Budget Pontiac Engines comparisons: Mild to Wild

JayS.
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Budget Pontiac Engines comparisons: Mild to Wild

Post by JayS. »

EDIT: I am going to keep an index of the page for each engine on this tread at the bottom of this first post. If a new engine gets posted I will edit this to give a page location (as long as the website provides means to do so.)

In the not to distant past the 455 was the go to Pontiac street machine engine. Now we have 3” main stroker kits, cast and forged cranks, turn key rotating assemblies, big cid aftermarket blocks, and several head options. Several of us have quite a few Pontiac projects going on right now.. All street engines, 450-700 hp N/A engines and a 900-1000 hp boosted engine. Often hobbyists complain that the Pontiac is expensive, certainly some engines are. I am going to start posting cost and results as we work on them. Keep some running totals of the cost and compare performance on these STREET engines here on PSP. Maybe we will swap one of these to aluminum heads and compare that too. Feel free to to add YOUR engine into the mix and I will add it here on the page index. I am going to compare rotating assembly costs, rotating weights, machining, pistons and ring packs, cams, heads and what ever else we run into.

Here is the line up:

PAGE 1-3 1972 455, Econo build, # 62 d port, mildly ported, cast pistons, stock rods w/arp bolts, offy dual quads, headers

1977 400 W-72, 4.25” stroker w/main girdle on 500557 block, fully port 6x-4 heads, JE domed pistons, N crank, 6.8” eagle h beam rods, stock appearing

1970 400 RA IV 4.25”, 614 heads, DSS dished pistons, Eagle forged crank and I beam rods, stock appearing

1966 389, 4.21” Stroker, #96 ported D port, DSS pistons, eagle H beam rods, N crank, Warrior intake and headers.

1960 389, 3.75” stroke, Speed Pro pistons, Eagle H beam rods, Arma crank, Ported 96s, holley street dominator, turbo charged
Last edited by JayS. on August 10th, 2020, 9:22 am, edited 12 times in total.

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Bill Boyle
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Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by Bill Boyle »

Many of have found out along the way that it's in the details...and of course what one can reasonably afford. With all the engines you've listed, keeping track of modifications, costs, and posting results will surely be beneficial to any Pontiac enthusiast looking to upgrade their current engine combination. As always, I look to improve power for the street but am always interested in power that was unheard of back in the '60 and '70s.

[Getting 600 hp to the ground safely on a street car not equipped with ABS /traction control has to be an unbelievable driving experience. :shock: ]
"Dedicated to keeping the classic Pontiac engine alive."
Image,Image,Image
1979 Trans Am: 400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, Pypes 2.5 SS dual exhaust X pipe, Comp 276AH10 cam, Scorpion 1.65 RR, 800 Q-jet, stock intake & tuned HEI; original owner.

JayS.
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Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by JayS. »

For certain 5-600 hp can get little hairy on the street without the rest of the combo matched for the power. Probably the drive train and cost of the drive train to make these all manageable should be another topic when we get further.

We may switch some of the heads around on the engines all said and done. One engine is going to get prepped for NOS. I think I will start with the 455 and different directions it can go if so desired and tally up the cost if it were to receive some upgrades.

Phil400
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Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by Phil400 »

Cool idea, I'd very intrested in the econo build, Poniac parts aren't easy to come in my neck of the woods and gotta add about 30-35% to the costs, exchange rate, duties etc
78 T/A 4 Speed, mine since '99, Third and final owner as long as I'm alive.

JayS.
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Joined: June 23rd, 2020, 2:44 pm

Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by JayS. »

3B08BC33-8F42-4CBE-8DAD-F63C47B64F36.jpeg
Here are the total cost for the 455, about $1880. That is with a custom solid flat tappet cam from Bullet and edm solid lifters. The ram air 4 engine and this engine both are getting the same cam and have the nearly same compression(9.8 scr on the RA 4, 10 on this). All said and done we will get to line them up and see how they match up, A body against A body, dual quad d port against the Ram air 4 judge with a q jet :o

