Hot Rod Forum : Hotrodders Bulletin Board

Hot Rod Forum : Hotrodders Bulletin Board (http://www.hotrodders.com/forum/)
-   Engine (http://www.hotrodders.com/forum/engine/)
-   -   Can you guess this piston dish?? (http://www.hotrodders.com/forum/can-you-guess-piston-dish-220690.html)

txdude350 06-18-2012 01:35 PM

Can you guess this piston dish??
 
I am trying to calculate my CR and was hoping someone could take a stab at guessing the dish size of the piston. I suppose I will be buying some clay and a graduated beaker if not. IF I must go this route, do I measure it all the way across flat, or just the "eyebrows"??? In other words, do I include the big circle too? what about the outside circumference where it sort of slants downward?

Pic
Pic 2 (Smaller and Better lol
Here is some info on the car/engine

74 Nova
350 Block
305 heads with 1.97/1.50 valves (58cc stock... also have to verify this)
Supposedly the pistons are Keith Black, but I haven't been in the bottom end yet.

Thanks

txdude350 06-18-2012 02:27 PM

Actually my compression ratio is a bit over 11:1 right now. Which is why I am tearing it down.

How can you make such a generalized statement about 305 heads on a 350?

Forgive me for trying to crunch the numbers and get it right. The damn engine hasn't ever run right.

txdude350 06-18-2012 02:57 PM

Well... What do you think about this that I found. I have 416 heads btw

There's a fella over on HotRodders.Com that swears by 416 reworked heads, FireBird88 I believe is his handle. Do a search on that site/engine forum for 305 heads on a 350; there are a ton of posts. Butch/56sedandelivery.

Taken from This site

txdude350 06-18-2012 03:34 PM

I don't know... I just swear that this problem is mechanical. I have ruled out electrical issues. Maybe I'll go get the heads checked out.

But with the stock 58cc and about a -5 cc piston (guy at machine shop guesstimate) I am getting over 11:1 CR. I figured this was the problem.

I think the only way to be sure is to actually check the volume of everything.

lmsport 06-18-2012 03:50 PM

A stock replacement piston has about 8cc volume.

6426yy 06-18-2012 04:17 PM

With that big of a dish you can't be at 11:1. I've also ran 305 heads on a dish piston 350 with no problems, on junk gas in a 4000 pound truck with 3.08 gears no less. I'm not sure what problem you were having before but I don't think you have too high of compression.

68NovaSS 06-18-2012 11:52 PM

Quote:

Originally Posted by txdude350
Well... What do you think about this that I found. I have 416 heads btw

There's a fella over on HotRodders.Com that swears by 416 reworked heads, FireBird88 I believe is his handle. Do a search on that site/engine forum for 305 heads on a 350; there are a ton of posts. Butch/56sedandelivery.

Taken from This site

What's the point in posting this?

454C10 06-19-2012 06:07 AM

Looks like a typical 12cc dish to me.

plus the piston is most likely down 0.020" below deck. Maybe more.

727cc/cylinder (355 cid)
64c heads
8cc head gasket (0.040")
4cc deck height
12cc piston

(727+64+8+4+12) / (64+8+4+12)= 9.26

with 58 cc heads cr will be around 9.86:1.

Would need 48cc heads to get 11:1 with those pistons and a typical head gasket.

cobalt327 06-19-2012 08:36 AM

Quote:

Originally Posted by 454C10
Looks like a typical 12cc dish to me.

plus the piston is most likely down 0.020" below deck. Maybe more.

↑X2! A 5cc "dish" will be the valve reliefs of a flat top piston.

txdude350, what is the engine doing or not doing that has led you here?

txdude350 06-19-2012 08:58 AM

Ok fellas, my bad... I didn't realize how much I was loosing with these pistons. That being said, the car runs terrible to be at 9anything:1. It's almost embarrassing.

It just doesn't have the power it should. My dad and I have had 3 different carburetors, 2 new distributors, the list goes on.

When I take of it's just slow as all get out. My old 97 Taurus 3.0 V6 was quicker off the line.

A buddy of mine says I should change the torque converter, but hell IDK. Any ideas/suggestions?

txdude350 06-19-2012 09:00 AM

Quote:

Originally Posted by 68NovaSS
What's the point in posting this?

I posted that because I just so happened to come across someone talking about the same guy I was talking to, and also talking about the same heads that I am using. Small world, I guess.

cobalt327 06-19-2012 09:04 AM

Quote:

Originally Posted by txdude350
Ok fellas, my bad... I didn't realize how much I was loosing with these pistons. That being said, the car runs terrible to be at 9anything:1. It's almost embarrassing.

