I came up on a great deal, but now I have a dilemma!

So I was on Craigslist looking for a TA performance 455 timing cover and didn't think I would find one but it was worth a shot before looking on the forum. Well I found new one and the guy was selling it with a blue printed and balanced shortblock , New TA 1.65 roller rockers, New TA block girdle, New SP2 intake, New TA alluminum valve covers, New Double roller timing chain and complete ARP bolt kits. He said he wanted $2000 for everything. So after I found all that out I asked him who built the shortblock and does he have all the paperwork for the build. He said yea so I went to take a look. Wow is all I have to say. A really good shop out here in Northern California built the short block and did a great job with Ross pistons, TA Sportsman forged rods and all the oiling mods. Well at the end he said he needed the money and gave it all to me for 1500 bucks. So now to my dilemma. The compression is to high with my fully ported iron heads, about 11.5 and I wanna use pump gas and now I don't know if my cam choice is good. I purchased the TA 288-98H because it has ok street manners but is running the 1.65 roller rockers too much with this cam? Is there any downfall to this cam with such a high compression. If I have to mix race gas then so be it but I really like this cam after all the research I did. Maybe get some TA aluminums a little later. Any help would be appreciated.

 

You will be mixing racing fuel with that ratio, iron heads and that cam, possibly even running straight racing fuel.

I ran 10.8:1, iron heads and the much more aggressive TA 308S cam and that engine was living on the ragged edge with 93 octane.

Even if you have to change pistons, if that engine is built right and unhurt, it's a helluva deal. Pretty much too good to be true unless the guy is simply desperate for his next crack fix, and you know what we say when something seems too good to be true...but just add up the cost of the intake, rollers and front cover and other goodies!

P.S. You will need a TA SP1 to run with your iron heads, the SP2 is for the TA tall port aluminum heads.

Devon

 

Joe,I solved that problem easily.Get yourself a set of Cometic head gaskets,they have them [as far as I know]up to 120th.80th you loose 1 point of compression,120th you loose 2 .BrunoD.

 

That would be an easy way to get compression down, but I'd hate to kill the quench by doing that. There's been a lot of discussion about how good quench helps control detonation; it would be a shame to drop a point of compression this way only to find you still have detonation issues on pump fuel.

FYI I've only seen the Buick 455 Cometics up to 0.051", but maybe they make thicker ones yet.

Devon

 

And if you still want race gas....mix 91 with Tolune. 4 parts Gas,1 part Tolune works nicely.

 

You will get an octane boost that way, but not much. In one test I saw, 30% Toluene added to 70% Sunoco 91 (which actually measured an (R+M)/2 of 92.1) only got the mix up to an (R+M)/2 of 95.5. Can't hurt to try though, just don't inhale the stuff or get it on your skin.

Devon

 

4 parts 91=364
1 part Toluene =114

Total = 478 divided by 5 = 95.6

"Quote"

Mindful of the evil reputation of octane boosters in general, toluene is a very safe choice because it is one of the main octane boosters used by oil companies in producing ordinary gasoline of all grades. Thus if toluene is indeed harmful to your engine as feared, your engine would have disintegrated long, long ago since ordinary pump gasoline can contain as much as 50% aromatic hydrocarbons.

Toluene is a pure hydrocarbon (C7H8). i.e. it contains only hydrogen and carbon atoms. It belongs to a particular category of hydrocarbons called aromatic hydrocarbons. Complete combustion of toluene yields CO2 and H2O. This fact ensures that the entire emission control system such as the catalyst and oxygen sensor of your car is unaffected. There are no metallic compounds (lead, magnesium etc), no nitro compounds and no oxygen atoms in toluene. It is made up of exactly the same ingredients as ordinary gasoline. In fact it is one of the main ingredients of gasoline.

Toluene has a RON octane rating of 121 and a MON rating of 107, leading to a (R+M)/2 rating of 114. (R+M)/2 is how ordinary fuels are rated in the US. Note that toluene has a sensitivity rating of 121-107=14. This compares favorably with alcohols which have sensitivities in the 20-30 range. The more sensitive a fuel is the more its performance degrades under load. Toluene's low sensitivity means that it is an excellent fuel for a heavily loaded engine.

Toluene is denser than ordinary gasoline (0.87 g/mL vs. 0.72-0.74) and contains more energy per unit volume. Thus combustion of toluene leads to more energy being liberated and thus more power generated. This is in contrast to oxygenated octane boosters like ethanol or MTBE which contain less energy per unit volume compared to gasoline. The higher heating value of toluene also means that the exhaust gases contain more kinetic energy, which in turn means that there is more energy to drive turbocharger vanes. In practical terms this is experienced as a faster onset of turbo boost.

 

I agree the commetic gaskets can open up some options!

You should let us know the volume of the piston valve reliefs as well as the piston depth from the deck of the block so we can help you calculate the static compression and we can go from there. Also let us know the cc of the iron heads you have.

 

Another option is to install the cam straight up and put the intake lobe center at 116 degrees instead of 112.

The DCR will drop .350
If the engine has a SCR of 11.5 the DCR will drop from 8.25 to 7.9

With a SP1 intake manifold you will see a shift in the torque band to a slightly higher rpm and will make more horsepower while trading off some low end torque

However with the higher Static compression ratio there is more torque to work with through out the whole rpm range anyway.

I can't find the post but JW has done this before with good results.

