MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

Go to Thread: PreviousNext
Go to: Forum ListMessage ListNew TopicLog In
Goto Page: 12Next
Current Page: 1 of 2


castlesid
Kevin Jackson
Sidcup UK
(361 posts)

Registered:
11/18/2007 10:38AM

Main British Car:
1975 MGB GT Rover V8 4.35L

Buick 300 Heads.
Posted by: castlesid
Date: January 31, 2008 12:22PM

I'm using a pair of alloy Buick 300 Heads on a new 4.35 Rover based engine and have a couple of queries.

1, How much can be safely machined off the heads? as I need to reduce the combustion chamber volumes to a maximum of 47cc from their existing 54cc.to achieve the desired compression ratio. The only flat top pistons I could get have 5cc valve cut outs which has thrown my calculation out somewhat.

2. Are there any manifold matching problems with the Buick heads on to a rover 3.9 block? I was thinking that as the Buick heads have more material in both the height and width of the Inlet port areas that the heads may sit a liitle higher than the old Rover heads in which case it may be beneficial to actually machine some material from the head mating surfaces. The height of the Rover Inlet port is I think 38mm and the Buick 300 is 44mm. I will be using a Rover type inlet and want to avoid a head to manifold mating problem.

3. I have been told that the existing Buick Ex, valve seats are quite hard, and should be ok for unleaded use.

Any information would be gratefully received.

Regards.

Kevin Jackson.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: Buick 300 Heads.
Posted by: BlownMGB-V8
Date: February 01, 2008 08:18PM

Kevin, based only on my experience with the 215 heads I'd say you can go only to the point where the milling cutter barely kisses one of the valves. That was about .040" on the Olds 215 Jetfire head (Same as Olds 4bbl and very similar to the Buick 215 head.) so I would expect it it be in the same ballpark. This would vary of course depending on your squish, or how far down the bore the piston sits at TDC and with the slightly larger chamber there might be more room on the 300 heads. 7cc could be a good bit to remove from a head, though I have gone .090" on a different brand of engine with good success. (You will get a bigger compression increase by milling the block.) I expect you might get by with something like that if the valves will clear, but haven't cut up a head to verify. Sonic checking might answer the question though. As far as alignment afterwards though I don't see that being a problem.

What happens when using the 3.9 block and intake I can't address, best to fit them to the block and see.

Your valve seats should be just fine.

Jim


castlesid
Kevin Jackson
Sidcup UK
(361 posts)

Registered:
11/18/2007 10:38AM

Main British Car:
1975 MGB GT Rover V8 4.35L

Re: Buick 300 Heads.
Posted by: castlesid
Date: February 02, 2008 03:44PM

Jim,

Thanks for the response, as the Keith Black chevy 305 pistons will be approx 30 thou below the deck at TDC subject to a test build and measure, it would seem sensible to machine the decks. I have been told by one acknowledged expert that I should not take more than 10thou off the decks which seems rather minimal and would not have much effect on compression as it would only reduce the deck volume by approx 1 1/2 , I think I would have to reduce the deck heights by 30thou to have any real benefit, do you think this is workable, if so with a 20thou mill on the heads it should put me back where I want to be with a static comp. ratio of approx. 9.8/1. I will obviously have to machine the manifold to fit

I was also wondering about the head bolt holes and if they would need increasing in depth to compensate for the reduced deck height.

It's always the problem when you build a mongrel engine, that as soon as you change one thing, everything else has to be adjusted, but I'm enjoying the process and the finished engine will have a bore of 94.89mm (3.736") and stroke of 77mm. (3"0)
for a capacit of 4355cc or 265CI so should be fun! just need to pick up some timing gear and adjustable push rods to complete the list of components. Forgot, do the push rod holes on the 300 heads need enlarging to use adjustable push rods, they seem to be 8-9mm. or .315" the push rods are 5/16" whch is approx the same dimension so it looks like I will have to enlarge them, how much do they need to be enlarged?

