FrontEngineDragsters.Org Forum
Technical => Matt Shaff's Engine Shop => Topic started by: bfalfa55 on March 30, 2016, 04:01:16 PM
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I know I could build my 350 more or anything bigger but I want to see what I can out of this little engine with a modern cam grind and better parts than an old school build. The engine is a 56 265, .060 over that has been balanced. It has cast dome pistons (still need to cc the pistons), 327 rods. It should be in the 10.5 to 11:1 comp range. It will be a street/strip engine. I am planning on using Comp Cams Extreme 4x4 Hydraulic Roller cam, .474 lift int & exh., duration 230 and 234 @ .050, 111 LSA. Being more limited to 1.94 intake valves due to bore size, I am planning on using a set of 1991 L98 Aluminum Corvette heads, 58cc chambers. WIth all this information put into Comp Cams CamQuest, it seems it should be a strong running engine. Reading one of your other posts here in the Engine Shop, I saw you say many people port their heads too much for smaller cubic inch engines. I always thought that could be the case, glad I read that from somebody with more experience than myself. With stock flow showing 196 cfm @ .500 of lift, I only planned on porting them enough to clean them up and make them even. What ultimate flow numbers do you think would be good to shoot for based on the info. I have given ? Also, I am running a single plain manifold with a 650 dual feed, double pumper for a carb and roller tip rockers. I would appreciate any help from all of the rest of the FED groups expertise !
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I found my 355 too light on power. Had to move up.
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I have 2 283's sitting in building and have thought about building one for true Jr. Fuel car.Modern solid lifter cam,good set of heads and valvetrain,11:1 or so and 90% or so load.Run it high gear only with high rear gear. How long would it live? No idea ,but dang it would be a blast until the big blast of parts.
Right now I'll stick to getting car done and playing with little Hemi I have.
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A buddy of mine held the record in SS/P in his 55 Chev I think it was around an 11.60 with a 265 and an itty bitty carburetor. Pretty sure he keeps the RPM's below 9000
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I have been in contact with a 55 Chevy SS/O, SS/N driver who runs times similar to that. I figure with modern technology, a strong running street/strip engine can be built better than what you could make back in the good old days. I have tried to pick parts that would also work with a small blower in the future like m avatar pic shows.
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The top improvement needed is something around a 6.2 rod and a lot shorter compression height piston. On that 56 block, I cut a small groove in the #5 cam bore to connect the oil holes so it will oil the lifters without the cam having a flat. Do this before installing the bearing.
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Thanks Van. The oil groove issue I know. Before finding this engine with domed pistons, I considered using after market domed 305 pistons and using GM 5.94 in rods. I figured this would be a more cost effective way to get after market pistons that wold be similar to the bore of a 265.Why is a longer rod setup a big improvement ?
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A longer connecting rod will reduce the rod angle to the cylinder centerline. Less rod angle will reduce piston side loading so there will be less friction and less cylinder wear. The long connecting rod also allows the piston to stay at top dead center longer as the mixture ignites. That gives the combustion pressure more time to build before it starts to shove the piston down the cylinder. All this would result in additional power being produced along with a decrease in cylinder wall wear.
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Thanks Roger, that makes sense. Is there any formula or way to figure out the percentage of power increase you would get from one rod length to the next ? For example, if using 5.7 rods made 400HP, how much more power would 5.94 rods or 6.2 rods make as was suggested earlier ? Or is it something that would just have to be measured on the dyno ?
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The conventional wisdom says that a rod-to-stroke ratio of 1.6 to 1.8 is a real good for a high performance engine. With a 5.7” rod and the 3” stroke in your 265 the rod-to-stroke ratio is 1.9; 5.7/3=1.9. With the 5.94” rod the ratio goes up to 1.98 and will probably do little good in producing more power as you are already over the sweet spot for rod length. The new engine I'm building for my altered has a 3.625” stroke with 6” rods resulting in a rod-to-stroke ratio of 1.65 and I’m very satisfied with it. Just my 2 cents.
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Roger's info is correct, but in your case the issue is the block is way to tall for that short stroke. The best fix is to run a long rod, this moves the pin up in the piston. The now shorter piston just lost a lot of weight and with the pin higher in the piston the side thrust is way better. Go to any piston Co. web site and look at MODERN racing pistons, they are very short & used with long rods. Compression heights around 1.0 to 1.2 are the norm in small blocks.
