n100

Alright so I built this engine maybe 8 years ago, not really knowing at all what I was doing. While it ran decently, A: I want more power and B: it always pinged no matter how it was timed. I searched for years for leaks or anything else so it is getting a rebuild nonetheless.

I am set on keeping the vortec heads and already have an "Alex's Parts spring kit" to solve the lift problems of vortec heads.
I also picked up a Quikfuel Slayer 600 carb and am set on using it too.


Here's what the engine is right now:

350 4bolt block. Pistons are .023-.025 in the hole
Frankenstein quadrajet carb. (never worked very well at all)
Vortec 906 heads
Comp Cams XE262h flat tappet cam
Long tube headers
Edelbrock Performer manifold (EDL 2116)
.02 in steel shim gasket (MRG 1130g)
Chromoly pushrods (EDL 9630)
Hypereutectic +6cc flat top pistons (SUM 17351C)
GM HEI distributor
TH400
Unknown stall
3.08 rear end


My goal is to make as much hp and torque as possible while still running pump gas. A big one with me too, which some may not agree with, is I want it to sound lopey and have a mean hit at idl, which I am aware can have a tradeoff with power. The XE262 was just way too tame for me.

I am also waffling with the idea of turning it into a 383, and will if necessary, however i"s like to keep my budget to around $2000 max. Most all of the labor will be done by me which I am confident in, however specialty things will be handled by a shop if need be.

Any help or suggestions on which way to go would be much appreciated! I will respond to this thread as often as I can. Thankyou guys!

TCracingCA

TCracingCA

jackson

OP
with flattops & Vortecs (~ 64cc chambers) it probably has about 9.5:1 to 10.5:1 CR.
Seems you're going to rebuild and do it on $2K budget
Seems you expect a larger cam.

Suggest you find a later model crank & block ('87-2002) which has OE roller lifters or capability & One-Piece rear main seal ...build that.
Keep the Vortecs! Perhaps drop compression with small dish pistons... you Must control pinging!

Kacyc3

Its pinging because your compression is high summit calc says 10.16 and with a stock stall and 308 gears puts a load on the engine before its operating range , I swapped a set of vortecs on my truck, with a small dish and valve relief,.041 thick head gasket its was still 9.2:1 compression, also vortecs do not require as much timing so make sure you keep it around 30* I think is what I read where they plateau as far as timing.

Next a big lopey cam and stock stall with 3.08 gears will be miserable, the big cam is designed for high rpm and you need a big stall or correct gears, you have neither.

Thumper cam will give you the sound you want but arent high hp cams, if you want the lopey cam sound and high HP its going to cost more than 2k to get a new cam, a stall (you should rebuild the trans to handle the higher HP), and/or swap in new gears.

cv67

Good points...sounds like you need to get your carb situation ironed out,sit down and plan, price and evaluate.

n100

Thanks for the replies everyone! I always felt like the compression was too high, however like I said I built this 8 years ago and was very new haha.

It seems as though I need to address a few things besides the engine, which if that's the case I can up my budget for those. Gears and stall will be added into the budget then. I just meant the $2000 budget for engine only. I'd like to run either 3.55 or 3.73. And I suppose the stall will have to go hand in hand with that and the engine hp?

As far as the engine goes, I believe the consensus then is with Vortecs and a stock deck to run a dished piston for pump gas?

If that's the case maybe I should just go 383? I'm assuming if I do, cam choice will be different than a 350?

cv67

Yes. If you do 383 consider a 2.00 intake and some porting to help out. You can leave stock valves in it and port but youll be leaving plenty on the table..slippery slope.
The crank kits are so close to the same it really makes no sense rebuilding to keep the same CI it wont be any faster. That longer stroke makes a difference
BKBroiler has a vortec headed 383 wiht a mild cam perhaps he can posted what he did...driveable and runs low 12s

OldCarBum

The very first thing to consider is what you plan to use your car for and how you plan to drive it.
If you want a light to light racer or plan to run it at the drags occasionally, then build it with the big cam, converter and lower rear gear ratio's.
If you are running on the open highway, winding roads and want roll on acceleration, then build it with a cam that is going to work at your operating rpm's on the open roads and keep the 3.08's or even a set of 3.36's to keep your rpm's where they need to be.
Running a camshaft with an operating range of 3000 to 7000 rpm, with big lift and duration will do you no good if you want to roll down the highway in the rpm range of 2500-3000 rpm and your engine never sees over 6000 rpm.
Everything needs to work together and deciding what your use of the car will be is really number one.
Then research and plan the entire car around your intended use.
But first fix your detonation issue.
Keep us posted.

OMF

With the pistons, heads, and the steel shim head gasket you have, your going to be in safe territory compression wise......countless engines have had this mod including mine. I think you should stick with what you have...a 383 will exceed your budget.

