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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
I'm putting together a new top end package for my 355.
Comp Cams XR288HR: 288/294, 236/242 @ .050", .555/.576 w/ 1.6rr.
Lightly ported RHS Pro Torker heads by AMS Engines. 5 angle VJ. Bowls cut, blended valve guides. Short turn work. Chart attached.
Usual assortment of parts. 750 BG VS carb, RPM Air Gap intake, 1 5/8 LT headers, 3" cat back, cut-out before muffler (thankfully).
Dyno simulations are showing peak HP from 6000-6500 (essentially flat at that point).
The weak exhaust system notwithstanding, does that sound about right?
I'm not looking for HP estimates or time slips. Just whereabouts peak power might be.
Lightly ported RHS Pro Torker head. 4.03" fixture bore. Bowl blending. Short turn on the exhaust.
DynoSim graph. 288 is solid red line. Exhaust input to reflect small tube headers and mufflers.
I would expect peak in the lower 6200 range due to smaller heads and dual plane intake. Light porting
If it had a bit larger head runner and ported dual plane or small single plane, it would peak 6600 imo hold power out very well to 7k. Need something like a 195-210 runner head to really let that cam rip
I can't say I disagree with you.
With the as delivered 170 cc intake runner, (arguably larger now with porting but not by much), the as tested flow numbers are down by about 10% compared to the AFR 195 cc street head. With 256 cfm @ .500" (4.03" fixture bore) vs 275 cfm @ .500" (4.06" fixture bore), it puts me a disadvantage.
That said, the main focus on this build was to raise my peak HP RPM over what I was getting with my last couple of cams. That was the XR276HR and another similar custom profile using XFI lobes ( which on the intake was 274 adv and 224 @ .050"). I think that combination was camshaft limited as opposed to where I'm at now with the limitation being the heads. Thinking is HP peaked at 5500+/-. I shift a 6500, 1-2 and 6000, 2-3.
Interesting thought about the dual plane vs single plane. My understanding is that the Air Gap intake is good to higher RPMs over the more conventional dual plane. Kind of a best of both worlds. There was some testing done with the RPM Performer intake and various thickness's and styles of spacers. Results varied and were largely application specific (as in it all depends...). Something I might experiment with later in the season.
HP peak notwithstanding, I can see torque below peak being less. That in itself will probably slow the car down in the 1/8th. Perhaps the extra HP above that will make up for it. It certainly is going to need a different converter.
Thanks for your insight. Always appreciated.
Cam has a 110 LSA w/ 106 ICL. I'm thinking about dialing it in a couple of degrees advanced. It's something that I can mess with having the Cloyes Hex-Ajust timing set. Haven't decided on that yet.
This cam was originally installed in this same shortblock and topped with AFR 195 street heads. Typically saw 7000 rpm but generally shifted around 6800 on the 1-2. Valvetrain is solid enough. You know I like the Beehive springs (Comp 26918). Have Ti retainers and short travel lifters. Crower full roller rocker (1.6). Never an issue in that regard.
Seeing that you have experience with this cam and the L31 heads gives some credo to this build. Essentially what I have is a heavily ported Vortec head. More flow on the intake side and considerably more on the exhaust. This package will love an open header with the right length extension. Again the simulation shows that this new build will be producing about 75-80 more hp at 6500 seeing as the old set-up had long since given up by that RPM. That's what's driving this upgrade.
As for gearing and converter, last year, when the fuel problems weren't giving me fits, I'd launch (footbrake) at about 2000 and cross the stripe at about 5500. The TCI 10" converter didn't work all that well when compared to when this engine was in the Chevelle and had a properly spec'd Yank. I doubt very much I'll change the rear gear but certainly have my eye on a better converter. If I can keep RPMs above peak torque then I'll definitely be quicker. That'll wait until next season though.
For that cam and intake combination, I would say that 6,000-6,500 HP peak seems about right. I agree that your small intake ports will hurt you at the top end. I do like the flow numbers from .400 through .600 though, very consistent. That says something about the port work. This provide good flow throughout a wide area of the cam's lift profile. Helps make up for the low peak flow number.
This combo of yours should work very well. You can always move to a larger head later on.
adding a 1" open carb spacer and port matching the intake or switching to a single plane would probably help.
seems pretty obvious your exhaust is whats killing top end power. un-bolting your exhaust and adding some collector extensions looks like it would really help big time.
do you think a rev-kit would help any, or waste of time/money?
