I emailed Dan at http://danielcrowerracing.com/ and asked if he could do a regrind. He said yes, $120 a cam. I then asked what I could expect as far as power gains with a slightly milled head, to which he came back with about 10-14rwhp gain in mid-top end when properly tuned.
10-14rwhp when properly tuned... from a cam... seems far fetched...
For the $120 a piece for cams, $240 for a few hp doesn't sound too bad. I just wonder how much "a few hp" would really be in the rear world.
I dont know why i'm already doing it since it's still July, but i'm planning a winter build on my engine that's currently using oil.
Plans:
1986 vt700 engine build
vt800 cylinders (vt800 has the same bore as vt750, with different rods and crank to stroke it to 800cc, it uses the same base and head gasket as the vt700 as well as the same cam chain)
83 vt750 pistons with new rings
milled head to bump compression (unsure of how much is able to be removed)
reground cam
I'm unsure if i want to cut out the air box on the bike and make a new backbone with 1.5" tube to use a different fuel tank and get rid of the 2 tanks and a fuel pump. But either way, i'm replacing the stock air filter set up with something as high a flow as I can get it but still able to be driven in the rain.
Ideas? Opinions? I don't want to get rid of the bike and I like to tinker, so I don't really want to hear "get a bigger bike" or anything. Mine is unique
It sounds very interesting. You did a lot of research too. I wonder if it will really be a screamer when all done.
Just thinking about guys that hot rod a car and add compression and stroker kits, and cams, etc, they can also add a bigger carb to the mix. But these CV carbs are limited on changing jet sizes I believe. So is that going to be a resriction on horsepower gain in the end? Then again, one fellow on here is talking about adding a Weber carb to his bike, so I guess many things are possible.
I thought about making a manifold and using a sportster 883 carb, but i'm not too sure I want to do that. I'm skeptical on the 10-14rwhp gain that he told me. If a stock 83 750 makes about 66 (what i'm assuming my motor would make with 750 pistons) and i build mine to a 750 with a cam and slightly increased compression, if it even get's 10hp from the cam that's about 76hp. Plus the exhaust (short drags with minimal baffle to increase low end) and a high flowing filter... 78ish hp wouldn't be unheard of i don't think. But still... very skeptical on the 10-14rwhp thing. Also, I'm assuming the 66hp spec for the 83 is at the crank and not the rear wheel.
I have an '83 also and have seen that 66 HP figure too. I never thought about where it was measured. But most all cars tell the HP on the engine before the drive train. Since the shaft drive on these bike takes a little more HP away from the output, I wonder how you can get to that 10-14 HP at the wheel. And what would "proper tuning" consist of? Curious!!!
I am not that familiar with this particular engine, but offer general advice.
IMO a cam change could give that kind of increase as long as the intake and exhaust system can keep up.
It will be at the expense of low end power and possibly the rev limit will have to be raised and advance curve tailored to suit, new valve springs will be required to handle the cam change.
Valve to piston clearances will need checking, new cam chains should be installed, especially in light of milling the heads.
The hydraulic valve adjustment may need abandoning in favor of manual adjustment.
You may have to re-gear the bike to make up for the lost bottom end torque.
The clutch may need beefing up to handle the power increase.
The life expectancy of the engine will be reduced, by how much is anybody's guess, but since it is a Honda you are not starting with a hand grenade and it is unlikely you will end up with a "nickel rocket".
I'm in process of looking at 'improving' the later 750 engine based on the smaller VT family and it at 40-odd hp on a good day is a lot softer target and my goal is where yours sits stock.
I haven't thought about the hydraulic adj valves causing an issue, I've never had an engine that had hydro adj valves... i'll have to do some research on that one.
I'm also not sure that it will need heavy duty valve springs or not, if it will require it i'll have to keep looking at sport bike valve train to find some that fit or something since again, no aftermarket.
Regearing isn't possible because of the shaft drive, it's a love hate relationship with shaft drive and I.
There is no support for clutch upgrades that i'm aware of, but i just learned that is uses a conical spring and should be able to be shimmed like a viscous type LSD diff.
My intake and exhaust parts should be able to flow a ton once I get it made compared to stock.
I'm not an engine builder, i just found parts I know will physically bolt together and operate. If I wasn't swapping a cam it would be bolt on. But i want MORE........... going to have to talk to my machine shop for advice on the above.
