[Mastif]

On my 67 396 motor, (closed chamber, 215 heads) I see the cylinders bores at the top with the notch to one side, I am guessing for valves clearence?

Now, on my 71 402 motor I have not pulled the heads to look to see if they have the same notches, I know this is a open chamber motor (820 heads).

The question is,,, can I stick the #215 closed chamber heads on the 71 402 motor with the 270H Comp cam and have no clearence issues, and if I can, what is the CR going to be?

 

[Mike]

You'll need to check the pistons to head.
Likely they will hit.

 

[Mastif]

I have done a search, and seems like most say there should be no issues. I am hoping that someone who has been there will chim in.
Thanks, Mark

 

[Mike]

Just which 71 402 do you have ?
Might be able to narrow down the piston .
And what's a 420 head ?

 

[Mastif]

Sorry, #820 heads
All I can say is it is a 71 402 motor.

 

[kettbo]

Mark,

Your 215s will fit fine on the 71 engine...and give it a nice compression boost.
The notches in the top of the 396 engine decks was for the larger valve hi-po heads. With the 215's smaller size valves, no issue at all.
CR will be 9.9:0---10.25:1 depending upon the specifics of your engine but I'd lean toward the lower rather than the upper end of the range that I gave.
With the classic 270H cam...a pretty nice street 396/402, good power, manners that you can live with.

 

[Mastif]

Thanks Kettbo,
Thats the word I have been waiting on. I am leaning toward the 270H cam, but not 100% stuck on it. I am open to other options, but do want to get something ordered today or tomorrow if possible.
mark

 

[kettbo]

Lots of nice cams for the 396....
Summit sells two of the classic Crane grinds...$89, now under the Summit label
one is the old 284H12 230*/.544"/112 LSA
another is 282H08 226*/.533"/108 LSA

Compare these to your 270H cam
Why are you stuck on that cam?
LUN 60202 or maybe even 60203
Don't be in such a hurry to choose a cam.
What gears? Use? Converter?
Off to go play with the car so will check out who has posted advice later.

 

[Mastif]

I do like to looks of that Summit Cam 282H08 226*/.533/108 LSA
Now, how would this cam work in a stock converter car?

 

[SS402]

And what's a 420 head ?

idk, but it sounds refreshing.. lol

 

[SS402]

Stay away from the older Crane designs that Summit rebadged and all the Summit brand camshafts in general, junk compared to modern designs like those from the Lunati VooDoo series.
Always check the P/V clearance when installing any cam that has more lift than the one that came out.
Hold the CR down to 9.5:1.

 

[kettbo]

Stay away from the older Crane designs that Summit rebadged and all the Summit brand camshafts in general, junk compared to modern designs like those from the Lunati VooDoo series.
Always check the P/V clearance when installing any cam that has more lift than the one that came out.
Hold the CR down to 9.5:1.

Depends on what the OP intends...
For a mild cruiser,,,,perfect.
I've seen some pretty fast mild cars running those same ol "junk" cams

Yes, always check all clearances. Ensure your springs are matched to your cam choice and heads are set-up correctly.

 

[Mike]

George ,after looking at the NHRA replacement pistons ,seem's it would have flat tops.
With the heads being anywhere from 101cc to 109cc per different sites ,the CR would be about 8.5 w/101 and 8.0 w/109.
That's using Bowling & Grippo C/R calculator.
That what your getting ?

 

[kettbo]

Mike,

I'll respectfully disagree. I really want to swear the 71 and 72 402s had the small dome piston like the 66-70 units and they simply went to the OC chamber to lower CR.

(ok, nosing through my ample stack of reference books:thumbsup

I looked at Colvin "Chevy by the Numbers 70-75, pg 118. 1971 402/300 horse has a small dome piston. Same on pg 120 for the 1972 piston. I believe the DOME is 12.1cc.

 

[Mastif]

Thanks for the input and help guys.
I am going to take a few days and really look into the Cams for the best selection, now I am thinking maybe the Summit cam may not provide the power brakes enough vac.
Maybe the Voodoo is the way to go.??????

 

[kettbo]

I do run the Crane 282H08 in my 8.8:1 454 in my 70 Elky. Nice driving vehicle with a mild stall and street gearing. Full wt, just off the street, 1st passes were 13.3s then 13.2s. I did have to tune carefully to get the power brakes to work well the first day it ran. Other than that, smooth-sailing.

 

[SWHEATON]

MIKE ,IF I REMEBER CORRECTLY DIDNT YOU AND MYSELF BUMP HEADS ON THIS SAME COMP ISSUE APPROX A WK OR 2 AGO? I RUN THE SAME SETuP & GEORGE IS 100% CORRECT ON WHAT HE'S SAYING ABOUT THE COMPRESSION & 215 HEADS FITTING THE 71 402 TOO.

IN 71 GM KEPT SAME SIZE DOME PISTONS FROM 69-70 L35 & L34 MOTORS WITH 10.25.1 COMP THAT WERE 325HP & 350HP. BUT GM NSTALLED THE LARGER CHAMBERED 820 HEADS IN 71 & LATER YRS TO LOWER COMPRESSION AND THATS THE ONLY DIFFERENCE.

GEORGE IS ALSO 100% CORRECT THAT SOME OF THOSE OLDER CRANE SINGLE PATT CAM DESIGNS SUMMIT PICKED UP ARE GREAT PERFOMERS IN A STREET PERF MOTOR.

I RAN THE 284H12 IN MY 396 4SPD WITH 3.31 12 BOLT FOR 10-11 YRS,IT WAS A STRONG PERFORMER FOR BEING AN OLD SCHOOL DEISGN AT A CONSIDERABLE LOWER COST TOO.

ACTUALLY WISH HAD HAD INSTALLED A NEW CRANE CAM OF SAME PROFILE BECASUE I MISS THE HOT SOUNDING IDLE IT HAD ,WAS EASY ON VLAVETRAIN, HAD GOOD PERFROMANCE ,ALONG WITH GOOD STREET MANERS TOO WITH EHOUGH VAC @ IDLE FOR POWER BREAKES TOO.

SCOTT

 

[Mastif]

Kettbo,
As I said, I like the looks of the 282H08, but the brakes are giving me reservations. Do you think I can get by with it?
Also, why should I not consider the Comp 280H?

 

[badrad]

Also, why should I not consider the Comp 280H?

It's the cam cores Comp uses, very soft compared to other brands and known to go flat very easy.

 

[kettbo]

Why? Because it is smaller! Less lift on a given duration. Lots of better stuff out there!

Here is the classic 280 cam
280 230*/.520"/110 LSA
then look at this:

Old Crane/New Summit cams
282H12 226*/.533/ 108 LSA
284H12 228*/.544"/ 112 LSA

Here are some UDHarold cams from Lunati
60202LUN 219/226* .530/.542" 110 LSA
60203LUN 227/233* .542/.554" 110 LSA

A bit extreme for a street 396 but a lotta stupid power here:
Isky 280 232* / .565" / 108 LSA
they will know you are coming through the drive thru if you have this cam....don't know about your power brakes though!

I am not a cam designer but I have played with BBC in hi-po street cars for 35 years of my 50 years. IN post #16 I chose the 282H08 to boost my low and midrange power in my 8.8:1 compression 454. Street engine. Yes, the power brakes work. I would have preferred 110 or even 112 LSA for a bit better manners but I was trying to optimize grunt. 454s tame what would be a pretty stout cam in a 396.