For that cam and intake combination, I would say that 6,000-6,500 HP peak seems about right. I agree that your small intake ports will hurt you at the top end. I do like the flow numbers from .400 through .600 though, very consistent. That says something about the port work. This provide good flow throughout a wide area of the cam's lift profile. Helps make up for the low peak flow number.
This combo of yours should work very well. You can always move to a larger head later on.
Interesting observation doc. I'm only guessing here but my thinking is that these RHS heads are patterned after the Vortec. Looking more closely at the low lift numbers, they do flow very well so that would be something they have in common. That they outflow them is better still.
As for the port work, Louis at AMS Racing Engines has a solid reputation.
Lots of high zoot stuff goes through his shop and he was very accommodating and engaging when we spoke.
As for larger heads, once this combination is dialed in and I feel the need to go faster still, it's time for a whole new deal. It would be an LSX swap.
adding a 1" open carb spacer and port matching the intake or switching to a single plane would probably help.
seems pretty obvious your exhaust is whats killing top end power. un-bolting your exhaust and adding some collector extensions looks like it would really help big time.
do you think a rev-kit would help any, or waste of time/money?
The graph seems to reflect opinions posted here so I think I know where this is going and what to expect.
Yes, the exhaust on this car has always been the bottleneck in performance. The headers themselves aren't too bad. It's the single 3" to one lonely muffler out back that's the issue. That muffler is part of the Flowmaster cat-back kit I put on the original chassis over 12 years ago. It probably flows 300 cfm. And that's optimistic. Once I know I have the fuel issues sorted out and have a couple of decent passes under my belt, I'll undo the cut-out ahead of the muffler and tune to that. I fully expect a 110 mph trap speed on a good air day. Ultimately, I'll place cut-outs at the appropriate length along the y-pipe and open them up on track days.
The carb spacer is something I'll experiment with if the current combination isn't performing as I feel it should. Any data I've come across as to whether they help on the RPM Air Gap has always pointed to "try it and see" .
As for a rev-kit, I've never had the need for one. This valvetrain is pretty solid. Light springs and retainers. 7/16ths studs. From what I've found from similar builds is that it handles 7000 rpm. At least in the short term drag racing blasts it's seen. At what point a rev-kit is needed I can't say but my thinking is that if everything is built to spec, then it shouldn't be needed. Certainly not at these power levels.
Ohh, but you're doing so well with the SBC. Just think what you could do with 50 to 75 more cu ins. I love seeing the numbers coming from the latest 421 and 427 builds.
I'm finally planning to move away from the TPI myself. I've had fun with it and it did very well against a field of hot muscle cars on its one trip to the dragstrip. Could have been in the 12s with better tires. The wimpy rear axle keeps me from going there. Someday I'll do the 9" Ford swap. I'm 5mph behind you at the trap and that's not so bad for full length TPI.
I'm staying with my ACCEL DFI and swapping on an Edelbrock Pro Flow intake that I'll cut open, port to my liking and maybe even add a few cu ins to the plenum when I weld it back together. I hope that with my ported G2s, I'll make good power to 6,500. Eventually, as in when I save up enough pennies, I'll do a Dart SHP based 406 and have my TFS G2s gone through and flowed. I like to think they flow about 270 with my port work, they were 257 out of the box and also have good mid lift flow. We'll see what they do when the head shop puts them on the flow bench.
There's certainly something to be said for the old Gen 1 SBC. On one hand, it's relatively affordable. Especially considering that the rest of the infrastructure is already in place. I.e. Headers, engine mounts, and the rest. On the other hand though are it's limitations until you get to the exotic (such as the aftermarket blocks and bullet proof rotating assemblies) and then there goes the price point advantage.
It's interesting to me when I think back, (way back) that my original 307 with the tried and true double hump heads (that I built back when I was an auto tech student) eventually became a 400 cid with the same heads, cam and intake. I was scared away from proceeding with the 400 by my machinist (cylinder walls splitting at the head bolts). I've been with the 350 platform ever since (there was about a 2 decade hiatus as my kids grew up) but to have those additional 50 cubes today. I'd be in the 11's easily.
For now though, I've got this fresh top end, some decent heads (I think) a bigger cam and a few other plans. We'll see where it gets me. Certainly not 11's but I'm hoping an improvement over my personal best of a corrected 12.4x @ 109. (actual time slips say 12.6 @ 107).
We'll see.
Again, thanks for your insights.
It'll be interesting to see if anyone else posts up an opinion. I like the real world experience perspective.
All you really need is a great set of heads. Save up for a set of ported profiler 195-210's or afr's and it will turn 7k rpm and make 400+ whp like cammed ls1's.
