108 lsa in the winter

General engine tech -- Drag Racing to Circle Track

Moderator: Team

DaveMcLain
Guru
Guru
Posts: 2669
Joined: Thu Jan 06, 2011 8:57 am

Re: 108 lsa in the winter

Post by DaveMcLain » Wed Oct 18, 2017 12:52 pm

A stock 265 Chevy cam is ground with only a 107 degree lobe sep. There is no magic. It works and idles just fine because the duration is only about 175 at .050.

MoPar_Kid
New Member
New Member
Posts: 32
Joined: Thu Mar 17, 2011 6:14 am

Re: 108 lsa in the winter

Post by MoPar_Kid » Wed Oct 18, 2017 6:28 pm

kimosabi wrote:
Wed Oct 18, 2017 12:20 am
400 sbc, 10.7:1 sbc here. 232 108 cam, 360 lobes. No choke Qjet, aluminum heads, performer rpm intake. Cold starts = feather the throttle for a short minute. I don't pump the gas until I've cranked it 5 seconds. If I pump the gas first it might fire and oil might not be everywhere it should at start. It drives alot BETTER in the cold. Much snappier. Cold air is great!

Yes I do occationally run it in -20C and it's an all forged engine. A good suggestion is to install a coolant heater.
Thats almost identical to my setup just in bowtie form. My biggest concern was fouling plugs etc and just all around stubborn cold blooded pig not wanting to maintain idle, which really Id be ok with until it got up to temp. Usually with electric choke thats easy to work around.

What kind of vacuum do you pull at idle with that setup?

MoPar_Kid
New Member
New Member
Posts: 32
Joined: Thu Mar 17, 2011 6:14 am

Re: 108 lsa in the winter

Post by MoPar_Kid » Wed Oct 18, 2017 6:30 pm

DaveMcLain wrote:
Wed Oct 18, 2017 12:52 pm
A stock 265 Chevy cam is ground with only a 107 degree lobe sep. There is no magic. It works and idles just fine because the duration is only about 175 at .050.
Intresting.. Never knew a factory cam for any manufacture would be narrower than 112. But I suppose with short duration its non issue. However on 408 cubes I imagine a 237/242 will not be so docile

MoPar_Kid
New Member
New Member
Posts: 32
Joined: Thu Mar 17, 2011 6:14 am

Re: 108 lsa in the winter

Post by MoPar_Kid » Wed Oct 18, 2017 6:39 pm

GARY C wrote:
Tue Oct 17, 2017 10:10 pm
When I built my 400 Pontiac engine the Pontiac consensus has always been wide LSA 114is but David Vizards program called for a 108 and so I tried it, with it tuned right and no choke it will maintain an idle on it's own very quickly and is not fussy if I need to start it and move it around without waiting for it to warm up. The problem could get worse if you combined that with to much duration.
I guess I dont know what makes ponchos so torquey if its runner design, mixed with cam profile, but I know the general rule is they dont like to rev, or so Ive read. Which is odd for an over square engine. Ive been told you dont build a poncho like you would a chev. They're short winded stump pullers etc. So I can see why the consensus would be a wider lsa to broaden the power curve. I have a 76 grand prix 400, dont know a lot about ponchos other than mine is a smog turd with 100cc chambers and 7.7:1 compression lol
Last edited by MoPar_Kid on Wed Oct 18, 2017 6:57 pm, edited 1 time in total.

MoPar_Kid
New Member
New Member
Posts: 32
Joined: Thu Mar 17, 2011 6:14 am

Re: 108 lsa in the winter

Post by MoPar_Kid » Wed Oct 18, 2017 6:55 pm

Geoff2 wrote:
Wed Oct 18, 2017 5:02 am
A 108 LSA [ or 104 for that matter ] will be no more temperamental than a 116 LSA, iiiiiiif the duration is correct for the application. See David Vizard's 128 rule on this forum.
This is true, but to take advantage of the added flow Ill need to hang those valve open a bit longer than what would be considered "streetable" for the winter. I dont expect a 237 will idle very smooth (and thats ok). My machine shop was also second guessing my cam choice saying a 108 on that duration will be a bit much for a heavy truck especially in the winter. I think itll be just right myself, or so I wanna believe lol
77cruiser wrote:
Wed Oct 18, 2017 9:02 am
What's your definition of winter? 20 F or -20 F

Depends, its North Dakota. Just like MN, overnight lows can dip down to -20 easy. Typically 5-25

