355 H.O. Engine Build HELP

mainboarder3108

New Member
Nov 24, 2022
2
Hey Guys,

I am rebuilding my first engine and I am really trying to do it as smart as possible. I have absoulutely no problem with the physical part, but might need some advise from someone with more experience in the theoretical.


So here is what I started with:
3970010 2 Bolt Chevy 350 Block 0.030 Bored over
Stock Crank
Stock Rods
Pistons currently Silvolite with 1.540 Height and +13cc
3998993 Heads with 1.94 /1.5 and 76cc

Thats what I already bought:
Edelbrock Performer Intake
Edelbrock 600cfm 1406 Carb
14014416 Cast Iron Chevrolet heads 1.84 / 1.5 and 58cc

What I want to buy:
Summit Racing Cam Kit SUM-K00172 (See spec sheet)
Fel Pro Performance Head Gasket Bore: 4.100 and CT 0.015
Summit Pistons 1.540 Height and +6cc SUM-17351C-30


Also I want to do a good porting job on the heads and install 1.94 and maybe 1.6 Valves.


So basicly I end up with:
3970010 2 Bolt Chevy 350 Block 0.030 Bored over
Stock Crank
Stock Rods
Edelbrock Performer Intake
Edelbrock 600cfm 1406 Carb
14014416 Cast Iron Chevrolet heads 1.94 / 1.6 and 58cc ported (see flow numbers below)
Summit Racing Cam Kit SUM-K00172 (See spec sheet)
Fel Pro Performance Head Gasket Bore: 4.100 and CT 0.015
Summit Pistons 1.540 Height and +6cc SUM-17351C-30

Calculations say I will end up with a 10.49:1 Static Compression Ratio and a 10.036:1 Dynamic Compression Ratio (See Calculation below). I will run this on 91 Octane (European Super95) anyways. Also I am still a student and really, really tight on budget..

This will be a motor for a fun street vehicle with a 4 speed manual and 2.72 gears (I drive a lot on the highway..) and if I get more than 300hp I am definitely more than happy!

Right now my main concerns are that the iron heads are getting too hot because of the high comression and its starts pinging.

I am really looking forward for some overall tips and enhancement proposals!

Thank you






flow numbers #14014416
Stock 1.84" valve in ported intake
[email protected] 28"
.05...........29.4
.10...........57.4
.15...........88.3
.20.........122.1
.25.........152.2
.30.........172.9
.35.........188.7
.40.........201.8
.45.........213.3
.50.........217.8
.55.........220.7

Modified 1.9" valve in ported intake
[email protected] 28"
.05...........33.0.........+3.6
.10...........65.3.........+7.9
.15...........98.2.........+9.9
.20.........129.8.........+7.7
.25.........158.5.........+6.3
.30.........181.3.........+8.4
.35.........200.4.......+11.7
.40.........217.2.......+15.4
.45.........230.0.......+16.7
.50.........227.2.........+9.4
.55.........221.4.........+0.7
 

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sandlapper

Veteran Member
Oct 9, 2020
1,653
SE CSA
welcome to NastyZ28 --- ? about where in the world are you located ?
*Assuming you did not have block's decks milled; those 1.540" pistons, and resulting huge deck clearance, are killing any possible quench effect.
*Understand you're working within a budget and with what you have on hand --- but those x416 heads are holding you back.

^don't settle for the cheapest piston on earth: choose some with much taller compression height and with a much thinner metric ringpak.
^sell or trade all those x416 heads & x993 heads for something better.
^choose a plan to get your quench height to approx 0.035" to 0.040"

***you might be better off to use your x993 heads With Pistons having a small 3.5cc Dome like SLP-8KH618CP30 at summit --- their 1.560" CH would get you a good quench And a manageable compression ratio. Certainly not Ideal but within a budget
 
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2ndGenCrazy

Veteran Member
Aug 18, 2011
906
Upstate New York
Dynamic is closer to 9.45.
You do not use .050 when calculating DCR.
I would also use a better piston to reduce deck clearance as sandlapper mentioned above.
 

kenny77

Veteran Member
Lifetime Gold Member
Jul 31, 2001
3,363
Ft. Lauderdale, FL
Couple things jump out as just strange here, that you might re-think

Your not going to get anything good out of a 416 head inspite of what some chart says somewhere. They might have the worst intake ports of all chevy heads....porting can be a mixed bag
You won't come off the stoplight at all with a 4 speed and 2:73 rear gear. You will be overheating/ warping some clutches and flywheels though....while that guy on a bicycle pulls away from you.
 
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G72Zed

Veteran Member
Sep 8, 2015
4,241
Canada
Very good advice from the members thus far, in addition, I would keep the SCR about 9.25 to 9.5 max for this build/combo.

Large P to H clearances, inefficient chamber shape combined with high static CR with short @ .050 cams in a under geared car is not a good recipe.