Regards,

Kevin.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: Buick 300 Heads.
Posted by: BlownMGB-V8
Date: February 02, 2008 05:56PM

Kevin, I couldn't see much harm in going up to .030-.060" on the deck and .040" on the heads. You could probably go more than that if you had piston clearance. Best method with the head bolts is to helicoil the block and check for bottoming. Odds are you'll be fine. If not, you can buy hardened washers and double up on them easily enough, or grind down the bolt ends. I prefer to either use long helicoils or double up on them.

Typically you would want to mill the head face that meets the intake so that an unmodified intake will fit. Should be the same amount of material that came off the head and deck. You can play with this for best fit of your chosen intake. The lifters should be able to accommodate this much variation, of course they may be more prone to pump up compressed that far, causing valve float before reaching your target redline. I'd try the stock pushrods first though. You can get a pushrod kit that allows you to cut the tube to length and then insert the end and this works well. In some cases you can even pull the end back out for further shortening. You don't have to be exact at all on the length but try to cut them all the same. Within 1/64" is just fine. Or you can just buy the tubes and use ends cannibalized from an old set of pushrods. These will be much lighter than adjustables.

For the holes you need enough clearance that the pushrod can go through it's full range of motion without hitting the head. The rocker end will move laterally as the rocker pivots. Also allow for some bowing of the tube under compression. Since the head is aluminum you can probably get away with minimal clearance though as long as nothing touches.

Jim


castlesid
Kevin Jackson
Sidcup UK
(361 posts)

Registered:
11/18/2007 10:38AM

Main British Car:
1975 MGB GT Rover V8 4.35L

Re: Buick 300 Heads.
Posted by: castlesid
Date: February 02, 2008 09:13PM

Jim,

Thats a great help.regarding the machining.

I was thinking that the pushrod holes needed relieving more in the plane of the rockers so there is additional clearance as the rockers move through there arc of operation plus probably a bit of clearance at the sides to allow for any lateral movement of the pushrods themselves.Probably easiest to elongate the holes toward the centre of the heads with a rat tail file and just clean up the sides for comfort.

Kevin.


castlesid
Kevin Jackson
Sidcup UK
(361 posts)

Registered:
11/18/2007 10:38AM

Main British Car:
1975 MGB GT Rover V8 4.35L

Re: Buick 300 Heads.
Posted by: castlesid
Date: February 06, 2008 07:49PM

Jim,

When you say machine the inlet port head faces by the same amount do mean if a total of say 50 thou has been removed from the decks and heads that you take 50thou off off each head inlet face or 25thou of each making a total of 50thou.

My higher maths is pretty rusty these days but remember that with a 90degree angle that you use a sine ratio but that's about it.

Also I asked above about the pushrod hole enlaegement to take 3/8" adjustable pushrods and would appreciate a bit of advice about those as well, We should start the block machine work next week once i get the bloody pitons out of British Customs!!

Kevin.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: Buick 300 Heads.
Posted by: BlownMGB-V8
Date: February 06, 2008 09:46PM

Kevin,
If you view the block, heads and intake as a square (assuming the manifold/head parting line is at right angles to the deck and parallel to the bores) with the bores making up two sides, then it's pretty clear that anything removed from one of those sides also has to be removed from the opposite side to keep everything parallel. So yes, the total removed from block and head would be removed from the intake face, assuming also of course that both sides are milled equally. If the parting line is *not* at 90* the amount is different.

I really don't favor adjustable pushrods in an engine with hydraulic lifters. There is no need for them, it's something else to go wrong, they make the valvetrain much heavier and cause valve float to come on much quicker, and they are the very dickens to adjust with the engine running. (Adjustable rockers I like OK.) I feel you are better off with fixed length ones even if you have to change the length after running the engine to correct for an improper dry fit. Take a new lifter and using a screwdriver depress the plunger and take note of the amount of travel, I think you will be very surprised at just how far they move. If the lifter is effective at doing it's job over the entire range you could be out probably +/- 1/8" or more and it would still work. That's a heck of a range and nearly makes an adjustable pushrod totally ineffective. Almost. What actually happens is that towards the ends of the range the "pump-up" or "anti-pump-up" characteristics of the lifter do tend to change somewhat, so that at the tight end of the range the lifter may contribute to valve float at high rpm's sooner than at the midpoint, and at the loose end it may leak down fast enough to occasionally cause lifter tap. Right in the middle is where you want to be, but you can get there easy enough with fixed length pushrods. Just measure the length needed fully compressed and fully uncompressed and split the difference. Then after break-in if you need to make a correction you can go longer or shorter as needed, and a move of .040" is probably not too much. One adjustable pushrod is sometimes useful in taking the measurements, and if you really want to use them it's up to you of course but you'll need to talk with your machinist about what is needed to make them fit. What I already said about clearance should apply, as well as making sure no part of the adjustment mechanism makes contact with the head, the rocker or the rocker shaft. Your thoughts about how to do it make sense.

