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Old 06-05-2018, 09:53 AM   #1
Sadlerracing529
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1971 350 question

I have a 1971 chevy 350 out of a 1971 c10. It's a 3970010 block with 882 heads and factory 2bbl. Am I correct that this engine would have -12 cc dished pistons? What would the compression be? What would compression be using these same heads and flat top pistons?
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Old 06-05-2018, 10:57 AM   #2
ka_jd7and1
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Re: 1971 350 question

Stock compression ratio would be around 8.5:1. Flat tops would bring you up around 9:1.
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Old 06-05-2018, 11:59 AM   #3
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Re: 1971 350 question

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Originally Posted by ka_jd7and1 View Post
Stock compression ratio would be around 8.5:1. Flat tops would bring you up around 9:1.
Thanks for the info
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Old 06-05-2018, 12:07 PM   #4
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Re: 1971 350 question

Any horse power/torque estimates with the following combo?
Flat top pistons, 882 heads, comp magnum 270h cam, edelbrock performer dual plane intake, holley 650 double pumper, Doug's long tube headers, Mallory unilite distributor.
Going in a 1963 chevy c10 backed by a t5 most likely. Just a cruiser that I want to feel quick and be able to roast the tires in
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Old 06-05-2018, 10:41 PM   #5
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Re: 1971 350 question

I’d guesstimate 250 hp due to low compression, poor heads, too much cam, wrong carb.
It’ll be soggy on the bottom end and likely hard to roast tires with which could be a good thing considering the weak tranny.
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Old 06-05-2018, 11:03 PM   #6
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Re: 1971 350 question

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Originally Posted by geezer#99 View Post
I’d guesstimate 250 hp due to low compression, poor heads, too much cam, wrong carb.
It’ll be soggy on the bottom end and likely hard to roast tires with which could be a good thing considering the weak tranny.
yep, sometimes "less is more". A stock 350 with a good timing curve and the right gearing should smoke a tire (and a t5) in a pickup truck without breaking a sweat.....
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Old 06-06-2018, 12:02 PM   #7
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Re: 1971 350 question

You're gonna hate that Mallory Unilite...

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Old 06-06-2018, 11:10 PM   #8
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Re: 1971 350 question

Everything I listed I have laying around except the cam and flat top pistons. That cam is what comp recommended for my set-up when I called so it's interesting to hear such negative feedback from all of you. This is just a dirt cheap temporary motor to get the truck on the road for now. What cam would be a better choice?
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Old 06-06-2018, 11:55 PM   #9
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Re: 1971 350 question

A better cam would be one with nearer 210 degrees at .050, .430 lift and a wider lsa like 112 degrees or a bit more.
At least they didn’t recommend a thumpr cam.
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Old 06-06-2018, 11:59 PM   #10
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Re: 1971 350 question

Sorry, I shouldn't have been negative, just the day I had yesterday. I once considered a t5 myself but after researching them I felt that they really wouldn't hold up over the long term to anything but gentle driving. I also discovered that many of them seemed to have a very low 1st gear which would result in either grabbing second midway thru an intersection or just simply taking off in second gear. At that point I kinda thought it was more suited for a stock inline 6 and I pursued other options. My point about "less is more" was about having a well mannered cruising motor. You want to keep your power curve where you do your driving. I'll leave it to more experienced engine builders to recommend an actual cam, but I will say i kept my mine on the conservative side and used the Melling MTC-1(old school r.v grind, pretty much a Summit 1102) which was economical and combined well with my Performer EPS manifold and dual exhaust. I do hope your Mallory has a vacuum advance because street driven motors kinda need that to feel "peppy" in traffic. Again my apologies for being snide yesterday. It was just a bad day.
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Old 06-07-2018, 05:16 AM   #11
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Re: 1971 350 question

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Originally Posted by geezer#99 View Post
A better cam would be one with nearer 210 degrees at .050, .430 lift and a wider lsa like 112 degrees or a bit more.
At least they didnít recommend a thumpr cam.
Thank you
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Old 06-07-2018, 05:24 AM   #12
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Re: 1971 350 question

I understand the t5 is weak, I understand the heads I have suck. I was just curious about hp to expect from slapping this together. I am just doing what I can with what I have for right now as I am at a busy time in life with a kid on the way...I already have the real build fully planned out, just trying to do some good old hot rodding on the cheap with parts I own from previous builds that are now just sitting on the shelf
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Old 06-07-2018, 07:14 AM   #13
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Re: 1971 350 question

I used to run a 270 advertised duration cam in my 79 C10 with stock heads and pistons. I have no idea what the .050 duration was now. I could not get any traction with that truck. It would just spin tires (no posi). Ricers would easily smoke me at red lights. I threatened to put some big mud tires on it to see if those would spin so easily. I didn't get the chance because it floated the valves and bent one. Sometimes a 270 cam can still be mild and torquey.

Those Edelbrock performer cams are about 220 @ .050 and I think those are very mild. I never disagree with Geezer but he seems to like cams a little milder than me.
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Old 06-07-2018, 09:16 AM   #14
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Re: 1971 350 question

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... I am just doing what I can with what I have for right now as I am at a busy time in life with a kid on the way...
Yo, Sadlerracing. The vast majority of us that own these old trucks have been in your shoes. I don't believe many of us had an unlimited bankroll when we stared out and most of us still don't. Like you, we sometimes slap things together just to get the trucks going.

I will tell you that not one of the posts above are trying to be negative or give you bad vibes. I have read many posts by these guys and they're merely telling you what their experiences have been to give you a heads up. Ultimately, as in anything else, it's your truck and your decision. Keep us posted on your progress.
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Old 06-07-2018, 11:02 AM   #15
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Re: 1971 350 question

The "parts on the shelf" engine I am putting in my truck now is spec'd as such:

.030 over 350 (slightly decked, will be about 9.2:1 compression ratio)
TRW forged flat tops, polished beam stock rods w/ ARP bolts
Stock cast crank
441 heads, 76cc chamber
Isky 256 Supercam (.425/.425 lift, 202/202@.050, 112* LSA)
Edelbrock Streetmaster intake
Holley 600, vaccum secondaries
HEI (don't remember what brand)

I am thinking about putting 1.6 rockers on it because I have some, but we'll see how it runs without them first.

I also have a World Class T5 out of a '94 Camaro V6 that the truck will (eventually) be getting once I have time to go through it. They are rated for 300 ft lbs, and I am not going to be racing or hammering the shifter. I work 20 miles out of town and it would be nice to have an overdrive gear.
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1978 Impala 2-door, race 350/T350 - the new race car, in progress

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Old 06-07-2018, 11:56 PM   #16
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Re: 1971 350 question

I think that if you choose a flat top piston that has only 2 valve reliefs and a proper pin height, you will have just a slight more compression and running the HE270 Magnum cam will be fine. Not all flat tops are the same. The piston I am talking about is Speed Pro H631CP.
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