DCR, well, it's just that, dynamic, it's ever changing and the "formula's" don't take into account timing chain stretch, valve train accuracy and flex, leak %, intake inlet charge temps or VE%.

Here's a quick and dirty handy "chart" that let's you "see" things in a different way.
 

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mainboarder3108

New Member
Nov 24, 2022
2
First of all thanks to all of you for the quick response!

@sandlapper
Thank you :) I am from Germany, but this kind of knowlage about heads and casting numbers are not available here.. Yes, as in my calculation the deck clearance is about 0.045 with a 0.015 Head gasket its about 0.050 quench. Unfortunately these heads are not very common used therefore hard to sell. Before engine teardown i had a SCR of about 7.6:1 and i just wanted raise that with smaller heads. I thought domed pistons are heavier than dished pistons so reducing rotary mass and going for a smaller chamber didnt seem wrong to me. I got the 416 really cheap and on the other forums everybody says they perform quite well so I went for it. Why are the 993 better than the 416 in your opinion? At some point in the future I will upgrade to Aluminum heads, no dought - but for now I kinda have to take what I get..
It sounds like you think having a bigger chamber with a bigger piston is better than a smaller chamber with a smaller piston while lets say ASSUME airflow and rest of the variables are the same. Is that true and if so why? And what exaclty do you mean by quench effect?


@2ndGenCrazy
Thank you for your tip. With solid lifters absolutely. My though was when using hydraulic flat tapped lifters the lifters would compress roughly about 0.050 before starting to open/close the valve. Am I mistaken here?


@kenny77
Okay, why are the heads so bad? Can you point that out a little more? :) And why is porting a mixed bag? If done right its just reducing unwanted turbulance by making better transitions between components, reducing sharp angles in the ports and smoothen the surface to decrease the "pipe friction coefficient" (i hope you know what i mean, sorry😅). If there are also downsides I am always interested to hear them!
Yeah, I though a lot about the gears. But to be honest they perform quite well. Definately not when I am racing or accelerating, without a question, but it stretches the shifting time to a fair amount and also on the highway it makes a huge difference if you go 4000RPM @ 90MPH with 2.72 or 5000RPM @ 90MPH with a 3.42 gear. The current clutch is 12" and handled the amount of torque quite well.


@G72Zed
Okay, tank you. Why so low? If you referring to the cam and pointing to the chart I see why, but why does it cleaely say at the summit specs that a minimum CR of 9.5:1 would be good? Wouldnt it be smarter to go for a CR > 9.5 and below the max CR of the comp chart, so somewhere between? Why is the P/H clearance so important? Isn´t it more or less the same as CR? Same question I asked sandlipper.
Mhh. Lets assume atmospheric air temp and pressure are not changing while the engine is already warm, than the DCR is not changing. Thats not what dynamic means in this case. The formulas are just giving me a rough idea what it could be, true, but its definately not constantly changing while driving or so. Yes, many variables are not considered, but most likely all of them would make the DCR decrease, so a calculated DCR of 10:1 could end up in a actual DCR of 9.5:1 and not in a 10.5:1. If you think otherwise I am happy to learn!

Sorry for questioning all your responses, but I am really trying to understand why something is considered to be good or bad and how certain things are how they are.. Thanks ✌️
 

sandlapper

Veteran Member
Oct 9, 2020
1,653
SE CSA
QUENCH - short tutorial

mainborder:
Why are the 993 better than the 416 in your opinion? At some point in the future I will upgrade to Aluminum heads, no dought - but for now I kinda have to take what I get..
It sounds like you think having a bigger chamber with a bigger piston is better than a smaller chamber with a smaller piston while lets say ASSUME airflow and rest of the variables are the same. Is that true and if so why? And what exaclty do you mean by quench effect?


sandlapper:
Usually, I do Not think a bigger chamber is better --- But only HERE --- where you have a small 58cc chamber in a lousy head --- only HERE do I think your 76cc chamber in a Marginally better head --- would yield an overall better result. --- I did write: it is "Certainly not Ideal" --- A MUCH better combo & result would be with forged flattops with thin metric ringpak in concert with some MODERN aftermarket aluminum heads OR OE GM iron Vortec heads (which also require a vortec-specific intake manifold). HERE in USA, good used Vortec heads are not too hard to find --- perhaps availability in Germany quite different.

Seems your current budget may not permit the Much better combo. Now it's YOUR decision: put it together with a combo of parts only marginally better than what you have now --- or --- save up for a larger budget. Frankly, I would not spend hundreds or thousands of dollars to make a half-azzed effort. I'd wait, save up and make a SINGLE complete & well-planned effort. You would be WAY ahead if you could locate a core, rebuildable Vortec motor (GM rpo L31 5.7L iron head and iron block as found in '96-2002 GM pickups-medium duty truck & suv & van with character "R" in eighth position of vehicle's 17-character VIN). Begin with that vortec L31 motor as your basis.

