Here's the deal, I have an '87 LG4 that I put TPI on, headers, gears, etc... (see sig) and I currently run about 14.6 in the 1/4. I just put in a "supposed" LT1 cam and a ported/siameesed TPI base on, and NO CHANGE, still 14.6, no change in MPH either. I feel that the stock LG4 heads may be the culprit, but is a 14.6 all they are good for? Anybody get more out of theirs? Please let me know!!

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GM Master Tech
ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
Whatever chip I feel like burning,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
3.73 Posi
4wheel Disc Brakes
Summit 1-5/8" headers, 2.5" Dynomax catback.

Best 1/8: 9.519@72.74

'97 Bonneville SSE

 

You can get more out of them with a lot of porting work (assuming they're not swirl port) - see "Daniel Burk's 'Porting the GM 305 Cylinder Heads'" article in the tech articles ( http://www.isthq.com/~dan/ported.html ). I believe he got very close to the 13's with his LG4-based car. 1.94" intake valves highly recommended.

Or, get World 305 S/R Torquers, put a very little effort into cleaning them up, and be in the 13's.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker 2055 headers, 3" Catco cat & 3" cat-back, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

To clear things up, the 87 LG4 heads are the exact same casting number as the 87-92 305 TPI heads. (it is still a bottleneck.)

The 88-92 TBI heads used a different casting number.

I am currently using a 87 LG4 heads, when I did my swap I checked things out and they had the same casting numbers as both of my TPI cars.

John

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87 Formula Yellow/Black

5.1 TPI Automatic
Baer 12" brakes 4 wheels, KYB AGX Adjustable Shocks & struts, Custom Leather interior, WAAAY TOO MANY MODS TO LIST

87 Formula TPI (5 Speed) Yellow/Gray STOCK

1967 Buick Riviera 430hp Turns high 14's (Not bad for 4300 lbs)

83 Camaro (Parts)
83 T/A (parts)

http://www.3rdgenformula.com

 

Bernard, how much work have you done with the VE tables, PE Tables and Spark?

I am finding the Spark tables are very important to extracting performance on a basically stock engine. Knock incidences are very pronounced with the stock heads and in spite of all my tuning efforts, I have never been able to eliminate it (I have reduced it, but not eliminate it).

I also found "capping" the Max Knock Retard @ WOT to only a couple of degrees really helped, but then I also found that I started to encounter audible knock and had to work on the Spark more to get the highest EFFECTIVE Total Spark Advance possible without detonating.

The stock GM heads do not like a lot of Spark Advance (after you compensate for the knock retard), but a difference of only a couple of degrees from the "sweet spot" also has a major effect on performance.

When I began all my tuning, my ECM was trying to give me 29* of spark advance @ WOT, but after adjusting for Knock Retard, I was lucky to get 20*. By capping the Knock Retard to 2*, I now get 28-26* of spark advance after adjusting for knock retard.

I also getting the spark advance as high and as quickly as possible (without detonating) and attaining 28* around 3200-3600 rpm (peak torque) and then slow decreasing to 26* after peak HP (around 4,400) rpm gave me the best performance while minimum detonation.

The decreasing of the Spark Advance after peak HP seems to be needed due to the "choking" effect of the TPI/heads. But from other guys with Vette Heads, it seems that I am darn close to where they are developing max power. GM heads with their small combustion chambers really don't like too much spark advance, but more than the stock GM settings.

A new set of heads would be nice, but I think some work on the mixture and Spark Advance will really help you too, if you haven't played too much with the all the little settings.

 

I Got 14.6's out of my LG4 all day long when it was in there, it still had the stock carb, stock distributor, and stock computer w/ stock chip. With a shortblock that was dead.

I did however have a vavle job, pocket porting and polishing and a summit 204/214 cam

With the thrashed shortblock it had a very distinct powerband from 3200-4600rpm and that was bout it, nothing above or below.

It was an 86 LG4 with 416 heads.

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It's always SOMETHING

 

I am running my 305 tpi heads on my 350 I have the 480 lift slp cam and had the heads redone with 1.94 stainless valves ported and polished. they will rev as high as 6000 but, really stop making power at 4500-5000 and I drop the clutch at 500 rpms and let them spin till the tires grip usually it will rev to 5000 then jumps down to 3500 thats when they grab. I keep it smashed till it hits 4500 and shift. thats the fastest way I can get going I don't know why but, right now thats all she will do. but, this is my proof that the heads can flow more.

 

Yeah, thats ported, polished, and larger valves, I'm talking about stock.

------------------
FREE CARFAX Record Check

If you live in Southeastern US, check us out!
South East Thirdgen

GM Master Tech
ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
Whatever chip I feel like burning,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
3.73 Posi
4wheel Disc Brakes
Summit 1-5/8" headers, 2.5" Dynomax catback.

Best 1/8: 9.519@72.74

'97 Bonneville SSE

 

I am sure mine is not the ideal setup being that the porting and valves help. I am sure you can get a stock set to runn what I am running. correct me if I am wrong but, I thought a stock 91 tpi 305 5-speed 3.42 rear was able to run 14.6 1/4 ? thats stock if I am right.

 

Oh, you meant "STOCK!", not "stock..."