Well guys currently my car has bested 11.62 natural on pump gas @ 119 mph,and am sure I have some more left in the combo. But here it goes ,Ive had my old p600 lying around and thought how fun it would be to throw her on with maybe 5 lbs psi and some race fuel.(non intercooled). First off do you all think my 255lph will keep up? and secondly will I be ok with 5lbs and race fuel with that compression? Thanks for any help.

The only way I can see it happening is if you change to a circle track like cam with about 230 degree duration at .050 and 106 lobe (or basically a cam with pleny of overlap) and run a water or alky injection, and keep the boost down like you say. of course if you totally switched to 100% alky for fuel you could probably do it that way too.

So you think way too much cylinder heat even with 114 oct
and conservative timing?

using the compression/boost calulator here

adding 5lbs of boost to your 11:1 would be the equivalent to running 14.75:1 compression!!

why would u run a cam with a lot of overlap? (106 lsa)
Isnt having both intake and exhaut valves open gonna
waste the benefits of a supercharger ?

Yes, but it will bleed off cylinder pressure to fight off detonation problems with that high of compression.

Those are not really that accurate,my 355 below with 10 lbs was over 15:1 I believe and that I run on pump gas.

Well he is saying a cam that would not be as effective with a blower would allow me to get away with the high compression
I am running along with a charger.
A cam that is more effective ie:112 lsa would build to much cylinder heat.


I think I am gonna call Procharger Monday and see what they think. Ill let yall know.

Richen up whatever mixture you are running right now considerably. Use 118 racing octane gasoline. Mind your timing (i would say around 25-26 total). Sure why not. If the she is stout enough and you take your precausions it will work but I would not maintain such a setup for a very long time. It will be edgy. My friend(Phills Performance Shop) runs 20psi of non intercooled highly uneficient roots blown boost with 8.5 compression. And he doesnt detonate even with 32 degrees total timing.(it runs its fastest at 25). And you are going to use an efficient centrifugal only running 5psi and being that its centrifugal it will develop most of it wallop at higher speeds. You will definatly be fine as long as you are careful.

Take care and good luck.

Thanks,
Thats pretty much what i figured. the combo should have no problem holding the power,Cat 3D Forged rods,Scat Crank,SRP Forged pistons. all rated 650 hp+
I,m sure with only 5 lbs I should be well into the 10s,but I may hold off a while to get some better natural numbers .
She has pulled 119mph natural with density altitude 2800ft,so I am kinda hoping to hit 120+ on a good air day. just my converter holding me back now...

Now what about the 255 lph pump?
I figure HP natural is around 480 flywheel,so maybe 5lbs would give 90 hp on top of that.
Thanks for any help.

here is a pic.

Right.. does a tight overlap diminish top
speed capabilities?

thx 4 the info

No, actually a tight overlap increases high Rpm power.
But in a boost application it bleeds pressure through the exhaust valve.

opps here is that pic,should work now.

The JYD (video in my sig) ran a 106 lobe cam (236’ @ .050”, 286’ Adv (.001”), .490” lift (.525” w/ my 1.6 rockers), and 106‘ LSA.) and on a 150 shot it went from 13.5-13.8 to a 12.00-11.90 so no the nitrous is not wasted.

The JYD has 10.4 to 1 compression which is plenty low and never blew a head gasket with any kind of fuel running the 150 shot, but did blow a head gasket a week after the nitrous cam install. The car doesnt feel faster but it has not been to the track yet.

see it was building more cylinder pressure after nos cam,there for you were wasting Nitrous.

oh yeah I have no doubt that it was wasting some, but my point is that bleeding some cylinder pressure off can sometimes benefit you with nitrous by allowing the exhaust to draw out that hugely excessive exhaust charge created by nitrous. Going with a massive cylinder pressure isnt always helpful, thats why the HOTT cam isnt generally ideally suited to power adder use, it makes massive cylinder pressure.

I'm assuming this isnt a daily driver?

Why dont you just go with a good NOS system i mean your going to need racing fuel with that high compression and to refill a with racing fuel will be the same with a NOS tank and

Daily, No - But very often, Atleast 100 miles per week.

