Author Topic: 1903 Won't Respond to Tip-In Procedure  (Read 3020 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

Offline bry593

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Re: 1903 Won't Respond to Tip-In Procedure
« Reply #96 on: May 26, 2021, 06:39:19 AM »
Still waiting on the cam.  Continued disruption in supply chain due to C19 response?  Gates, Xiden and the CDC certainly want to extend the pain until everyone receives experimental gene therapy.  Incremental destruction of your constitutional rights.  Not to mention, I still don't have a cam.   >:(

Offline tayto

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Re: 1903 Won't Respond to Tip-In Procedure
« Reply #97 on: May 26, 2021, 12:32:09 PM »
My vote is still for the GM cam i posted above even though a few less degrees duration. Than the howards cam. I have been waiting dor a missing piece from my flowmaster exhaust kit for over 3 months now. also helping a friend with his 1950 dodge and we bought a parts carb for it and have been waiting over 6 weeks. Yet my rockauto orders are delivered in 3 or 4 days.....