For those of you who have high powered motors (like more than 350ish horse), and say that you can run easily on pump gas...is this easy as in running 89 no problem, or easy as in...pushing 93...running 94 or 95 if you can get it, basically just non-alcohol.

350'ish isnt that much and could easily be done on 87 / 89 octane.

I should be pushing up to 450 ( maybe 500 when im done but that is pushing it ) on 94 octane ( canada has higher octane hehe )

I'm planning on approx. 525 hp and will run pump gas. I believe it is the compression ratio that comes into question here, not the horsepower. These guys will let you know. graemlins/thumbsup.gif

The ability to run on pump gas has many more factors involved than just static compression ratio...HP has bery little if anything to do with it. What does factor into pump gas ability is proper quench distance, combustion chamber efficiency, as well as cam timing.

My 414 ci bbc is right near 600 hp at the flywheel and is both street driven and raced on 93 octane.

I understand that HP in itself doesn't have anything to do with octane, but I was just asking because from what I've heard it seems that higher compression=more power, so I was starting to wonder.

I had a 10:1 static, 214* @.050 cammed 383 that took 91octane all day long with vortec heads.

I HIGHLY doubt the 11:1+, 230* @.050 version of this same motor will take 91octane though :D

Yeah.....what 10secBU said. ;) I'm no expert on this subject, but the engine that I will be putting in my chevelle will be putting out around 400hp w/o the nitrous....500-550 with.......and i'll be running it on 93 octane.

Why do you ask soccerguy045? I'm just curious. Planning on building a serious powerhouse?

Our stock, except for headers, 396-375 HP Chevelle runs fine on 91-93 octane unleaded. Running a lower temperature thermostat helps. A long duration cam will bleed off cylinder pressure at lower rpm and help as well. Don't get lean on the jetting either. We are running 4:10 gears so the engine never lugs along. Outside temperatures where we live seldom ever get over 90 degrees in the summer, so I don't know how well engines run in the hotter climates. With a foot of snow on the ground, our cars aren't going anywhere for quite a while. :mad:

My 540 runs great on 93 octane and it is well over 700 hp. You should be fine if your planning on having less than 400. I wouldn't be scared to run Regular unleaded.

My 10.5 SCR, 8.19 DCR, aluminum headed 540 dynoed 696HP @ 6100 rpm, 690TQ @ 4800rpm on 93 octane pump gas purchased by me personally at a BP station across the street from, and on the day of, the dyno session. :cool:

As 10secbu said, but to answer the question mine is 10.2:1 (7.55 DCR) and in the upper 600's for HP, I have raced on 89, but use 93 regularily.

Im running just shy of 11:1 compression in my "high hp" 350 and had no troubles on 90 octane, im sure i could get by on 89 even.

Another at 600+ with 93 octane. I haven't had the urge to try it with less though.

8.7:1 + 7-8psi boost on 91 octane, not dyno'd but guessing 800hp. graemlins/thumbsup.gif

Its all about dynamic compression, engine/oil temps, A/F ratio and gears. Not about HP. Big inch motors make gobs of power on pump gas, using low compression. Old LT1s and L88 wont run on pump gas well at all, and the L88 barely made 600 HP in race trim.

All I can add to the HP v ocvtane debate is that I calc my DCR at 8.6:1, run the engine hot and lean ( thats what it likes), and its on the cusp of not liking pump. In fact, I bought Mobil premium 93 outside the track in Albany last year, and had to pull over and disconnect my vacuum advance it was rattling so bad on passing. Sucked because my MPG was down to 11 going 75 mph. 330 miles, I would have rather had full timing in it and got 15. Filled up with Sun94 en route. Reconnect the vac advance. A-OK.
Go figure. Bad batch of gas likely.

Oh , the 427 probably only does 435 hp, like air cleaner sticker says. :cool:

Originally posted by pegleg71:
Yeah.....what 10secBU said. ;) I'm no expert on this subject, but the engine that I will be putting in my chevelle will be putting out around 400hp w/o the nitrous....500-550 with.......and i'll be running it on 93 octane.

