midge54

so what type of head gasket should i be looking at to reduce my quench to about the .040 mark

skinny z

That's difficult to say considering you don't know exactly what your piston deck height is or your valve relief volume.
If you assume (not a good idea) that the piston deck is .025" in the hole, then anything short of a .015" will keep you outside the preferred .040" quench. A gasket that thin with the shorter cam you intend to use MAY push your compression ratio beyond acceptable levels.
That said, I use a Victor Reinz .025" gasket. pn 5746.
Remenber that the quench is not the be all\end all of your build. Just a target to shoot while keeping your target compression ratio in mind.

86LG4Bird

iTrader: (1)

Get your quench right and then pick your cam accordingly.
I'd want at LEAST 10.0 CR with that 262 cam with Vortec heads.
Fast burn heads like the Vortecs make better power with more compression and less timing advance than vice versa.
If you're lucky, you'll measure your deck clearance and find that you'd have even less than .040" quench clearance with an .015" gasket.
We run strokers to 7000 rpm with .030-.032" quench. You just better make sure you measure EVERY cylinder! Line bored, perfectly squared blocks. I know that's for an engine more extreme than yours, but my point is that if your TIGHTEST cylinder has a .035" quench, you have margin.

InfernalVortex

iTrader: (4)

I've run into detonation problems here and there, but with premium gas and a good tune I dont have issues. I make sure to buy what I perceive to high quality gas, though. But Im afraid to push the timing too far, timing advance is currently set to max out at 33 degrees. I think if I had some regular 083's with this setup I'd have a lot more problems.

midge54

now how do i measure all of these things, i think the reliefs on my pistons are 5 cc

midge54

Also what do you guys think my estimate horsepower is going to be out of this build, I'd love to be around the 350hp mark but I figure my cam and exhaust will be my hinderence

InfernalVortex

iTrader: (4)

Well if you build what I have, Im making around 290-300hp at the flywheel. If you want 350 you're going to have to cam up.

midge54

yea i figured my cam would be my downfall, although i went with what summit recommended to me, kinda sucks though considering my 4 banger makes that much horsepower, just for reference, what cam would be streetable and push me towards that 350hp mark

InfernalVortex

iTrader: (4)

Well you got a Comp xe262... all you have to do is buy another flat tappet cam. The lifters you have will certainly work on whatever flat tappet cam you end up with. The cam alone will range from $100 to $140 depending on brand. The one you have is NIB, you should be able to sell it easy. They're great cams for 305's, IMO.

With vortecs, I'd go with a Voodoo 60102 or xe268 if you are more concerneda bout drivability. 60103 or xe274 if you'd rather have more power and start crackin at 350hp. They're stout cams and should put you in that range. The power band for the 268 and 60102 are around 1600-5800 if I recall. For a 60103 and xe274, the power band is around 2000-6000. Thats reasonable, and about as high as you would want for a street car.

You will trade off drivability for the power of the larger cams to get to that power range, but it will be reasonable. The cam you have, should you choose to run it, should net you gobs and gobs of torque and will be very fun. It will NOT be slow - it will be a blast!

midge54

I think in the interest of time and my budget I'm going to just run the cam I bought. You say it'll give me a ton of torque which is good since I love seat of your pants feeling in cars plus I'm not building a race car. However on day I plan to yank the engine again and stroke it to a 383 so I can change to a higher cam then

midge54

Can someone explain to me exact how I measure my deck height to determine what my quench will be

midge54

Also I talked to the guy here at lunch he said he zero decked on of his 350 engines he wasn't sure if it was mine or not so I'll prob need to find out which brings me back to how do I check, also if premium fuel isn't enough I.e 93 octane around here will octane booster do the trick or will I have to fill up with 99 or 112 octane, we have both locally

skinny z

I would doubt that your block is zero decked. That's something done by individuals that are getting pretty deep into their builds.
However, that said, checking deck height is relatively simple. It depends on the range of tools you have and your level of experience.
It's really just a matter of measuring the distance between the piston and a straight edge laid across the bore when the piston is parked at top dead center. That can be done to an acceptable degree of accuracy with feeler gauges. The difficult part is determining when the piston is actually AT tdc.
With a suitable socket on the balancer bolt, rotate the engine in the normal direction (that is clockwise when viewed from the front) and as the piston selected approaches the top of the bore, measure with your feeler gauges until the smallest gauge possible will fit between the straight edge and the piston crown.
advance the piston, measure and repeat. It make take a few tries to get it right as the piston will eventually start moving back down the bore and the gap will increase. You can repeat the procedure as many times as necessary until your confident that you've measured the closest approach of the piston to the straight edge.
That's the basic method 101 when no disrespect intended to you or your abilites.
Chances are, you'll find the gap to be about .025" - .030" unless of course, the block HAS been decked. Either way you'll find the value you're after and can make an informed decision from there.
FYI. My block, (an 010 casting like yours) has piston deck heights ranging from .025 to .034". That's with aftermarket pistons, reground crank. stock resized rods and an undecked block. That's how production tolerances stack up sometimes and why "blueprinting" an engine can be a lot of work.
As for the fuel issue, I think you'll find the 91 or 93 octane will get the job done provided your DCR doesn't get beyond about 8.1:1 or so. That's why you need to get an accurate account of your engine dimensions so as to calculate your SCR and then the DCR using the cam selected.