The reason why I just didnt go with a good N2O sytem, because I have the charger from my other car just lying around.
It would have been nothing to just throw it on and fab an intake tube.
But I have just discovered some more gains and got down to 11.55 @ 120 , also decided to go ahead and swap to long tube headers. I'm thinking I will get the car down to 11.30's @ 121-122.
That is still all natural, on pump gas and 9" ET streets.
So I hate to put on a power adder before I have the car maximized.

man you run 11's man i dont even run that on the 1/8

I have a question for you guys. WHy is it that a few ford guys around my area all run like 10-10.8 compression and they all run t-trim blowers running like 16-20lbs of boost and can get away with it ???? Now I am a firm believer in low comp motors with boost, but what are they doing to be able to do it problem free??

Drew

There's a few ways to get around that. First you can use an alky/water injection setup to prevent detonation, it comes on at a certain boost level. When running boost it's reccomended to run a timing box with a boost retard, you can set it to back out 1-3 degrees of timing for each lb of boost, at least MSD boxes anyways, some others may provide more adjustability. If the chambers are polished and coated along with the piston tops with heat resistant ceramic coating that will let them get away with more compression as well. Running a big cam will bleed off cylinder pressure at lower rpms. Running really rich will hide the detonation monster, but not for long. They could also be running race gas, a mixture of race gas and pump gas (1 gal 114 for every fillup of 93 or whatever), or they could be running fuel additives. I'm sure there's more things than that, but that's what I could think of off the top of my head.

There is also the issue of cylinder head design. I don't know what the angle is on the Ford heads but the 23* setup on Chevies is more prone to detonation than say Olds Heads.

Oldsmobiles, i believe, have almost 0* heads and 11:1 compression on pump gas NA is absolutely no problem for them. The better head design allows them about an extra 1 unit of compression ratio because the heads fight detonation that much better than chevy heads.

Anyone know what the valve angle is on Ford Heads? The lower the angle the easier detonation is to fight off. Therefore these compression ratios with that much boost might not even be on the ragged edge for Fords. Still, I don't know because i don't know the ford angles.

This is what I have been told so I am just reciting information. I do believe this to be correct though.

You’ve got the right question but you’re barking up the wrong tree for the answer.

Flatter valve angles typically make a combustion chamber ‘swirl’ less (if you’re lucky leaving some tumble), which makes them more prone to detonation. Lower valve angles do allow the port a much better angle at the back of the valve which makes them typically flow more.

Ford heads have a pretty high valve angle (at least 20*, I know that there are 20* heads for fords, but I don’t know what stock is), but small block ford intake ports are laid out in a way that forces the flow to get dumped out of the inboard side (as opposed to the outboard side like on a chevy) of the intake valve which prevents any real meaningful swirl/detonation control. The end result is that with similar combinations, typically SBF’s become detonation limited .75 – 1 compression ratio higher.

If you want to see a nice compromise head, look at the LS* and small block mopar heads (since at least the late 80's). Both have a proper port entry and a 15* valve angle, giving both good port flow relative to the port size and both are very detonation resistant.

Cool

5 psi is nothing
two rules 1. feed it enough extra fuel. 2. feed it high octane fuel.
(110+ octane race gas, Methanol, propane)

As long as you feed the motor enough high octane fuel you can run lots of boost with a high compression ratio.

Don't have to compromise the cam.

Won't have to compromise the total ignition timing any more than nessessary either. A supercharged motor can use near-normal timing as long as it is fed enough extra fuel. And of high enough octane. Ignition retard is a crutch used to avoid detonation under boost when there is not enough octane.

Consider adding a alcohol/ water injection system too.

I'd be looking into a second auxillary fuel system.
the alcohol/ water injection can be all, or a portion of this extra boost fuel.
Propane is also a good auxillary boost fuel. It's high octane.

More boost will make more power and heat. Your piston ring gaps can butt while under boost,if they are too tight.
Cooler non projected tip plugs will help too.


remember any thing more than modest ignition retard is a crutch.

But start out rich and retarded and tune up.

Excessive cylinder pressure:

Do you guys think that it would be a problem to run a cc306 cam w/ a 300 shot?

Thanks for the info but that idea has been scratced,
I put the blower back on the 82 last week.

Got the 87 down to 11.2 natural
82 went 10.9 @ 129 with a real bad bog i'm tuning out, but atleast the MPH is there so the HP is.
Both car on pump gas.

As for Timing being a crutch, so is excessive fuel.
Either is just means of reducing cylinder heat.

<b>As for Timing being a crutch, so is excessive fuel.
Either is just means of reducing cylinder heat.</b>

I thought retarding the timing generates MORE heat but lessens detonation by providing a later spark...

Retarding timing changes where the heat is made… the exhaust gets hotter, usually the chambers get cooler because less of the fuel gets burnt in the chambers and more in the exhaust.