108 lsa in the winter

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MoPar_Kid
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108 lsa in the winter

Post by MoPar_Kid » Tue Oct 17, 2017 8:14 pm

86 W150 4,400lbs
10.3:1 408 stroker (cast crank & pistons)
RHS 360X heads 300cfm @ .500
Port matched RPM intake 670 VS holley
3spd auto 2500 stall 3.21 gears
91oct NA

I know a 108 is gonna be a bit temperamental. But a part of me says DO IT.. Being the heavy weight that it is I want all the torque down low. With a 2500 stall I think it's a good match. I'm just worried about -20 cold starts. Hoping to hear some opinions of others who have actually had experience with such a nightmare.

My other option is a little wimpy 224/224 .485/.485 @ 110. Not enough to take advantage of my heads. This isn't a daily driver, but do need it to be reliable.

RCJ
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Re: 108 lsa in the winter

Post by RCJ » Tue Oct 17, 2017 10:03 pm

I drove a 230/230 at 107 installed at 103 as a daily driver for years.4 speed with 3.70 gears.I don't remember it being any more temperamental in the cold than a 268 comp.

GARY C
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Re: 108 lsa in the winter

Post by GARY C » 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.

tresi
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Re: 108 lsa in the winter

Post by tresi » Tue Oct 17, 2017 10:54 pm

Your increased compression will help a lot over a low compression motor.

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Re: 108 lsa in the winter

Post by GARY C » Tue Oct 17, 2017 10:57 pm

tresi wrote:
Tue Oct 17, 2017 10:54 pm
Your increased compression will help a lot over a low compression motor.
True! I ran a 268 ah on a 108 in my Pontiac and it's 222@ .050 with a 1.65 rocker a little over .500 lift if I recall correctly but at a little over 9.1 compression I would not want to go any bigger.

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Re: 108 lsa in the winter

Post by MTENGINES » Tue Oct 17, 2017 11:31 pm

My shop truck for a few years was a 3/4 ton suburban with 496 bbc 9:1 and a 255/265 .720/.720 108+4, had a Victor o with a barry grant mighty demon 850. no choke. it would start on a cold minnesota winter just fine, at -20 or -30 i had to put some gas into it. and be in the truck for about a minute or 2, but i think the 1200rpm warm idle is what kept it alive until it got warm.

I dont think lobe separation has anything to do with cold winter driving being bad, in fact the colder dense air should make it have light switch power. the carb tuning and ignition timing have more to play.

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Re: 108 lsa in the winter

Post by MoPar_Kid » Wed Oct 18, 2017 12:07 am

Jeez, I didn't even list cam specs.. My bad..

237/242 @ 108 LCA 105 ICA

.365/.370
.548/.555 @ 1.5:1
.584/.592 @ 1.6:1

IO 13.5 BTDC
IC 43.5 ABDC
EO 52 BBDC
EC 10 ATDC

I'll certainly be limited with 1.5 rockers and 670cfm carb for now, but I've got 15hrs of porting on my heads with a cnc port matched intake that I think will be better suited with the larger cam. Not that the smaller cam wouldn't perform ok, Id just like the narrower power curve for a heavy truck. That and a choppy idle 8)

My plans are for 4.56 gears with 35's and overdrive so it's going to be a bit of a high rev motor for which the cam would be better suited, maybe retard cam couple degrees and switch to a 1.6 rocker and larger carb when that time comes

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Re: 108 lsa in the winter

Post by kimosabi » 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.

Geoff2
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Re: 108 lsa in the winter

Post by Geoff2 » 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.

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Re: 108 lsa in the winter

Post by pastry_chef » Wed Oct 18, 2017 7:58 am

GARY C wrote:
Tue Oct 17, 2017 10:10 pm
the Pontiac consensus has always been wide LSA 114is
You're not kidding,
Over on http://forums.maxperformanceinc.com/forums/

Like an allergy over there.
They panic considering the move from their favorite 112 LSA just down to 110 LSA.
Mike R

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Re: 108 lsa in the winter

Post by 77cruiser » Wed Oct 18, 2017 9:02 am

What's your definition of winter? 20 F or -20 F
Jim

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Re: 108 lsa in the winter

Post by GARY C » Wed Oct 18, 2017 11:58 am

pastry_chef wrote:
Wed Oct 18, 2017 7:58 am
GARY C wrote:
Tue Oct 17, 2017 10:10 pm
the Pontiac consensus has always been wide LSA 114is
You're not kidding,
Over on http://forums.maxperformanceinc.com/forums/

Like an allergy over there.
They panic considering the move from their favorite 112 LSA just down to 110 LSA.
I think that comes from the old Ram Air cams, I fell for that in my early Pontiac days.

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Re: 108 lsa in the winter

Post by RevTheory » Wed Oct 18, 2017 12:16 pm

I had a hell of a time with cold starts (-20 F.) on a tight lsa/high-overlap cam but that was before I learned just how important (read: vital) initial timing was. I bet I had a 24* centrifugal curve on a distributer that needed 10* or less. 383 Chevy, 242/242 at .050, 106 LSA, solid-roller, chokeless Demon carb, air-gap intake.

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Re: 108 lsa in the winter

Post by pastry_chef » Wed Oct 18, 2017 12:30 pm

GARY C wrote:
Wed Oct 18, 2017 11:58 am
I think that comes from the old Ram Air cams, I fell for that in my early Pontiac days.
One forum member paid for the Vizard Cos-cam - was suggested to go with 106 LSA.
So many there were telling him it would only be a detonation monster.

Another had Straub custom design one, was setup on 108 LSA.
A popular forum Qjet tuner said it was a terrible choice for the guys combo.

Just silly. LOL
Mike R

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Re: 108 lsa in the winter

Post by GARY C » Wed Oct 18, 2017 12:36 pm

pastry_chef wrote:
Wed Oct 18, 2017 12:30 pm
GARY C wrote:
Wed Oct 18, 2017 11:58 am
I think that comes from the old Ram Air cams, I fell for that in my early Pontiac days.
One forum member paid for the Vizard Cos-cam - was suggested to go with 106 LSA.
So many there were telling him it would only be a detonation monster.

Another had Straub custom design one, was setup on 108 LSA.
A popular forum Qjet tuner said it was a terrible choice for the guys combo.

Just silly. LOL
I remember one I read about with Cos Cam on a 106 and the guy modeled it and it showed to be the best out of the three he modeled but it sounded like he still wasn't willing to try it. Not sure if thats the same one or not.

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