Twin Turbo Skylark 350 Progress by sean Buick 76

11 minute(s) of a 265 minute read

Well today I picked up a cool car! I am going to put a Buick 350 with forged pistons and a single turbo kit in there and back it up with the CK Performance 200r4 trans and make it a street/strip car. I am planning to paint it all black myself and have fun with it and not worry about scratches or rock chips. The rear end is a fully built and spooled 10 bolt with 4.88 gears. With the gears and overdrive trans I will be able to launch it like a bastard and still drive the highway. I could not resist it and the price was right! I have been around this car for years, it was last running 10.35 in the quarter with a 6.0 LS engine and it hooks and goes straight so it should be a lot of fun!

I am not into the stroker builds personally or large overbores I will stick with 355 cubes either boosted or NA...

I have considered doing a mild NA build with so much gear it could still run well... Will likely go single Turbo though as I have the kit and it would be easy to get it to run fast. Plus boost is addictive. The sound is fantastic and no need for high compression big cam etc...

This will be a low buck fun car no alum heads or expensive parts.

I have built plenty of good running 350s,old street versions with self done head porting, mild cans that kept the low rpm torque etc. And yes I may build an NA engine but not a max effort one.

Yes Anthony's engine was 630 hp at 5 psi but they did raise the boost after that and that is where the higher HP estimate came from after they swapped to a higher boost level they never re dynod.

I have a nice engine here that just needs 60 thou milled off the block (pistons are 60 thou in the hole) and it would be 10.5:1 with diamond pistons and hershe rods and I have 2 big flat tappet solid lifted cams new in the box. That would be a good combo and cost me nothing. This block is all blueprinted and align honed and internally balanced with arp studs in the mains. I likely won't ever use it for boost as it was setup to run iron heads and if it was zero decked it would be too high of compression for boost and the alum heads... And for the alum heads I want a zero deck piston like in my girdled engine.

Or my other engine I just got back with the high compression TRW forged pistons would be 10.5:1 with some 48 CC ported heads I have and steel shim gaskets. That one is proven reliable bottom end with 74 rods arp etc. It may not have stayed reliable under high boost but it handled the abuse fine at about 580 crank HP on low boost. It only has about 500 miles on it, most of them about 120 mph lol!

8/27/16

Got some better pics of the new car and getting parts together for an iron head NA engine.

Some rod weight info:

Herche rods are 542 grams I measured them today on my good scale. 

The eagle rods we just had done are 580 grams

And from an old post we have the weights of the stock rods and the Nascar take outs: 

The H-beam nascar takeouts for Andy's engine weigh about 530 grams.

So all in all I am happy with the weight savings of any of the aftermarket rods that we have available all of them are much lighter than stock, and also much stronger. 

This is the cam I am stuffing in there:

http://www.crower.com/buick-350-comp...m-292-fdp.html

I will have to have 60 thou milled off the block, and then use the steel shim gaskets but it will give over 10.6:1 compression with these heads. TA roller rockers. the Herche rods, Diamond pistons, X factor intake, Holley 750 carb. MSD dist, just stuff I have kicking around. It will not be optimum but it will run well I am sure. I will drive it around a bit on the street but more of a track car. 

Better pics: 

Got the rear end opened up and holly crap its a 5.57 gear, WOW!! This may just run okay without boost.

Crunching some numbers with the 200R4 trans and 26" tall tires and 100% converter lockup via toggle switch:

RPM at 65 MPH would be 3135 RPM which is not that bad actually and the car would not be driven long distances on the highway.

RPM at 125 MPH would be about 6030 RPM so that would be good for a relatively low HP engine to run fast in the quarter. Lots of torque multiplication.

The last time this car ran with a Th400 trans it would have been revving the below RPM and actually more due to converter slip:

RPM at 65 MPH would have been 4700 RPM
RPM at 125 MPH would have been 9000 RPM

Will be using fully ported iron heads with oversized valve and TA roller rockers.