Keep in mind --- as you change the weights of the pistons etc --- you should expect to pay a shop to balance the "new" rotating assembly. You must plan & budget for that; it's just another aspect of the process of assembling a hi-po motor.
 

tom3

Veteran Member
Aug 1, 1999
14,953
ohio
I think with your location and situation the reworked small chamber heads with the 1.94 valves will work ok with the cam and new pistons. And when money permits an upgraded set of heads you could probably get a 50hp boost.
 

G72Zed

Veteran Member
Sep 8, 2015
4,241
Canada
First of all thanks to all of you for the quick responses


@G72Zed
Okay, tank you. Q1- Why so low? Q2- If you referring to the cam and pointing to the chart I see why, but why does it cleaely say at the summit specs that a minimum CR of 9.5:1 would be good? Q3- Wouldnt it be smarter to go for a CR > 9.5 and below the max CR of the comp chart, so somewhere between? Q4- Why is the P/H clearance so important? Q5- Isn´t it more or less the same as CR? Same question I asked sandlipper.
Mhh.Q6- Lets assume atmospheric air temp and pressure are not changing while the engine is already warm, than the DCR is not changing. Thats not what dynamic means in this case. The formulas are just giving me a rough idea what it could be, true, but its definately not constantly changing while driving or so. Yes, many variables are not considered, but most likely all of them would make the DCR decrease, so a calculated DCR of 10:1 could end up in a actual DCR of 9.5:1 and not in a 10.5:1. If you think otherwise I am happy to learn!

Sorry for questioning all your responses, but I am really trying to understand why something is considered to be good or bad and how certain things are how they are.. Thanks ✌️

First off, welcome to NastyZ. Secondly, since this is your first build, may I suggest that you should purchase a few "How to Build/Modify/Hot Rod" books that are available for the SBC.
I know that's old school in the land of the interweb and YouTube, but there's something about having your own books to just read/study and make notes and let things absorb in a different way.

Secondly, I guess it's easier/quicker for me to just cut to the chase and give my answer/opinion based on your posts information and my experiences rather than explaining/detailing the "why's" of my answer. Lot's of very talented folks in this forum that have, and will chime in, but everyone has a different view or take on things based on their own experiences.

Q1- The cam states on Summit that it likes a min. of 9.1 CR and up, and given the tight 106 LSA and the engine specs you describe is the reason why I dotted the chart on the lower end.

Q2- The Summit site states a min. of 9.1 CR

Q3- No, the cam is built on a tighter 106 LSA, and basic components like the heads/build dictates the lower line, as build/parts quality go up, you can push up in the charts range.

Q4- When you minimize P to H clearances, you maximize squish, quench and effect the burn rate/flame travel and a host of other things. Tighter the better without hitting.

Q5- No, it's not. It's one time when raising the CR by way of reducing the P-H distance gives more SCR, but and at the same time, makes the engine less prone to detonation.

Q6- I'll cut to the chase, save yourself from going down the "DCR rabbit hole".

I base my "work" on conclusions and results rather than assumptions, some "formulas" are great, some so-so, others are a complete waste of time.... engines don't care about formulas....they are not good at reading or at math LOL.

Now, I'm off to the dyno for a offshore BBC build project.

Hope my A's answered some of your Q's.
 

CamaroDoc

Veteran Member
Sep 13, 2003
2,351
Skiatook, Okla. 74070
G72Zed has some good advice. I am mid build of a very similar combo myself. The 416 heads are just fine with a little pocket porting and runner cleanup. 1.6" exhaust valves might be ok but do NOT install 1.94" intake valves in this small chamber. The shrouding created between the valve and chamber wall will actually restrict airflow. The 1.84" valves create very high port flow velocities and will give a very efficient burn and great throttle response.
Use a stock height FORGED flat top piston with 2 valve reliefs and your thin .015" head gasket. This should yield about .035" of quench on both sides of the chamber which is perfect for a good fast burn rate. Domes slow down the burn rate and require more ignition lead timing.
The rest of your combo should be fine but I would also add using an air gap style dual plane intake or at least blocking off the exhaust heat crossover passages to the intake manifold. Also run a 160 degree thermostat. This combo works great on 91 octane although conventional wisdom says the compression is too high. The large amount of quench will fight any tendency to detonate as long as you don't lug the engine. BTW, This combo makes in excess of 400 hp with a Holley 3310 carb. I had an identical engine in my 72 RS before it got stolen. I got the car back but not the drivetrain. It had a saginaw 4 speed with 3.50 low first gear and a 2.41 posi out back. It was a little slow off the line but ran consistent 14.50s at 119mph through the quarter mile.
The suggestion on getting some books was a good one, also. A really good one is "How to Build and Modify Small Block Chevy Cylinder Heads" by David Vizard. Get a copy before you do anything to those heads. When looking for bang for the buck performance, compression trumps airflow every time. The best results will be achieved by the smallest chamber with the smallest (or no) dome.
 




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