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 (6470 posts) Registered: 10/23/2007 12:59PM Main British Car: 1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS |
Max valve size for 4.0/4.6 heads?
Anyone know how large you can go on the valves for these heads without changing the seats?
I've seen valves about .050" larger for both ex and intake. That hardly seems worth the trouble and expense unless the old ones have to be replaced. Jim |
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mgb260 Jim Nichols Sequim,WA (2463 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?
Rimmer bros and the Wedge Shop sell larger valve for the Rover heads. Pretty close to the Buick 300 sizes. Years ago I changed the seats and used Ford 2.3 SOHC 1.74 IN and 1.5 EX valves in a 300 head. Probably could in the Rover also.
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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 |
Re: Max valve size for 4.0/4.6 heads?
That'd be a substantial increase. The intake is about 1.570 and the exhaust is about 1.350. The alloy 300 heads have a little larger intakes and smaller exhausts, around .040 difference in each case I think. There is slightly over 3/16 between the valves so I expect that'd be about the limit.
Just for reference the TA heads have the valves repositioned and can go bigger, up to 1.6 and 2.0 in although we decided a 1.9 made more sense. Jim |
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mgb260 Jim Nichols Sequim,WA (2463 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?
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Airwreckc Eric Cumming RTP, North Carolina (249 posts) Registered: 05/28/2020 10:10AM Main British Car: 1972 MGB-GT (working on a Sebring project) Buick 300-4 V8 |
Re: Max valve size for 4.0/4.6 heads?
In case anyone is interested, here's a slightly less expensive alternative. Price is 1550 GBF plus 200 GBF (core). They are CNC ported and the size of the valves is 1.63" intake and 1.4" exhaust. I've asked for flow numbers.
[johnealesroverv8.co.uk] |
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mgb260 Jim Nichols Sequim,WA (2463 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?
Eric, Plus shipping back and forth. Wedge Shop (TWS) might be more like their Stage 3 too.
Edited 1 time(s). Last edit at 12/08/2022 03:20PM by mgb260. |
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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 |
Re: Max valve size for 4.0/4.6 heads?
Saw those, not real impressed with the valve sizes. I mean if I'm spending $18 each for valves I'd want to get a little more than that I think. Probably just stick with the originals, they seem to be in good shape.
Jim |
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minorv8 Jukka Harkola (269 posts) Registered: 04/08/2009 06:50AM Main British Car: Morris Minor Rover V8 |
Re: Max valve size for 4.0/4.6 heads?
Hi,
1,63" intake and 1,40" exhaust valves are typically available and fit factory seats. Thatīs what I have fitted in my Rover heads. One thing to consider: I have not had much luck finding uprated springs (read inexpensive) for Rover heads. Sure there are double springs available but all the additional parts + possible machining start adding up costs. Also quality of rockers and rocker shafts is pretty poor. I have a pair of new rockers shafts that have smaller OD than worn factory shafts. These came from a reputable source in UK. Jukka |
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minorv8 Jukka Harkola (269 posts) Registered: 04/08/2009 06:50AM Main British Car: Morris Minor Rover V8 |
Re: Max valve size for 4.0/4.6 heads?
Here is a link to a UK magazine article from mid 90īs when P38 type 4,0 / 4,6 litre engines arrived. It has some useful info about component dimensions
[drive.google.com] |
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Airwreckc Eric Cumming RTP, North Carolina (249 posts) Registered: 05/28/2020 10:10AM Main British Car: 1972 MGB-GT (working on a Sebring project) Buick 300-4 V8 |
Re: Max valve size for 4.0/4.6 heads?
Jukka,
That's a very useful article. I'm curious about one thing. The article says the 4.6 heads have a combustion chamber of 28 to 31 cc, while I think I've read somewhere else that they are 22 cc. Am I missing something? That would make a big difference in my calculations. |
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Airwreckc Eric Cumming RTP, North Carolina (249 posts) Registered: 05/28/2020 10:10AM Main British Car: 1972 MGB-GT (working on a Sebring project) Buick 300-4 V8 |
Re: Max valve size for 4.0/4.6 heads?
Carl,
Probably need to get my eyes checked. Thanks for the confirmation--now have to redo my calculations. |
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MGBV8 Carl Floyd Kingsport, TN (4512 posts) Registered: 10/23/2007 11:32PM Main British Car: 1979 MGB Buick 215 |
Re: Max valve size for 4.0/4.6 heads?
"So, in addition to deleting these bolts a new thicker composite head gasket has been introduced, and the deck height has been reduced by a corresponding amount."
Say what?! In all these years, I have never heard that the deck height was changed. "...and the production conrods and pistons remained weak." Do the Rover V8 engines not use a forged connecting rod? I know that the Buick/Olds 215 does. |
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Airwreckc Eric Cumming RTP, North Carolina (249 posts) Registered: 05/28/2020 10:10AM Main British Car: 1972 MGB-GT (working on a Sebring project) Buick 300-4 V8 |
Re: Max valve size for 4.0/4.6 heads?
Carl,
I did read somewhere else that the later Rover heads used a thicker gasket and that the combustion chamber was accordingly reduced by shaving the head--I *think* that's what the article was trying to say, but it made it sound like it was the block that was reduced, which I don't think was the case. Still wondering where I saw that 22 cc reference... Not sure about the Rover rods, though. |
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MGBV8 Carl Floyd Kingsport, TN (4512 posts) Registered: 10/23/2007 11:32PM Main British Car: 1979 MGB Buick 215 |
Re: Max valve size for 4.0/4.6 heads?
Yes, Rover shaved the heads to compensate for the thicker composite head gasket. I think they are wrong about the deck height.
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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 |
Re: Max valve size for 4.0/4.6 heads?
That would explain the change in chamber volume.
The 340 used cast rods, pretty sure the 300 did too. One of the early mods to the 215 was to use small journal SBC rods which were forged. How certain are you that the 215 rods were forged? That 22cc number may have been my fault, I had mentioned that as a piston dish volume because I had some notes from an old engine build that contained that figure. But apparently I never actually used it so as far as I know it doesn't apply to any build. 22cc would be a VERY small chamber volume. Jim |
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Airwreckc Eric Cumming RTP, North Carolina (249 posts) Registered: 05/28/2020 10:10AM Main British Car: 1972 MGB-GT (working on a Sebring project) Buick 300-4 V8 |
Re: Max valve size for 4.0/4.6 heads?
Ha, no worries on the chamber volume--my numbers do work a bit better now, though :)
I have also read that the 215s had forged rods--I think that was from a spec sheet posted on the V8 Buick site. |
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