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Thanks for all the engine info. I think I will just stick with what this engine is for my street/strip fun. I am thinking about building some nostalgia race car of some kind. I have more 265's to choose from in the garage !
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FINALLY a positive, forward update. My oldest daughter is now married, so I can spend some money !
I did a full cc job of my dome pistons in the bore. I will be right in the 10.5:1 compression ration depending on what head gasket I use. I have to use 350 style due to the mods the previous owner did to the top of the bores. So, my question is: what is the thinnest 4.03 bore diameter gasket I can use that will work with my L98 aluminum heads ? If I use a shim style gasket I will be around 10.68:1 if I use a .028 thick gasket I will be around 10.48:1.
I don't care if the gasket is pricey, as long as it won't cause me issues with the aluminum heads.
I also must add, piston is .015 down the bore, so I can't go too thin.
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less than .030 between the pistons and the head with steel rods and normal piston clearance I run pistons on the loose side so i need a little more you can get shim gaskets .016-.018 thick and you can get gaskets that measure your bore size most of the gaskets I use are custom
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Just put together a street machine engine with steel shim head gaskets. Used a 0.015 thick gasket and when visiting with a company rep, he told me the final compressed thickness of the gasket is between .022 and .024 inches in thickness. That is because it is embossed (stamped) round the holes. You can’t compress it back to original shape cause the stamping process stretched the metal. An option is to use a Multi Layer Stainless steel gasket (MLS). You can get one that has a 4.06 bore and is .027 thick, even when compress cause it isn’t embossed (they also come is various thicknesses). Shim gasket $45, MLS $150. Both work with aluminum heads, should work with your compression ratio, and both need smooth surfaces to seal correctly. Hope this helps.
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I posted this before and was hoping I would get some of your thoughts. I have edited it and put a suggested cam from a Lunati rep. on the phone. Let me know what you think.
http://www.gmperformancemotor.com/parts/10105117.html
I am thinking these gaskets will work well, I just have to get them and make sure they are a match with the areas the original engine owner modified on the top of the cylinder bores. He scalloped areas to match the head gaskets he was going to use. Not the best thing for a little engine like this but they only take away 2cc's away from my compression but that isn't going to hurt me because I will be at 10.5:1 even with them. I am trying to see if I can just get them from a Chevy dealership parts counter in case they aren't compatible.
These will put me at a .043 quench. I also have a porting question for you guys. The flow numbers I have found for L98 Aluminum heads are just about right for this size engine as they are. Should I clean up all through the ports OR just do enough clean up to true up things and take out the imperfections ? I don't want to take away what little low end torque I will have so this is why I ask.
This is the cam I was looking at and ironically it is the exact cam Lunati suggested when I talked to them. Not purchased yet, ordering my gaskets so I can get to porting my heads.
Voodoo Retro-Fit Hydraulic Roller Cam & Lifter Kit - Chevrolet Small Block 270/278
[IMG]
Product Description
Lunati’s Voodoo series of camshafts deliver more area under the curve than any other series of camshafts. This means more throttle response, quicker acceleration, more vacuum and better efficiency. These factors, combined with maximum horsepower and torque, make Voodoo camshafts the perfect choice for a wide range of high performance applications.Retro-Fit Hydraulic Roller. Strong power increase in mildly modified engines with excellent throttle response. Will work with stock converter in 383-up c.i.. Likes 2000 RPM converter in 350 or less c.i. applications. Likes 3.23-3.73 gearing. Largest choice for inboard/outboard marine applications. Has noticeable idle and likes headers.
Advertised Duration (Int/Exh): 270/278
Duration @ .050 (Int/Exh): 219/227
Gross Valve Lift (Int/Exh): .515/.530
LSA/ICL: 112/106
Valve Lash (Int/Exh): Hyd/Hyd
RPM Range: 1800-6000
Includes: Cam & Lifters (#72330-16)
Part Number: 20120711LK
Previous Part Number: 60111LK
Jobber Price: $605.56
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i would do the valve bowls, a good valve job, gasket matching
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It looks like the head gaskets with the stainless fire ring will work fine with your compression. The camshaft should idle fairly well and make power to 5,500 or even 6,000rpm. While the air flow of those heads look pathetic at first, your stock heads should flow close to the same amount of air needed to feed your 265” engine at .50” lift as a set of stock Dart Pro 1 230cc heads flow to feed a 383” engine. I say put it together with the parts you have using the cam you quoted and let us know how it runs.