Why do you ask soccerguy045? I'm just curious. Planning on building a serious powerhouse? Well the reason I was asking was I was just curious first off all, but secondly I was hoping this summmer to build a really nice 406-408ish sbc. My friend in his '68 Camaro SS has a 406 that has '550 hp', which I'm beginning to think is more and more BS the more I hear about it. 11.5:1 compression on '69 Z/28 heads and a solid lift cam is all he knows about it. Besides that, my friend has a rotary-powered RX-7, which could honestly beat my Chevelle's non-built-to-performance 350. I could possibly live with my friend's Camaro beating my Chevelle, but not that RX-7. So, I was hoping to build a really nice motor, but at the same time (which I guess is contradictory to building a powerful engine), I'm starting college in the fall, and I can't afford bad gas mileage while having to run 93. So, I thought it'd be a fun little project to research, mix and match parts, and try to get the most horses possible out of 87/89ish octane. Besides the fact that after I rebuilt my 350 all I've wanted to do is build another engine. So that's the little story of why I was asking, in a nutshell.

It can be done. My 540 initially dyno'd at 732 hp on 93 octane. A couple of years later, head porting, new cam and intake made 825 hp on 93 octane again.

I run very tight quench.....028 total! Pistons are .009 OUT of the blcok.

No problems in Houston heat...38-40* timing...11.06 static compression.


JIM

Understood. I have a couple of friends like that. This one has a 51' chevy truck with a 468 in it that he said is putting out 600hp. The funny thing is he only ran a 14.4 LMAO. He has 3.73 gears, a TH400, and no spin off the line. Kinda funny how those things work huh?

Anyway.....I was just thinking about your little delima and I have an idea. I don't know if you want to/ or can afford to put the money in it (i'm also a college student making about $5k a year so i understand :( ) but I was thinking that you could put a Fuel injected LT1 in it. I guess you can pick them up, with around 70k miles on them, for $1500. I realize it would take a little bit more work than what you probably want to do, but it should get you better gas mileage. It sounds like you will be using it as your daily driver? so you will have the comforts of fuel injected reliability, and it still puts out about 300-325hp. *shrugs* possible idea??

either way....good luck. I'd say buy a beater, keep the chevelle in the garage during winter, and drive it whenever you can. I also had to use my 71' as a daily driver for awhile and it SUCKS!


In the recent car craft there's an article about a guy who built a car (don't remember what it was) with 660hp??? something like that, got 25mpg and that was on...89 or 93oct. expensive though....but that is a combo that works for sure.

My car should make >600rwhp on wonderful California oxygenated 91 octane once it's back together. Jody's (camcojb on the board) procharged 540 big block motivated '69 Camaro made 828rwhp on 91 octane, blowing apart a blower hose at 5500 rpm. Probably would have made 900rwhp if the hose held. Don (a friend of Jody's) has a Procharged 406 small block in his '69 Camaro which made 683rwhp/634 rwtq on pump gas.

It is very possible to make big power on pump gas, you just need to carefully plan the components and get the tune right as there is a smaller margin of error than with more forgiving high octane race gas.

Troy

My 506" BBC is right at 600hp and 10.5:1 compresion and will be driven and raced on 93 octane.

Never had mine on a dyno, but if I had to make a "guess", I would say it is in the 525-550 hp range at the flywheel.

I am running right at 10:1 SCR (7.7 DCR) with iron ovals and an Isky solid roller. The cranking pressure was at 190 psi.

No problem with 93-94 octane pump gas. Never even a hint of detonation. This is with the timing set at 38-39 deg total.

Factors affecting the ability to run on pump gas are:
1. dynamic compression ratio (which takes in effect of cam timing, static compression ratios, combustion chamber size and swept area,)
2. quench and head design (end gas burning)
3. head media type (alum vs iron)
4. ignition timing and curving
5. A/F ratios
6. engine temps
7. incoming charge temps
8. RPMs working range
9. Fuel quality

Horsepower, cubes, torque, have nothing to do with it directly, but do dictate certain elements/specifications that end up effecting octane requirements.

I recently built a 383 stoker, 8.55 DCR, 440hp+ and it runs on 89 :D

"I recently built a 383 stoker, 8.55 DCR, 440hp+ and it runs on 89 "

That's the highest I've ever heard of. You must have got everthing just right. A fellow on ChevyTalk said he was at 8.4 DCR and ran 87 octane. Personally, I wouldn't even try running that low of octane with anything over 7.8 DCR, and even then I'd be prepared for problems. Could you post your engine and chassis specs?

