Slant Six Forum :: What are the largest valves you can install on a slant six without cutting into the cylinders?

the crankshaft would twist the block and break it, so the bottom end was made heavier. The 225 would have the same problem with a "modern" head.

Tilley did this. Think he used 1.8X int and 1.40 exh sizes. Flowed like crazy on the intake - 230 CFM? Engine made 355 HP on engine dyno, IIRC. His best was 370 HP with a head with more std valve sizes.

Lou

Quote:

the crankshaft would twist the block and break it, so the bottom end was made heavier. The 225 would have the same problem with a "modern" head.

Not sure I follow why a better flowing head would affect block integrity?

Quote:

the crankshaft would twist the block and break it, so the bottom end was made heavier. The 225 would have the same problem with a "modern" head.

Not sure I follow why a better flowing head would affect block integity?

Author:	Rick Covalt [ Thu Sep 23, 2021 6:56 am ]
Post subject:	Re: What are the largest valves you can install on a slant six without cutting into the cylinders?
Yes I think so Greg. I think my engine builder up here would have the ability to do this. I figured with the slant 6's better flow on the exhaust side, you may be able to run a smaller exhaust valve and move the intake to improve it some more. If i live long enough I'd like to try it.

Author:	Dart270 [ Thu Sep 23, 2021 9:00 am ]
Post subject:	Re: What are the largest valves you can install on a slant six without cutting into the cylinders?
Tilley did this. Think he used 1.8X int and 1.40 exh sizes. Flowed like crazy on the intake - 230 CFM? Engine made 355 HP on engine dyno, IIRC. His best was 370 HP with a head with more std valve sizes. Lou

Author:	Greg Ondayko [ Fri Sep 24, 2021 5:10 am ]
Post subject:	Re: What are the largest valves you can install on a slant six without cutting into the cylinders?
Thanks! Good to know Lou and Rick, I will hafta investigate this on my next head(s) I have plenty of cores around to get modded. and 3 that are already somewhat skookum / Mike Jefferyfied.. But I can always build another one. Rick what is the info for that engine builder that you use? Greg

Author:	Rick Covalt [ Fri Sep 24, 2021 6:07 am ]
Post subject:	Re: What are the largest valves you can install on a slant six without cutting into the cylinders?
Kriners racing engines.Chambersburg,PA. Clint kriner is who i work with. They are someone you can trust 100%. I will see Clint Sunday and will ask if they have the abilty to do the offset guides.

Author:	slantzilla [ Fri Sep 24, 2021 9:47 am ]
Post subject:	Re: What are the largest valves you can install on a slant six without cutting into the cylinders?
I am guessing the seat has to be moved too, or at least replaced so you have enough meat to grind out?

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Author:	Rick Covalt [ Mon Sep 27, 2021 2:42 am ]
Post subject:	Re: What are the largest valves you can install on a slant six without cutting into the cylinders?
I spoke to Kriner's yesterday and they were not aware of any offset guides to do what we are saying. They would likely be custom one off pieces. It sounded as though we are better off doing all the things we are already doing. Good valves, bore notch and larger overbores. Not that this couldn't be done, but it would be a lot of work and $$. They really are too busy to want to try and do something like this anyhow.

Author:	GregCon [ Mon Sep 27, 2021 4:16 am ]
Post subject:	Re: What are the largest valves you can install on a slant six without cutting into the cylinders?
I wouldn't think an offset guide would be hard to make...or better, you'd just press in a solid guide then drill the new hole where you wanted it. If you drilled the hole in the guide before installing it, you'd be obligated to clock the hole properly.

