*dot*head question

[HWB]

I recently obtained a 748 *dot*head to replace my 1127 N shim style head, i have at my disposal 1127 N cams, 1127 rocker style cams(89-90) and pristine condition 748 cams (*dot*head).

Im unsure at this point what gives me the best performance  out of this build any help would be appreciated i understand some cam sprockets need to be swapped ? also what compression ratio am i looking at ?  

Cheers

[no class]

seeing how you have so many extra cams..... I can take the 89-90 1127 cams if you are up to sell a set .... and you should keep the 750 cams ... the shim cams are obviously of no use for the dot head .

[HWB]

:') gotcha

[wraith]

You can't use the shim type cams on the dot head, I would say the 89-90 cams the dot head cams will work as well but people say they are a bit soft?

Use your cam sprockets that comes with the engine 

But it all depends on what you are calling performance? Do you want too end or bottom end torque? 

Don't know about compression as most put these heads in b12

[no class]

are the 750 cams from the gsxr or teapot ?

[slayer61]

DOT head + DOT cams would seem like an obvious choice. Am I missing something? 

[HWB]

4 minutes ago, no class said:

are the 750 cams from the gsxr or teapot ?

Dot cams from gsxr 748

[no class]

the 748 cams are your best bet .

[Dezza]

11 minutes ago, slayer61 said:

DOT head + DOT cams would seem like an obvious choice. Am I missing something? 

750 j/k and 750 teapot both have dot heads but cams are different, I think .

[HWB]

28 minutes ago, no class said:

the 748 cams are your best bet .

Im confused  

[no class]

confused? how so ?  

[HWB]

Wraith said theyr soft, and i got it you wanted the 1127 89 cams since theyr better ?  now its the dot cams ? Sorry guys im in uncharted territories here with the dot thing, the head is going to get ported and the cams dialled, i just mean which profile has the best lift and duration for my application seeing ita going on a ported head. Looking for torqy midrange 

[no class]

I was not trying to trick you out of those 1100 cams .... I will glady take the 750 cams if it makes you feel better 

[HWB]

I know mate and i appreciate you and everyone taking the time to help me out cheers

[slayer61]

27 minutes ago, HWB said:

Wraith said theyr soft, and i got it you wanted the 1127 89 cams since theyr better ?  now its the dot cams ? Sorry guys im in uncharted territories here with the dot thing, the head is going to get ported and the cams dialled, i just mean which profile has the best lift and duration for my application seeing ita going on a ported head. Looking for torqy midrange 

My mistake then. The *DOT* head was originally on the slingshot 750. It was a higher revving, big bore, short stroke engine. The "Slingshot" cams aren't what you're looking for. 

[HWB]

Just now, slayer61 said:

My mistake then. The *DOT* head was originally on the slingshot 750. It was a higher revving, big bore, short stroke engine. The "Slingshot" cams aren't what you're looking for. 

Awesome! So whats my best bet ? The 89 1100 cams or 86 1100 cams (can buy them tomorrow) or 86 750 cams ?! 

[no class]

use the highest lift cams you have .... measure the height ( tallest point of the lobe)with a vernier caliper ... measure the  base circle .... subtract the bc from the height and that is your lift dimension .you can slightly play with torque  by  cam timing .... advancing the intake cam moves the torque figures lower down the rev range . the slingshot 88-89 cams are great .... so are the 89-90 1100 cams . 

[no class]

[SiBag]

OK lets clear a bit of the confusion.

The DOT head was used on the 750 Tpot (up to 97 I think) and on the GSXR 750 J/K 1988 to 1989

The 750 Tpot cams are the cams that are described as "Soft" and not the best for performance.

The GSXR 750 J/K and the GSXR 1100 K share the same cams (Part numbers 12721-17C00 exhaust, 12711-06B03 inlet) These are the cams you want to use.

Edited March 27, 2021 by SiBag

[HWB]

Ok thats perfect actually 

Any idea on the comoression ? Im guessing its a slightly different number for everyone but is it somewhere in the 11s ir 12s ? 

[Dezza]

A dot head will raise and change the angle of the carbs so depending on what frame the engine is going in and the carbs to be used, this may cause clearance issues. See the carb interchangabilty sticky at the top of the oil cooled section for pics .

[SiBag]

I believe on the Blandit 1200 the head swap raises the compression by 1 or 1.5 points due to the smaller combustion chamber in the DOT head.

I suspect it will be similar for the N motor (potentially up around 11 to 11.5 : 1), but I'm sure an adult will correct me shortly..

[wraith]

Sorry for the confusion with my first post, I thought you had the teapot dot cams which are soft  but as above if it the gsxr 750 dot cams they are as good as the early 1100 cams.

Just to throw a spanner in the works I'm told the b12 heads have a better flow and respond better to porting than the dot heads? Just what I've seen posted on here  but won't increase the compression.

[HWB]

3 hours ago, Dezza said:

A dot head will raise and change the angle of the carbs so depending on what frame the engine is going in and the carbs to be used, this may cause clearance issues. See the carb interchangabilty sticky at the top of the oil cooled section for pics .

Yeah i already read that sticky thoroughly, the head is going on a 92 1127 frame with 38 faltties, ive heard someyhing about the alternator needing a bit of grinding, ill see when i get there i guess.

Thanks for all your help mate cheers

[Magoo]

You may not need to grind the alternator bit with the dot head on as this will raise the carbs by a noticeable amount.