Ls is only good for its superior head from factory. Thats where you gotta spend money for sbc to go fast
All you really need is a great set of heads. Save up for a set of ported profiler 195-210's or afr's and it will turn 7k rpm and make 400+ whp like cammed ls1's.
Ls is only good for its superior head from factory. Thats where you gotta spend money for sbc to go fast
I hear ya.
Funny story. While I was sitting on these tired RHS heads I was shopping around for an alternative and the ProFilers were at the top of my list. Then I got to thinking about what was a reasonable amount to spend and decided to refresh what I had and run them. Needed guides and a valve job after 25 000 miles (my fault for not checking geometry after a short block swap). The guides led to new intake valves, then I wanted to cc the heads, then I discussed porting (with Charlie at AMS) and then one thing led to another and here I am having invested just about what it would have cost to go a different route. (Canadian dollar was really in the tank at that time and it added 30 points to my purchase).
I understand the importance of good heads, it's a make or break deal really.
But, here I am, and I'll see what this lump can do. I'm still a ways off from putting it all back together.
In the meantime, I'm bench racing!
Well with less than optimal heads, make up for it with cam gear stall and rpm! It should run hard
That's the plan...kind of.
Unfortunately, I think this season I'll be the classic "poster child" for a mismatched combination.
Big cam, not enough gearing or converter. The converter may wait until next year unless my ambition level goes up a little. The gearing...I doubt I'll ever move on that. Lots invested there too and the trouble I went through to get what I have set up properly was a royal pain. Still there always seems to interest in these factory Danas.
Your manifolding does not support your camshaft duration. U need at least 1 3/4" headers or even the 1 3/4" to 1 7/8" stepped header. Then a good single plane intake like a Victor Jr.
Your 1.6 rockers are stressing your vlv springs more than gaining any power. Return to 1.5 rockers.
Get a good 4" exhaust like from Mufflex.
Those heads aint that bad, just dont flow any more above 1/2" lift which tells me flow pattern is changing and undesirable. U have plenty of duration but your manifolding is for lower rpm power. Changing to a shorter cam maybe a better answer than manifolding then. What is your compression pressure now? Going to the larger duration cam is only gonna lower it. U want at least 180psi for a performance motor.
All valid points and something I'll have to build towards.
But...
The more I'm thinking about it the more I'm inclined to go back to the shorter cam.
These heads prior to porting where part of the same shortblock with a 224/230 @ .050" hydraulic roller. Static compression was 10.39 and cranking pressure was 200+ psi (at 600' above sea level). Timing was the issue. A few changes pulled the cranking pressure back to 180-190 psi however other problems (fuel related) kept me from dialing in that package 100%.
So that's were I'm at now.
SCR is 10.26:1 and with the cam installed straight up the DCR should be about 7.85. I can estimate the cranking pressure to be about 160 at this altitude. THAT'S the real kicker right there.
I know that the package is mismatched at this point but there's nothing I can do to raise the compression ratio. That cam could use 11:1 to really work well. Even at that SCR my cranking pressure isn't likely to be more than 180 up here. Piston to head clearance is .040". The heads have been through the mill once already.
As for the exhaust, I know I need something better. I've plans to put cut-outs as collector extensions so that'll help on track days. As for a 4" setup, I'm more inclined to go with Holley's new dual arrangement but either would be huge improvement over the single 3" and Flowmaster muffler.
While this thread was more about what my peak HP rpm would be with the 288 and not about the combination, it was inevitable that the conversation would go this way.
Cam has a 110 LSA w/ 106 ICL. I'm thinking about dialing it in a couple of degrees advanced. It's something that I can mess with having the Cloyes Hex-Ajust timing set. Haven't decided on that yet.
This cam was originally installed in this same shortblock and topped with AFR 195 street heads. Typically saw 7000 rpm but generally shifted around 6800 on the 1-2. Valvetrain is solid enough. You know I like the Beehive springs (Comp 26918). Have Ti retainers and short travel lifters. Crower full roller rocker (1.6). Never an issue in that regard.
Seeing that you have experience with this cam and the L31 heads gives some credo to this build. Essentially what I have is a heavily ported Vortec head. More flow on the intake side and considerably more on the exhaust. This package will love an open header with the right length extension. Again the simulation shows that this new build will be producing about 75-80 more hp at 6500 seeing as the old set-up had long since given up by that RPM. That's what's driving this upgrade.
As for gearing and converter, last year, when the fuel problems weren't giving me fits, I'd launch (footbrake) at about 2000 and cross the stripe at about 5500. The TCI 10" converter didn't work all that well when compared to when this engine was in the Chevelle and had a properly spec'd Yank. I doubt very much I'll change the rear gear but certainly have my eye on a better converter. If I can keep RPMs above peak torque then I'll definitely be quicker. That'll wait until next season though.