Thanks for the info and relevant experience with your Nova. This one is a 75 Omega with a 77 Skylark front clip. A car like this I would not be too worried about fuel mileage, and I will have the car hauler done before this is done so I can piggy back the cars anywhere I want and not have to worry about breakdowns or issues at the track I can just winch it on and drive home... Best of all I will not have to use my trailer its a pain in the butt trailering. I know you mentioned before that a turbo diesel would be a better option for the car hauler and that is what I am doing now its a 2000 E-450 with 7.3 Turbo Diesel and a tank that costs about $900 to fill up LOL!

Roller rockers are 1.6 ratio

I am not sure if Burton is making the roller rocker kits again? Last I heard he was understandably annoyed because there was a ton of interest in turbo kits and then he made them and had very little sales so not sure whats up...

I looked up the specs on the trans and torque converter package and it is a 3400 Stall converter so that will flash up nicely...

8/30/16

I am not interested in more than 10.5:1 and that is the max I could get with these spare parts I have. Not interested in stroking the engine, 355 cubes is fine and I think the big solid cam is enough for the combo.

The head flow numbers are:

1.92 and 1.55 valves

INTAKE

.050 - 35
.100 - 62
.200 - 118
.300 - 177
.400 - 218
.500 - 249
.600 - 258

EXHAUST

.050 - 28
.100 - 54
.200 - 104
.300 - 147
.400 - 177
.500 - 179
.600 - 180

I did some dyno testing on a hot 350 with 1.92/1.55 valves on a 355 cube Buick 350 a long while back with a single plane custom intake, 10:1, large cam, large tube headers etc. Note there was a typo it was a 350 not a 455.



We were not going any higher than 6500 RPM due to stock rods however with better rods there was more RPM potential in the engine if not for the rods.

This was with the very first single plane intake that I had built and the engine used was Rob Margel's that he let me use for testing.

As a generality I feel that the optimum operating range for a close to stock Buick 350 with ported heads is 2500-6000 RPM. Any time you push up to 6500 or 7000 RPM the reliability and maintenance needs will be effected. Sure with fancy parts and high $ builds 7000 may be a reasonable goal for peak HP, but like always the idle to 3200 RPM range will be losing torque as a trade off for the high RPM power.

This is where I come to the conclusion that turbocharging is the best way to make about 450-600 crank HP with the 350:

1. You can use the stock bottom end and get adequate compression without milling the block or custom pistons
2. You can use a mild cam that does not give up the bottom end torque
3. You can extend the RPM range of the engine with properly sized turbos, my engine was peaking in HP at about 5500 RPM (Poston 114 cam) before boost and it kept rising past 6300 with boost
4. You can make good power with 4-6 PSI and no intercooler and then it simplifies the setup not having an intercooler. 4 PSI is enough to turn a stock 350 into a healthy engine.
5. Even without expensive head porting or alum heads you can still make 450 HP at the wheels as we proved with my old car as it had stock heads on it, 9:1 and also a Poston 114 cam, this was at 10 PSI with intercooler.

yes we do have to dial in the tune up and ensure that #3 cylinder is getting the right amount of air and fuel and we are not sure yet if it is a carb issue, manifold issue, or if it is making so much torque the engine mount is twisting so hard on the block that the block distorts. Is MPFI the answer or can it be dialed in with the carb? We will see. Either way on low boost things are happy and long living, it is when the boost is raised that both me and the new owner of my other car are blowing out #3 head gaskets while the rest of the engine is happy. Adding exhaust temp probes in the headers to gain more data, and going to try to systematically rule things out and get things happy in all 8 cylinders. it is no issue for me to do a MPFI but this is not an option for a great many people that may be on a tight budget so I am not going to be too quick to get away from the carb.

I set the rev limiter at 8000 RPM on this run, just to see what would break and although I thought it was a spun rod bearing initially it actually turned out to be that the timing chain broke and the bottom end of the engine looks fine, including the stock rods and pistons. The heads are in good shape too, no issues to be found.

I did this as a test dummy to see what the stock 350 bottom end can handle, take pics of the broken rods or pistons etc for my book but the engine survived 17 PSI and 8000 RPM.

Turn up the speakers, it sounds good!