Author Topic: 1903 Won't Respond to Tip-In Procedure  (Read 2109 times)

Offline bry593

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Re: 1903 Won't Respond to Tip-In Procedure
« Reply #90 on: May 01, 2021, 01:23:25 PM »
Still waiting on the cam. 

In the meantime, I learned about the GM 395 cam currently in the HT383.  It was a Mercruiser marine cam originally.  Boat cams are designed to prevent reversion.  On shut down, reversion (due to overlap) will suck water back into the engine - hydrolock.  Generally, a marine cam has very small overlap and early intake closing.  That in turn makes the dynamic compression ratio extremely high.  This is why the HT383 has engine run-on and WOT detonation (87 pure gas).

GM 395 Camshaft Specs:
246/256 196/206 109 3A
49 ABDC 8.10 DCR 33 OL
.431/.451

Howard's Camshaft 180225-12 Specs:
260/266 207/213 112 4A
58 ABDC 7.69 DCR 39 OL
.450/.465

The new cam will delay intake valve closure by 9 degrees, reducing the dynamic compression ratio by .4 points.  Overlap is also improved by 6 degrees.    Hopefully this will be enough.

Offline tayto

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Re: 1903 Won't Respond to Tip-In Procedure
« Reply #91 on: May 01, 2021, 09:17:51 PM »
FWIW, you can get a GM roller cam p/n 94666492 for about $100 USD. While there are some various claims for duration, I recently put one in a friends boat as he was on a budget. My degree wheel said 202/210 @ 0.050” 112 LSA, 0.300”/0.310" lobe lift (.450/.465 w/ 1.5 rockers).

BTW, this cam has NO fuel pump lobe. An electric pump will be required

Offline bry593

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Re: 1903 Won't Respond to Tip-In Procedure
« Reply #92 on: May 03, 2021, 06:55:50 AM »
Thanks, I did see that.  It's a Crane Compu-Cam 2032.  Back in the day, this was a lumpy street cam for an L98. 

GM 492 Camshaft
270/276 214/220 112 4A
63 ABDC 7.44 DCR 49 OL
.452/.465" LIFT

Primary reason I did not use is lack of fuel lobe (plus a need for new valve springs).  However, the specs are decent for a street 383 with 9.1 CR.  The 383 would tend to mellow it out. 
« Last Edit: May 03, 2021, 07:11:29 AM by bry593 »

Offline tayto

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Re: 1903 Won't Respond to Tip-In Procedure
« Reply #93 on: May 03, 2021, 06:12:30 PM »
Like I said, my degree wheel said differently. Don't know if they have changed the grind,but I was nearly 10* less than the 2032 grind on intake&exhaust. Hydraulic camshafts are $400 to $600 Canadian so its a no brainer for EFI SBC. It's a shame about the fuel pump lobe or I probably would have ran with with some 1.7 roller rockers for a bit more effective duration on my recent truck engine build. I ended up using a Howard's 180235-12 on my 10:1 sbc. Looks like 1 step up from the one you are waiting for. Anyway,goodluck!

Offline bry593

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Re: 1903 Won't Respond to Tip-In Procedure
« Reply #94 on: May 06, 2021, 01:02:23 PM »
Interesting.  How do you like that cam for a daily truck?

I considered the 180235-10.  It looked like a fair match with 49 overlap and 57 ABDC.  I saw Howards also offers a -12 (112 lobe separation).

Offline tayto

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Re: 1903 Won't Respond to Tip-In Procedure
« Reply #95 on: May 06, 2021, 08:35:37 PM »
I unfortunately only put 1000 miles on it last summer, had some issue with lifter bores and am only now getting it back together (waiting on exhaust). I will keep you posted during the next month.Hoping to get it on the road by the end of the month