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Alright engine gurus, how close to the bore should the fire ring of your head gasket be to the bore ? Due to the scalloped shapes at the top of my bores, the head gaskets I bought are right at the edge of them. I don't have a picture at the moment but thought I would ask first. I may be limited to a certain bore/combustion chamber shape since this was done to the block, so it brings up another question: How thin of a had gasket can I run with aluminum heads ?
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Alright engine gurus, how close to the bore should the fire ring of your head gasket be to the bore ? Due to the scalloped shapes at the top of my bores, the head gaskets I bought are right at the edge of them. I don't have a picture at the moment but thought I would ask first. I may be limited to a certain bore/combustion chamber shape since this was done to the block, so it brings up another question: How thin of a had gasket can I run with aluminum heads ?
1) I've always considered OK as long the fire ring doesn't overhang into the cylinder bore.
2) In my mind, minimum thickness is closely depended on gasket type (composite, steel shim, MLS, copper, ...), not cylinder head material.
Now let's hear the pros.
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I reordered my gaskets and will have to run a 4.125 bore, .039 gasket. This will give me a .054 quench and 10.15:1 comp. Taking .010 more off the block will put me at .044 and right about 10.5:1. I don't know if doing that is worth it or not for the effort. Thoughts ?
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The block I just had machined measured 9.025” height stock. Add that with a stock .039” gasket and the quench from Chevrolet is .064” and they run fine. No reason it wouldn’t work with what you have, unless the deck surface isn’t flat. Unless you use some poor quality gas detonation shouldn’t be a problem I would think at that compression ratio.
Or spend about $150 to surface the block and use your gaskets. Milling adds about .35 point of compression which adds about 3 HP on a 300 HP engine. Check it out at this website. (Results are not absolute but it puts you in the ballpark)
http://www.wallaceracing.com/hp-cr-chg.php
Or if your deck surface is flat spend about $150 on some Cometic MLS gaskets with a 4.100” or 4.125” bore and .030” thick to end up with a .045 quench.
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Thanks Roger, that is what I was hoping to hear. The block has already been decked flat and I got my data from the same calculator from Wallace Racing ! I have been using a number of their stuff online, it seems to be pretty good, better and more consistent than some of the others I have seen and used. If I was trying to squeak out every ounce of juice for a race engine, I might do it. But this being more of a double duty engine, I don't mind some of the trades offs for a little street driving.
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Based on where my cam RPM range is 2,300-6,300 RPM, .218/.228 duration @ .050, .503/.503 lift. 112 LSA hydraulic roller, do any of you think I will benefit from an X pipe or an H pipe in my 2 1/4 inch exhaust system ? I read some conflicting information as to how it may benefit or hurt my little 265. I would like to hear your suggestions or if you think it isn't worth the effort at all.
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I don't have an opinion on the exhaust cross over.
I know this will open up a new slew of peoples opinion's but.......
I don't think that camshaft is going to make any power past 5000 RPM.
Now most of the small engines we dyno are 302 ci and bigger.
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I am interested in hearing why tou feel that would be the case. I am not arguing it, just gathering intelligent opinions.
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I based my opinion on the last of 3 camshafts you mentioned.
Matt
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The RPM range I listed for the last cam came from talking with a Lunati rep. The actual range for a 350 chevy was 1,800-5,800, he said the smaller cubes would shift up 500 RPM. Did they give me miss information by telling me the RPM range would increase when it is actually going to decrease ? I have always been under the impression that the range has to increase to get more power out of a small cube engine. This engine will be just below 10.2:1, with the aluminum L98 heads, with 1.94/1.5 valves. With that cam and these heads, do you think it is going to choke cylinder flow by the time it is at 5,000 RPM ?