midge54

I have brake feeler gauges so I can definitely take the measurements

skinny z

I would start with a .040" gauge and advance the piston up the bore until it doesn't fit anymore. Drop to a .035" gauge and continue. If you advance too far, it's ok to reverse direction of the crank rotation (and then start again) provided you don't back out the balancer bolt.
It'll be interesting to see what you come up with. The gap determined, combined with your selection of head gasket will give you your quench value.

InfernalVortex

iTrader: (4)

And with that, we can stop speculating on compression ratios and know exactly what you have to actually give you some very useful advice.

midge54

Feeler gauges hit at about .40

InfernalVortex

iTrader: (4)

.040 I hope?

A lot of aftermarket pistons dont use the stock deck height as a reference point, they assume you will deck the block (why they do this is beyond me... but whatever). So they put the pin on the piston .020 inches higher in the piston (So the top of it sits lower in the block) or they lower the top of the piston, not sure to be honest, to keep the piston-deck clearance in a reasonable range for decked blocks. The exact height varies by block and piston etc etc, but the published height for 350s that is common is "1.540" pin height or compression height. 1.560 is generally preferred for performance builds because iwth a non-decked block you end up with (in theory!) your pistons .025 in the hole. With a 1.540 height piston, you get .045 in the hole according to the numbers. So you either have 1.545 compression height pistons, your block was decked .005, or thats just tolerance stack from various manufacturers.

Either way your compression ratio and ideal quench are going to be down a good bit. Since the motor isnt completely built yet, I would consider ditching those pistons for some that bring the piston higher in the block so you can maintain a good quench distance. This is something I wish I had paid attention to when I put mine together. I got lucky and it turns out my pistons were 1.560 compression height, but I never measured so I will never officially know exactly what it is until I pull my heads off. And it's one of those things I regret. If I had to do it again I would do whatever it took to get a tight quench and build it properly.

midge54

My pistons look to be the 1.565 height pistons do maybe I didn't measure the deck height well enough ie not on tdc because at one point the .030 looked to be tight

wrhjr81

Cant go wrong with vortec's ya u have to change intakes valve covers but over all it makes it easier to work on ur engine after wards n e ways. Imo vortecs r the best next to high dollar alloys. I dynoed 408 hp on a 355 vortec heads rpm intake 1.5 roller rockers headers and a comp 280h cam.

InfernalVortex

iTrader: (4)

What?! Tell me more!

I was considering a 280H but 400hp sounds crazy... is that flywheel? I could believe 340-350... tell me about your setup.

And Vortecs arent the only heads with centerbolts out there. I dont understand that kind of logic. If I see perimeter bolt iron heads I automatically dismiss them as junk the majority of the time. I love centerbolt heads for the ease of sealing, though.

InfernalVortex

iTrader: (4)

Stock block deck is 9.025 inches.

Stock deck height - ( [Stroke/2]+Rod Length + compression height ) = theoretical piston/deck clearance.

9.025 - ([3.48/2] + 5.7 + 1.565 ) = .020

Thats your theoretical... but youre getting .030 or .040.

Make sure you do it over the center of the piston (over the pin) just in case you're pushing the piston down around the wrist pin's axis and increasing your measured clearance.

midge54

I measured in the middle between the valve reliefs and I know for sure that .025 still had a gap so it's not that I really don't want to have to buy a new set of pistons cause this is a recently built engine

InfernalVortex

iTrader: (4)

Well... people run em like that all the time. It's up to you. It's just one of those little things that makes a difference between an engine that's below average vs an engine that's way faster than it should be.

piston to deck clearance is what it is. Did you check every cylinder or just one? I would just run the thinnest gasket you can and call it a day.

midge54

I only measure the one cylinder, so what types of compression ratios am I looking at

skinny z

My stock block 350 with aftermarket Mahle pistons has piston below deck heights of .026 to .035". That's not unusual when using stock crank, rods. That's how the tolerances stack up.
You should try a couple of other cylinders and try to zero in on some precise numbers. Better data equals better results.