Merlin 540 ci.........675/700 horses,on pumpgas!!!!!!! :D

EDDY merlin.

"I recently built a 383 stoker, 8.55 DCR, 440hp+ and it runs on 89 "

That's the highest I've ever heard of. You must have got everthing just right. A fellow on ChevyTalk said he was at 8.4 DCR and ran 87 octane. Personally, I wouldn't even try running that low of octane with anything over 7.8 DCR, and even then I'd be prepared for problems. Could you post your engine and chassis specs?
Pat, was that with aluminium heads?

Gene was saying that he was right on the edge using 93-94 octane pump gas with a DCR of 8.6 and aluminium heads.

What do you think is the limit (DCR) of 93-94 octane pump gas with iron heads without being right on the ragged edge? Sounds like 8.5-8.6 might be the limit for alloy heads. Would iron heads be more like 8.25?

I'm in the very early planning stages of my next motor (most likely a 496). When running your program,(picking cams and SCR) I get a little nervous when the DCR gets to around 8.2 (especially when I may use a little N2O).
I want the most out of my next combo but I don't want to live on the edge either.

"I recently built a 383 stoker, 8.55 DCR, 440hp+ and it runs on 89 "

I dunno about that either. Because i was runninga 383 with a bit less DCR and it blew a rod bearing jsut because my timing advanced a bit to far ( which would basically be the same as running on 89 )

I'm only making 325 HP, that's what the air cleaner sticker says. I runs fine with 93 octane and 40 total.

Originally posted by 71454Chevelle:
What do you think is the limit (DCR) of 93-94 octane pump gas with iron heads without being right on the ragged edge? im running an 11:1 iron head rect port 427, basically an L72. with a comp 305h magnum the dcr specs out between 7.5-8.0, depending on cam advance.

i didnt build this engine, but i have had the heads off to check to check pistons etc... the only thing i didnt do was to put a degree wheel on and check how far the cam was advanced.

it runs great on 93 octane with 38 total timing, i have no signs of detonation at all whether it be audible or visual (plugs).

i dont know if im on the ragged edge or not, probably not. but i would say im close.

Originally posted by 71454Chevelle:
</font><blockquote>quote:</font><hr />"I recently built a 383 stoker, 8.55 DCR, 440hp+ and it runs on 89 "

That's the highest I've ever heard of. You must have got everthing just right. A fellow on ChevyTalk said he was at 8.4 DCR and ran 87 octane. Personally, I wouldn't even try running that low of octane with anything over 7.8 DCR, and even then I'd be prepared for problems. Could you post your engine and chassis specs?
Pat, was that with aluminium heads?


Gene was saying that he was right on the edge using 93-94 octane pump gas with a DCR of 8.6 and aluminium heads.

What do you think is the limit (DCR) of 93-94 octane pump gas with iron heads without being right on the ragged edge? Sounds like 8.5-8.6 might be the limit for alloy heads. Would iron heads be more like 8.25?

I'm in the very early planning stages of my next motor (most likely a 496). When running your program,(picking cams and SCR) I get a little nervous when the DCR gets to around 8.2 (especially when I may use a little N2O).
I want the most out of my next combo but I don't want to live on the edge either. </font>[/QUOTE]Darren, The 87 octane at 8.4 was with Vortec heads. He said, though, that during the hottest part of the year he puts 91 in.

Nearly all the info I have on this subject came from David Vizard's books. He never states whether it applies to iron or aluminum heads. Nearly all the discussion in the books is about iron heads. So, I'd guess, he is talking about iron. Unless someone is after every smidgen of power, I would stay below 8.25 for iron heads. I suspect, but don't know, that aluminum could go to 8.35 without problems. For racing engines, the situation is different, usually temps are under much tighter control, and they don't have to run under the wide variety of conditions that a street engine has to. This allows them to run higher at a DCR. Often, with strip engines, mixing some high test with pump gas isn't a problem.

Originally posted by Pat Kelley:
Unless someone is after every smidgen of power, I would stay below 8.25 for iron heads. I suspect, but don't know, that aluminum could go to 8.35 without problems. For racing engines, the situation is different, usually temps are under much tighter control, and they don't have to run under the wide variety of conditions that a street engine has to. This allows them to run higher at a DCR. Often, with strip engines, mixing some high test with pump gas isn't a problem. So basically aluminum can run higher DCR on lower octane because they don't hold heat as much, so therefore the lower temp won't cause detonation due to heat?

