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phongshader
Justin Brown
Ca
(50 posts)

Registered:
02/19/2010 04:03PM

Main British Car:
Locost Lotus 7 2.3 Duratec

authors avatar
Re: Beating a dead horse? Bore x Stroke x 300 heads
Posted by: phongshader
Date: September 27, 2016 10:22AM

Jim,
The v6 valves couldn't have possibly used the stock 300 seats?!? Or did you mean stock v6 seats?
I'm sold on using the valve sets from V8tuner.com because of the simplicity of it, no conglomeration of different parts from different cars trying to achieve something that should work...oh wait that's exactly what I'm doing on the bottom end. I know it doesn't make sense but it makes me feel better. My original question regarding the valves was will it take more machinist time to install one set over the other... that is 1.63" Inlet Valves and 1.4" Exhaust Valves VS 1.692" SS Inlet Valves and 1.455 SS Ex. Valves. I know they aren't as big or badass as the v6 valves but simpler and cheaper...not race car ;-)

So I think I may have found a piston that could be a viable replacement for the Chevy 305 piston
[www.summitracing.com]
3.7008(IN)
94.0(MM)
Hypereutectic, Flat Top
4 Valve Reliefs
.030 Offset Floating Pin
“COATED SKIRTS”
LY7 Engine.
COMP HT: 1.262 PIN DIA: .944 Offset
The only problem I see is the pin offset. I understand what the pin offset is for but I don't know how it will affect the deck height of the piston in the bore. This set up with no wrist pin offset the piston is out of the bore .002" but I don't know what the height will be with the offset.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5600 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: Beating a dead horse? Bore x Stroke x 300 heads
Posted by: BlownMGB-V8
Date: September 27, 2016 12:00PM

A .030" offset will have very minimal effect over the length of the rod. Actually,.000075" subtracted from the height with a 6" rod, and a little pin offset is good in a street engine. The math is easy. Draw a triangle, make 6" the hypotenuse and .030 the short side. To solve for the long side, square 6", square .030' and subtract from 6 squared, then take the square root of the result. Your phone's calculator should have a square root button. It's one of those fun calculations to play with just to see what it does but very useful any time you can put your dimensions into a triangular shape.

Anyway the result is less than a tenth of a thousandth of an inch. Thinner than spider silk.

Sounds like a good candidate. I like the idea of going zero deck, flat top, .040" gasket, and then removing the lug in the chamber to keep the compression reasonable. Valve reliefs are not needed but will further lower compression, so removal of the lugs might not be needed.

Jim


MGBV8
Carl Floyd
Kingsport, TN
(3445 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

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Re: Beating a dead horse? Bore x Stroke x 300 heads
Posted by: MGBV8
Date: September 27, 2016 01:42PM

Great find. That looks like a good choice coupled with the 3.4 stroke. Should be very close to 11:1 compression without taking the lug out of the chamber. I would leave it if you can. It is supposed to aid swirl, I think.

I usually just ignore the pin offset. Like Jim said, it's insignificant.

I could use that piston, as well, if I deck the block. I wonder how available they are. United Eengine does not show them with their search engine. Had to dig thru the Silvolite catalog.

I take that back. I am not decking it that much! :)



Edited 1 time(s). Last edit at 09/27/2016 03:03PM by MGBV8.


MGBV8
Carl Floyd
Kingsport, TN
(3445 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Beating a dead horse? Bore x Stroke x 300 heads
Posted by: MGBV8
Date: September 27, 2016 03:15PM

Quote from Kevin Jackson from the UK. He built a 4.35L V8 using 305 Chevy pistons. He also hangs out on the UK based V8 Owners Forum.
Quote:
With the Rover there are plusses and minuses in using the various blocks, the 3.9 blocks are normally reliable as far as liner slip is concerned, but limited to two bolt mains but are fine for an engine that is not going to rev beyond 6000 RPM which, with a long stroke crank is as far as you would wan't to go.

The 4.0 blocks are to be avoided at all costs as those engines were built from the worst quality blocks with a high degree of core shift, the 4.6 grade blocks are a little better but still suffer from line slippage from cracking behind the bores.