skinny z

Vortec headed 350 goes 108 mph in the quarter in a 3750 lb chassis.
Get your calculator out and figure out THAT horsepower number.

midge54

my calculator says 443 hp at the flywheel, thats good

midge54

is there that much difference between your camshaft and my camshaft that there is over 100hp difference

skinny z

22 mpg hiway too.

midge54

thats awesome, definitely has a good tune, i ran infernal vortecs trap speed of 102 with a 3550lb car and it came out to 353 flywheel hp so thats where i roughly should be also

InfernalVortex

iTrader: (4)

You know , I actually use your car + my car as a baseline for comparison when looking at cams on vortec heads. I dont know how accurate the horsepower figures are on these calculators, but I know your car's weight and trap speed and I know what cam and heads you're running. if the calculator says you're making x hp and putting down x times at x weight, I can compare that to my build and try to go faster.

Anyway, by my calcs, you were making 370hp at the flywheel. From what I've noticed anecdotally, it seems a roller cam one step smaller in duration than a modern flat tappet cam will make about the same power. For example the xr276 at 224/230 duration makes about as much power as an xe274 at 230/236. I think it's a little bigger of a difference than that, but it seems about right. Obviously power bands and streetability are more different, and you know as well as I do that roller cams are a huge advantage in every way, but Im talking straight horsepower.

I dont know if you're making 250hp or 800, but I do know I always use the same calc, and it says Im making 300fwhp (And can go 13.2 in a 3550 lb car), and you're making 370fwhp (and trap 108 in a 3750 lb car). So I figure if I go to an xe274 I should be within 10-30hp of you according to my scale, and therefore capable of 106-108mph trap speeds and then I know I should be capable of running 12 second quarter miles.... with a driver mod anyway.

I know people say that's just theoretical math mumbo jumbo, and honestly it is, but I used a slightly different scale than ol' midge here, hence my much lower numbers. But when I hear ol' dude with the 280H (230/230, .480/.480) making 400hp and you with the XR276 making 370... It really makes me scratch my head. I didnt know all these calculators were so far apart.

midge54

i actually calculated everything from a virtual engine calculator i found online that does compression ratio using different aspects, horsepower from different aspects etc and i came up with those numbers

InfernalVortex

iTrader: (4)

Just use the same standard for comparison and you'll get an idea what it will take to get to certain trap speeds, and from there you'll know how close you are to your ideal 1/4 mile time.

skinny z

Of course there are plenty of other variables besides the head and cam that build horsepower. One thing it seems a lot of 3rd gens suffer from is an inadequete or poorly spec'd exhaust. I'm convinced that in my own combination, there are another couple of tenths and few more mph if I were to have a true dual exhaust and a system that develops zerro or near zero backpressure. That said, once I'm satisfied with this seasons racing baseline, I'll be experimenting with collector cutouts of varying lengths.

midge54

From everything I've read the 15ths are supposed to come factory with higher flowing walker exhaust systems, prob not as good as magnaflows and what not

skinny z

Here are some numbers I've run using these variables. Bore 4.030", stroke 3.48", 64cc heads, 6cc valve relief, head gasket diameter 4.100". Comp cams 262/270, 110LSA,106ICL.

Gasket Piston SCR DCR
.026 .025 10.0 8.44
.026 .030 9.88 8.34
.026 .035 9.77 8.25
.040 .025 9.67 8.17
.040 .030 9.57 8.08
.040 .035 9.46 7.99

skinny z

I must be missing something. What's a 15th?

86LG4Bird

iTrader: (1)

My calculator says 314 rwhp (that's an SAE-corrected number). Assuming a fairly efficient auto trans with an 18% driveline loss, that's 383 hp at the flywheel.
Myself and a few others in the ImpalaSS racing crowd deemed this one the most accurate years ago by comparing cars that had dyno numbers with their trap speeds:
http://turbo400.com/cherry/HP_Calcul...alculator.html

It's always been accurate to within 5% for my own vehicles with dyno numbers and trap speeds.

skinny z

That particular combination dynoed 282rwhp/283rwtq on a DynoJet.
Very loose 10" convertor which by all accounts appears to flash to 4000.
I can't speak for the calibration of that particular dyno however at only 18% drivetrain loss (which I've considered before) the trap speed/vehicle weight numbers don't add up. Perhaps upwards of 25% would not be unreasonable in this case considering the numbers are as unique to the dyno as they are to the vehicle being tested.