It just doesn't have the power it should. My dad and I have had 3 different carburetors, 2 new distributors, the list goes on.

When I take of it's just slow as all get out. My old 97 Taurus 3.0 V6 was quicker off the line.

A buddy of mine says I should change the torque converter, but hell IDK. Any ideas/suggestions?

To begin with, supply us w/ALL the specifics you know about this vehicle!

The cam specs are going to be very important, as is the rear gear ratio and torque converter stall speed (they need to be matched); a stock '74 Nova rear end may be geared very high (low numerically, like a 2.73). Next is the timing curve and how much initial timing is being used, as well as the total timing.

You can use this page as a guide for giving info- and more info is better than less. ;)

lmsport 06-19-2012 09:15 AM

Quote:

Originally Posted by txdude350
Ok fellas, my bad... I didn't realize how much I was loosing with these pistons. That being said, the car runs terrible to be at 9anything:1. It's almost embarrassing.

It just doesn't have the power it should. My dad and I have had 3 different carburetors, 2 new distributors, the list goes on.

When I take of it's just slow as all get out. My old 97 Taurus 3.0 V6 was quicker off the line.

A buddy of mine says I should change the torque converter, but hell IDK. Any ideas/suggestions?

I dont think there is any KB piston with that quench-killing bevel around the top.

Do a compression test. Anything less than 120psi is bad.

What camshaft do you have? If its a Comp, I would look there.

txdude350 06-19-2012 09:15 AM

I knew this would come in handy. I started a word document with all my specs. It's a work in progress so bear with me.

GM Block Casting Number
3970010
1969-1979 || 350 ci. || 185 low power || 370 high power || 2 or 4 Bolt Main || car, truck, Vette

Suffix Code on Block Behind Alternator
TKB ||1976 || 350 || conv.cab || VIN: L LS9 || HP: 165 || 4 BBLS || Applications: C-10 & 1500
TKB ||1979 || 350 || conv. cab, m/t || VIN: L LS9 || HP: 165 || 4 BBLS || Applications: C-30 & 3500

Heads Casting Number
14014416
58cc chambers, 1.84/1.50 valves @ stock
Has had 1.97 intake valves put it in

650 CFM Holley

Edelbrock Torquer 2 Intake

4:56 rear end posi (Had stock gears in it before I did a rear end swap)

Cam Specs


I do not know anything about the torque converter.

cobalt327 06-19-2012 03:29 PM

Quote:

Originally Posted by txdude350
I knew this would come in handy. I started a word document with all my specs. It's a work in progress so bear with me.

GM Block Casting Number
3970010
1969-1979 || 350 ci. || 185 low power || 370 high power || 2 or 4 Bolt Main || car, truck, Vette

Suffix Code on Block Behind Alternator
TKB ||1976 || 350 || conv.cab || VIN: L LS9 || HP: 165 || 4 BBLS || Applications: C-10 & 1500
TKB ||1979 || 350 || conv. cab, m/t || VIN: L LS9 || HP: 165 || 4 BBLS || Applications: C-30 & 3500

Heads Casting Number
14014416
58cc chambers, 1.84/1.50 valves @ stock
Has had 1.97 intake valves put it in

650 CFM Holley

Edelbrock Torquer 2 Intake

4:56 rear end posi (Had stock gears in it before I did a rear end swap)

Cam Specs


I do not know anything about the torque converter.

That cam should give excellent low end torque in a 350 SBC, and given the 4.56 gears, it ought to shred the tires at will- so something is definately wrong here!

What is the initial timing set at? You can do a little research on timing, here is a page that may help you get up to speed (ha) w/the effects of timing on the overall performance of the engine.

Bottom line is I'm thinking you may not have enough initial timing. This may be because the dynamic compression ratio has you up against a detonation problem; a quick fix for that is to use less initial timing- but that can have a very bad effect on performance.

You need to see where you are now; if it's low I would suggest you try around 16 degrees BTDC, but this may require you to limit the mechanical advance so the total timing (initial plus mechanical) doesn't exceed 36 degrees or so.

I'd also suggest along w/a compression and/or leakdown test that you put a vacuum gauge on the engine and see what the vacuum is at idle. Check for vacuum leaks if there's any chance you may have one. The engine should idle pretty smooth w/that cam, so if it's loping/missing at idle, there's a problem that may be ignition (or possible carb) related.


All times are GMT -6. The time now is 09:48 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.