I have a slightly smaller cam, 231/239 @.050" on a 110. Its installed in my LT1 with AFR195's on top.
It will easily go to 7000rpm. It took a long while to get used to the fact that it makes power all the way to the rev-limiter, so I bounced off it a few times when i wasn't concentrating on waiting for the shift. Just hit it too fast to believe.
I have a slightly smaller cam, 231/239 @.050" on a 110. Its installed in my LT1 with AFR195's on top.
It will easily go to 7000rpm. It took a long while to get used to the fact that it makes power all the way to the rev-limiter, so I bounced off it a few times when i wasn't concentrating on waiting for the shift. Just hit it too fast to believe.
I'd be more comfortable with a cam that size. I feel like I'm stepping outside the way rest of the engine has been put together. Dual plane intake (albeit an RPM Air Gap), small headers, even the gearing. The converter I can deal with. The there's the post below.....
Originally Posted by Orr89RocZ
run the big cam lol it will be fine. Dont worry about dynamic comp
You sound a lot like my old racing buddy (whose shortblock and cam I'm building now). Go big or stay home.
I've followed your approach to a few builds you've been involved with and the DCR comment is always there. That said, you don't feel that a measly 160 psi cranking pressure and the associated loss of low speed torque is significant?
While I might be gaining upwards of 75 hp at the 1-2 shift, which by the way is my reasoning behind this whole upgrade, won't be offset by the loss of torque below peak? 50 ft/lbs at 3000 rpm is very palpable. I know I'd feel the difference. Remember that's it's a real street car first and a weekend drag racer second. Obviously I'm rethinking my drag racer first approach. There'll be a need for a lot of supporting parts to make it really quick (although that can come later).
Or should I just keep it in 1st gear while I'm cruising the streets looking for Hondas?
I like this. A poster that actually listens and participates in his own thread.
Sorry but a large duration cam and low compression leaves u without much throttle response no matter what stall TC u have. It may fly once up in the power band but take a little nap until it gets there when u step on it. Dont see how thats any fun on the street. Yea once u get the shift points nailed the 1/4 mile times maybe good or even better but again u have to start somewhere and on street that maybe 2nd or 3rd gear. It will feel more like a lawn mower than a hot rod until it comes up on the cam somewhere after 3,000rpm.
Good luck.
Last edited by cardo0; 05-08-2016 at 06:14 PM.
Reason: spelling
I understand the relationship between cam duration, or more specifically overlap, and compression ratio very well. I made a deliberate effort to try and maximize that effect with my last build and was looking to emphasize low engine speed torque. However with cranking pressures north of 200psi, I couldn't keep it of detonation without pulling a lot of timing out of it. Lesson learned although it was pretty quick for what it was eventually going to a corrected 12.4 @ 109 with a 224 @ .050" cam, lazy timing curve and ailing fuel system.
That said, this 288 cam and short block were part of another package with a similar CR to what I'll end up with and that car was also quick. I forget the figures exactly although time slips were 12.4 uncorrected with a similar mph as my earlier build. I'm thinking very low 12s using the DA correction factors. It was always faster than my car in a heads up race, where ever we raced.
That's what has me where I am today.
I have no illusion that it won't suffer down low. I think that's inevitable given the numbers. If I were building this where I used to live, at lower altitude, cranking pressure would be about 180 psi. That would be just dandy as I've learned that CR isn't nearly as important as an optimal timing curve. However, up here, where I'm living now, cranking pressure is likely to be closer to 160 psi. That has me concerned. That said, as this thread has pointed out, that isn't necessarily all that bad.
More to the point though, and the point of this thread which I'll repeat, is where it'll make it's peak HP. Seems that between 6000 and 6500 is the consensus and that's the number that interests me the most. With the 10" TCI converter, I shifted at 6500 on the 1-2 (with the old combo) so the drop into 2nd isn't so far down the RPM range. Problem was, the engine had since quit making power long before that. If this new cam makes the steam I think it will at 6500, then I'll be flying in comparison. I might lose the race up to the first hundred feet or so but beyond that the extra HP should carry me through.
At least I'm hoping it does.
And if I get away away without running 94 octane, so much the better. Plus it gives me a safety margin too.
Then I have to get another torque converter but that'll be something I'll start another thread about. I think that'll be real game changer.