"I will make it fit standard valve springs , we only raise the lift a tiny bit .040” thou maybe max. plus 6- 8 degree duration."
So that answers the question about valve springs, but not the hyd lifters. I'd think if he welds and regrinds the lobes that the valve adjuster would still function perfectly, but if he regrinds the heel to increase the lift is where it may have problems.
I'm assuming that if the lift is raised .040" that .040" would be ground off of the heel of the cam. This would require the stock lifter to be .040" longer to take up the extra space. I am unsure if that is possible with a stock valve adjuster.
I'm also unsure on the head milling. I really want to because the cam should decrease off idle performance and the increase compression should make up for that some, and... more HP. I also read that when milling the head it retards cam timing. I'm not sure how you readjust for that without an adjustable cam gear because I'm assuming that's less than moving the cam one tooth in the chain. It's not worth it to me to have adjustable cam gears made.
I don't really know anything about the hydraulic lifters Honda uses in this application, but in automotive engines such things if they don't bleed down fast enough can actually pump up lifting the valve, this usually caused by cam profile duration, lift increase and rpm not allowing enough time for normal function. Makes a dandy rev. limiter. As you point out if the base circle of the cam is cut down it can also potentially bring on a problem of being out of design range.
If you can get a handle on how much the cam would be retarded by milling the head, the camgrinder may be able to allow for this, since it is a custom weld and grind job.
Was that engine or family members user in performance applications or racing programs?
If so that might be a source of pieces such as adjustable cam gears etc.
I know the PC800 is related, but I've never heard of people hot rodding them, but somebody might have.
I know that in the case of my '99 750 Shadow, many of the performance pieces intended for the NT650/Hawk GT/Bros will fit out of the box or can be made to fit with little work.
No race applications. From what i gather the answer to more power is a bigger bike when it comes to shadows. The PC800 i doubt anyone modifies, i saw one of them once. Looked like a cross between a scooter and a motorcycle lol
The bigger bike thing doesn't make sense to me since an 86 1100 makes 78.5hp and 73lbs of torque (i've read. another source states 67hp) but weighs 585lbs wet when my 700 shadow makes supposedly 58ish hp stock and currently weighs 455lbs wet (i weighed mine).
power to weight if all else were equal:
86 vt1100 - 7.45lbs per hp (if 78.5hp) or 8.73lbs per hp (if 67hp)
86 vt700 - 7.58lbs per hp (mine's about 40lbs lighter than a stock one)
It probably doesn't amount to a hill of beans in this case, but don't forget to add in rider weight when doing comparisons.
For example, an extreme case:
When I was a teen I weighed 145 lbs and had a very fast Ducati 250, it weighed 230lbs with gas in streetable trim, about 7 lbs per hp without rider, now days (BTW the bike still exists) it would probably need a tow to get on cam with me aboard.
You can grind a cam without welding it, the valves have to be 'lifted' to meet the cam afterwards. This allows you to not have to worry about the welds falling off.
I just sent them an email as well. I'm doing some work for a guy that in the end will cost him about $250, I might just buy a set of cams online and have them ground. I just ordered vt800 jugs yesterday. Anyone have a line on a pair of 1983 vt750 pistons OR 1988 vt800 pistons? I think even a PC800's pistons will work.
Better check the differences between the 750 and 800 pistons since the 800 is effectively a stroker motor using many of the same pieces, depending on how it was handled by Honda the piston pin location may be higher in the piston than the 750.
would be cool to put the vt800 crank and rods into my cases with the 6 speed trans since the vt800 were only 4 speeds. but that's more than I want to get into
Well that's good to know for others who may follow in your path and Honda is meticulous when it comes to part number accuracy.
The unavailable 750 & 800 piston 13101-ML5-000
The available in Europe and probably Canada piston for PC800 is 13101-ML5-670
I am no expert in this interchange stuff and my understanding of Honda parts numbers might be out to lunch and hopefully somebody here can give some better deciphering.
My understanding of Honda Part Number is the first one is the item group, the second one is the model on which it first appeared and the third references supplier, production revisions, and cosmetic differences. So based on the above I'd think that that there might be some hope of interchange and a source of new pistons and rings and it is worth exploring further.
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Honda Shadow Forums
1.6M posts
82.9K members
Since 2007
Welcome to Honda Shadow Forum. Come in and discuss any Honda Shadow models: VT1100, VT250, VT750 and the VT500.