A link showing the effects of intake air temperature on detonation. Show's how a properly setup cold air intake, can reduce detonation dramatically. Note; where it says "airplane" substitute "BB Chevelle"

http://www.americanaviationinc.com/effectsNavajo.html

OLD Gm aluminums, which dissipate so much heat that you MUST use a 195 thermostat to keep it warm. Also quench is .045". Timing curve comes in pretty slow to 2800 and is all in by 3350.

I really do think its the heads that allow it.I don't know. I would NEVER even try to run a 8.5+ DCR on 89. Kinda foolish if you ask me. Detonation at WOT and 6500+ rpm is a wonderful metalbender.

Taylor, I think you could build a decent motor to run on 89 but as you can clearly see here, the way to 500+ hp on 89 is through cubes.

I personally never had a HP goal. I was just trying to 'engineer' a good combination using retro parts. I encourage you to do the same. Engineer a good combination. I would shoot for a dynamic compression that allowed 87-89 octane, maybe 7.75 BUT you have to have everything else in place too. Good gearing, timing curve, quench etc. If you havent visited Pat's DCR page, please do so. Pat's page was KEY in my latest iteration of the 427.

Don't ever believe HP claims. 550hp in a 68 Camaro would give him a 125+mph trap speed in the 1/4 mile. Bet he don't do that. And a 550 hp sbc is UNDOUBTEDLY a very high compression motor. My friends old LT1 is 11:1, with that huge Chevy 2nd gen cam, and while stout, he figures 450 , maybe. 93+ octane.

Unfortunately alot of BS is thrown around car circles. At least we can say that the BS stops here. But when you're learning, you must wade through it.

Originally posted by 427L88:
OLD Gm aluminums, which dissipate so much heat that you MUST use a 195 thermostat to keep it warm. Also quench is .045". Timing curve comes in pretty slow to 2800 and is all in by 3350.

I really do think its the heads that allow it.I don't know. I would NEVER even try to run a 8.5+ DCR on 89. Kinda foolish if you ask me. Detonation at WOT and 6500+ rpm is a wonderful metalbender.

Taylor, I think you could build a decent motor to run on 89 but as you can clearly see here, the way to 500+ hp on 89 is through cubes.

I personally never had a HP goal. I was just trying to 'engineer' a good combination using retro parts. I encourage you to do the same. Engineer a good combination. I would shoot for a dynamic compression that allowed 87-89 octane, maybe 7.75 BUT you have to have everything else in place too. Good gearing, timing curve, quench etc. If you havent visited Pat's DCR page, please do so. Pat's page was KEY in my latest iteration of the 427.

Don't ever believe HP claims. 550hp in a 68 Camaro would give him a 125+mph trap speed in the 1/4 mile. Bet he don't do that. And a 550 hp sbc is UNDOUBTEDLY a very high compression motor. My friends old LT1 is 11:1, with that huge Chevy 2nd gen cam, and while stout, he figures 450 , maybe. 93+ octane.

Unfortunately alot of BS is thrown around car circles. At least we can say that the BS stops here. But when you're learning, you must wade through it. I have visited his page. It's helped out quite a bit, but for some reason cam timing and DCR and quench are something that is taking me a bit longer to grasp.

About the friend's 550 HP claim, his mechanic dyoned it with a different cam at 13:1 and got 600 he said, and now thinks his 11.5:1 has 550. I know he doesn't, and his trap speeds were only 97MPH. He refuses to dyno as he 'doesn't have anything to prove.' I had asked about this on a previous post, don't have it on hand though.

I am trying to engineer a good combination because I realize you have to have a good working combo so the motor won't just crap out on you and then you're stuck. However, HP is always fun, am I right? graemlins/thumbsup.gif Anything better than my current 260ish HP 350, if it's even that-and that's at the flywheel.

