Do I have good heads/crank for a blown 327?! --- - Team Camaro Tech
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post #1 of 12 (permalink) Old Mar 2nd, 07, 10:17 AM Thread Starter
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Question Do I have good heads/crank for a blown 327?! ---

I wrote down the numbers that were on my block/crank when I was in the engine a few years back. Well I want to add a 142 weiand blower and was wondering if the heads/crank I have are good enough .... or if I should upgrade (its all stock, but GOOD stock parts). How do I find my compression ratio....the pistons have been in there for 20 years, lol ( they have 4 divots on the top ).

*** #4577 (front ) and CMT (rear ) of crank = Forged Steel, SMALL journal, 3.25" stroke (arent the SMALL journals the best, and forged is great too?)

*** #3884520 , # gm26, #H1 6, # gm32, # G286 = 60cc chamber, 1.72" intake and 1.5" exhaust ( all the info I could find ).

Thanks, if I should upgrade, PLEASE offer advice ---

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post #2 of 12 (permalink) Old Mar 2nd, 07, 10:27 AM
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Re: Do I have good heads/crank for a blown 327?! ---

All SJ 327 cranks are forged, so you've got the standard deal there. If I was going through the trouble of building a blower motor, I would use an aftermarket head.
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post #3 of 12 (permalink) Old Mar 2nd, 07, 10:32 AM
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Thumbs down Re: Do I have good heads/crank for a blown 327?! ---

Quote:
Originally Posted by alwayscode390 View Post
....the pistons have been in there for 20 years, lol ( they have 4 divots on the top ).

*** #4577 (front ) and CMT (rear ) of crank = Forged Steel, SMALL journal, 3.25" stroke (arent the SMALL journals the best, and forged is great too?)

*** #3884520 , # gm26, #H1 6, # gm32, # G286 = 60cc chamber, 1.72" intake and 1.5" exhaust ( all the info I could find ).

Thanks, if I should upgrade, PLEASE offer advice ---
Small journals are not as strong as large journal cranks - small is better ONLY in that they have less surface area, and thus less drag on bearing surfaces, which makes them desired for some type of engine uses - But, not usually blown unless it's a dedicated match race engine.
The smaller surface area concentrates the loading in a smaller area and increases the forces the bearing surface is subjected to during rotation. The surface is also exposed to higher bearing surface speeds due to it's smaller dia. A large journal crank spreads the load over a greater area and surface speeds are lower, which is easier on the bearings.

The heads are to small to work well with the flow needs of a blower motor.

If the pistons have '4 divots' on them, they are probably lower compression cast units - not something that will hold up well in a blown motor ...

You need to study blower set-ups and engine buildups for this type of use.
It is necessary to build a lower end that will hold up to increased pressure and HP output.
As well as an upper end that takes advantage of the blowers flow capacity.

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post #4 of 12 (permalink) Old Mar 2nd, 07, 10:41 AM Thread Starter
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Re: Do I have good heads/crank for a blown 327?! ---

Hey, thank you both VERY much. I guess I will go with a new stroker billet crank (do they make small journal strokers....or do I have to mod the block?), and ported aluminum heads with bigger valves (suggestions?) .

The cam in the car is the old "l79" cam 222 222 .447 .447 with 114. I know the larger the lobe separation , the better for a forced induction engine right? Too bad that cam isnt strong enough for what I want (500+ hp). Looks like a full rebuild with 4 bolt mains is on its way to my garage....haha

Is it worth it to go all out and make it a "roller cam" engine while I am at it? I was looking for something a bit different than my lt1 ... and it seems I am going that route anyway.

I appreciate it ---

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Last edited by alwayscode390; Mar 2nd, 07 at 11:31 AM.
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post #5 of 12 (permalink) Old Mar 3rd, 07, 11:03 AM Thread Starter
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Re: Do I have good heads/crank for a blown 327?! ---

Help !!! ---

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post #6 of 12 (permalink) Old Mar 6th, 07, 11:59 AM Thread Starter
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Re: Do I have good heads/crank for a blown 327?! ---

Anyone? Are the AFR 195cc heads good ?---

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post #7 of 12 (permalink) Old Mar 7th, 07, 06:37 AM Thread Starter
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Re: Do I have good heads/crank for a blown 327?! ---

What is involved with changing my 67 block to a large journal crank, and a roller cam? $$$ and work wise.....Thanks ---