Since you sad you didn't really know what your doing in your post I'll explain this in baby steps.....
It's likely too much ignition advance that's causing your "pinging." You set initial advance by turning the distributor, and centrifugal advance is set by adjusting the spring weights on the flyweights underneath the rotor cap. Set your engine up so the vacuum advance line is pulled off at the distributor and plugged ( so it doesn't affect the idle mixture setting), and your timing light is ready to go. You'll need a timing tape on your harmonic balancer to record these accurately.

We need to know what your timing curve looks like to help out in that area first, so make a chart like this and then do some testing and recording then report back. All your timing should be in by 3000 rpm and with those heads it should be a max of 32-33 degrees.
RPM TIMING
Idle =
1000 =
1200 =
1400 =
1600 =
1800 =
2000 =
2200 =
2400 =
2600 =
2800 =
3000 =

BKbroiler

As cuisinartvette mentioned, I have a 383 with Vortec heads, auto trans that runs 12.30s consistently. I originally had an XE262 flat tappet cam and it ran well, but I did have pinging issues - at part throttle, going up a hill type of situations. For that reason and because I thought the cam was a little too mild, I switched to a hyd roller cam, 225/232 duration, .535/.550 lift. That stopped the pinging and took 2 tenths off the ET.
You have the right idea about gears. When I switched from 3.08 to 3.73, that took 4 tenths off the ET. A higher stall converter is critical also. Mine is 3,000 stall and works very well in street driving.

gkull

The ping problem is the 262 cam being so little duration that it causes too high of DCR

http://cochise.uia.net/pkelley2/DynamicCR.html

n100

Well the engine is apart right now so I cant test the distributor curve at the moment. I'll see if I can get in touch with the manufacturer today. I believe it is a Skip White distributor

Interesting info about the 262 cam. And awesome link! I will read up on and learn about DCR. So my pinging problem "may" not have been to high of static compression?

Regardless of the 262, I was always under the assumption that 10:1 was right on the verge of pump gas?

gkull

The static compression ration of up to the 12.5 range is possible on 93 octane super unleaded. I have two street motors with 11.2 and 11.7 11.2 just requires about 236@.050 intake duration and the 11.7 requires about 250 intake duration to keep the DCR down below 8.4.

n100

Ah this is making so much more sense now! Thankyou for the explanations.

Off topic a bit, but out of curiosity, what is keeping from running let's say a theoretical 15:1 or more on pump gas, given that the duration was long enough?

gkull

15 to 1 would require such a big cam that it might not run very well at street rpm

many years ago Comp cams made cams requiring 12.5 for pump gas for one of the car rags testing.

intake reversion and poor mpg limit the higher compression

OMF

I did a test using this site http://www.wallaceracing.com/dynamic-cr.php
And these are the results I came up with for your cam that closes 57 degrees ABDC.
Static compression ratio of 10.0:1.
Effective stroke is 2.88 inches.
Your dynamic compression ratio is 8.45:1 .
Your dynamic cranking pressure is 175.65 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of o PSI is 8.45 :1.

I really don't think your true compression ratio is that high, as getting a true 10:1 with vortecs and flattops is tough....I bet it's closer to 9.5:1
Static compression ratio of 9.5:1.
Effective stroke is 2.88 inches.
Your dynamic compression ratio is 8.03:1 .
Your dynamic cranking pressure is 164.35 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 8.03 :1.

It's too bad you have it apart, you could have done a compression check and see where you land compared to the above figures.

Here's a link to your cam specs
http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=85&sb=0

n100

I see, thanks for the knowledge!

Oh man, so many conflicting facts. I appreciate you doing the tests sstocker31. It is a shame that I did not do a compression check before. That may have cleared some things up.

Regardless however, the engine is going to be rebuilt. I plan on keeping the vortec heads, and the FT block. The heads will be clearanced for UP TO .550" lift, however I am aware vortecs dont make much power north of that. I would like to run close to .500" or upwards of that though.

Let's say I stick with the 350 stroke, will my cam selection be the same as if I went 383? Trying to do this right this time!

OMF

Generally the cam companies use the 350 inch engine to predict the rpm range for a cam. if you have a larger size engine (383,406) use one or two sizes larger to get the same rpm range, and same thing the other way with smaller engines.....one or two sizes smaller.
The only cam company that I've seen do this for you in their catalog is Crower.
If you tell us what kind of driving you plan on doing, we can help select a cam for you or at least steer you in a direction.

n100

Well I haven't quite decided yet if I'm going to stick with a 350 or stroke it. However a big thing for me is a mean sounding idle. Apart from that I plan on more spirited light to light/ autocross style driving rather than a whole lot of freeway cruising

The car will see a drag strip maybe twice a year