Thanks for everyone's help, too, I've really learned a lot just by reading these posts.

bbc 408ci 11.7 to 1 compression 262/273@.050 cam with .600 lift on the exhaust.....12.20's at 110 in street trim......at 3600 lbs.....ran daily and raced with 87 octane fuel.........150 psi cranking compression.........shift points just over 7000 rpms...........with 150 hp nitrous shot ran 87 or 92 octane with a bottle of 104 booster..........this engine ran for 6 years like this.........

Originally posted by soccerguy045:
</font><blockquote>quote:</font><hr />So basically aluminum can run higher DCR on lower octane because they don't hold heat as much, so therefore the lower temp won't cause detonation due to heat? </font>[/QUOTE]I would say higher DCR OR lower octane. Probably not both. No guaranties that it will work. I don't have the resources to do the testing required smile.gif .

Originally posted by Pat Kelley:
A fellow on ChevyTalk said he was at 8.4 DCR and ran 87 octane. Pat.. Was that "MD" ? He and I e-mailed each other quite a bit during our 406 projects.

It's been a while but I think it was Steve Streeter (I think that was his name).

My engine dynoed at 490 HP, 12.1:1 compression 9.38 DCR, 92 octane, no detonation. I may not have hit a 600 HP rating on pump gas BUT, my motor is only 350 CID. The trick was in the heads. For the record when it went back into my EC I put in some thicker head gaskets, only because the piston was kissing the heads, just barely.

Originally posted by Aaron Kelley:
My engine dynoed at 490 HP, 12.1:1 compression 9.38 DCR, 92 octane, no detonation. I may not have hit a 600 HP rating on pump gas BUT, my motor is only 350 CID. The trick was in the heads. For the record when it went back into my EC I put in some thicker head gaskets, only because the piston was kissing the heads, just barely. =====
Aaron,
I have built & dynoed an awful lot of engines & while I will not say it can't be done,,, I believe you need to recheck your figures as far as your static & dynamic compression numbers go ;)
Just my opinion from a lot of years doing this ;)

BTW, assuming your EC weighs about 3800lbs it will take about 400 engine HP or so to run 109

I know I sound dumb, but what is the difference dynamic, static, and just regular compression ratio??

Originally posted by aubreyt213:
I know I sound dumb, but what is the difference dynamic, static, and just regular compression ratio?? This is one thing that I seem to stumble on, but I believe it works like this:

Static compression is the pressure inside the cylinder (when the engine is running) per compression stroke, or one revolution from TDC to BDC?

And then dynamic compression is the compression when you're first cranking your engine to start, because the piston doesn't always stop right at TDC or BDC. I think static compression (SCR) is always higher than dynamic (DCR).

That's about the extend that I am understanding, and that might not even be right. The link in Pat Kelley's sig might help you out some.

I run 87 octane in my 71. approx 450hp 454. best e.t.is 11.86 w 1.60 60ft. I ran 92 once and the car slowed approx 1 tenth. put 87 back in and picked up back to normal e.t. Comp is around 10.5 and I run 38 total timing.

Originally posted by Bret:
I run 87 octane in my 71. approx 450hp 454. best e.t.is 11.86 w 1.60 60ft. I ran 92 once and the car slowed approx 1 tenth. put 87 back in and picked up back to normal e.t. Comp is around 10.5 and I run 38 total timing. That's an aspect about octane and fuel burning that I think is interesting. I've learned you basically want the fuel to burn the quickest and cleanest without detonation for the best power. My friends like to think 'well I don't know what octane my car needs but I'm going to put 93 in it because it's the best!' I just think, 'Maybe if it cleans your system, but if you're going to run a race better on 89 because it's burning quicker, than why put in 93?'

Of course I guess you'd have to experiment a little on if you detonate under higher RPMs when racing and such, and I suppose some people probably just like the insurance of a higher octane.

Wolf if you don't think I'm using the calculator correctly why don't plug the numbers in for me. If I'm wrong please show me.

Bore 4.00
Stroke 3.48
Combustion Chamber 54
Head Gasket thickness .015
Gasket bore 4.100
Piston to deck 0
Flat top piston 7.2 relief

Cam UltraDyne
292/302
108 LSA
102 ICL

Respectfully, I know you have WAY more time on the dyno, and have built more engine than me. But the combo was planed out with a experienced builder, who primary occupation is porting heads and building engines. I did the assembly work and took the measurements with the exception of the valve relief. The reason for low MPH I have a conveter that is sliping to much at the top end. That is the only explantion I have for that.
If you still question my numbers ask UDharold. He knows the builder I used. His name is David Endrigo.

