Slant Six Forum :: sick /6 motor

Slant Six Forum https://www.slantsix.org/forum/

sick /6 motor https://www.slantsix.org/forum/viewtopic.php?t=62889	Page 1 of 3

Author:

Crizila [ Tue Oct 02, 2018 6:14 pm ]

Post subject:

sick /6 motor

After getting some horrendous results on my leak down test, I finally pulled the head off my 225 /6 motor. As I suspected, blown head gasket in #4 hole. Also the valves seats were in really bad shape. Whom ever did the last valve job, didn't know what they were doing, as the valve seats were all over the place - some sunk, some seats almost off the valve face, some valves with almost no margin left on them. Heads gonna need new seats, valves, springs, and guides. On the plus side, no grooving on the block from the blown gasket. Gonna pull .090" off the head surface and bolt it back on. Might do some minor bowl porting. Cylinder bores are stock and the taper measures in the .015 to .022" range.

Attachments:

blownhead gasket4.jpg [ 232.02 KiB | Viewed 7256 times ]

Author:	slantzilla [ Tue Oct 02, 2018 10:58 pm ]
Post subject:	Re: sick /6 motor
Now would be a great time to just grind the seats out and put in bigger valves John.

Author:	Dart270 [ Wed Oct 03, 2018 7:26 am ]
Post subject:	Re: sick /6 motor
You might have had valve recession, so stainless valves would help that. Most of the 1.70/1.44 oversize valves are stainless. I am not sure who is selling them now - SI Valves?? Best, Lou

Author:

Crizila [ Thu Oct 04, 2018 5:19 pm ]

Post subject:

Re: sick /6 motor

Soooo, Got my head back from my machinist - new stock valves ( back cut @ 25* ), springs, guides, seals and head milled .090". Combustion chambers CC,ed at 48CC's. With stock bore / stroke, .042" compressed gasket thickness, pistons .163" down the hole, I ended up with 8.79:1 CR. I did not run the numbers with stock combustion chambers ( wouldn't hold fluid ), but the CR had to be ridiculously low.

Attachments:

48ccchambers.jpg [ 220.18 KiB | Viewed 7180 times ]

Author:	slantzilla [ Thu Oct 04, 2018 5:29 pm ]
Post subject:	Re: sick /6 motor
7.5ish would not be unusual John. Tolerances were very "liberal" from Ma Mopar.

Author:	Crizila [ Thu Oct 04, 2018 8:29 pm ]
Post subject:	Re: sick /6 motor
Quote: 7.5ish would not be unusual John. Tolerances were very "liberal" from Ma Mopar. Holly Molly! Factory spec is 8.4:1. Well, on the plus side, I should still be able to run "tom cat piss" without a detonation problem.

Author:	67regal [ Thu Oct 04, 2018 10:09 pm ]
Post subject:	Re: sick /6 motor
Nice work, I'm interested in what you've done because I'm tossing up between just headwork like you fit a budget option..... vs ground up rebuild. I think I might be surprised by the improvement of just the work you have done to my tired /6. Thanks for sharing.

Author:	67regal [ Thu Oct 04, 2018 10:13 pm ]
Post subject:	Re: sick /6 motor
Quote: You might have had valve recession, so stainless valves would help that. Most of the 1.70/1.44 oversize valves are stainless. I am not sure who is selling them now - SI Valves?? Best, Lou Hey Lou, if those are the oversize valves, the stock ones must be quite small? Silly question, but why would you go oversize? What's the main benefit and what other matching components do you have to have to make it work the best? Thanks

Author:	Dart270 [ Fri Oct 05, 2018 4:15 am ]
Post subject:	Re: sick /6 motor
Stock are 1.62/1.36". You should do some bowl porting/blending to take advantage of the bigger valves. Otherwise, they will only help performance at all speeds. I usually mill the head to raise compression to at least 8.5 or 9:1 and (if increasing CR) put in a mild cam like the Howards cam I just posted about. Lou