Anything else I can help with, you know where to reach me.

Jim



castlesid
Kevin Jackson
Sidcup UK
(361 posts)

Registered:
11/18/2007 10:38AM

Main British Car:
1975 MGB GT Rover V8 4.35L

Re: Buick 300 Heads.
Posted by: castlesid
Date: February 07, 2008 01:49PM

Jim,

Thanks for the advice, over the course of today I have come to the same conclusion regarding the adjustable push rods, so have ordered up some heavy duty fixed length ones and will rely on shims to set the preload.

Just so I am completely clear regarding the amount to machine from the heads/manifold joints, if 50thou total is taken from each head and the block I take 50thou from each inlet port face.

Kevin


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: Buick 300 Heads.
Posted by: BlownMGB-V8
Date: February 07, 2008 07:54PM

Right on Kevin. Say you take 20 off the head and 30 off the block you take 50 off the intake side. Generally though, .030" or less won't require it, you can get that much by using shim style head gaskets if available. Suggestion: Fit up the heads and gaskets and see how the intake fits with the type intake gaskets you plan to use. If it rides high cut a little extra off, if it rides low cut a little less. Watch the fit in the bolt holes in particular. You can juggle things here to get a near perfect fit. I once had an extra .030" cut off so that I could go from a shim intake gasket to a composite one and it worked perfectly.

Because of your mix-n-match your pushrod length may not fall in the sweet spot, but I think you are on the right path. The small block Buick motors use a solid pushrod but if you like a tubular one can be used instead. It may require the holes to be drilled out larger (maintain the same amount of clearance as with the originals) but they are somewhat lighter and have the other advantage that you can buy cut-to-length kits. Seems the last set of pushrod tubes I bought came from Racer Brown but they aren't hard to find. It's just plain jane chrome moly tubing anyway, you could buy it in standard lengths of 10 or 20 ft if you have a set of ends to insert. Done this way you can get your pushrod length perfect at little cost. The ends are generally inserted using a small press or can be driven in with a soft hammer if done with care.

Jim


castlesid
Kevin Jackson
Sidcup UK
(361 posts)

Registered:
11/18/2007 10:38AM

Main British Car:
1975 MGB GT Rover V8 4.35L

Re: Buick 300 Heads.
Posted by: castlesid
Date: February 08, 2008 06:19AM

Jim,

Thanks that clarifies the picture, I was also thinking that because the inlet port size on the Buick 300 heads are approx 44mm and the rover ports are approx 38mm it might be an advantage if the rover manifold sat a little higher so as to get a better match between at the roof of the port which I believe is more important.

What we could do is a trial fit and see where the manifold sits, and if the bolt holes are low in relation to the manifold holes we could file the holes on the manifold to allow it to bolt up ok and give us a good match with the port roof, what do you think?

I am only going to use the Performer manifold and Edelbrock carb as a temporary measure. I have all the hardware for a hotwire EFI but this is going to require an after market ECU and I will probably be using Megasquirt and will port the EFI manifold to properly match the 300 port sizes, fortunately the composite gaskets ports exactly match the Buick 300 heads which is a nice coincidence and will be a useful template for the manifold porting.

Kevin.


MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: Buick 300 Heads.
Posted by: MGBV8
Date: February 08, 2008 03:07PM

I suggest you rethink this approach.

That is a lot of metal to remove from the block & heads. I don't think that formula is quite right, Jim. There is a reason hotrodders refer to it as "angle milling" the heads. Of course, it does depend on the engine.