Static compression is your "compression ratio" that is commonly used to describe a motor. Your dynamic compression is the mechenical relationship between your cams intake closing angle and the actual compression. Compression cannot begin until the intake valve is closed. so therefore if a motor has 10:1 compression and a 280* actual duration cam. It will have a higher "DCR" than that same motor with a 310* actual duration cam.
Aaron Kelley: are you running that 292/301, 259/267@.050 UD solid cam? If so i have some questions for you.

Originally posted by Aaron Kelley:
Wolf if you don't think I'm using the calculator correctly why don't plug the numbers in for me. If I'm wrong please show me.

Bore 4.00
Stroke 3.48
Combustion Chamber 54
Head Gasket thickness .015
Gasket bore 4.100
Piston to deck 0
Flat top piston 7.2 relief

Cam UltraDyne
292/302
108 LSA
102 ICL

Respectfully, I know you have WAY more time on the dyno, and have built more engine than me. But the combo was planed out with a experienced builder, who primary occupation is porting heads and building engines. I did the assembly work and took the measurements with the exception of the valve relief. The reason for low MPH I have a conveter that is sliping to much at the top end. That is the only explantion I have for that.
If you still question my numbers ask UDharold. He knows the builder I used. His name is David Endrigo. ===
Aaron,
No disrespect intended.
All dynos read different. Mine happens to be very conservitive compared to some others but that isn't what I was questioning.
The power numbers are very believable for a 12.0 engine with a good hyd roller
I have done quite a few pretty mild 350's at 10.0 with flat tappet hyd cams in the 420 range.
I don't need to run those numbers I know they will be over 12.0 if they are correct.
The only thing I question is running pump gas with 12.0 static & a dynamic compression of over 9.0 ;)

Withouth having read the whole thread, don't you think that your total deck height is short (.015=0+.015?) Especially with the hyd. cam that will tend to have some valve float. What did your piston to valve clearances ended up being?

Just curious.

Yanniz why do I need to add the head gasket twice? I entered it in the formula already as the head gasket thickness. With the piston to valve clearance question...Once the bottom end was assembled I took measurments I found they were way to close. So I had the piston notched by a machinist. I don't remember what we ended up with.

Wolfplace I don't know why you don't believe me. Do you think I would come on here and lie because my life is so boring, my only hobby is to come on Team Chevelle and dream up engine combos? OK well close but I don't dream up pretend engine combos... :D


Really the gas came from Texaco. We drove the engine to the dyno in Elma Washington. Broke the engine in and started making pulls. My builder read the plugs after the pulls and they looked good. Have you ever heard of the fast burn heads GM makes?

I gotta run. I have a weld test I have to do today.

what total timing were you running? sure you could do it, but i wouldnt feel safe going over 30 degrees with 12:1 heh.

Originally posted by Aaron Kelley:
Yanniz why do I need to add the head gasket twice? I entered it in the formula already as the head gasket thickness. With the piston to valve clearance question...Once the bottom end was assembled I took measurments I found they were way to close. So I had the piston notched by a machinist. I don't remember what we ended up with.

Wolfplace I don't know why you don't believe me. Do you think I would come on here and lie because my life is so boring, my only hobby is to come on Team Chevelle and dream up engine combos? OK well close but I don't dream up pretend engine combos... :D


Really the gas came from Texaco. We drove the engine to the dyno in Elma Washington. Broke the engine in and started making pulls. My builder read the plugs after the pulls and they looked good. Have you ever heard of the fast burn heads GM makes?

I gotta run. I have a weld test I have to do today. ===
Aaron,
Don't get your shorts in a bunch smile.gif
I didn't say I didn't believe you, I was questioning the compression numbers.
I am not even close to implying you are lying or anything like that.
As I said, no disrespect to you or your engine builder intended.
If my wording sounded like that you have my complete apologies smile.gif
.
If in fact the compression ratios were right for the dyno runs I can just about guarentee they will not be a reliable combination to run in a daily street combo over time.
As you already found out, the quench will become less than zero at rpm with a .015 quench but it makes for a very efficient chamber short term & was done in the engine masters challenge.
I have run .025 to 7500+ in circle track engines without problems but don't really recommend it.
Yes I have heard of & used the fast burn heads & personally seen 11.5 with them out of the box but with closer to 8.4-8.5 dynamic & this engine ran fine on pump gas most of the time. It did not like hot weather & did start having problems after it got some miles on it, probably due to a little carbon buildup.
They are an excellent head, probably the best head GM has come up with for the SB.