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Take a look at a dyno test performed on a Chevrolet 350ci/290hp crate engine as delivered from Chevy to Westech and modified with only a RPM manifold and headers, then draw your own conclusions. The crate engine had 8-1 compression and stock iron 76cc heads with 1.94-1.50 valves. The camshaft specs from Chevrolet are:
222*/222* duration @ .050”, .450”/.460” lift. 114* LCA hydraulic flat tappet
This cam is somewhat similar to the last two you listed but unlike those you listed it has the disadvantage of being flat tappet.
I have to ask myself if a modified Chevy 350 with a somewhat similar cam to the ones you listed can make 330hp at 5500rpm, then why wouldn’t the two last cams you mentioned work as well in your engine and rpm even higher due to its smaller size and increased compression. Can’t help you with the x-pipe deal, I use zoomies.
Chevy 350ci/290hp modified by
Westech with RPM intake & headers
Horse Power Torque RPM
100 270# 2000
160 280# 2875
240 345# 3750
305 340# 4625
325 325# 5250
330 315# 5500
(Figures pulled from a graph)
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I apologize for responding late to your posting.
Working at our shop by day and putting up a new building at night.
Mine are only opinions because I have no dyno history with small bore engines.
I know we see improvement on air flow going from a 4.000" bore to a 4.060" bore and that adds power.
Your running an engine with a bore of 3.935". Reducing the 4.000" bore by .065" also would slightly reduce air flow.
Also the short stroke reduces the volume of air being pulled in.
If you lived a little closer I would cut you a deal on dyno time just to get the real answer.
Matt
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bfalfa55 – you know either x or h-pipe is termed a balance pipe as it provides a crossover point to equalize flow side-to-side in a V8. Engines create exhaust pulses due to firing order and to smooth out these low and high pressure pulses, a balance pipe maybe used to address the backpressure created. Backpressure simply slows down exhaust flow.
Most agree about x and h pipes and they both relate to sound and power. X-pipe is higher pitch noise and the h-pipe a deeper tone. Slight hp gain from x-pipe due to the venturi effect which allows exhaust gasses to exit combustion chamber faster (i.e. scavenging); the more cam duration, the more effective according to the experts. The 90 degree bend in the h-pipe provides more back pressure which increases low-end torque and maybe important in some cases.
My own experience 18 years ago in 1998, I bought a new Ford f150 and after a year, I had dual exhaust installed with an h-pipe. Prior to installing the dual exhaust, it ran 15.30-50s around 90mph on test night for fun. After the new exhaust, it still ran the same et/speed just over 5,500rpm. Whether you chose x or h or neither, my guess is your ’55 265ci results might be similar. Although no improvement on the track, it sounded faster. Alan
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The bore isn't even that big it is 3.81. Standard bore of a 265 is 3.75. It would neat to see what numbers would come from a dyno run. If I don't get just the engine on a dyno, we have a place local here that has a chassis dyno, so that will be the real tell all.
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bfalfa55 – you know either x or h-pipe is termed a balance pipe as it provides a crossover point to equalize flow side-to-side in a V8. Engines create exhaust pulses due to firing order and to smooth out these low and high pressure pulses, a balance pipe maybe used to address the backpressure created. Backpressure simply slows down exhaust flow.
Most agree about x and h pipes and they both relate to sound and power. X-pipe is higher pitch noise and the h-pipe a deeper tone. Slight hp gain from x-pipe due to the venturi effect which allows exhaust gasses to exit combustion chamber faster (i.e. scavenging); the more cam duration, the more effective according to the experts. The 90 degree bend in the h-pipe provides more back pressure which increases low-end torque and maybe important in some cases.
My own experience 18 years ago in 1998, I bought a new Ford f150 and after a year, I had dual exhaust installed with an h-pipe. Prior to installing the dual exhaust, it ran 15.30-50s around 90mph on test night for fun. After the new exhaust, it still ran the same et/speed just over 5,500rpm. Whether you chose x or h or neither, my guess is your ’55 265ci results might be similar. Although no improvement on the track, it sounded faster. Alan
Low end torque is always an issue with a 3 stroke engine, so if any balance pipe will help, I will certainly try it. I have extra exhust pipe the same size as what is on it now so it won't cost anything but time.
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Positively I agree to install balance pipe since it’s an enhancer, no negatives. Plus two items which might change your conclusion, no catalytic convertors and performance cam with more duration than oem.
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I was thinking 283 bore.
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I was thinking 283 bore.
That's what I figured. Many more 284's than 265's being built !