Well since we have good discussion going here i'll add something. Be careful with assumption on cranking press and take an updated press test before installing the cam so u have some kind of reference. U understand then that its the intake closing point that controls compression pressure. If it were my cam to install i would install it at least 8 degrees advanced, maybe even more. Everyone is fixed on using 4* adv on most cams as general knowledge to work but in your case i think u will see significant improvement with more intake c/l adv.
Also i think u will find your torque peak is the both same amount and rpm with those small headers. Cutouts will carry max hp to higher rpm though.
So good luck and let us know your results if u can. Good night.
Well since we have good discussion going here i'll add something. Be careful with assumption on cranking press and take an updated press test before installing the cam so u have some kind of reference. U understand then that its the intake closing point that controls compression pressure. If it were my cam to install i would install it at least 8 degrees advanced, maybe even more. Everyone is fixed on using 4* adv on most cams as general knowledge to work but in your case i think u will see significant improvement with more intake c/l adv.
Also i think u will find your torque peak is the both same amount and rpm with those small headers. Cutouts will carry max hp to higher rpm though.
So good luck and let us know your results if u can. Good night.
I did a pile of "exiting interview" testing before I tore it apart. Compression test, cam position and valve train geometry so I would have the information going forward.
I've done some dyno simulation with the cam installed 4 degrees advanced. That's in addition to the 4 degrees ground into the cam. I haven't done 8 degrees though but I'll run an analysis to see what the computer says. That said, 4 degrees didn't do much. Maybe +10 ft/lbs below peak and about 5 hp less up top. It also rolled peak HP RPM from essentially flat from 6000-6500 to more of a peak around 6200. In a nutshell, it's what you would expect. More area under the curve for torque and less for HP.
I'm still thinking about installing it advanced. I have the Cloyes timing set (HexAjust) and moving the cam around means that I don't have to drop the pan or remove the timing cover. If I feel a change is needed, it's not too much of a pain.
Regarding the headers, again using DynoSim, I've deliberately choked the exhaust to more accurately represent what I have in the chassis. That would be small tube headers and mufflers. One of the biggest single changes I can make (in the program) is change that input value to a large tube header. I can add to that further by running open headers. It reflects what you would see in the real world. Not so much for actual values, but for the effects. Cut-outs, I know, will have a significant impact. With the right length open collector, everything moves up. Torque, HP and their relative RPMs.
I figure (at the pace I'm going), I'll have the engine reassembled and have some baseline testing done within a month. I still haven't ordered the parts I need to reassemble the heads.
Unfortunately no. I wish I did though. That I actually went ahead and had them ported and flowed was something that I hadn't really planed on. At least I have that information to work with.
Originally Posted by Orr89RocZ
With same converter as before, it may come out tad slower. Then again it might not, but once optimized with right stall speed, it will gain everywhere
Slower with the same converter is what I expect but if it doesn't I certainly won't complain. If it reacts to a new converter as the Monte Carlo did, then I'll be thrilled. That was a couple of tenths in a drivetrain that's similar to mine. 355, 700R4, 3.73 gear, about the same weight. It even had the same TCI 10" for the baseline tests. That vehicle is my official bogey for performance. That means I need a 12.3 time slip. I'm not sure I'll get that up here. Not until the fall anyway when the DA comes down from 4000'.
Somewhere I know 57kid is laughing. He says he deals with 10000' DA in the heat of the summer!
Been busy lately and just now read through this thread.
Thoughts:
This is the first I've heard that the AirGap is any better at all up high than the standard RPM Performer.
With the small port heads and 2-Plane manifold, 1-5/8" headers aren't going to hold you back.
A 70 hp gain at 6500 rpm sounds extremely optimistic. The heads aren't going to let that happen. And the 2-P manifold has already started to limit you by that rpm also.
I think your peak will be at 6200 with cutouts open. Again, the heads' CSA, and to a lesser extent the intake, have the overriding influence on that. The added cam duration boosts the peak and keeps the curve higher after the peak.
The 288 cam will lose the race to the 274 with the TCI converter, and will be about equal with a Yank SS3600 TC. To really get the bang out of the 288 cam, you should be running better heads, a single plane intake, and about a 4200 stall TC. With a 280 cam in my 350 ci LT1, I went from 1.55 to 1.43 60's and 11.4's to 11.1's switching from a Yank 9.5" SS3600 to an 8" ATI 4200. But to make it driveable with that much stall, you'd probably want more than 3.73 gearing.
The RPM Performer and AIR Gap I believe aren't that much different. I think the comparison was to the Performer intake. That said, I'm figuring this two plane to still be in the game at 6500, but only just. That's fine because 6500 will be red-line with perhaps a couple of hundred RPM for overspeed. All the parts in the mix were originally selected for their compatibility, the 274 included. As a whole it worked pretty well. I can see how the 288 may prove problematic but it's what I have and I'm more or less committed to moving forward with it.