Probably the biggest problem I have is your post can lead some who are building engines to believe this is a viable combination for a street engine which in my opinion it isn't in almost all cases.

Never the less, I will completly agree yours is an impressive & well done combination with great HP numbers.
Even with thicker head gaskets which assuming .039 felpros puts you at about 11.3 & 8.7, it is still probably going to be about 475 on the dyno & losing 25-50HP putting it in a car is not at all unusual unless you were running all accessories, air intake & temp & the same exhaust on the dyno which puts your MPH well within reason. ;)


Good luck with your test & again, I apoligize if my post sounded disrespectful.

Wolf I was just being a little sarcastic... :D .I do agree with you. The 12:1 CR is a bit much for a 100% street car. My car is a car that drives on the street but primary function is bracket racing mix with some fun. The engine made more power with the 92 octane than with 110. The timing was set at 32 degrees. When we switched from the 110 to the 92 we saw an increase of about 7 HP and 1-2 ft/lbs of torque. If I would have thought of it when I was at the dyno. I would have tried mixing some fuel like a 95.

BTW your 100% correct. My post could lead someone to believe this is a viable way to build a combo. The reason it ran on pumpgas is because this.

1 the heads
2 the cam
3 proper timing
4 a little luck

No need to apologize I've read your post before and I know you don't go out and attack people. Your a good guy were lucky to have you on this forum. It's my b-day tomarrow I'll be 27.

I've tuned a 11.3:1 SCR, 9+:1 DCR 351 W with 0.040 quench, TFS twisted wedge heads, in a '67 Mustang Fastback and a 4 spd. We get by with 92 unleaded supreme together with 104 octane boost (although I question whether the octane boost does any good).

When we first put it together there was no noticible detonation, but over time it began to ping (I assume due to carbon build-up) We retarded the timing and richened the carb and got by for a while. Next, we tightened up the advance curve, leaned the carb back down, and installed the coldest plugs Autolite makes.

We also run a 160° thermostat. The advance curve is real tight too. 9° initial with mechanical beginning at 1,500 rpm and pulling 24° by 4,500 rpm.

Although it works and has been on the road for five years now, I'm not certin I'd consider it a complete success. I think this combo is on the verge; one bad tank of gas or an extra hot day and it risks detonating itself to death. Although it runs strong and sounds great with all that compression, I can't help but wonder if it would run a little better with less compression and a looser advance curve.

Aaron, you don't need to add it twice.
If your piston is at 0 deck and you have .015 gasket, your total deck height is .015...

You should be .070 or above on the Intake and .100 or more on the exhaust.

I have been dealing with this the last couple of weeks for the motor that I am building in my garage...please pay attention to your clearances, with .015 total height you might be too close..

See you at the track in a while smile.gif I guess there is a T&T session on Feb 28th, which I will not make....

Originally posted by yanniz:
Aaron, you don't need to add it twice.
If your piston is at 0 deck and you have .015 gasket, your total deck height is .015...

You should be .070 or above on the Intake and .100 or more on the exhaust.

I have been dealing with this the last couple of weeks for the motor that I am building in my garage...please pay attention to your clearances, with .015 total height you might be too close..

See you at the track in a while smile.gif I guess there is a T&T session on Feb 28th, which I will not make.... Yanniz,
I think you are confusing piston to valve clearance with quench which is piston to head clearance.
As Aaron pointed out a total deck height of .015 is too close to run but is a completly different thing than p/v clearance. This is accomplished with the valve notches in the pistons which Aaron posted he had deepened to avoid contact.

Aaron,
Thanks for the kind words & happy birthday.
Mine was today but I have a "few" years on you,, actually our daughter has a couple of years on you :D

Originally posted by Aaron Kelley:
It's my b-day tomarrow I'll be 27. What's up Aaron...Happy B-day man...glad to hear you're 27 years young and still kicking ;)talk to you laterz