With the mildly worked over head with 240 cfm intake and 180 cfm heads should make right around 480 HP @ 5500 rpm. If it falls short of that will be due to the bore taper from the rering std bore. I am also going to compare the standard OEM bob weights for balancing against a .030” oversized Speedpro L2359f forged piston. I have a couple generations of Speedpro 455 forged pistons, I will weight them and see if they are the same, and post the pictures and show the the changes Speedpro did to the same part number. The later pistons have the ring pack in a different position and the valve reliefs are different cc’s. I have compared them before, just not in this much detail. :geek:

The compression for this engine is 9.8 SCR. I cut a dish in the pistons to drop the compression using a lathe. Total piston dish volume is 18 cc. The heads are 75 cc. The pistons are .003” below the deck, with no decking/machining. The crank only needed polishing.

We can do most of the head work machining. Even though that really wasn’t a cost for us, I added the machine work if it was hired done just to be fair. Some of the other engines have extensive head work done, even to the point the cost for the heads eclipsed this WHOLE build. :cry:

The short block was checked and did not require any machining. Typically the big end of rods bore at least need $120 worth of machining, these passed. Majority of the work was on the heads, posi seals, and a valve job for new valves. Guides were a little loose on these heads, the econo fix is knurling. No hardened seat or anything fancy, remember this is the Econo build.

This figures to be $3.91 per HP if it make the hp goal. That is not including the intake manifold or carbs. I don’t have the carbs yet anyway. The 2x4 offy intake runs around $250-$350 for a use one.

The cam is a Ultradyne 280/288 247/255 .525/.540 with a 112 lsa. The stock rockers need to be check for clearences.

I could have done an off the self hydrualic cam with Rhoads for about $50 less. I have a melling spc-8 can I bought for $113.50. Add a set of Jegs brand lifters to the melling cam for $60, the melling 1.65 rocker and $99 comp 995 spring and the total would be a savings of about $200. But if you wanted to cut a corner the non edm solid lifter would have been $60 cheaper. This Ultradyne profile with the edm oiling is very durable.
Last edited by JayS. on August 2nd, 2020, 5:55 pm, edited 2 times in total.

JayS.
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Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by JayS. »

Here are some pistons OEM type forged pistons that are found in 455s. The early factory cast piston this build has were used 70-72 measure 1.503 on the compression height. This build the pistons are .003” below the deck. The later 455s have a bevel the outside and are slightly lower compression, I am not sure what the comp ht is. But the replacement cast pistons are ALL 1.48-1.482 on the comp ht.

Theses are photos of some old forged l2359f and l2365f the comp ht is 1.497. The TRW L2365F and the first generation of Speedpro L2359F pistons were identical as seen here:
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Last edited by JayS. on July 27th, 2020, 3:20 pm, edited 2 times in total.

JayS.
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Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by JayS. »

The second generation of L2359F pistons came in the 1990s. With the same 1.497 compression height, but a much different piston skirt. Personal opinion, this generation is the strongest of the Speedpro pistons. The skirts are the weak compared to a aftermarket forged. Not a huge difference in strength between these speedpros. Ring pack and compression is the same as the earlier generation TRW and speedpros.
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JayS.
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Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by JayS. »

At some point Speedpro added the coated skirts to the later generation of L2359F. But then sometime in the last ten years Speedpro changed the ring pack, the rings come higher in the cylinder bore. I am not sure but I think they may have lowered the compression height to 1.48 like the cast pistons (they still list it as 1.497!). They kept the skirt design like the second generation, but reconfigured the valve reliefs. They have a straight down cut across the center where the valve reliefs are. You can kind of see the edge on this photo, the latest pistons the edge is deeper, making the valve reliefs appear to have a little more volume also. I will weight them and see if they are the same.
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9D108B9F-3B9E-43EF-BEC5-C4659F765A3A.jpeg (42.18 KiB) Viewed 253 times

JayS.
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Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by JayS. »

59F7564F-BE2D-400D-8966-478AF71C94C8.jpeg
Here is the dished pistons for this econo build. .125” deep. I have too cc them to check the cc’d because it goes into the factory reliefs. As is these are 14cc counting the dish and what is left of the factory reliefs. Once 1 is done I will copy each one. Shooting for 18cc, more needs to be taken off the outside of the dish.