[forum.britishv8.org]


Blown v8
Bryan Phipps

(41 posts)

Registered:
03/10/2013 04:52PM

Main British Car:


Re: Beating a dead horse? Bore x Stroke x 300 heads
Posted by: Blown v8
Date: September 27, 2016 03:15PM

When TVR took the 4.6 out to 5.0L (305cu.in) the bore was left at 94mm,and the crank was offset ground,to give a stroke of 90mm
with this combination,Chevy 6" rods fit,(with a small filing job done on the bearings) with floating pins,and a good quality piston,
I used forged diamond "blower" pistons in mine,with total seal rings,I have part numbers if needed !


phongshader
Justin Brown
Ca
(50 posts)

Registered:
02/19/2010 04:03PM

Main British Car:
Locost Lotus 7 2.3 Duratec

authors avatar
Re: Beating a dead horse? Bore x Stroke x 300 heads
Posted by: phongshader
Date: September 27, 2016 03:26PM

Carl,
I found them here: [www.uempistons.com] pg 78
I would think that with the valve reliefs in the piston I might get a cc or two of piston volume to lower the compression a bit. I get 10.8:1 on the UEM calculator with 0 piston volume but I think I can pick a cc or two of piston volume from the valve reliefs, I'll say 2,and with that extra volume drops the CR to a more manageable 10.5:1 There's another piston listed in the catalog identical to the 1758HC, the 1765HC that has a about a 6cc dish which would drop the CR to around 10:1. I just haven't been able to find some one who actually sells it.

I see that you already found the catalog



Edited 2 time(s). Last edit at 09/27/2016 03:30PM by phongshader.


MGBV8
Carl Floyd
Kingsport, TN
(3445 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Beating a dead horse? Bore x Stroke x 300 heads
Posted by: MGBV8
Date: September 27, 2016 07:04PM

Yeah, I found it in the catalog. I have been wearing that website out for many years. I put Keith Black 11:1 pistons in my Camaro 25 years ago.

I was just surprised that searching for your part number returned " There is no product that matches the search criteria."

Usually you can get info like this.

[www.uempistons.com]



phongshader
Justin Brown
Ca
(50 posts)

Registered:
02/19/2010 04:03PM

Main British Car:
Locost Lotus 7 2.3 Duratec

authors avatar
Re: Beating a dead horse? Bore x Stroke x 300 heads
Posted by: phongshader
Date: September 27, 2016 11:16PM

That's where I got my Olds pistons 25 years ago.
I looked through Chris Gill's build on MGEXP to try and get some info on his valve setup but it was very thin. Do you, or anyone, have any info/part #s on his setup? How do the stock valve length compare to the Chevy valve lengths?


mgb260
Jim Nichols
Sequim,WA
(1896 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Beating a dead horse? Bore x Stroke x 300 heads
Posted by: mgb260
Date: September 28, 2016 06:57AM

Justin, I'm the one who recommended the GM 2.8/3.4 V6 valves for Chris's build. I assumed he would get new seats for the valves. Looks like he cut the diameter down to use the stock seats. About the same as the larger valves you listed. The ex valve is .030 longer and he uses custom length Smith Brothers pushrods with upper tip 215/300/340 ball size and lower 350 Buick ball size for though the pushrod oiling with 350 Buick lifters. The shim under the rockers is for geometry for the longer valves plus blocks the head oil hole.Info on this page:

[www.mgexp.com]


phongshader
Justin Brown
Ca
(50 posts)

Registered:
02/19/2010 04:03PM

Main British Car:
Locost Lotus 7 2.3 Duratec

authors avatar
Re: Beating a dead horse? Bore x Stroke x 300 heads
Posted by: phongshader
Date: September 28, 2016 09:55AM

Jim,
Thanks for the additional info. This just confirms my choice to go with the V8tuner valve set. With the exception of enlarging the valve seats it's pretty much a straight swap, well maybe new exhaust valve seats.


phongshader
Justin Brown
Ca
(50 posts)

Registered:
02/19/2010 04:03PM

Main British Car:
Locost Lotus 7 2.3 Duratec

authors avatar
Re: Beating a dead horse? Bore x Stroke x 300 heads
Posted by: phongshader
Date: July 06, 2018 07:29PM

Reviving this thread, I'm looking for a good head porter in California to do up my 300 heads. Any recommendations? I'm in the SF bay area and I'd prefer not to ship them to Missouri to get the work done.


phongshader
Justin Brown
Ca
(50 posts)

Registered:
02/19/2010 04:03PM

Main British Car:
Locost Lotus 7 2.3 Duratec

authors avatar
Re: Beating a dead horse? Bore x Stroke x 300 heads
Posted by: phongshader
Date: August 17, 2018 10:01AM

Wow! No recommendations for a west coast shop to port some 300 heads? All right how about recommendations for any shop to do up some 300 heads?


roverman
Art Gertz
Winchester, CA.
(2900 posts)

Registered:
04/24/2009 11:02AM

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

Re: Beating a dead horse? Bore x Stroke x 300 heads
Posted by: roverman
Date: August 22, 2018 05:55PM

" Mc Kenzies" ,(spell check), north of Oxnard, CA., ported my Merlin F85 heads,(Real Steel). They flowed quite well throughout the lift range. Spec's are posted on this site. I suspect also, "West Coast Racing Cylinder Heads", would perform good porting.
Good Luck, art.
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