Polishing and Porting a 1500 engine

[billspit]

I am doing a minor porting job on my 1500 Spitfire cylinder head before it goes to the machine shop for new guides and valves and skimming. I have the competition manual that is for the MK1 through MKIV. They show how to alter the shape of the combustion chamber on the Mk I by angling down a side of the chamber. They show nothing in regards to the MK IV head, which is almost the same as my 1500, but different from the MkI. So, does anybody have the 1500 manual and does it show any grinding inside the combustion chamber of the head.

Thanks

 

[DougF]

Are you referring to Kas's competition manual? Not being a Spitter, I don't know what is available. But I have that manual if it is any help.

 

[billspit]

Yes this is Kas's comp manual that was done years ago, not any of his new stuff. Pretty much too late anyway. The head is going to the shop today.

 

[aeronca65t]

Smoothing the ports will help, but be really sure that manifold bores matches the cylinder head ports as well as possible....that's really more important and easier to fix.

And if you are still using the single carb manifold, you would do well to replace it with the twin carb setup...that's a HUGE boost
(I think I could make something better than the stock single carb manifold with plumbing parts from Home Depot)

You can take 0.110" off a stock head with no issues (really, more), but you may need to run high test fuel.

One thing to keep in mind about the 1500: as you improve intake flow, this really helps in the high end RPM. But the 1500 is a very long stoke engine and will not survive very high RPMs for long (I limit my 1500 racer to 5800 RPM).

 

[billspit]

aeronca
I pretty much did what you suggested, matched the ports and removed any obvious casting flash. I did try to smooth out the exhaust, but its pretty narrow and hard to get the finer polishing pads inside.

I have a European intake twincarb and exhaust. I have to find a down pipe though. I've heard about the sealing problems with this exhaust and may spring for a proper 4-2-1 header instead and sell my manifold on ebay. I have two 4 into 1 headers I acquired years ago, but I think they are for earlier engines.

This is going to be a street engine and no high revs.

 

[aeronca65t]

aeronca
.....I have a European intake twincarb and exhaust....

Excellent! :thumbsup:

 

[Paul Slice]

Hello Bill,

hope everything is going fine with you.

Is the engine you are building going into the red Spit that you got from me?

If so, would you please show some pictures of your progress on the car, if you have had time to work on it.

Sounds like it is going to be a strong running motor.

good luck,
Paul

 

[vettedog72]

Bull
Ask you machine shop if they are aware of a new (?) process for polishing ports where by an abrasive paste is flowed through the ports with a polished results. There are differing opinions of "polish"; some applications of some motors benefit from both intake and exhuast high polish where the TR's, from what I read do better with smothed intake and polished exhuast. Which way are you going with the Spit?

 

[billspit]

Hello Bill,

hope everything is going fine with you.

Is the engine you are building going into the red Spit that you got from me?

If so, would you please show some pictures of your progress on the car, if you have had time to work on it.

Sounds like it is going to be a strong running motor.

good luck,
Paul

Yes Paul this is that car. I worked on the car body until cold weather set in last fall. I pulled the engine and have been diddling with it since then. The block is done and waiting for the cyl head. This has been the slowest engine build I've ever done. I had an old differential rebuilt with a new 3.63 ring and pinion to put into the car. Then my 3.89 in my MK I went out, so I slapped the 3.63 into that car. It it too high for 1147cc of screaming fury. I will likely put it into your car once the engine is done. Then I will be on the lookout for another 3.89 for the Mk I.

I worked on the only dent that is on the car yesterday. Did pretty good, but some of the dent cannot be reached from inside with the tools I have. I'm probably going to be repainting it the original color, even if it is almost a Gamecock color. I really would like a dark BRG color, but don't want the fight repainting the inside. I continue to be amazed how rust free the car was.

I can send you some pics of the engine. Pictures of the car won't impress you because it doesn't look as good as when I got it from you.

 

[billspit]

Bull
Ask you machine shop if they are aware of a new (?) process for polishing ports where by an abrasive paste is flowed through the ports with a polished results. There are differing opinions of "polish"; some applications of some motors benefit from both intake and exhuast high polish where the TR's, from what I read do better with smothed intake and polished exhuast. Which way are you going with the Spit?

This is going to be a street car with a little autocrossing thrown in if available. I don't want the intake polished as it is not a race car. I am aware of the process you are referring to and have seen it marketed by extrude hone.

I am a tiny bit disappointed by my visit to the head shop. They have no clue to the spec of a Spitfire and said they don't have books that have it. They do have Serdi machine, but weren't going to use it until I mentioned it. They also could not tell me how much I needed to cut the ehad to get to the CR I wanted. This shop was recommended by Hap Waldrop, so I'm keeping my fingers crossed.

Well the head shop just called. Seems I sent all exhaust valves. However, seems they do have reference material.