All things being equal, that is the intake, heads and headers, the 274 had it's peak around 5500. By 6500, it's down considerably. By comparison, the 288 is still making power at 6500. 70 hp? Perhaps a little overstated. Depending on how quickly the 274 tails off and how much he 288 holds on, I would think 50 hp isn't out of the question.
Your analysis of the power peak and it's profile are consistent with the computer modelling. Peak HP is relatively flat from 6000-6500. It looks like the entire powerband moves up the chart by about 500-750 rpm in comparison.
As for the torque converter, stated earlier, I can see the 274 being the better performer with the TCI. Certainly up to the 1-2 shift. Possibly the 1/8th. More converter, I'm sure would make up a large part of that. Much like your two converter comparison, +1/10th in the 60' and 3/10ths in ET... That suits me. That's also comparable to the Monte Carlo as mentioned above.
Peak torque should be around 4500. What converter it'll take is something I haven't researched too deeply.
I had forgotten about this guy. Stock Vortec heads and Air Gap on a 355 with the 288 cam. Turns 6800. His drivetrain combination is more drag race than mine (TH350, 4.11 gears, 4500 stall) but the the cylinder head/camshaft combination caught my attention.
I had forgotten about this guy. Stock Vortec heads and Air Gap on a 355 with the 288 cam. Turns 6800. His drivetrain combination is more drag race than mine (TH350, 4.11 gears, 4500 stall) but the the cylinder head/camshaft combination caught my attention.
My fav example lol but take notes. You wanna go fast with so so heads, you gotta cam up and turn it hard. 4.11 and 4500 stall
Right.
If you're gonna shift that 288 cam at 6500, you won't get the benefit from it.
Although I have much better heads and a more rpm-oriented intake on my LT1 350, even with a power peak at 6400 rpm, I shifted at 7000-7100 rpm for best 1/4 mile ET. 280 cam, 4200 TC, 4L60E trans, 4.88 gears, 30" tires.
My fav example lol but take notes. You wanna go fast with so so heads, you gotta cam up and turn it hard. 4.11 and 4500 stall
Originally Posted by 86LG4Bird
Right.
If you're gonna shift that 288 cam at 6500, you won't get the benefit from it.
Although I have much better heads and a more rpm-oriented intake on my LT1 350, even with a power peak at 6400 rpm, I shifted at 7000-7100 rpm for best 1/4 mile ET. 280 cam, 4200 TC, 4L60E trans, 4.88 gears, 30" tires.
Notes taken and understood.
Traction was difficult enough with the old combination. Such is the life of a guy who brings his daily driver to the dragstrip.
I can't imagine the 4L60E/700R4 first gear and 4.88 rear gears. You must leave like a Super Stocker. I can see why you need a 30" tire.
My results will be interesting to say the least. Not necessarily fast, but interesting.
As for the shift point, 6800 would be better still. Especially with the current converter. The only reason I shifted the 274 (pre-ported heads) at 6500 was to get a more favourable RPM spot to drop into 2nd gear. Going to 6800, will be better still although all indications are the torque will be less at that point (274 vs 288).
I had forgotten about this guy. Stock Vortec heads and Air Gap on a 355 with the 288 cam. Turns 6800. His drivetrain combination is more drag race than mine (TH350, 4.11 gears, 4500 stall) but the the cylinder head/camshaft combination caught my attention.
Kevin (skinny z) PM'd me and sent me the link to this thread. I havn't been on here too much lately and don't really look anywhere except in the organized drag racing thread.
I figure i will give an update on my car and some of the things that i have done differently over the years and saw some good and some bad results of it.
First, the car is still running just as good as ever. I did recently make a change to an aftermarket EFI but the system had a problem and i sent it back and now have the carb back on. I just had the car out last week where it was running 11.60-11.70. On my shift point being 6800, i have changed that as of middle of last season and it now is 6500. I have shift light set to 6300. I noticed that the car actually liked a lower shift point contrary to what i see most are saying in here. Mind you, i am not saying what my car does is right, its just real life experience and back to back testing at the track. I have been fortunate enough to race in the points at my local track the last 4 years and have been able to get a lot of passes. I was adding it up recently and i think this engine combination has had near or more than 800 passes.