Kevin,

The money you will spend on machining the block & heads would go a long way towards a custom set of forged pistons that suit your application.

You will have to assemble the short block & measure the deck height first before doing any milling. If you are really .030" in the hole, a Chevy 6.0" rod might be the ticket.

Seriously consider custom pistons before cutting up the block & heads.


castlesid
Kevin Jackson
Sidcup UK
(361 posts)

Registered:
11/18/2007 10:38AM

Main British Car:
1975 MGB GT Rover V8 4.35L

Re: Buick 300 Heads.
Posted by: castlesid
Date: February 08, 2008 03:36PM

Carl,

Thanks for the imput, I have a set of Chevy 5.85" rods, already machined to fit the Rover crank with ARP bolts which were quite economical at £250.00 and the pistons have just arrived in the UK again Chevy 305 flat tops with 5cc valve reliefs, agreed Chevy 6" rods would have solved the deck height problem, but I was not aware that you could get them and they would still need machining to fit the Rover. As for a set of custom made forged pistons in the UK you are talking about at least £800.00

The Keith Black Chevy 305 Hypereutectic from Summit only cost me £143.00 including a decent ring set.

Once the pistons clear customs and are delivered, we will bore the block and do a test build to determine all the critical dimensions, and I can then make decisions. Should happen in the next couple of weeks s will report back with my findings.

Thanks again,

Kevin Jackson.


MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: Buick 300 Heads.
Posted by: MGBV8
Date: February 08, 2008 05:06PM

Kevin,

I was just going ask you what rod you were using. Three years ago I was scratching my head trying to find a decently price performance piston for a 3.9 buildup. After many, many hours I came up with the same piston that you are using. The catch was that I needed to find a rod that would make up for the pin height difference. The Chevy 6" small journal rod was the ticket. That was for a non-stroker application so I was curious how you were using the same piston with a 4.2L (??) crank.

This may help what I was concerned about in my earlier post:

[www.goodson.com]

Also if you angle mill the combustion side of the head, taking off more meat from the spark plug side, it can affect cc more than straight cutting. It will also give a bit more favorable angle to the valves. The intake side of the head will have to be angle milled correctly to compensate.

Good luck!


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: Buick 300 Heads.
Posted by: BlownMGB-V8
Date: February 08, 2008 08:34PM

Now just hold on Carl, are you milling the heads, or angle milling them? If a standard milling job as in cleaning up the mating surface, .010" is common and up to 30 or 40 thou is pretty common too. Ten is about the least you can take off and get a good cut and removing warpage can easily go 20. Do that twice and you're at 40 so I don't see how that is a lot of metal. I can see where you'd need to remove a lot to angle mill a head but that would change the valvetrain geometry, the header clearances, and generally foul up the head bolts. I realize racers go to great extremes sometimes but to do this on a Rover motor just to cut more volume out of the combustion chamber seems to me like going into uncharted territory, and doesn't strike me as a very good idea, since it also throws the intake faces out of square. As long as that angle is 90* the 1:1 ratio holds and that greatly simplifies things. No trig needed to know how much to remove. Now it's true that some engines don't use a 90* angle between the deck and intake but I'm pretty sure the Rover does, so I can't think why this would be difficult or cause problems.

Anyway, there are always other ways to get there of course. If longer rods do the trick more easily and cheaply, why not?

Jim


castlesid
Kevin Jackson
Sidcup UK
(361 posts)

Registered:
11/18/2007 10:38AM

Main British Car:
1975 MGB GT Rover V8 4.35L

Re: Buick 300 Heads.
Posted by: castlesid
Date: February 09, 2008 06:47AM

Carl/Jim

I have just done a calculation and if you used the Chevy 6" rods the pistons would be approx 116 thou out of the bore ie. the extra .150 - the 34thou clearance I have at the moment.

The block height of the Rover is 8.96" centre of crank to decks.

The stroke is 77mm. 3.03" so the calculation is half stroke 1.515" + 5.85" +1.561 (Compression height of 305 KB piston)

= 8.926" so I appear to be theoretically 34 thou down the bores.

So if I machine the decks say 25thou puts the pistons 9thou down the bores + tin gasket at 18thou gives me 27thou clearance piston to head face which should be ok, but any comments?.