Author:	Crizila [ Fri Oct 05, 2018 10:24 am ]
Post subject:	Re: sick /6 motor
Quote: Nice work, I'm interested in what you've done because I'm tossing up between just headwork like you fit a budget option..... vs ground up rebuild. I think I might be surprised by the improvement of just the work you have done to my tired /6. Thanks for sharing. I forgot to mention that the exhaust valve seats were replaced also, as the recession was just too bad to save them. I have to continually keep myself in check on this project and stay with my original plan and allotted budget - a nice driver for 12K. Remember, this was a junk yard car. Bigger valves with 5/32" stems, Port work, all crossed my mind ( not to mention pulling the engine and doing it all ). I think that just getting the head straightened out will put me in the "nice driver" range. Down the road, I might buy a complete used 225 and make it something more than a "nice driver". I have learned over the years to have a plan to start with and stick to it. "Well, if you want to do it the right way " - That comment always equates to more $, and it's easy to say when it aint yo $! I will probably do a little port matching and bolt things back together. On another note, there is an article in the November issue of Mopar Muscle entitled "Making slat 6 sense". They said that all /6 exhaust manifolds had a 2 1/4" outlet. Not so. Mine measured 2". I will be running a 2" exhaust pipe ( to match the 2" exhaust manifold outlet ) in to a 2 1/2" inlet 2" dual outlet Flowmaster muffler with dual 2" tail pipes. Should be more than adequate for a stock 225. The other part of this article was about updating your point ignition with a new D.U.I. ignition. Beside their HP improvement claims being in the fantasy land range, ( just my opinion and especially if you are already running an electronic ignition system on a stock motor), the D.U.I. ignition does not have a vacuum advance system, which the article claims you do not need with the new D.U.I. ignition. Aint buying that one ether, especially for street operation.

Author:	67regal [ Sun Oct 07, 2018 4:12 am ]
Post subject:	Re: sick /6 motor
Quote: Stock are 1.62/1.36". You should do some bowl porting/blending to take advantage of the bigger valves. Otherwise, they will only help performance at all speeds. I usually mill the head to raise compression to at least 8.5 or 9:1 and (if increasing CR) put in a mild cam like the Howards cam I just posted about. Lou Thanks Lou, that's exactly what I'm aiming for. Will this be ok on a bottom end that has not been rebuilt? And I can't find the specs of the Howard's cam you mentioned? Thanks

Author:	Dart270 [ Sun Oct 07, 2018 6:06 am ]
Post subject:	Re: sick /6 motor
Assuming your rings are OK, you should be fine. Did you do a compression test, by chance (engine warmed up), before you tore it down? Here is the link to the Howards cam discussion: http://slantsix.org/forum/viewtopic.php?f=19&t=62844 The search function is very helpful on this board. If you search "howards" then that thread comes right up. Lou

Author:

Crizila [ Sun Oct 07, 2018 7:12 am ]

Post subject:

Re: sick /6 motor

Quote:

Assuming your rings are OK, you should be fine. Did you do a compression test, by chance (engine warmed up), before you tore it down?

Here is the link to the Howards cam discussion:

http://slantsix.org/forum/viewtopic.php?f=19&t=62844

The search function is very helpful on this board. If you search "howards" then that thread comes right up.

Lou

Thanks for the link. I'm running a NA motor. Did both a Comp test and leak down test. Both were really bad. Leak down showed most the leak past the valves ( both in & ex). I'm sure it could use rings ( taper measured around .015 to .022 ), but I'm not going there right now.

On another note, check out the attached pics. While looking in to the thermostat housing hole I found two lengths of wire in the water jacket. The one I removed ( laying on the head in one pic) came out of the water jacket on the port side of the comb chambers. The other wire is still in the head ( other pic ) and it is on the lifter side of the chambers. Just started to fish it out in that pic. ????????????????? I have no clue as to how they got in there or why.

Attachments:

wire in head 3.jpg [ 252.18 KiB | Viewed 7055 times ]

wire in head 1.jpg [ 204.93 KiB | Viewed 7055 times ]

Author:	ceej [ Sun Oct 07, 2018 8:57 am ]
Post subject:	Re: sick /6 motor
The wires are part of the casting process. Once casting is complete, the sand is removed, but the wire that holds the sand during the pour remain in place. CJ

Author:	67regal [ Sun Oct 07, 2018 5:22 pm ]
Post subject:	Re: sick /6 motor
Quote: Soooo, Got my head back from my machinist - new stock valves ( back cut @ 25* ), springs, guides, seals and head milled .090". Combustion chambers CC,ed at 48CC's. With stock bore / stroke, .042" compressed gasket thickness, pistons .163" down the hole, I ended up with 8.79:1 CR. I did not run the numbers with stock combustion chambers ( wouldn't hold fluid ), but the CR had to be ridiculously low. Thanks for posting up the info - when you milled the head 90 thou, did you need shorter or resized or new pushrods? Cheers

Page 1 of 3	All times are UTC-08:00
Powered by phpBB® Forum Software © phpBB Limited https://www.phpbb.com/