90' ZR-1 Lingenfelter Corvette #699
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post #8 of 12 (permalink) Old Mar 7th, 07, 07:15 AM
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Re: Do I have good heads/crank for a blown 327?! ---

Quote:
Originally Posted by Vintage 68 View Post
Small journals are not as strong as large journal cranks - small is better ONLY in that they have less surface area, and thus less drag on bearing surfaces, which makes them desired for some type of engine uses - But, not usually blown unless it's a dedicated match race engine.
The smaller surface area concentrates the loading in a smaller area and increases the forces the bearing surface is subjected to during rotation. The surface is also exposed to higher bearing surface speeds due to it's smaller dia. A large journal crank spreads the load over a greater area and surface speeds are lower, which is easier on the bearings.

The heads are to small to work well with the flow needs of a blower motor.

If the pistons have '4 divots' on them, they are probably lower compression cast units - not something that will hold up well in a blown motor ...

You need to study blower set-ups and engine buildups for this type of use.
It is necessary to build a lower end that will hold up to increased pressure and HP output.
As well as an upper end that takes advantage of the blowers flow capacity.
The bearing surface speeds are decreased with a small journal crank, not increased. The medium journal SBC crank will have main bearing surface speeds 6.5% faster and rod journal speeds 5% faster than a small journal crank. If you're continually running very high rpm's this may become a factor, but at the moderate rpm's of a street driven motor you would probably notice no difference.
I think a small journal 327 would make an excellent mild blower motor.
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post #9 of 12 (permalink) Old Mar 7th, 07, 12:17 PM
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Re: Do I have good heads/crank for a blown 327?! ---

Quote:
Originally Posted by alwayscode390 View Post
What is involved with changing my 67 block to a large journal crank, and a roller cam?
It's probably NOT cost effective to use any of your 327, if you want to make any serious HP.
What are your HP goals??
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post #10 of 12 (permalink) Old Mar 8th, 07, 05:06 PM Thread Starter
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Talking Re: Do I have good heads/crank for a blown 327?! ---

Quote:
Originally Posted by onovakind67 View Post
The bearing surface speeds are decreased with a small journal crank, not increased. The medium journal SBC crank will have main bearing surface speeds 6.5% faster and rod journal speeds 5% faster than a small journal crank. If you're continually running very high rpm's this may become a factor, but at the moderate rpm's of a street driven motor you would probably notice no difference.
I think a small journal 327 would make an excellent mild blower motor.

Hey, thanks for the support

My hp goals were going to be around 500hp to the wheels. I will probably leave the crank since its forged, go .030 overbore w/ 4 bolt splayed main caps, go to a roller cam custom made for the smaller blower, 5.7 eagle h-beams, ported afr or dart heads (opinions?), 1.6 comp magnum rockers, the weiand 142 and that b&m superjection fuel injection setup I have for the blower with modified fuel rails and injectors. Finish it off with true duals and longtubes, beef up the th400 and get a stall....and replace the 10 bolt with a 12 bolt when it finally snaps. Sound good? Cost effective doesnt really matter. I just dont want another stroked 350 like my lt1....sorta going for something "different". That stock crank should be stong enough right....or should I get it nitrided too? Thanks---

Are there guys running meth injection setups on blowers like this or is it not worth the trouble? I plan on running a wideband for a decent idea on my tune too ---

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post #11 of 12 (permalink) Old Mar 8th, 07, 05:24 PM
 
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Thumbs up Re: Do I have good heads/crank for a blown 327?! ---

Balanced rotating assembly here!

Forged flat-top pistons and rebuilt stock rods w/ aftermarket bolts.

That cam will do fine for a 144 blower, imho.

Heads, use a stock, big valve 76 cc chambered head that has screw-in studs and go! I think they are stock '71, Z-28 type heads or a big exhaust valve 400 head that you put big intakes in and screw studs??

And use Fe-pro's #1094, .015" thick shim headgaskets too and your CR will be right at 8.6 to 1 which should be great for a blower motor!!

pdq67

PS., and I would do no more than a quick Sat. afternoon bowl-blend and a "dingle-berry" port casting flash removal to help them out beside's the standard 3 angle, 30 degree back cut valve job!!

NOTE!! Nothing fancy here at all!!!

IF anything, ask for a more up to date SOLID LIFTER cam........



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post #12 of 12 (permalink) Old Mar 8th, 07, 06:05 PM Thread Starter
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Re: Do I have good heads/crank for a blown 327?! ---

Sweet, that helped alot....thanks ---

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