Paul

 

Yea I was trying to sell or trade the SP2 for a SP1 or I'll just use my Eddy Performer intake. The heads are some 70,71 fully ported Kenne Bell replacement dated heads (1240149). I don't know the actual CC but I think stock they were 71cc's.

 

Yea I coudn't believe it either Devon. I knew he didn't know to much about Big Block Buicks and the TA parts he had because he kept referring to the new parts as T and A performance not TA. He bought a GS and the motor from some guy locally and ended up selling the car but the guy that bought it didn't want to pay extra for extra short block and parts so thats when I came in. He had know idea what he had.

 

You can also run the stock gas tank for your 93 and a 5 gallon cell for race gas. That's what I did for my Stage 2 with 12.5 comp. Cruise on the 93 and get to the track and switch. (I have valves in the trunk.) You can also use an RV tank switch to electrically change tanks from drivers seat.

Bottom line is if you get into it with 93 on the street you could hurt it but that's kinda good....keeps me out of jail. :3gears: :laugh:
Part throttle cruising won't hurt it.....
It's cool to drive in the gate of the track switch tanks and put slicks on and run low 10s. And then drive back home. Even if you don't win that's a victory in itself.

 

Joe

I found Jim Weise's comments on installing a wide angle, short overlap cam without advancing it. It was on the "Sneaky 500 HP"thread.

http://www.v8buick.com/showthread.php?t=183826&highlight=Sneaky+500

Specs are on post #1

TA 290H cam- 238/238@.050- Actual was 239/238- Advertised- 297/297@.006(as measured)- cam ground on a 118 LSA
Cam installed at 118* ILC

Comments on post #16

Scott,

That is something I struggled with.. Yes, your right, you can pick up DC by advancing the cam, but all my dyno sim programs showed a dramatic drop off in TQ and HP by doing that. The issue is there is only 2* of at .050 overlap.. so you start closing the exhaust valve really early by advancing the cam. Right now, the @.050 valve intake open/exhaust close events are happening right around TDC, and bear the greatest resemblance to a "standard" type configuration. As installed, the Intake open is at 1* BTDC, the Ex close is at 1* ATDC.

In example.. this cam, on a 112LC, installed at 108, will open the intake at 11* BTDC, and close the exhaust at 3*ATDC, for a total of 14* of @.050 overlap. This is typical of performance camshafts- open the intake before TDC, and close the exhaust ATDC.

I believe what would happen, if I advanced the cam, say 6*, and closed the exhaust valve earlier, would be to kill all the scavenging effect of the headers.

Quite frankly, had this motor not made the number, I would have moved the cam timing on the dyno. I may play with this in the future, by my sims have always shown the correct trend in the past, in regard to cam timing.

JW
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Setting the TA288-98 intake lobe center at 116 degrees will give you a 7.9:1 dynamic compression ratio and you should have no problem running on 93 octane gas.

Paul

 

Wow Paul that is really good info. I had no idea you could bring the dynamic compression down that way. So would the compression still be at 11.5? I wonder if Jim Weise could chime in and say if this would work the same for my cam. Thanks Paul that brings a whole new twist to the build.

 

I take it the block wasn't machined for a girdle as you just sold one?
From the looks of the one deck they were not machined. What kind of paper work do you have for this engine? Do you know the bearings used and clearances?
Ray

 

Don't put all your money down on the Dynamic Compression Ratio recommendations just yet. There are many more variables that impact detonation resistance. Do not go into this lightly.

Devon

 

Ray the deck is stock and not machined. The paper work I have says what was purchased and used. Teflon Dual groove cam bearings were used. It doesn't show the clearances though.

 

Joe

The static compression of 11.5 is determined by the volume of the combustion chamber, the volume occupied by the thickness of the compressed head gasket, the volume between the top of the piston and the block deck when the piston is at TDC and the volume in the piston dish and/or piston valve reliefs.

One of the things you need to do is to measure these volumes so you know exactly what static compression ratio you are working with.

The Dynamic Compression ratio is determined by, when the intake valve closes on the seat (.006" lobe lift) after BDC.

Also Devon is correct in that there are other things in addition to cam timing you can address to decrease the tendency towards detonation.

Polishing the combustion chambers so there are no sharp edges or bumps that can get hot and cause pre-ignition.

Good cooling system including the TA high performance water pump, thermostat temp, ignition system, ect.

With all the above considerations you should be able to use around a .040" head gasket for good quench and be able to run 93 octane on the street.
As previously suggested, when you get to the track, use a higher octane fuel to be safe.

The one possible problem would be the 1.65 ratio rocker.
There is more pressure on the hydraulic lifter causing them to pump down at higher rpm.

Devon

Even though the 308S cam is more aggressive than the 288-98,
the 308S cam set at a 104 ILC actually closes the intake valve 4 degrees sooner than the 288-98 set at 116 giving a .35 higher DCR than the 288
and thats not taking the valve lash into consideration which drops the valve on the seat even sooner.
That may be one of the reasons you were on the ragged edge at 10.8:1 with 93 octane gas.

Paul

 

Convert it and run alcohol :3gears:

 

I didn't see this suggestion breezing through this, but what about just getting some SE1 aluminum heads? Then you could probably get away with the compression ratio, a regular thickness head gasket, and get away with 93 octane pump gas. Not to mention having an engine that'll really move whatever you put it in.