GARY C
Guru
Guru
Posts: 3322
Joined: Tue May 14, 2013 10:58 pm

Re: 108 lsa in the winter

Post by GARY C » Wed Oct 18, 2017 7:55 pm

MoPar_Kid wrote:
Wed Oct 18, 2017 6:39 pm
GARY C wrote:
Tue Oct 17, 2017 10:10 pm
When I built my 400 Pontiac engine the Pontiac consensus has always been wide LSA 114is but David Vizards program called for a 108 and so I tried it, with it tuned right and no choke it will maintain an idle on it's own very quickly and is not fussy if I need to start it and move it around without waiting for it to warm up. The problem could get worse if you combined that with to much duration.
I guess I dont know what makes ponchos so torquey if its runner design, mixed with cam profile, but I know the general rule is they dont like to rev, or so Ive read. Which is odd for an over square engine. Ive been told you dont build a poncho like you would a chev. They're short winded stump pullers etc. So I can see why the consensus would be a wider lsa to broaden the power curve. I have a 76 grand prix 400, dont know a lot about ponchos other than mine is a smog turd with 100cc chambers and 7.7:1 compression lol
Thats mostly due to the factory head being to small for the cubes, they are like any engine with the right size head, compression and cam they will rpm according to the combination.
The factory 6x-4 head is probably around 155 cc give or take so they tend to run best shifting around 5600.
If you wanted peak power in the 6 to 6500 range you would probably want something in the 200 to 210 range generally speaking.

RCJ
Expert
Expert
Posts: 566
Joined: Wed Jul 25, 2007 6:15 am
Location: Oklahoma

Re: 108 lsa in the winter

Post by RCJ » Wed Oct 18, 2017 8:31 pm

What can happen is the motor "falls off the cam".At 1800rpm it runs poorly at 2000 it hits hard.

pastry_chef
Member
Member
Posts: 97
Joined: Wed Jul 07, 2004 10:06 pm
Location: Ottawa, Canada

Re: 108 lsa in the winter

Post by pastry_chef » Wed Oct 18, 2017 9:13 pm

RCJ wrote:
Wed Oct 18, 2017 8:31 pm
What can happen is the motor "falls off the cam".At 1800rpm it runs poorly at 2000 it hits hard.
A higher stall torque converter will take care of that.
Mike R

RevTheory
Guru
Guru
Posts: 2115
Joined: Thu Sep 04, 2014 6:45 am

Re: 108 lsa in the winter

Post by RevTheory » Wed Oct 18, 2017 11:14 pm

MoPar_Kid wrote:
Wed Oct 18, 2017 6:55 pm
Geoff2 wrote:
Wed Oct 18, 2017 5:02 am
A 108 LSA [ or 104 for that matter ] will be no more temperamental than a 116 LSA, iiiiiiif the duration is correct for the application. See David Vizard's 128 rule on this forum.
This is true, but to take advantage of the added flow Ill need to hang those valve open a bit longer than what would be considered "streetable" for the winter. I dont expect a 237 will idle very smooth (and thats ok). My machine shop was also second guessing my cam choice saying a 108 on that duration will be a bit much for a heavy truck especially in the winter. I think itll be just right myself, or so I wanna believe lol
77cruiser wrote:
Wed Oct 18, 2017 9:02 am
What's your definition of winter? 20 F or -20 F

Depends, its North Dakota. Just like MN, overnight lows can dip down to -20 easy. Typically 5-25
I've heard that argument twice. Wait until it blows through 400 ft.lbs. at 2,500 rpm on the dyno. My smaller engine with more overlap than yours would fire off a pair of 35 inch mudders without so much as a hiccup from the carb.

Again, make sure your initial timing is right and don't sweat it.

kimosabi
Member
Member
Posts: 133
Joined: Sat Feb 22, 2014 5:01 pm

Re: 108 lsa in the winter

Post by kimosabi » Wed Oct 18, 2017 11:17 pm

MoPar_Kid wrote:
Wed Oct 18, 2017 6:28 pm
kimosabi wrote:
Wed Oct 18, 2017 12:20 am
400 sbc, 10.7:1 sbc here. 232 108 cam, 360 lobes. No choke Qjet, aluminum heads, performer rpm intake. Cold starts = feather the throttle for a short minute. I don't pump the gas until I've cranked it 5 seconds. If I pump the gas first it might fire and oil might not be everywhere it should at start. It drives alot BETTER in the cold. Much snappier. Cold air is great!

Yes I do occationally run it in -20C and it's an all forged engine. A good suggestion is to install a coolant heater.
Thats almost identical to my setup just in bowtie form. My biggest concern was fouling plugs etc and just all around stubborn cold blooded pig not wanting to maintain idle, which really Id be ok with until it got up to temp. Usually with electric choke thats easy to work around.

What kind of vacuum do you pull at idle with that setup?
It pulls ~13" vacuum. I run 91 octane and 29deg total timing, 17 initial, no vac advance. Not at all cold blooded after a minute in the driveway feathering. Spark plugs look good even though I know I'm a tad on the rich side. I did that because of compression and 91 octane.

Geoff2
Expert
Expert
Posts: 573
Joined: Mon Nov 09, 2015 4:36 pm

Re: 108 lsa in the winter

Post by Geoff2 » Thu Oct 19, 2017 5:04 am

The Mopar Perf Hemi cams have LSAs from 104 -108, with the replacement cams for the early hyd & mech Street Hemi both on 106 LSA.

Post Reply