hotrod Chris Craft Hercules flatty - need advice

[dave brode]

Engine info;

I took Mr. Vines' advice and quit worrying about the rods. I did use bb chevy rod bolts, as the caps were quite loose on the stock bolts. The rods were 9 gms out heavy to light, 7 of which was in the caps. The stock pin is .875", and the rods were opened to the mopar .901" size to allow use of 225 slant six pistons, which had to be shortened by .035" for .010" positive deck height. I fashioned spacers that allowed the pinch bolts to be snug and hold the rod end to just slightly larger than the stock pins while the small end was machined. I pinned the main caps in place after pecking them around to get the main bores at least close to round. The slant piston and 5/64" ring combo is apx 80 gm lighter each than the $400 a set split skirt stock type.

1.720"/1.5" valves from '87 2.5 S-10 are correct length and slightly larger on the stem [.3135"], which required reaming the guides from the stock .310 stem size, which removed the guide wear. Valve to head gasket clearance is an issue, and I may cut the valves down slightly.

I'm going to use a -8 hose from the brass oil pu box to the pump rather than the stock -6 size, and change the oil flow route for a full flow external filter. I'd like to fashion a windage screen or tray. The boat applications have 3/8" copper external lines on the engines for oil cooler plumbing. No filter, but bypass filters were common [none on the 4 engines that I have here]. No thermostarts either.

Dave

p.s. - what would a safe guide to stem clearance be? Iron guides, chromed stem stock type valves. Sealed Power intake, Enginetech exh.

[PackardV8]

FWIW, I've converted a few flathead six intake valve guides to positive seals. This allows running enough clearance without excessive oil consumption. In addition to the economics of lessened oil consumption, no oil in the combustion chamber is good thing for preventing detonation on sustained WOT running.

[grandsport51]

We used to use Aeroshell 15W50W on those flatties Ashless and awesome Anti-wear additive pkg
Just add full flow oil filter. Plus I worked on a couple of those Chris Craft engines with triple carbs

IMG_2607.JPG

They ran pretty good @400O revs.

[groberts101]

Some cool old parts. Quick "dummy poster" question.. what is the reasoning for the angled carbs and oil pan arrangement. Mounting angle.. or to keep things more leveled out once the bow is up on its plane?

[grandsport51]

It’s for shaft angle to get prop clearance from boat bottom many old Chris runabouts ha an 18 degree
Angle which is pretty inefficient but truthfully
I worked on a dozen or so woodys on Fla and those
Chris Crafts went really well.
When they were the largest manufacturer of boats on earth, they would post the speeds of all their boats
And they would achieve the advertised speeds.
Dave B

[Truckedup]

FWIW, I've converted a few flathead six intake valve guides to positive seals. This allows running enough clearance without excessive oil consumption. In addition to the economics of lessened oil consumption, no oil in the combustion chamber is good thing for preventing detonation on sustained WOT running.

Hey Jack, do know what was done to the early 50's Nascar Hudson 6's tuned by Yunick to get , I believe, over 200 HP?

[grandsport51]

Read this Smokey article.
He was some character!
Dave B http://www.hotrod.com/articles/ctrp-0801-smokey-yunick/

[dave brode]

There are 4 engines in the "KL" group [L = longer 4.250" stroke]
KL - std K cam, one big carb. 105 horse at 3200
KLC longer cam, one big carb 120 horse at 3800 - the original engine to the '56 boat is this engine - it needs attention too.
KFL longer cam, 2 smaller carbs from std K engine 131 horse - pic of one of these is back in the thread. - the '57 engine that I'm working on.
KBL - longer cam, 3 downdraft carbs. 131 horse.

Mr. Vines, if I may ask, what would you set the guide clearance at? With or w/o seals? Thanks.

DaveB - thanks for the Smokey article, I haven't seen that one.

All: - please see my post on valve spring requirements. Last post on page 2.
Thanks.
Dave

[pamotorman]

why would flat head engines need intake valve seals as it is not like OHV engine where the oil can run down the valve guides because the oil is supplied above the guide. the oil in a flat head is running away from the valve guide.

[groberts101]

why would flat head engines need intake valve seals as it is not like OHV engine where the oil can run down the valve guides because the oil is supplied above the guide. the oil in a flat head is running away from the valve guide.

Wouldn't guide leakage, in either direction, be predominantly caused by pressure differentials created between the combustion space and crankcase.. rather than gravity alone?

[PackardV8]

why would flat head engines need intake valve seals as it is not like OHV engine where the oil can run down the valve guides because the oil is supplied above the guide. the oil in a flat head is running away from the valve guide.

Wouldn't guide leakage, in either direction, be predominantly caused by pressure differentials created between the combustion space and crankcase.. rather than gravity alone?

For true; intake vacuum is far stronger in moving hot oil up/down the guide than is gravity. That's why many OHV engines only have intake valve stem seals.

[groberts101]

why would flat head engines need intake valve seals as it is not like OHV engine where the oil can run down the valve guides because the oil is supplied above the guide. the oil in a flat head is running away from the valve guide.

Wouldn't guide leakage, in either direction, be predominantly caused by pressure differentials created between the combustion space and crankcase.. rather than gravity alone?

For true; intake vacuum is far stronger in moving hot oil up/down the guide than is gravity. That's why many OHV engines only have intake valve stem seals.

Right. And that little telltale puff of smoke on startup is from gravity doing the rest of the job after the engine has sat during cooldown.

[Keith Morganstein]

p.s. - what would a safe guide to stem clearance be? Iron guides, chromed stem stock type valves. Sealed Power intake, Enginetech exh.

I’ve done various marine L-head engines and the valve stem to guide clearance spec is kind of wild at .003”.

I have no idea why it’s so much. I set them at .002” and had no trouble.

[PackardV8]

p.s. - what would a safe guide to stem clearance be? Iron guides, chromed stem stock type valves. Sealed Power intake, Enginetech exh.

I’ve done various marine L-head engines and the valve stem to guide clearance spec is kind of wild at .003”.

I have no idea why it’s so much. I set them at .002” and had no trouble.

Keith, flatheads are bad old days rebuild technology. A hand driven guide, hand reamed, probably had to be guesstimated at .003". Most shops building them had no dial bore gauge. There were Shop Manual specs as to how much sideways wiggle. I know because my first paid mechanic gig was at fourteen, working in a boat shop.

Today's air installed guide, machine reamed and then machine honed and dial bore guaged to .002", with a chrome-stem valve and today's oil, is a much different environment for the stem/guide than the bad old days.

[dave brode]

Thanks, Gents. I'm working with bad old times tooling, and i'm a bit less than .002". I'll open them some.

Anyone care to comment on 70/140 valve spring pressure being ok?

Dave

Copied from earlier post:

The stock springs, probably from 1957, have 21# seat, 41# open! I found springs from a 1.6 Honda that I think will work well. Sealed Power has stock Honda replacements, Crower has what looks like a nicer spring for the Honda about the same money. Both are 212 lb/inch. They are less than .900" diameter and pretty tall, there are not many choices.

The cam was reground [using the correct master] by CamCraft. The tappets were also reground and are 1.200" diameter. With lash set at .010"/.012", seat timing is 265/263. At .050" rise [no lash allowance] duration is 234/236. Lift is .353 less lash. Depending on what retainer and lock I use, I can get anywhere from 50-80# seat and 120-150# open. The combo that I'd like to use would give apx 70/142#, but I will vary from that if I should.