On the subject of gear and converter. The car used to have a 3500 stall and a 3.73 gear and it ran an 11.71 best. The new best with the 4500 stall and 4.11 gear is 11.56(on motor). I have installed nitrous and the car has ran a 10.69 at 130 mph with a 100 shot. That was also shifting at 7200 as the car ran through the gears like crazy on nitrous. One thing that i don't remember if i posted before, but i let the trans shift the 1-2 shift on its own and then i shift the 2-3 at 6500. But, the 1-2 shift is really short and shifts at 6000. Many people have come up to me at the track and ask me why i don't lengthen out my 1-2 shift as they say it sounds like it shifts as soon as i take off. So, i tried it and carried the 1-2 to 6500 and the car ran about .05 slower. I have tested this multiple times now and every time the car runs slower. Like i said earlier, this is from experience not necessarily what should be right. If i tuned my car the conventional way it should be tuned then i probably would be in the 12's still. I think this is where people underestimate seat time and really learning the car. Being a bracket racer i was forced to do this, as consistency is my goal not the fastest time slip (however, i do still like going faster, lol).
Something i don't mention too often as most people do not believe me but i do have pictures from back in the day that prove this is that the vortec heads are stock. They are not ported and only thing i have done is install Alex's vortec springs on them to allow for the cam i am running.
Also, my car 60 foots in the 1.55-1.58 range. This actually used to be better with the 3500 stall. Once i installed the 4500 the 60 foot slowed but the mph picked up as well as consistency which is what i was after. However, on the nitrous i did happen to get a 1.40 60 foot time and averaged around 1.41-1.44 on nitrous.
I have recently installed a bmr trak pak torque arm and have started to see my wheels come off the ground again. I had recently put travel limiters on as with the new converter the wheels were not leaving the ground and this slowed my reaction time at the track. So i have removed the travel limiters and with the new torque arm the car is leaving with the wheels in the air again. I also changed from a 8" wheel to a 10" wide to better spread out the 28x10.5 slick i am running.
Anyway, if anyone has anymore questions I'd be happy to answer. The car wouldn't be as quick as it is if it wasn't from the help of many on this board. I remember getting tore into pretty bad when i first announced i wanted this to run 11's. But i learned a lot from everyone and applied what they told me.
Here's a picture taken last week of the car taking off just to prove it still can do it, lol. It's actually a picture of a picture so quality is not the best.
Oh and incase you're wondering. This past winter i did change the ground effects from an 84 style to the 85-90 style. I have wanted this look for awhile and finally decided to do it.
Thanks,
Greg
Last edited by GreggymacZ28; 05-11-2016 at 10:17 AM.
... On my shift point being 6800, i have changed that as of middle of last season and it now is 6500. I have shift light set to 6300. I noticed that the car actually liked a lower shift point contrary to what i see most are saying in here. Mind you, i am not saying what my car does is right, its just real life experience and back to back testing at the track.
On the subject of gear and converter. The car used to have a 3500 stall and a 3.73 gear and it ran an 11.71 best. The new best with the 4500 stall and 4.11 gear is 11.56(on motor). I let the trans shift the 1-2 shift on its own and then i shift the 2-3 at 6500. But, the 1-2 shift is really short and shifts at 6000. Many people have come up to me at the track and ask me why i don't lengthen out my 1-2 shift as they say it sounds like it shifts as soon as i take off. So, i tried it and carried the 1-2 to 6500 and the car ran about .05 slower. I have tested this multiple times now and every time the car runs slower.
...the vortec heads are stock. They are not ported and only thing i have done is install Alex's vortec springs on them to allow for the cam i am running.
Also, my car 60 foots in the 1.55-1.58 range. This actually used to be better with the 3500 stall. Once i installed the 4500 the 60 foot slowed but the mph picked up as well as consistency which is what i was after.
The main point of this thread was to try and determine where this new engine combination might peak in terms of horsepower. More specifically, (and the two go hand in hand) is where I should be shifting.
Greg's combination is a little different than mine.
I got more 1st gear overall at about 10%. (TH350 1st x 4.11 rear) = 10.35 overall vs (700R4 1st x 3.73)= 11.41 in 1st.
Second gear is 6.24 vs my 6.04. (The dreaded 700R4 1-2 split.
He's lighter, has an 1 3/4 header but the same intake. I have better flowing heads (10% at .100", 20% at .500").
Overall, this is telling me that this combination should work. From his postings, it's easy to see how much the converter makes a difference. I can imagine that the move from the 3500 to the 4500 stall would from an improvement point of view be similar to what I might expect with a change.
But...this isn't about the converter (although it will be soon enough). It looks like the thinking here (from all who have offered opinions), regarding peak HP RPM (and shift points) is that 6500 seems to be a reasonable target even if the cam has more in it (which would be realized with a larger runner head).