Author:	Dart270 [ Tue Sep 28, 2021 4:34 pm ]
Post subject:	Re: What are the largest valves you can install on a slant six without cutting into the cylinders?
I like the solid guide stock idea and drill new hole. Bet that's what Tilley's guy did... Lou

Author:	Tim Keith [ Sat Oct 02, 2021 11:02 am ]
Post subject:	Re: What are the largest valves you can install on a slant six without cutting into the cylinders?
The Jaguar 3.8 E type (3.43" bore x 4.17" stroke) could use as large as 2.1-inch intake valves and was rated as high at 265 hp, but had trouble maintaining its mechanical integrity at high rpm. The max recommended rpm was 5,500, they would come part at high rpm. That's why the block is known as a "boat anchor", the crankshaft would twist the block and break it, so the bottom end was made heavier. The 225 would have the same problem with a "modern" head. I'd be okay with a more boring approach to update the Sputnik era slant six - a head that flows about like the 2.5 K-car head (8.9:1 CR if the posted spec is true), which was only rated at 100 hp. Extrapolated to 3.7 liters that is 148 hp - that's stock 318 2 barrel territory. When the 2.5 was replaced with the Jeep 2.5 with the larger bore of the AMC motor, the hp over the Mopar four increased a whopping 25 percent to 125. The K-car head didn't flow as well as it might, they settled on torque being more important for the majority of customers as the cars grew somewhat heavier. Maybe the target could be 160 hp net on 87 octane, giving up some low-mid torque. The 7.3 Ford v8 looks as if it has inline valves, but there is a 1.8 degree cant to the valves. Every bit helps. 150 hp on 87 octane isn't much, but its a decent baseline to work with.

Author:	Rick Covalt [ Sun Oct 03, 2021 4:17 am ]
Post subject:	Re: What are the largest valves you can install on a slant six without cutting into the cylinders?
Quote: the crankshaft would twist the block and break it, so the bottom end was made heavier. The 225 would have the same problem with a "modern" head. Not sure I follow why a better flowing head would affect block integity?

Author:	Jase [ Sun Oct 03, 2021 6:07 am ]
Post subject:	Re: What are the largest valves you can install on a slant six without cutting into the cylinders?
Dart270 wrote: Tilley did this. Think he used 1.8X int and 1.40 exh sizes. Flowed like crazy on the intake - 230 CFM? Engine made 355 HP on engine dyno, IIRC. His best was 370 HP with a head with more std valve sizes. Lou Does this suggest that the bottleneck is elsewhere, and a valve can be oversized, in relation to effective wet flow type improvements? Does the 370 HP head still exist?

Author:	slantzilla [ Sun Oct 03, 2021 9:20 am ]
Post subject:	Re: What are the largest valves you can install on a slant six without cutting into the cylinders?
Rick Covalt wrote: Quote: the crankshaft would twist the block and break it, so the bottom end was made heavier. The 225 would have the same problem with a "modern" head. Not sure I follow why a better flowing head would affect block integrity? Better head=more rpm. More rpm=crank issues. I don't think we'd see that much trouble on a Slant. The crank and block are fairly tough. I wick mine up pretty good, never even eaten a bearing so far.

Author:	Dart270 [ Sun Oct 03, 2021 1:18 pm ]
Post subject:	Re: What are the largest valves you can install on a slant six without cutting into the cylinders?
Tim is just talking about another engine altogether. 225s are good to north of 6200 RPM reliably w/o crank issues (probably 6500), if the engine is built at all well. Lou

Author:	slantzilla [ Sun Oct 03, 2021 8:05 pm ]
Post subject:	Re: What are the largest valves you can install on a slant six without cutting into the cylinders?
My old motor I shifted at 6500, this one is 6300. Both went over 7000 some.