Swept volume of a cylinder = 544cc + 50cc head + deck and gasket at 5cc + piston cut outs 5cc = 604cc divided by 60cc


This will give me a static compression ratio of 10/1 which will be fine with the gas we have over here, we have the option of using Shell V Power which will support compression ratios in excess of 11/1

I an using a Crower 50232 cam which has ,488 lift and advertised duration of 276 Inlet + 281 Exhaust at .050 and should match the flow characteritics of the Buick 300 heads very well.

I have done the maths on this so many times as I was terrified of getting it wrong, one decimal point out and your screwed but having rechecked it all again this morning it appears to be ok, I hope!

Great news. I have just had a card saying that the pistons have cleared customs and no import duty payable, only our dreaded VAT at 17.%

Kevin.



MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: Buick 300 Heads.
Posted by: MGBV8
Date: February 09, 2008 09:26AM

That gets you to less than optimum quench.

[kb-silvolite.com]

You may have to do some juggling, but I think it would be better to take more off the heads & less from the block.

I don't understand why you were unable to get KB 266 (0cc) or even KB144 (-.5cc) (this one is on Ebay) pistons.


Jim,

Adding up ".030-.060" on the deck and .040" on the heads", I though .100 for a street engine seemed like a lot. Maybe not. Doesn't look like Kevin needs to go that far. Come to think off it, I think I shaved the heads on my Camaro .040 way back when.


castlesid
Kevin Jackson
Sidcup UK
(361 posts)

Registered:
11/18/2007 10:38AM

Main British Car:
1975 MGB GT Rover V8 4.35L

Re: Buick 300 Heads.
Posted by: castlesid
Date: February 09, 2008 05:36PM

Carl,

Unfortunately the KB 266 is not currently in production, it was the one I originally was going for. I did look at the KB144 but thought, possibly incorrectly that it would give me too much compression because their calculator give 11.5/1 with 54cc chambers, at that time I was still at the learning stage and wasn't fully understanding all the factors regarding piston selection!

If 40thou is the minimum clearance between top of piston and head then clearly I will have to rethink, and only remove a max of 12 thou from the decks, I certainly don't want the pistons getting too friendly with the heads! My thinking came from information on another site which stated you could run safely with 25thou of squish/quench but I'll go with the advice of the people who make the pistons, I should have picked that up earlier.

Just done a recalculation and if I take 12thou off the decks and machine the heads to give 50cc chambers, use tin gaskets (18thou) I can still achieve 9.775/1 which is quite acceptable.

I have certainly learnt a lot about engine building in the last month or so. I will get my engineer to accurately cc the chamber volumes as I have an idea that they have already had a shave or two. I did a rough measure with a chemists medicinal measure and could only get approx 47cc into one chamber, that would be ideal but my measuring could be very inaccurate, so will have it done properly.

Carl thanks for all your help, it's much appreciated.

Kevin.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: Buick 300 Heads.
Posted by: BlownMGB-V8
Date: February 09, 2008 10:17PM

You might as well take the dish into account when figuring how much to mill the heads. You should be able to let the valves protrude below the mating surface by that amount, or if your pistons have valve reliefs, perhaps more. Also consider milling the decks enough to allow you to use composite gaskets. Easier to find and generally better sealing.

Jim


castlesid
Kevin Jackson
Sidcup UK
(361 posts)

Registered:
11/18/2007 10:38AM

Main British Car:
1975 MGB GT Rover V8 4.35L

Re: Buick 300 Heads.
Posted by: castlesid
Date: February 10, 2008 04:45AM

Jim,

Once I have the pistons we can measure it all and then make hopefully th right decisions.

Thanks,

Kevin.


MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: Buick 300 Heads.
Posted by: MGBV8
Date: February 10, 2008 10:30AM

"Carl thanks for all your help, it's much appreciated."

Listen to Jim. He knows waay more than I do about many things, probably most things. :)

At the end of this thread is what I have/had planned for my 3.9 engine:

[forum.britishv8.org]
Goto Page: 12Next
Current Page: 1 of 2


Sorry, only registered users may post in this forum.