Phil400
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Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by Phil400 »

Jay, how much more Piston to wall clearance does the standard speed pro forged piston need over a cast OEM piston?
78 T/A 4 Speed, mine since '99, Third and final owner as long as I'm alive.

JayS.
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Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by JayS. »

Speedpro recommends .003” on the l2359. A cast piston is usually .0015-.002 piston to skirt. I like .004” piston to skirt clearancs on theses for the street.

The Speedpro forged replacement pistons are designed so that the skirts do not expand much. If you flip the pistons upside down and look at the oiling holes on the l2359’s and the stock 400 forged pistons the oil hole that are drilled through the oil ring are oval shaped or slotted. Speedpros has made some racing forged pistons that have round oil holes and the skirts are stronger, but expand a lot more. Even though the alloys are the same the racing pistons require more clearence.

Speedpro has their own alloy, (at least they claim they do (vms-75) it is similar to the 4032 alloys commonly used on the street.

Here are the round oil hole on the racing style speed pro
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Here is a oem type skirt oil ring slot(above and below) . You can see why it is not as strong! It has a large part of the skirt not connected to the top part of the piston and does not expand as much. Mild applications this type skirt does not require much piston to wall clearance, similar to a cast piston.
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Last edited by JayS. on July 28th, 2020, 12:10 pm, edited 3 times in total.

Phil400
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Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by Phil400 »

Ok thanks.
78 T/A 4 Speed, mine since '99, Third and final owner as long as I'm alive.

JayS.
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Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by JayS. »

This 455 reringed engine has .0045 bore taper from were the top ring groove is to the bottom of the bore. That is what it measured breaking the glaze with a standard hone. I am over sizing the bore and adding a .001” on this, using a fixed hone (lisle 15000) . Most of the metal is removed at the bottom of the bore, it ends up squaring the bore taper up a little more. Then the final finish on the bore is with a dingle ball hone. If you do not have tools to measure the bore taper with these cast piston the removing the ring glaze and scores need to be clean up and that is about all that should be done. The final bore taper after I am down is .0035. We have reringed some engine that had .008 taper and the rings seem to seal without issues, it depends on what the bore size is though. On a Pontiac 4.151 bore after .005” bore taper it should really be bore and use oversized pistons, but on lower rpm engines you can rering them with close to .008” bore taper. It sounds like a lot, but when guys bore engine without torque plates the bores can distort nearly as much. You will ussually have a better ring seal with a reringed engine braking the glaze than an engine that went to the machine shop and bored/honed the engine without a tq plate for oversized pistons. When the bore taper gets to be more than .005” there are fair power losses when the engine is turned hard. Most noticeably above 5000 rpm.

We don’t use file to fit rings on engines like this , if you did you would want to push the ring down to where it comes to in the bottom of the bore.

Phil400
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Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by Phil400 »

If one wanted to upgrade a cast rotating assembly to forged, without a re-bore just hone with a dingle ball could it be done?
78 T/A 4 Speed, mine since '99, Third and final owner as long as I'm alive.

JayS.
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Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by JayS. »

On a 455 you couldn’t because the top ring on the forged pistons goes up higher into the bore. That is unless you found one of the older piston version like I had pictures of. The rings are in the same position as the OEM pistons on those.

Since we are talking about this, the l2262f forged 400 piston may work in place of a standard cast piston in a 400. I don’t think speed pro ever messed with the ring pack on those. I would have to double check, I think they would work. On lower performance 400s the clearance for the forged pistons is .002” (about the same as a cast piston). That would be for a 350 Hp 400 and smaller hp 400s. The RA3 400 and a 455 forged speed pro are suppose to be at least 003”. Which is do to more thrust on the skirt, rpms on the 400, extra stroke on the 455. If you spent some time honing it wouldn’t take much to make a forged piston work. Best results would be with a fix hone and enlarge to bore slightly for a little more clerance, then lightly hit it with a ball hone for the final finish.
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The flex hone does ok for this also. If your trying to remove a little metal for extra bore clearence it would be better than a ball hone. Ball hone are for braking the glaze, and for cylinder finish. Ball hones are not meant to remove much material. This flex hone can do both if you use the right stones.
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