86LG4Bird

iTrader: (1)

You're absolutely correct. In your case, the driveline "loss" would be closer to 25%.
That 18% is for an extremely efficient or locked converter. BTW, the only converters I've run in my own vehicles that I consider extremely efficient have been a Yank 3000, a Vig 3000, and a Yank SS3600.
Your 10" flashing to 4000 would certainly fall out of that category. Most converters over 3000 rated stall will not come close. But nevertheless, they still put up better ET's than their dyno numbers would indicate. I saw 20 rwhp difference locked versus unlocked on an Edge 3400. It ET'd within hundredths of the Yank SS3600, but was down 2 mph unless I locked it 200 ft before the traps.

Edit: Hey, wait a minute......that looks like TCC lockup at 100 mph on your dyno run. If you're confident of the weight number of your car for that 108 mph run, then I'd have to say your dyno was pessimistic.

skinny z

You know that's interesting that you would say that.
The dyno operator said the same thing. There's only one problem. The TCC circuit was disconnected. No power wiring to the solenoid whatsoever so I don't know what that blip is on the graph.

midge54

15th anniversary trans am is what this engine is going in

86LG4Bird

iTrader: (1)

I'd bet money the TCC locked. That's the exact same signature I get when I lock any of mine. A blip where the engine inertia shows up as a power/torque peak, and then the curves settle to a trajectory that's offset above pre-lockup. There are strange things that can happen in the valvebody as pressures go up that can block the exhaust flow from the TCC circuit, which ends up applying the clutch.

skinny z

I was thinking along the same lines. Electrically I know it's out of the circuit but hydraulically, I haven't a clue.
Interesting bit of information though. Thanks.
Here's a question for you. Isn't there a risk of overpowering the clutch when applied manually in high gear? You start pushing 400 ft lbs of torque through it.....

86LG4Bird

iTrader: (1)

Yes, there is, in any gear at WOT. I don't do it as a matter of practice; only in limited cases for data-gathering purposes, or in a case where I think a 1/4 mile run may be a new personal best

The 12" converters and the 9.5/10" billet converters are a lot more tolerant of it, and of course the triple disk lockups are built to take it.

But I'd never do it repeatedly on a budget 9.5" unit that's built from GM V-6/4cyl converter cores. The clutch engagement surface in the cover will warp from the heat of a slipping clutch, and it's a downward spiral from there.

skinny z

Nice ride (I had to look that one up. Not up much on the Firebirds despite having one).
Didn't mean to hijack your thread. Good information is sometimes hard to come by.

midge54

I don't mind, the car had the original 305 however the original owner ran it so hard it blew two main bearings 4 rod bearings destroyed the crank, burnt the lobes off the cam and has the cylinders so warped they'd have to be punched at least .040 over to try and fix. The bill was too much so I decided time for 350

Danny515

If you've got the coin to drop decent cash on head gaskets - which is not really somewhere to skimp anyway - then you can easily run a more expensive, thinner gasket. Easiest solution to reducing squish without having to tear down or spend the money on machine work. Even if your actualy below deck height turns out to be .030, if you run a .015 gasket it will drop your squish to a good number. Now it will raise your compression a bit. Figure roughly a quarter to half point depending on the actual deck height. If this isnt something that concerns you then you're good. I have a true zero deck and I run a .039 gasket and its just fine. As with alot of the details of a build, you can take alot of time,energy and money to build a truly dead on motor. Its just determining your ceiling as far as expense. If you have $10k to put into it, then you have alot more options and decisions to make on how to spec it out and what exactly to have done. When money is a leading factor, there are certain limits and tolerances you will have to accept.
Theres nothing wrong with not having an ultimately professionally built motor. All of us have probably built a motor - whether our first or tenth, that we had to skimp on. The important part is making sure you spend where its necessary.
Production motors are built with a squish close to .060. Ive built motors with a high squish because I didnt have the ability to buy new pistons or spend on machine work. Sure its not ideal for performance, but with a properly set up motor, and to get it in the CR desired, it will work fine. There is room for upgrade and improvement on any one of our motors, and any one we've ever built or installed or raced.
If your measurements are correct and you run a .015 gasket you should easily reduce your quench to somewhere in the 40's roughly.
But I do warn - better a motor builder than me has popped a motor trying to get clearances too close. I understand theories and ive heard and used all the formulas and calculations and understand the idea that everyone would like to have a fairytale motor, but more important than making sure your squish is as low as possible is making sure your piston/valve/valvetrain etc clearances are good. You can get your squish as low as you want, but if the valve and the piston start making out, all that goes down the drain.

Danny515

Ive always remembered interviews I read years ago from Ken Duttwieler and John Ligenfelter. Duttwieler uses a 50 or better squish in the production motors he builds, and Ligenfelter strongly recommended caution when using a 40 squish point. Just an example of how much care needs to be taken in this area of a build and how important it is to be sure everything clears and operates as intended without issue.