I'll be doing what we all do when we're sorting through a new combination and that's get some seat time and keep making passes.
Greg. Quick question: What was your 1st converter?
1st converter was actually a red-neck 3500 stall. It was probably 15 years old, lol. But i really liked that converter.
I think your setup looks pretty good, i would say the only thing i see that would be the biggest thing holding the setup back would be the 700R4. But then again I'm not a big fan as i only had mine in for 30 minutes with my 355 before it blew.
This transmission has been a trooper. It was rebuilt twice by the same guy (the 2nd time after about a month of use). He paid more attention for the 2nd go around and put in better clutches and steels. I did the TransGo shift kit. Doing service on it this spring, I found a lot of metal attached to the pan magnet so I don't know how long it'll last. I doubt I'm putting much more than 400 ft/lbs through so that may explain why it's lasted this long. If it survives the season, I may swap it out and get a new converter at the same time. Time will tell.
I've thought about changing transmission types but that means I have to ditch my custom crossmember and possibly the exhaust. We found that with the right converter, the big spread between 1st and 2nd gear in the 700 isn't a big deal. And I know the 700 can be built to last. My friends upgraded to the 4L60E (or maybe 4L65E) and he swears buy it. That behind his 454 LSX which dynoed 650 chp so it's a tough transmission.
Speaking of exhaust, what do have after your 1 3/4" headers?
As of right now, I just have dual 3" pipes that are about 18" extensions dumped, no mufflers. But i have a dual 2.5" exhaust with an x-pipe and magnaflow mufflers that I run as well. I have ran in the 11.60's with the exhaust on. I actually didn't experience any change with or without the exhaust. I run open headers so i can hear my car. When racing some of the guys in the pro class at the track i couldn't tell if it was my car or there car and so going open headers fixed that.
I have thought about going to a single 4" though. Might be something i try next winter.
That's probably the biggest single difference between our cars other than weight. (It's at 3650 with me). I have a 2.5" into single 3" y-pipe over the axle to a Flowmaster cork. Probably flows 300 cfm at best. I have a cutout just ahead of the muffler and back to back testing has shown a couple of mph and a little more than a tenth in the 1\8 th. I'd like to do the cutout thing at about the same spot you have your collectors. That alone would be huge improvement. That you at least have duals and a short exhaust system in general helps your cause for sure.
If it were my cam to install i would install it at least 8 degrees advanced, maybe even more. Everyone is fixed on using 4* adv on most cams as general knowledge to work but in your case i think u will see significant improvement with more intake c/l adv. [/QUOTE]
Keep in mind there is a cost to everything. Increasing cam advance to improve cranking pressure and low rev torque in turn reduces upper rpm ve and power. Need to consider what the cam is intended for. The 288 is intended for broad torque curve and top end power.
I run the ZZX Cam(240@ 050) with 10.2 static. That puts dcr somewhere just south of 7.5. The only issue I have is low speed fuel tuning. Otherwise, it's very drivable. The 3500 stall makes it even better.
On my upcoming build I will probably go with 8.2 to 8.5 dcr, but no more. Orr said it well. Dcr is only part of the equation, ve through the engine's power band can push cyl pressure way
beyond that of a smaller cam with higher static cr.
I have been thinking of installing the cam in an advanced position. 4 degrees doesn't do much in simulations. I haven't tried 8 degrees.
In as much as the DCR is a tool, it does give a pretty fair indication how much cranking pressure you're likely to produce. This 288 cam installed straight up would produce about 160 psi in a compression test. That to me is a little low but I've also learned not to get too hung on the number either. Still, there's room for improvement. I know I can handle iron heads and cranking pressures closer to 190 easily enough. My experiment with 205+ was a bit much. If I crunch a few numbers I can get a good idea of what the 288 installed 8 degrees advanced would have for cylinder pressure and it looks to be in excess of 200 psi. That advanced position puts the IVC event at 62 degrees (rather than 70). Makes a big difference.
For what it's worth, DCR with the cam straight up is 7.85.
8 degrees advanced is 8.37.
All of this said, I am building this for more top end steam. I've been in the torque producing way of building these engines long enough and now I'm looking for HP north of 6000 RPM rather than being all in by 5500.
I'm starting to think that way.
4 degrees would bump my compression pressure to about 180 psi ( closer to 190 where I used to live.) That's very manageable. Up here, the 8 degrees advanced is still less than 195 but when I drive across the country again, I'll be dealing with exactly the same problem when I first assembled these heads on to this shortblock. That was a mistake.
05-04-2016, 04:04 PM