Author:	Tim Keith [ Tue Oct 05, 2021 6:28 pm ]
Post subject:	Re: What are the largest valves you can install on a slant six without cutting into the cylinders?
Rick Covalt wrote: Quote: the crankshaft would twist the block and break it, so the bottom end was made heavier. The 225 would have the same problem with a "modern" head. Not sure I follow why a better flowing head would affect block integity? The Jaguar XK6 was iffy at 7,000 RPM - which 2.1-inch valves and straight/short intake ports can support. They weren't drag racing motors, often were in 24 hour endurance races. They won LeMans many times. The blocks cracked because the long stroke (4.17-inch) crankshaft flexed. The factory race teams could afford to spend money to strengthen the block - to use titanium connecting rods, but the heavy OEM ofactory blocks were built like they were for tractors. The motor works well when the weight was under 2,500 lbs, but when the sedans approached 4,000 pounds they couldn't emphasize high RPM like the lightweight E-Type coupe can. All XK6's have seven main bearings, but the block is a late 1940s design, influenced by WW2 aircraft. There is quite a bit of aftermarket support for these oldies, much of it not all that expensive. A few months ago Jaguar began producing a new 4.2 liter block. Many of the junked 4.2 sedans you may come across have cracked blocks - from a cooling design defect that is now resolved - wasn't a big issue in the U.K. or northern U.S. states and Canada, but in California to Florida they often cracked during the summer. These motors were the inspiration for inline six motors like the 2JZ, which has a much better block design. Jaguar pushed the bore of the XK6 4.2 liter block to 3.63-inch on a 4-inch bore center spacing, only the 4.2 is where the cooling defect caused upper block cracking. The 3.8/3.4 block doesn't suffer from the heat related cracking. There are different XK6 heads, the E-type is a hemi combustion chamber, some have 35-degree valve angle. The 4.2 is an emissions "quench" head with more shallow valve angle, but it can accept pretty big valves too. When it does not overheat and its well maintained the DOHC motors can last 300,000 miles, they are really trouble free for the most part, and actually pretty cheap to hobby with if you find a decent sedan. There are still teams building new XK6 motors for fun. If you were nuts this head design would adapt to a slant six. I'm sure a new head casting would be needed, but unlike modern 4 valve heads, these have a lot of real-estate and generous water passages - pretty wide heads. The head studs are "wet", the studs pass through coolant - not a drilled thru-hole with all metal shoulders. Often you can't simply remove the head because of neglect - the bad coolant permits the studs to rust and swell. The bolt pattern is similar linearly to a slant six, but the width varies because the studs rise near the top of the inner camshaft tower. Its an antique, but : It does have a Hemi in it. You might be able to reuse XK6 camshafts. I thought about buying $40 used cam from Ebay to see if the bore spacing is like that of a slant six. You don't need the entire head or the block. If the cam lobes align with the cylinders of a slant six then you could use the Jaguar cams, intake and exhaust manifolds - if you can build the head casting. There are lots of cool aftermarket parts for the heads. There was a time when you could pickup an old E-type coupe for $1,000, but they sure are spendy now, and the the E-type hobby like to spend $$$$ https://www.stratstone.com/jaguar/e-typ ... -at-heart/ Edit: This is a street driven E-type. He claims the motor makes 360 lb foot torque, at least 350 hp with 9.7:1 CR. 4.528-inch stroke!!!! 2.00" valves. He has a rev limiter set to 6,600 rpm. If Chrysler had wanted to build a decent pushrod head it could have been a "poor man's E type". That's why they sold cheap V8s. This car weighs 2,200 pounds and cost $450,000 to restore, Leno said he used to see these for $800. A decent pushrod head wouldn't make this much power but with electrification of cars being pushed there will be a new nostalgia era for older cars and many folks will spend money. This is late '40s technology refined for the '60s. 1963 Jaguar E-Type - Jay Leno’s Garage https://www.youtube.com/watch?v=gRfT40efYJw Edit Oct 30 Another OEM head that could be a casting design pattern is the Toyota 3TC pushrod hemi. The pushrods appear to be in about the same location as a slant six. I'm suggesting this motor because 3TC valve train parts are relatively easy to find. The stock bore is just under 3.40-inch but they bore these to 3.50 inch. The 3TC has domed pistons. You might be able to have one of the companies that make pistons for these motors alter the piston pin location and size. The intake manifold might get pretty close to the inner fenders on a Valiant or Dart. There is still a decent aftermarket for the T series. Its a neat classic engine that resembles an old Chrysler hemi. Probably wouldn't work, but the pushrod design makes me curious.

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