup look like?


mgb260
Jim Nichols
Sequim,WA
(1750 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: 4.5/4.9 Cadillac V8
Posted by: mgb260
Date: July 10, 2017 06:14AM

Jim, Those are the stock rockers with the 93-95 3800 Buick V6 rollers instead of aluminum sled with tie bars that seem to break.
cadillac rockers.jpg



Edited 2 time(s). Last edit at 07/10/2017 07:07AM by mgb260.


MGBV8
Carl Floyd
Kingsport, TN
(3145 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: 4.5/4.9 Cadillac V8
Posted by: MGBV8
Date: July 10, 2017 10:08AM

The tie bars break because those puny little studs are flexing?


mgb260
Jim Nichols
Sequim,WA
(1750 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: 4.5/4.9 Cadillac V8
Posted by: mgb260
Date: July 10, 2017 10:50AM

Carl, That may be part of the issue. The 8mm bolt is pointed like a self tapping screw and has pulled out of the bridge also. One guy has redrilled and tapped for 10mm Allen bolt threaded through the bridge with lock nuts. If they would have used steel tie bars like Oldsmobile it probably wouldn't be an issue. You still need a way to guide the rockers. With the slots in the bridge you can use Ford pedestal roller or conventional 1.7 rockers also. 4.9 are 1.6 ratio. Dodge Magnum look similar and their base channels have guide plates for the pushrods. Dodge Magnum rockers pic:
Dodge magnum.jpg



Edited 2 time(s). Last edit at 07/10/2017 04:47PM by mgb260.


mgb260
Jim Nichols
Sequim,WA
(1750 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: 4.5/4.9 Cadillac V8
Posted by: mgb260
Date: July 10, 2017 12:51PM

Another interesting thread on rockers and cams.

[www.fiero.nl]


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5243 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: 4.5/4.9 Cadillac V8
Posted by: BlownMGB-V8
Date: July 10, 2017 01:14PM

That does need sorted out. There was an attempt to use SBC rockers on SBB heads by attaching a base plate but it resulted in stud breakage. Too much flex. I wonder if twin tie-bars would be feasible, intake and exhaust? Might be able to link the tie-bars together for more rigidity.

Jim


mgb260
Jim Nichols
Sequim,WA
(1750 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: 4.5/4.9 Cadillac V8
Posted by: mgb260
Date: July 10, 2017 01:20PM

Adapting parts from other makes or making parts specific for this motor for performance is the answer. It was never meant for a hot rod and just a daily driver/grocery getter.



pcmenten
Paul Menten

(235 posts)

Registered:
10/08/2009 10:40AM

Main British Car:


Re: 4.5/4.9 Cadillac V8
Posted by: pcmenten
Date: July 10, 2017 02:32PM

It's interesting to me the sled rocker design being used on other engines. I have a Ford Windsor block/ Cleveland head stroker motor and I insisted on using Crane high-lift sled-type rockers with two things in mind;

- The fulcrum has that squared alignment pedestal boss that prevents the rocker arm from rotating
- The sled design of the fulcrum makes the rocker center under the fulcrum and prevents side-to-side shifting.

I have heard that Cheby BB rockers would work on Cleveland heads but I had also heard that roller rockers tended to tick because of the lateral forces from the angle of the pushrod due to the splayed design of the valve angles. As the valve is opened, the centerline of the lateral forces of the pushrod crosses the centerline of the angle of the rocker, pushing it side-to-side.

My Clevor has a roller cam conversion with valve lift of .525".

Paul


mgb260
Jim Nichols
Sequim,WA
(1750 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: 4.5/4.9 Cadillac V8
Posted by: mgb260
Date: July 10, 2017 04:33PM

Paul, Maybe the Buick roller pedestal would work in the Ford rocker?


mgb260
Jim Nichols
Sequim,WA
(1750 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: 4.5/4.9 Cadillac V8
Posted by: mgb260
Date: July 12, 2017 04:14PM

Remote oil filter adapter from Chad's Porsche swap site:
oiladapter.jpg


mgb260
Jim Nichols
Sequim,WA
(1750 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: 4.5/4.9 Cadillac V8
Posted by: mgb260
Date: July 16, 2017 02:58PM

People have asked me my thoughts on porting the 4.9 heads. I agree with David Vizard's theories on porting. 52 percent of bore for max intake valve size and 80 percent of that for max exhaust valve size. This is to prevent cylinder shrouding. That calculates to 1.886 intake valves and 1.509 exhaust valves. SBC 1.84 and 1.50 305 HO valves would be ideal. Unshrouding chamber on outside of both valves and polishing to help prevent detonation at higher compression. Removing cast iron guides and replacing with tapered bottom bronze guides with .500 Viton seals. The floor of the port should be flattened in the corners dropping to the throat and bowl. An old head cut in two for intake and exhaust would be beneficial to see how far you could go. The intake manifold ports that curve around the pushrod hole can be ground out on opposite side to maintain width or a tube pressed in and ground down on that side. If you can get 200cfm intake and 150cfm exhaust at .500 lift, similar to ported SBF or Buick/Rover should support 350HP with the Delta E303 grind cam. Remember to use longer pushrods to compensate for reduced base circle of reground cam.



Edited 1 time(s). Last edit at 07/18/2017 11:17AM by mgb260.
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